Wood anemone (Anemone nemorosa), is a low-growing, rhizomatous herbaceous perennial in the buttercup family, native to the woodlands of Europe.
These spring ephemerals are one of the first plants to bloom, providing an abundance of single, white flowers, with prominent yellow stamens. Along with bluebells and wild garlic, the wood anemone is indicative that the woodland is ancient.
In the home garden, wood anemone makes a beautiful landscape flower in shady areas.
Name Origins
The name Anemone nemorosa means “windflower of the woods.”
Anemone comes from the Greek word ‘ánemos’ (άνεμος) which means ‘wind‘, hence the common name ‘windflower’.
Nemorosa is derived from the Latin word ‘nemoris‘, which means ‘of the forest‘, reflecting the natural habitat of wood anemone.
Anemone nemorosa
Botanical name:Anemone nemorosa
Family: Ranunculaceae
Common names: Wood anemone, Windflower, European thimbleweed, Crowfoot, Smell fox, Thimbleweed
Native area: Europe
Habitat: Woodland
Mature height: 25 cm (10 in)
Spread: 30 – 60 cm (12 – 24 in)
Flower colour: White
Bloom time: Early spring
Leaf colour: Green
Sun exposure: Full shade to part sun
Soil type: Well-drained, humus-rich soil
Soil pH: 5.5 to 7.5
Appearance
The wood anemone grows to a mature height of 25 cm with a spread of 30-60 cm. As rhizomes spread beneath the ground, wood anemone slowly forms a carpet on the woodland floor.
Leaves
Wood anemones have 2.5-5 cm long palmately lobed leaves divided into three main segments, with each segment further divided into narrower lobes, which gives them a feathered appearance. The leaf margins are irregularly toothed, and the leaves are arranged in whorls where they attach at the same point on the stem, below the flowers.
Flowers
Each flower has five to eight petal-like sepals, which are usually pure white but can sometimes have a pink or lilac tinge, on the reverse side. Sepals surround a cluster of yellow stamens at the centre. The flowers are 2.5 cm in diameter, and the shape is described as “radial” or “actinomorphic.” This means that the flower can be divided into two mirror-image halves in multiple ways along its central axis.
The wood anemone is a spring ephemeral, which means it quickly goes through its growth cycle early in the spring. It emerges in March to April, blooms, grows vegetatively and dies back in a short time frame. This allows the wood anemone to take advantage of available sunlight that reaches the forest floor before the canopy of deciduous trees leafs out.
The leaves emerge from the underground twig-like rhizome (an underground horizontal stem) in late winter to early spring. This is followed by the emergence of its star-shaped white flowers. Hoverflies and bees are major pollinators of wild anemones, and after pollination, pods develop from the flowers. The achenes, which have fatty attachments called elaiosomes, are dispersed by wind and ants that are attracted to these structures.
After flowering, the wood anemone continues to grow vegetatively. During this vegetative phase, the plant will grow leaves that photosynthesize to produce simple sugars. These simple sugars are converted to more complex carbohydrates in a process known as biosynthesis.
These complex carbohydrates are transported through the plant’s phloem, the vascular tissues that distribute nutrients throughout the plant. Once the carbohydrates reach the rhizomes, they are converted back into starches or other storage forms. These storage carbohydrates are packed into the cells of the rhizomes. This energy reserve is crucial for the plant to survive dormancy and regenerate the following year.
During this period, the rhizomes may spread, leading to the growth of new plants. By late summer the above-ground parts of the wood anemone begin to die back and the plant remains dormant from autumn until late winter. Energy is conserved in the rhizomes, which will remain dormant throughout the winter.
Each spring, the cycle begins with the rhizomes sending up new shoots. In the right habitat, wood anemones can form extensive carpets of flowers over time as their rhizomes slowly spread. They can also propagate through seed, although this is a less common method of reproduction for them.
Where is the Best Place to Plant Wood Anemone?
Wood anemones flourish under the canopy of deciduous trees, which provide dappled sunlight. The light conditions simulate the natural opening and closing of the woodland canopy through the seasons.
Soil should retain moisture without becoming too waterlogged. Incorporate organic matter such as mushroom compost or cow manure to improve soil structure, moisture holding abilities and provide nutrients for optimal plant growth.
How to Sow Wood Anemone Seeds
Sowing wood anemone seeds is a challenge due to their complex germination requirements, as well as the high percentage of sterile seeds.
The best time to sow wood anemones is in autumn when the seeds are fresh, and they will experience a period of cold stratification over winter. If growing in spring, seeds will need a period of cold stratification for 12 weeks. Place in a plastic bag in the refrigerator.
Location: Sow seeds in full shade to dappled sun.
Seed selection: Always select fresh seeds in late summer or early autumn. The seeds should be dry, brown and fall easily out of the seedheads when shaken. Check with local authorities if you plan to collect wood anemone seeds from the wild.
When to sow: If growing in autumn, sow the seeds in a container of soil or directly into a garden bed. Place the seeds on top of the soil mix as wood anemone seeds require light to germinate. Spring-sowed wood anemone seeds will have had to be cold-stratified before sowing (see above).
Watering: Water the seeds with a fine mist to settle the soil and ensure good seed-to-soil contact. Adequate moisture is crucial after cold stratification for the seeds to absorb water, which triggers the expansion and breaking of the seed coat.
Time to germinate: It typically takes 3-4 weeks for wood anemone seeds to germinate, but may take longer.
Growing Wood Anemone From Rhizomes
Wood anemone has developed a reproductive strategy that emphasizes vegetative propagation over seed dispersal. This is an adaptation to the stable, often undisturbed environments where it typically thrives, such as deciduous woodlands. Rhizomes should be healthy and firm, avoid dry, overly soft or shrivelled ones.
The best time to plant your wood anemone rhizomes is in autumn, a few weeks before the first frost. This will allow them to establish a healthy root system before winter.
Prepare the soil by loosening it to a depth of 30 cm, and mix in some compost or well-rotted cow manure.
Soak the rhizomes in water a few hours before planting to rehydrate them.
Plant the rhizomes horizontally in the soil about 5-7.5 cm deep, and about 10-15cm apart.
After planting, water the soil thoroughly to help it settle around the rhizomes.
Apply a layer of mulch after planting to conserve water and protect from harsh weather conditions.
As the plants emerge in spring, maintain water, especially if the weather is dry. Be careful not to overwater.
Apply a light application of a well-balanced fertiliser.
Remember, wood anemones die back after they have produced seeds, but will return the following spring.
How Does Wood Anemone Reproduce?
Wood anemone reproduces sexually through seed production and vegetatively through rhizomatous growth. The rhizomes grow horizontally just below the soil surface. As they grow, they extend outward from the parent plant they produce adventitious roots and shoots at nodes along their length. The roots anchor the rhizomes into the soil, while the shoots will grow upwards to become new above-ground plants. Rhizomatic growth is an effective way for the wood anemone to propagate itself, particularly in shady woodland areas where seed germination may be less reliable.
Flowers appear in spring and are pollinated by insects, leading to the production of seeds. Once the seeds mature, they are dispersed into the environment. Germination is a slow process, as wood anemones require a period of cold stratification to mimic the cold of winter.
How Fast Do Wood Anemones Spread?
Wood anemones are known to spread slowly and it is said that they can take up to 100 years to spread across a distance of about 2 metres, which equates to 2 cm per year. The rate at which wood anemones spread can vary depending on soil conditions, moisture, light, and competition from other plants.
Growing Wood Anemone in the Garden
Wood anemone is a shade-loving plant that is ideal for low-light areas such as under trees or in sheltered nooks. This characteristic allows wood anemone to illuminate low-light areas with its delicate blossoms, creating a woodland feel. With its adaptability to cooler, shaded areas, the wood anemone is an excellent choice for gardeners looking to bring life and colour to less sunny spots that might challenge other sun-seeking plants.
Wood anemone forms dense carpets of lush foliage over time, which makes it an excellent ground cover in shady areas. This dense growth in woodlands can help stabilise soil and prevent erosion during prolonged rainy seasons.
Caring for Wood Anemones
Provide a woodland-like environment with dappled shade or partial sun, and maintain a well-draining, nutrient rich soil. Keep the soil consistently moist, but be careful not to over-water which can lead to root rot.
Apply a light layer of compost or a balanced fertiliser with an equal ratio of Nitrogen (N), Phosphorus (P), and Potassium (K), such as a 10-10-10 or a 14-14-14.
Nitrogen (N) helps with leafy, vegetative growth.
Phosphorus (P) is important for root development and flower production.
Potassium (K) is essential for the overall health and vigour of the plant.
Since wood anemones are grown primarily for their flowers, and they have a period of dormancy after flowering, it’s not necessary to apply a high-nitrogen fertiliser. A balanced fertiliser will ensure that the plants have all the nutrients they need for healthy root development, flowering, and overall growth. During winter, protect the rhizomes in colder regions by adding an extra layer of mulch, and avoid excessive disturbance around the plant’s root zone.
Dividing Wood Anemones
The best time to divide wood anemones is in the late summer or early autumn after the foliage has died back and the plants are dormant.
Gently dig around the clump of anemones you want to divide, being careful not to damage the rhizomes. Lift the clump out of the soil with as much of the root system intact as possible.
Shake away any remaining soil and remove dead foliage from the rhizomes.
Carefully tease apart the rhizomes with a sharp knife (I find a bread knife is the best tool to divide underground stems and rhizomes). Each section should have at least one growth point (bud) from which new shoots can emerge.
Plant the newly divided rhizome sections immediately at a depth of 10 cm (4 inches). Provide plenty of space between them for growth.
Keep the soil moist but not waterlogged as the rhizomes establish themselves. Mulching can help to retain moisture and suppress weeds.
Ecological Importance of Wood Anemone
Wood anemone plays an important role in the ecosystem of temperate woodlands. As one of the first spring flowers to bloom, it provides early-season nectar for pollinators like bees, hoverflies and beetles. These insects are critical for the pollination of many other plant species, thus supporting the entire woodland food web.
Indicator of Ancient Woodland
The presence of wood anemones is an indicator of an ancient woodland, which are forests that have existed since 1600. Wood anemone contributes to the diversity of the ecosystems and its preference for stable, undisturbed habitats means that large colonies are a sign that the woodland is healthy and thriving.
Soil Stabilisation and Nutrient Cycling
The dense carpet of foliage formed by wood anemones stabilises the soil and reduces erosion, particularly in the spring when other plants have not yet grown. This ground cover acts as a mulch to maintain soil moisture levels. As the leaves die back, they decompose and add organic matter to the soil, enhancing its structure and fertility and promoting nutrient cycling.
Symbiotic Relationships
Wood anemone has a symbiotic relationship with ants (myrmecochory). The seeds of the wood anemone have a fatty appendage called an elaiosome, which attracts ants. The ants take the seeds to their nests to feed on the elaiosomes, thereby aiding in the dispersal of the seeds away from the parent plant. This process ensures wider colonisation and genetic diversity within the species.
Habitat for Fauna
The lush foliage provides a habitat for many small animals and invertebrates. The microclimate under the leaves can be a haven for small mammals, amphibians, and insects, offering them protection from predators and harsh weather.
Conservation and Biodiversity
By conserving wood anemone and its habitat, we are protecting a whole suite of associated species. The decline of native woodlands can lead to a loss of these plants and the complex web of life that depends on them. Efforts to conserve wood anemone habitats contribute to broader conservation goals, such as maintaining biodiversity, protecting native species, and preserving the ecological functions of our woodlands.
Is Wood Anemone Toxic to Cats and Dogs?
Wood anemone is toxic to both dogs and cats. The toxic compound is protoanemonin, which can be irritating and harmful to pets if ingested. If a dog or cat consumes parts of the wood anemone plant, they may experience symptoms such as vomiting, diarrhea, drooling, or abdominal pain. Contact with the plant can also cause skin irritation.
Given the irritant properties of anemonin and its potentially harmful effects, it is advisable to handle plants containing this compound with caution and to keep them away from pets and children.
Wood Anemone Story
Anemone was a beautiful nymph, and Zephyrus, one of the four Anemoi (wind gods)-Boreas (North), Zephyrus (West), Notus (South) and Eurus (East).
Zephyrus (also known as Zephyr) the god of the west wind, was married to Chloris (also known as Flora), the goddess of flowers and spring. When Flora discovered her husband’s affection for Anemone, she used her powers to turn Anemone into a flower, so she could no longer be with Zephyr.
Flora cast a spell that transformed Anemone into a delicate flower, causing Zephyr to lose interest in her. Boreas, the god of the north wind fell in love with Anemone, despite her being a flower. However, Anemone was not interested in him. In his frustration at being rejected, Boreas used his chilling winds to blow open the petals of Anemone.
Zephyr loses interest in Anemone as a flower preferring her as a nymph. However, Boreas another wind god (North Wind) represented the winter winds, fell in love with her despite her being a flower.
Boreas tried in vain to woo her but Anemone was not at all interested in him. An angry Boreas blows on her petals every spring.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
As an avid citrus grower with over twenty citrus trees in my garden, I have found citrus to be one of the easiest and most rewarding fruit trees to grow. Citrus is one of the most diverse species of fruiting tree, from the tart ‘acid citrus’ to the sweet and juicy oranges and dekopons. Not only does freshly picked citrus taste great, it also has ornamental value in the garden and the flowers produce a beautiful sweet scent.
The shape of the flower is ‘actinomorphic‘, which refers to its radially symmetrical shape. The peak blooming time is spring, but some types of citrus in temperate zones produce flowers and fruit year-round.
Most of us think of citrus as a Mediterranean fruit as it is widely cultivated there, however, it is not native to the region. Citrus originated in Asia. Bitter oranges (Citrus aurantium) were first brought to Europe by the Arabs, who had acquired them from Asia. They were probably introduced to Spain and Sicily sometime between the 10th and 12th centuries during the period of Arab rule.
Sweet oranges (Citrus × sinensis) are the most abundant citrus fruit in the world, and make up approximately 40% of all imports. Oranges are widely consumed raw, or juiced. China, Brazil, and the United States are the top producers of sweet oranges. dIn Japan, the yuzu (Citrus junos Sieb. ex Tanaka) and sudachi (Citrus sudachi Hort. ex Shirai) are popular varieties of citrus but are not widely cultivated in the Western world.
What type of fruit is citrus?
Citrus fruits are classed as hesperidium. Hesperidium is a type of modified berry that is made up of a tough, leathery rind, which protects the delicate pulp inside.
The outside of a citrus fruit consists of a thick, aromatic rind (exocarp and mesocarp), commonly known as the zest and peel. Beneath the rind is a white pith (albedo), and below that, the juicy segments (endocarp) which contain the seeds. The segments are filled with juice vesicles, which are specialised hair cells.
One of the distinctive features of hesperidium is its way of storing citric acid, which is stored in vacuoles of the juice vesicles, giving the fruit its characteristic tart flavour.
Dwarf vs full size
Dwarf citrus trees are great for decks, patios or small gardens. They typically grow to a height of 1.5 metres (5 foot), which makes it easy to harvest the fruit. The volume of fruit on dwarf citrus is generally the same as the full-sized counterpart.
Rootstock is responsible for the ultimate size of the tree. Dwarf trees are grafted onto rootstock to encourage dwarf growth habits. One of the most common dwarf rootstocks is a mutation of Citrus trifoliata, known as C. Trifoliata ‘Flying dragon’. This deciduous citrus relative is popular due to its hardiness and ability to induce dwarfing in the grafted tree.
Dwarf trees are easier to manage than their full-size counterparts and are more suitable for small gardens or container gardening. Full-size trees have a longer lifespan (50 years vs 25 years) and produce a higher fruit yield.
Both full-size and dwarf citrus are suitable for pots. As the pot will restrict root growth, a full-sized citrus will not grow as tall as it would in the ground.
Why are citrus trees grafted onto rootstock?
Grafting involves combining a rootstock with a scion. The scion is a cutting from a citrus tree with desirable traits, with the rootstock, which is a young tree with a robust root system, disease resistant and hardy to certain temperatures. The scion is secured to the rootstock so that their cambium layers align. This allows the scion to inherit the favourable traits of the rootstock, and ensure the citrus only produces the desired fruit.
Quick propagation of desired variety: Grafting allows for the reproduction of the exact genetic copy of a desired citrus variety, ensuring that the fruit’s quality and characteristics are preserved. Growing trees from seed is slower, and as many citrus trees are hybrids, there is no guarantee the seedling will have the same characteristics as the parent plant.
Disease resistance: Many citrus rootstocks have been selected for their resistance to certain pests and diseases, such as citrus tristeza virus, phytophthora root rot, and root nematodes. Grafting onto these rootstocks can help protect the scion (the upper part of the graft that will become the fruiting part of the tree) from these threats.
Improved tolerance to soil and climate conditions: Some rootstocks are more tolerant of certain soil types, pH levels, salinity, or climatic conditions than others. Choosing the appropriate rootstock can improve the success and productivity of the tree, even when grown in less-than-ideal conditions, such as areas with frost.
Control of tree size: Rootstocks influence the size of the mature tree, resulting in dwarf varieties that are easier to harvest and suitable for small areas.
Tree longevity: Some rootstocks can enhance the lifespan of the citrus tree, resulting in more productive years.
Common citrus rootstocks
Citrange (Citrus sinesis x Poncirus trifoliata) a hybrid that performs well in clay loams. Popular cultivars include ‘Troyer’ and ‘Carrizo’. Sweet orange (Citrus sinensis) grows well in sandy to medium loam soils but is less tolerant of heavy, wet soils, nematodes and root rot. Other pros include good fruit quality and vigorous growth.
Hardy orange (Poncirus trifoliata) is valued for its cold hardiness, resistance to various diseases including citrus tristeza virus and nematodes, and its ability to adapt to a variety of soil conditions. Poncirus trifoliata ‘Flying dragon’ provides the advantages of standard trifoliate orange rootstock, such as cold hardiness and disease resistance, while also inducing dwarfing in the scion, which makes it ideal for smaller spaces or container growing.
Sour orange (Citrus aurantium) is only suitable for lemons and limes. This rootstock produces high-quality fruit, thrives in a wide range of soils and has tolerance to root fungi, nematodes, and cold.
Are multi grafted trees recommended?
Also known as fruit salad trees, multi-grafted trees contain more than one species of citrus. For example, you may have lemon and lime, or grapefruit and orange. You cannot have different genera, such as an apple and an orange grafted tree.
The idea of multi-grafted sounds great, especially if space is an issue. You will often find that one of the grafts will take over the whole tree. I’ve had two grafted citrus, one was orange, lemon and grapefruit, and the other was lemon and lime. The orange, lemon and grapefruit became an orange tree, and the lemon and lime is almost all lime, with one small branch that gives me 1 – 3 lemons a year. The lime portion produces around 100 times a year.
Pot vs ground
Both dwarf and full-size citrus trees are suitable to grow in the ground or in large pots. People renting may choose to grow citrus in a pot so they can take it with them when they move. Potted citrus is also great for small gardens or decks. Some varieties of citrus such as kumquat and calamondin have ornamental value. I have three potted calamondins on my deck purely for their visual appeal. Calamondin isn’t a fruit I would normally eat (I will probably try my hand at a calamondincello this year), however, they make great ornamental citrus because they flower and fruit almost year around.
Bear in mind that fruit yield will be greatly reduced if the tree is grown in a pot. A mature citrus can produce up to 200 fruits in a season, compared to a pot-grown one which will only produce twenty. The productivity of a lemon tree is also influenced by factors such as proper pruning, adequate sunlight, appropriate fertilisation, sufficient water, and disease control. Providing optimal care and maintaining the tree’s health can help maximise its fruit production.
What is the best pot to grow citrus in?
The pot should be at least 40 cm (16 inches) in diameter and ideally as wide at the top as it is at the bottom. Egg-shaped or standard pots are ideal for your citrus. My preference is egg-shaped pots as they are more stable than traditional pots that tend to be much narrower at the bottom. Potted, citrus trees, especially when laden with large fruit such as grapefruits or oranges can be top-heavy and prone to toppling over in pots that are too narrow at the bottom.
Terracotta not only looks great, but the porous nature of terracotta can help to regulate moisture levels in the soil. The pot can absorb excess water when the soil is too wet and then slowly release it back into the soil as it dries out.
The terracotta pot on the left is fine for citrus as long as the tree is not too top-heavy. The egg pot in the middle is ideal and holds larger citrus well due to its overall more stable shape. The terracotta pot on the right tapers in at the top, which can make the removal of the plant more difficult when repotting.
When is the best time to plant citrus?
Spring is the best time to plant your citrus tree as the soil is warming up. This gives the tree a full growing season to establish itself before the colder weather sets in. If you’re growing the tree in a pot indoors or in a greenhouse, the planting time isn’t as critical, but again, spring is often the best choice.
Are citrus self-pollinating?
Almost all varieties are self-pollinating (also known as self-fruitful). A self-pollinating citrus can produce fruit without the need for another citrus to cross-pollinate. Citrus trees can also cross-pollinate with other citrus varieties, resulting in hybrid varieties. The fruit will remain the same, but the seeds within the fruit will be hybrid.
Even self-pollinating trees can benefit from cross-pollination, which can help to increase fruit set and yield. Gardeners may choose to cross-pollinate by hand or attract pollinators to the garden by growing a variety of flowers.
Bees and other pollinators play a crucial role in both self-pollination and cross-pollination by transferring pollen from the male parts of the flower to the female parts. Thus, while citrus trees don’t need another tree to bear fruit, they often do need pollinators.
How to choose a citrus tree
Look for healthy trees with fresh, mature green leaves and no evidence of damage to the leaves or stem. Fruit on a citrus tree is not an advantage, as it should be removed for the first 2-3 years to allow the citrus to put its energy into growth and not fruit production.
How to care for a citrus tree
As an avid fruit grower, I find citrus one of the easiest and most rewarding fruits to grow. I personally love the more tart varieties such as lemon, lime, grapefruit and finger lime.
Soil
Citrus trees grow best in soil that is aerated, well-drained, and sandy loams. If growing in the ground, clear the site of plants and plant roots as the citrus root system is concentrated in the top 30-50 cm of soil and it doesn’t like competition around the root ball.
Well-drained and aerated soil is vital for citrus trees to avoid root rot. Citrus trees do not grow well in heavy clay soils unless aeration, drainage or mounding is provided.
Optimal pH range
Citrus prefers slightly acidic to neutral pH between 6.0 and 7.5. Within this range, citrus trees can efficiently absorb essential nutrients from the soil. Soil that is too acidic (below 6.0) can result in nutrient deficiencies as acidic soil hinders the availability of essential nutrients such as phosphorus, calcium, and magnesium, leading to stunted growth and yellowing leaves. Soil pH that is too high, (above 7) can result in citrus trees that struggle to absorb zinc, iron and manganese, which can cause yellowing leaves with green veins.
Testing soil pH test is important to determine the pH level of the soil to ensure that the soil provides optimal conditions for their growth, nutrient uptake, and overall health.. Soil testing kits are readily available at garden centres or online. A pH kit will provide you with accurate information on your soil’s pH which will enable you to make adjustments. To lower alkaline soil, add sulfur, peat moss, or organic matter with high acidity. To raise the pH in acidic soil, apply lime or other alkaline materials.
Soil type
Citrus trees thrive in loamy or sandy loam soil, which provides a balance between good drainage and water retention. Avoid heavy clay soils that can hold excess moisture and lead to root rot. Incorporating organic matter into the soil improves its structure, drainage, and nutrient-holding capacity. Compost, well-rotted manure, or leaf mould can be added to enrich the soil before planting citrus trees.
Adequate drainage is crucial for citrus trees. Excessive moisture can lead to root rot as the soil becomes compacted, removing air pockets that are critical for the roots to obtain enough oxygen. If your soil has poor drainage, amend it with organic matter or create raised beds to improve drainage.
Nutrients
Citrus trees require a good balance of essential nutrients for healthy growth and fruit production. Conduct a soil test to determine nutrient deficiencies and amend the soil accordingly.
Nutrient
Functions
Deficiency Symptoms
Excess Symptoms
Nitrogen (N)
Nitrogen is crucial
macronutrient necessary for the manufacturing of amino acids, the building blocks of proteins that are necessary for the development of
cellular structures and plant enzymes that facilitate biochemical reactions. It also plays a significant role in chlorophyll production
that enables plants to convert sunlight into energy via photosynthesis. As part of the DNA and RNA structures, nitrogen is essential for cell
division and growth, influencing the overall growth rate of the plant,
leaf development, and seed and fruit production.
Yellowing or pale green
leaves (chlorosis), and stunted growth.
Excessive vegetative
growth at the expense of flowering and fruiting. May also make thick fruit rinds, delayed maturity of fruit and lowered juice content.
Phosphorus (P)
Phosphorous is a vital part of the ATP (adenosine triphosphate) molecule, which provides energy for many processes in the plant, including growth and reproduction. It is also
necessary for the formation of DNA and RNA, which carry genetic information for new cell growth. Phosphorous contributes significantly to root development which enhances nutrient and water uptake and is also
involved in flowering and fruiting, and seed development.
Stunted growth, delayed maturity, reduced
yield, and dark, sometimes purple, foliage. Puffy fruit, bumpy rinds and
open centre cores.
Interferes with micronutrient uptake (iron,
zinc, manganese, leading to deficiencies of these nutrients.
Potassium (K)
Potassium is involved in water regulation within the plant cells, helping to control the opening and closing of stomata, which, in turn, affects water usage and photosynthesis. As a vital component in protein and carbohydrate synthesis, potassium is essential for overall plant growth, development, and health. It is also key to the activation of many enzymes, strengthening plant cell walls and contributing to stronger, more disease-resistant plants. Potassium aids in the translocation of sugars, effectively distributing energy throughout the plant, which is particularly important for fruit and seed development.
Older leaves turn yellow
at the edges and between veins, weak stems.
High potassium can
interfere with the uptake of other nutrients such as calcium, magnesium,
and nitrogen.
Magnesium (Mg)
Central atom in chlorophyll, essential for photosynthesis. magnesium activates many of the enzymes involved in cell
growth and reproduction, contributing to the successful progression of
seed development. Magnesium is also essential for the creation of
adenosine triphosphate (ATP), the main energy carrier in all living
organisms, necessary for the energy-intensive process of seed formation
and maturation.
Intervenal yellowing (yellowing of leaves between veins), beginning with older leaves.
Rare, but may lead to calcium deficiency.
Zinc (Zn)
Zinc is a crucial micronutrient in plants, that is a vital
component in many enzymes and proteins and is involved in
the synthesis of auxins, a type of plant hormone
instrumental in regulating growth. It aids in the formation
of chlorophyll and some carbohydrates, and assists in starch
formation and protein synthesis, all of which contribute to
the overall growth and development of the plant.
Stunted growth, reduced
leaf size, and interveinal chlorosis, a condition where leaf tissue turns yellow while the veins remain green. In severe cases, deficiency
can also lead to necrotic spots or distorted leaves.
Excess is rare but can be
toxic to plants, potentially inhibiting plant growth and development,
and causing leaf discolouration, root damage, and reduced crop yield.
Manganese (Mn)
A vital micronutrient for plants, that is a
necessary cofactor in enzymes involved in photosynthesis, respiration,
and nitrogen metabolism. Manganese aids in the formation of chloroplasts
and is crucial for the process of photosynthesis, facilitating the
conversion of light energy into chemical energy.
Interveinal chlorosis in younger leaves and
necrotic spots.
Leaf discolouration or necrosis, root
damage, and inhibited growth. In alkaline soils, manganese may become
unavailable to plants, causing deficiency symptoms even when manganese
levels are adequate.
Iron (Fe)
Iron is a component of
many proteins and enzymes involved in photosynthesis, respiration, and
nitrogen fixation. It is a key constituent of proteins involved in electron transport, facilitating energy production and is also integral to chlorophyll synthesis, although it’s not part of the chlorophyll
molecule itself.
Yellowing between the
leaf veins while the veins themselves remain green, most noticeably in
young leaves. This occurs because iron is necessary for the formation of
chlorophyll, which gives leaves their green colour.
Seldom identified but can
cause bronzing or tiny brown spots on leaves, ultimately inhibiting
plant growth.
A commonly recommended ratio for citrus trees is 2:1:1 or 3:1:1 of N:P:K. So, for example, a citrus fertiliser might have an N:P:K ratio of 6-3-3 or 9-3-3.
Blood and bone contain nitrogen and phosphorous, to make it complete, add a quarter of a cup of sulphate of potash per kilo of blood and bone. Add fertiliser to moist soil in a band around the tree, starting at the drip line (outer edge of the tree), and work inwards, halfway towards the trunk. Rake, mulch, and water immediately afterwards.
Soil moisture:
Citrus trees require consistent moisture, but the soil should never be waterlogged. The goal is to keep the soil evenly moist. A deep watering every 7 to 10 days (depending on the weather and soil type) is typically sufficient for mature trees, while younger trees usually require more frequent watering. It’s important to water deeply to encourage the development of a robust root system that can access water lower in the soil.
Overwatering can lead to root rot. When the soil is waterlogged, the spaces between soil particles become filled with water, starving the roots of oxygen. Overwatering can also promote the growth of various fungi and bacteria that cause root rot. These pathogens are present in the soil in small quantities without causing problems. However, in the anaerobic (low-oxygen) conditions created by overwatering, they can multiply rapidly and start attacking the weakened roots.
Water
Although citrus are somewhat drought-tolerant, they prefer a consistent water supply to thrive. Water deeply and thoroughly, to ensure the water reaches the deeper roots. Deep watering encourages a robust root system, critical for the overall health and stability of the tree. Water in-ground citrus once a week, or twice a week for potted citrus during the drier months and less often in autumn and winter.
Sunlight
Citrus trees grow best in an open position where they receive a minimum of five hours of full sun each day during the growing season. Sun is necessary for growth as well as the accumulation of sugars in the fruit.
Harvesting citrus
Harvest your citrus when it has reached its colour. Most citrus fruits are ready to harvest from winter to spring, and they should easily be removed from the tree when it is ready. Fruit left on the tree for too long will eventually lose its flavour and become dry.
Citrus can be eaten fresh or stored for up to two weeks. Most people will find their citrus tree grows more fruit than the average household can use. Uneaten citrus can be processed into juice, marmalades, cordial, lemon butter, candied, or liqueurs, or shared with friends and neighbours. We share our limes with our neighbours, and they give us their excess lemons as our lemon tree is still immature.
Citrus Fruit
Ideal
Storage Temperature
Storage Life
Orange (navel)
3-7°C (38-45°F)
2-3 weeks
Orange (Valencia)
3-7°C (38-45°F)
2-3 weeks
Lemon
10-15°C (50-59°F)
2-3 weeks
Lime
10-15°C (50-59°F)
2-3 weeks
Grapefruit
3-7°C (38-45°F)
2-3 weeks
Tangerine/Mandarin
3-7°C (38-45°F)
1-2 weeks
Pomelo
7-10°C (45-50°F)
2-3 weeks
Buddha’s hand
10-15°C (50-59°F)
1-2 weeks
Tangelo
3-7°C (38-45°F)
2-3 weeks
Yuzu
3-7°C (38-45°F)
2-3 weeks
Sudachi
3-7°C (38-45°F)
2-3 weeks
Finger Lime
3-7°C (38-45°F)
2-3 weeks
Kumquat
3-7°C (38-45°F)
2-3 weeks
Calamondin
3-7°C (38-45°F)
2-3 weeks
Refrigeration can extend the shelf life of most citrus fruits, however, the best flavour is when the fruit is fresh. The storage life will depend on how ripe the fruit is when it is picked or purchased and how it is stored. Check your fruit regularly for any signs of spoilage.
Pests and diseases
Pest/Disease
Symptoms
Treatment
African citrus psyllid (Trioza
erytrea)
African citrus psyllid causes direct
damage to the plant and can transmit the lethal Huanglongbing (yellow dragon
disease, previously known as citrus greening disease).
Contact your local government
authority if you suspect your citrus has African citrus psyllid.
Asian citrus psyllid (Diaphorina citri)
Mottled leaves, stunted growth, yellowing, and leaf
drop.
Contact your local government authority if you suspect
your citrus has Asian citrus psyllid
Citrus fruit borer (Citripestis
sagittiferella)
Holes and cracks in the fruit skin,
fruit drop, and frass (insect feces) around the holes.
Contact your local government
authority if you suspect your citrus has citrus fruit borer
Citrus leafminer (Phyllocnistis citrella)
Curled or distorted leaves with silvery trails
Use a specific leafminer trap or pheromones
Citrus mealybug (Planococcus citri)
Chlorosis (yellowing) of the foliage,
as well as leaf drop, stunted growth and reduced crop yields
Maintain beneficial insects such as
the mealybug ladybird (Cryptolaemus montrouzieri), lacewing
larvae (Oligochrysa lutea) and parasitic wasp, Leptomastix
dactylopii. Keep ant populations down as they feed on the
sugar-rich honeydew and in return protect citrus mealybug. Mealybugs can be difficult to control with chemicals due to their resistance, waxy coating and their natural tendency to hide.
Citrus canker (Xanthomonas axonopodis pv. citri)
Water-soaked, corky lesions on the underside of leaves,
later becoming more raised and defined with a crater-like centre,
encircled by a yellow halo. The disease manifests similarly on fruits
and stems, presenting raised crater-like, corky lesions. Infected fruit
may fall prematurely, and if lesions girdle the stem, branches may
experience dieback. Left unchecked, can spread rapidly, significantly
diminishing fruit yield and quality.
Prune and destroy affected parts; copper sprays
Citrus tristeza virus (Citrus
tristeza virus)
CTV causes a disease known as quick
decline, where infected trees rapidly wilt and die, often within a few
years of showing initial symptoms. In other cases, CTV can cause stem
pitting, where the bark of the tree develops elongated pits or grooves.
Affected trees exhibit stunted growth, reduced fruit yield, and lower
fruit quality. The fruit from infected trees may be smaller and display
colour inversion, with the area closer to the stem remaining green while
the end furthest from the stem becomes fully coloured. CTV can also
cause seedling yellows in which young trees remain stunted and show
yellowing of the leaves.
No cure; use resistant rootstocks;
remove infected trees
Queensland fruit fly (Bactrocera tryoni)
Fruit damage, decreased crop yield, decreased fruit
quality
Monitoring (using fruit fly traps), sanitation (removing
and disposing of infested or fallen fruit), the use of protein and
insecticide baits, and in some cases, the use of male annihilation
techniques or sterile insect technique (SIT).
Red scale (Aonidiella aurantii)
Yellowing and wilting of leaves,
reduced vigour, and potential death of branches or entire trees if left
unchecked. The feeding activity can also cause fruit to drop prematurely
and result in a significant decrease in fruit quality, marked by
yellowish, red, or brown spots on the rind where the scales were
attached
Parasitic wasps (Aphytis
lignanensis and Aphytis melinus), ladybirds, chilocorus beetles and
predatory mites. Parasitic wasps are commercially available. Sticky
traps with synthetic red scale pheromones can be used to monitor for the
presence of flying red scale. Movento is an insecticide produced by
Bayer that is effective against red scale.
Root rot (Phytophthora spp.)
Brown or black roots become soft or rotted, in contrast to healthy roots which are firm and white. Above-groundsymptoms may initially be less evident but can include leaf chlorosis
(yellowing), wilting, and overall tree decline. As the disease
progresses, the canopy may thin and the tree may exhibit stunted growth.
Fruit production can be significantly reduced, and the fruit itself may
be smaller than normal. In severe cases, root rot can cause tree death.
Good water management, fungicides if necessary. Can be hard to treat once the roots are damaged.
Yellow dragon disease (Liberibacter
spp.)
Yellowing of the leaves in an
asymmetrical pattern, where one half or section of the leaf appears
blotchy yellow while the other part remains green. Stunted growth,
smaller, misshapen fruit that remains green at maturity, and has a
bitter, off-flavour. Fruit and flower drop increase, leading to reduced
yield. Additionally, the disease often leads to twig dieback, and in
severe cases, it can result in the death of the entire tree. The
symptoms may appear on a single branch at first and then spread to the
entire tree.
No known cure, prevention is key;
remove and destroy affected trees
Cold hardy varieties
Yuzu citrus
Satsuma mandarin (Citrus unshiu): Satsuma mandarins are among the most cold hardy of citrus trees, withstanding temperatures as low as -7°C (20°F). They are known for their sweet, seedless fruit and generally ripen earlier than other mandarins.
Kumquat (Fortunella spp.): Kumquats are very cold hardy, withstanding temperatures down to -7°C (20°F). They produce small, round or oblong fruit that can be eaten whole, including the skin, which is sweet and contrasts with the tart inner flesh.
Yuzu (Citrus ichangensis x C. reticulata): Yuzu is a unique citrus used primarily for its aromatic zest and juice in Japanese and Korean cuisine. It can withstand temperatures down to -7°C (20°F). The fruit is typically not eaten fresh due to its large seeds and minimal flesh, but the zest and juice are highly prized.
Trifoliate orange (Poncirus trifoliata): While not a true citrus, trifoliate orange is often grouped with them because of its similar characteristics. It’s incredibly cold hardy, surviving temperatures down to -10 degrees Fahrenheit. The fruit is generally considered inedible due to its bitterness, but it is sometimes used to make marmalade. Trifoliate orange is often used as a rootstock for other citrus to impart its cold hardiness.
Calamondin (Citrus x citrofortunella microcarpa): Calamondin is cold hardy down to -7°C (20°F). The fruit looks like a small tangerine and can be used as a tart substitute for lemons or limes.
Improved Meyer lemon (Citrus x meyeri ‘Improved’): This is a hybrid citrus fruit native to China. It is a cross between a citron and a mandarin/pomelo hybrid distinct from both parents. The Improved Meyer lemon can handle temperatures down to around -7°C (20°F). Meyer fruit is sweeter and less acidic than common lemons.
Keep in mind that even these more cold hardy varieties can benefit from protection if extreme cold temperatures are forecasted. Wrapping the tree, using frost blankets, or employing outdoor lights can help prevent damage. Also, microclimates, such as those provided by south-facing walls, can help increase the cold hardiness of citrus trees in the landscape.
USDA hardiness zones of citrus varieties
The USDA hardiness zone is a resource developed by the United States Department of Agriculture (USDA) to help growers determine which plants are most likely to thrive in a particular location. The map is divided into zones based on the average annual minimum winter temperature.
Citrus fruit
Ideal
climate
Orange (Sweet)
Tropical and Subtropical, USDA zones 9-11
Orange (Bitter/Seville)
Tropical and Subtropical, USDA zones 9-11
Grapefruit
Tropical and Subtropical, USDA zones 9-10
Lemon
Mediterranean, Subtropical, USDA zones 8-11
Lime
Tropical and Subtropical, USDA zones 8-11
Tangerine (Mandarin)
Tropical and Subtropical, USDA zones 8-11
Kumquat
Tropical, Subtropical, and Temperate, USDA zones
9-10
Buddha’s hand
Tropical and Subtropical, USDA zones 9-11
Tangelo
Tropical and Subtropical, USDA zones 9-11
Yuzu
Cooler regions of Temperate, USDA zones 8-10
Sudachi
Tropical and Subtropical, USDA zones 8-11
Finger Lime
Tropical and Subtropical, USDA zones 8-11
Calamondin
Tropical and Subtropical, USDA zones 8-11
Makrut (kaffir lime)
Tropical and Subtropical, USDA zones 10-12
Etrog (Citron)
Mediterranean, USDA zones 9-10
Pomelo
Tropical and Subtropical, USDA zones 9-11
How long do citrus trees live?
Citrus lifespan can vary depending on the species, the conditions it is grown in and how well it is cared for. Under ideal conditions, many citrus trees can live for 40-50 years. Mother Orange Tree is a citrus that was purchased in 1856 and still bears fruit.
The lifespan of a citrus tree can vary significantly depending on the specific variety, the conditions it’s grown in, and how well it’s cared for. However, under optimal conditions, many citrus trees can live for over a century.
The productive lifespan of commercial citrus tends to be 20-30 years, after which time, yield declines and the tree is less economically viable.
With proper care, you can expand the longevity of your citrus and ensure maximum yield. Grow a variety that is suited to your climate, fertilise regularly, prune away dead or diseased branches and maintain shape to allow for good airflow, and routinely check for pests and diseases.
How long does it take citrus trees take to reach maturity?
Most citrus trees are approximately 1 metre tall when they are sold. It takes up to ten years for citrus to reach maturity. Removing fruit from young citrus trees allows the tree to direct its energy toward establishing a strong root system and growing in size, which can lead to better overall health and greater fruit production in the long term.
Which variety should I grow?
This depends on your local conditions and personal preferences. If you live in a cool area, look for frost-hardy varieties. I have been growing citrus trees for twenty years, and have learned a lot along the way. These days I am more mindful of what I am planting, why, and if I will actually use the fruit. Also, factor in how much fruit you will use or give away. For example, I have two lemon trees (admittedly, they are different varieties). A fully mature lemon tree can produce over 200 lemons a season. Can you use or give away 400 lemons? For most people, one tree per citrus type is enough.
Fruit availability
Another point to consider is the availability of citrus in supermarkets or fruit shops. Oranges are readily available year-round and are cheap. My preference is to grow citrus that is more expensive, or rare varieties such as sudachi or yuzu that aren’t available in Australian supermarkets.
We grow yuzu, sudachi, makrut lime, Australian finger lime, Buddha’s hand, pomelo and tangelo, which are rarely, if ever available to buy from supermarkets or fruit shops in Australia. In addition to the difficult-to-buy varieties, we also grow calamondin and kumquat as ornamentals, the fruit is a bonus. Common citrus varieties include lemon and lime, to make limoncello and limecello. There’s a 15-year-old dwarf mandarin I planted for my young daughter who loved mandarins. We don’t tend to use the fruit, so give it away. I would like to try mandarincello this year with some of the fruit. We also have two orange trees, which will likely be given away as we don’t eat the fruit.
Is it true that urinating on a citrus tree is good for it?
There is some truth to this as urine contains nitrogen, which is an essential macronutrient. However, the downside to this practice is that human urine also contains salt, which can build up in the soil over time and be harmful to plants. If it is done often enough, human urine can create an unpleasant odour around the tree. To be honest, I would prefer to use a balanced fertiliser than human urine.
What are the biggest and smallest types of citrus fruit?
The largest citrus fruit is the Pomelo (Citrus maxima). This fruit can reach of up to 30 cm (nearly 12 inches) in diameter and can weigh as much as 2 kg (about 4.4 pounds) or even more.
The smallest citrus fruit is generally accepted to be the kumquat (Fortunella species). The fruit is usually about the size of a large olive.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
English and French lavender are two of the most popular and widely cultivated species of Lavandula. These scented plants are commonly grown in cottage gardens for their vibrant colours and fragrance. Despite their shared genus, English and French lavender have several different characteristics.
English lavender is somewhat misleading as it originated from the Mediterranean region. The name ‘English lavender‘ is thought to be due to its widespread cultivation and popularity in English gardens and its use as a perfume, particularly among royalty and nobility.
Used in a wide range of culinary
applications including baking, teas, syrups, liqueurs
Generally not used as a culinary herb
Medicinal uses
Traditional medicinal uses for relaxation, sleep aid, and soothing minor burns and skin irritations
Less commonly used for medicinal
purposes, but may share some properties with English lavender
Growth habit
Compact, dense and bushy
Looser and more open growth
Companion planting
Pairs well with roses, salvia, and other sun-loving perennials
Pairs well with drought-tolerant,
Mediterranean plants like rosemary, sage, and thyme
English lavender
Also known as true or common lavender, English lavender (Lavandula angustifolia) has been cultivated in the British Isles since the Roman era. The Romans recognised the benefits of lavender for its antiseptic, insect repellent, cosmetic, and culinary properties. The aromatic fragrance of English lavender was used by the Romans in bathwater, hence the name ‘lavender‘ which is derived from the Latin word ‘lavare‘, which means ‘to wash‘. Queen Elizabeth
To this day, English lavender is widely cultivated for its essential oils and fragrant flowers and is used extensively in aromatherapy, massage oils, candles, perfumes, soaps and as a linen and room spray. The fragrant flowers are used in the culinary world and impart a unique floral taste. English lavender can be used to create lavender-infused honey, jams, syrups, buttercream, teas and baking.
Flowers: English lavender flowers are typically deep purple, but can also be pale lilac or white. They are arranged in dense, terminal spikes that form cylindrical or conical flower heads. The flower spikes are held on erect, leafless stems that rise above the foliage.
Fragrance: English lavender flowers have a delicate, floral scent with sweet overtones and a hint of rosemary. The fragrance is described as relaxing and soothing and the buds are used in aromatherapy, perfumes, candles, food and beverages and beauty products.
Leaves: The leaves of English lavender are lanceolate, sometimes with a slightly broader base. The bright green colour of the leaves may have a silvery sheen due to the presence of fine hairs, which also give the leaves a slightly fuzzy texture (known as pubescent linear leaves). These leaves are oppositely arranged on the stems, growing in pairs directly opposite one another and attached directly to the stem without a petiole (leaf stalk). The edges of the leaves are smooth, without teeth or serrations, and the leaves also possess a pleasant, sweet fragrance.
English lavender leaves. Photo by Julia Wilson.
Uses: English lavender remains popular among gardeners. It is drought-tolerant, fragrant, and attractive to pollinators. It fits well in cottage, herb and Meditterean-style gardens. As an avid gardener and lover of lavender, English lavender is my personal preference. I love the simplicity and the fragrance of English lavender flowers and grow them in my herb garden.
French lavender
Also known as ‘toothed lavender and Spanish lavender‘, French lavender (Lavandula stoechas) is native to Spain, Portugal, France, Italy, Greece, and North Africa and is grown for its decorative ruffled purple flowers. While French lavender also has an aromatic scent, it is less sweet than that of English lavender with camphorous notes.
Flowers: The flowers are made up of multiple, cone-shaped flowerheads (known as a spike) with showy bracts (modified leaves) at the tip. Each flower consists of a calyx (bud), corolla (petals), stamen and pistil. The calyx is the outermost part which consists of small, leaf-like structures to protect the developing flower. The corolla is made up of petals, that are typically purple but can also be found in pink and white.
Fragrance: French lavender flowers have a slightly different aroma to English lavender. The scent is stronger and more pungent, with a sweet and floral scent that is accompanied by more pronounced herbaceous and woody notes. Some people describe the scent as being sharper and more camphorous and earthy than English lavender.
Leaves: The leaves are slightly narrower than those of English lavender, elongated, with a silvery-green colouration and covered peltate trichomes which produce and store essential oils. Fine, soft hairs, give the leaves a velvety texture (pubescent linear leaves). These hairs help protect the plant from water loss and intense sunlight, as well as give the plant its characteristic greyish-green, silvery appearance. The hairs found on lavender leaves are non-glandular and do not produce or store any essential oils.
Uses: French lavender is a popular ornamental flower in the garden, adding long-lasting colour and its characteristic odour. Unlike English lavender, French lavender is rarely used commercially for its scent.
Which lavender to choose
The choice between English and French lavender is personal. In my opinion as a lover of lavender, the French is far showier and makes a great choice for a decorative garden bed or in terracotta pots to add some colour to decks and patios.
From a price point of view, lavender plants are relatively inexpensive, and both types cost around the same amount. I love the simplicity and the fragrance of English lavender but generally grow both types in pots on the deck as well as in the ground near my vegetable patch to attract pollinators and add some colour. Interestingly, I’ve never had luck growing English lavender from seed, but the French lavender I currently have is self-sowing everywhere, not that I mind free lavender plants.
Both lavender varieties make great hedges but can become woody, so will need a hard prune once a year to keep them in shape.
Lavender flowers make great cut flowers and their beautiful floral scent will fill the room.
Conclusion
English and French lavender are both popular plants grown for their attractive flowers and aroma.
French lavender has showy flowers, while English lavender has less showy flowers, but a sweeter and more appealing aroma.
English lavender is used for its scent in beauty products, aromatherapy and in the food industry.
Both English and French lavender are great additions to the garden or deck and will reward you with months of beautiful flowers.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Sudachi (Citrus sudachi Hort. ex Shirai) is a small but mighty citrus fruit that is widely cultivated in Tokushima Prefecture, adjacent to Kochi Prefecture, famous for its yuzu citrus. The exact origins of sudachi are not fully known, it is believed to be a mutation of the yuzu citrus (C. junos), a hybrid of the ancient citrus papeda (C. ichangensis) and mandarin (C. reticulata), or a hybrid of yuzu and Tachibana orange.
While yuzu is the most popular citrus fruit in Japan, sudachi (すだち) is a close second, and for good reason. Its unique tart and refreshing flavour makes it a versatile ingredient in Japanese cuisine, particularly in ponzu sauce, sashimi, and grilled meats. The compact size and thin skin also make it easier to handle and use in cooking.
In Tokushima Prefecture, sudachi cultivation is a significant part of the local economy. Farmers take great care to grow high-quality sudachi fruit, which has helped drive the annual sales of this citrus fruit to 2.2 billion yen or 16 million USD. With its distinct flavour and versatility, sudachi is a valuable part of Japanese culinary culture.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Chillies contain a compound called capsaicin, which stimulates pain receptors in the mouth and tongue, causing a sensation of heat and burning. This happens because capsaicin binds to a receptor called TRPV1, which normally responds to heat, and sends signals to the brain that interpret the sensation as pain or heat. Interestingly, some people enjoy the “heat” of chillies, while others find it unbearable. This is because capsaicin also triggers the release of endorphins, which can create a pleasurable sensation for some individuals.
What is capsaicin?
Chillies, also known as hot peppers, contain a compound called capsaicin which is responsible for the burning sensation that they produce. When capsaicin comes into contact with the mucous membranes of the mouth or skin, it binds to a receptor called TRPV1, which is responsible for detecting pain and temperature. This binding triggers a series of chemical reactions that send signals to the brain, resulting in a burning or stinging sensation. Normally, TRPV1 would respond to thermal heat which would illicit an immediate protective response. If a burning hot piece of metal touched any part of our body, we would immediately feel pain and respond by removing ourselves from or dropping the object to prevent further tissue damage.
The amount of capsaicin in a chilli varies depending on the variety and can range from mild to extremely hot. The level of heat in chillies is measured in Scoville units, with higher Scoville ratings indicating a greater concentration of capsaicin. Interestingly, capsaicin is also known to have several health benefits, including pain relief and reducing inflammation.
Chillies aren’t the only plants that activate TRPA1, additional exogenous compounds include mustard oil, horseradish, cinnamon and wasabi.
Capsaicin chili pepper molecule. Used in food, drugs, pepper spray, etc. Skeletal formula.
Why do chillies produce capsaicin?
Plants have evolved a number of mechanisms to protect themselves against herbivory. Thorns on roses and blackberries, stinging trichomes on nettles, toxic compounds (phytotoxins) such as alkaloids, glycoalkaloids, solanine, amphiphilic glycosides and cyanogenic glycosides.
Chillies produce capsaicin as a means of defence. When an animal or insect chews a chilli, its strong heat is a deterrent. Ordinarily, this wouldn’t make sense as the purpose of fruit (chillies are classed as fruit) is for it to be consumed, which then disperses the seeds elsewhere when they pass out of the body. However, when mammals with teeth chew the chilli pod, the seeds are damaged and unable to germinate. Interestingly, birds have a different heat receptor which doesn’t induce a response to capsaicin, therefore they can eat hot chillies without the unpleasant (or pleasant) sensation of heat. As birds have no teeth to grind (and damage) consumed seeds and have a wide range, the seeds are widely distributed as they pass out of the body intact.
Scientists in Bolivia have come upon a second reason that chillies are hot. Capsaicin hinders the growth of the fungus Fusarium semitectum, which ordinarily would rot the fruit resulting in the death of the seeds within.
Where does the heat come from?
Capsaicin is synthesised in the placenta, the fleshy interior of the chilli pepper where the seeds are located. The placenta is the hottest part of the chilli and not the seeds. The capsaicin glands are located between the placenta and the seeds and are responsible for the production of capsaicin.
Capsaicin production is influenced by genetics as well as the maturity of the fruit. Some chillies produce more capsaicin than others, which is why some peppers are spicier than others. The amount of capsaicin is measured using the Scoville scale, which ranges from 0 (no heat) to over 2 million (extremely hot).
Scoville scale
The Scoville scale is a measure of the spiciness of chilli peppers and other spicy foods. It was created by Wilbur Scoville in 1912 and is based on the concentration of capsaicin, the compound responsible for the heat in chilli peppers.
Scoville scales range from 0 (no heat) to over 2,000,000 (extremely hot). The scale is a measure of capsaicin concentration in Scoville heat units (SHU). For example, a bell pepper has a Scoville rating of 0, while a jalapeño pepper has a rating of 2,500 to 8,000 SHU. On the other end of the scale, a habanero pepper can have a rating of 100,000 to 350,000 SHU, and the world’s hottest pepper, the Carolina Reaper, has a rating of over 2 million SHU.
How the Scoville scale measures the heat of chillies
Scoville organoleptic test: The original test uses dried chillies dissolved in alcohol to extract the capsaicinoids and then diluted in sugar water. This solution is placed onto the tongue of trained testers and is repeatedly diluted until the tester can no longer detect the heat. The Scoville score is assigned based on the number of dilutions required to eliminate the heat, for example, it will take 2,500 to 8,000 dilutions for Jalapeño for the heat to be removed. This test is not entirely reliable due to the different levels of tolerance people have. For example, I can often not detect chilli in a meal while my adult children are unable to eat it because it is so hot.
High-performance liquid chromatography (HPLC): This advanced test uses a machine to measure the capsaicin in a dried and ground chilli combined with a solvent. The machine measures the levels of compounds in the sample, producing a graph known as a chromatogram.
Why can some people eat hot chillies?
Some people are able to build up a tolerance to the sensation of heat by gradually introducing hotter and hotter chillies. From personal experience, I was extremely sensitive to any foods with the smallest amount of chilli when I was younger, however, even as a child, my brother enjoyed hot food. I have learned to love hot chillies over time, and now grow some of the world’s hottest chillies in my garden. I will never be able to eat raw habanero the way my brother does.
The sensation we experience when we eat hot food releases feel-good hormones and natural painkillers known as endorphins. Endorphins are released during sex, after running (runner’s high), and in response to pain or stress. In the case of chillies, there is no real danger (in most cases), so we can enjoy the endorphin rush without the danger of a real burn.
How to reduce the burn from a hot chilli
Unfortunately, as capsaicin is hydrophobic (does not mix with water) drinking water is not an effective antidote to the heat from chilli. Milk contains casein, a hydrophobic protein that displaces capsaicin from the sensory receptors.
One test with 72 participants was conducted to test the effectiveness of different beverages in reducing the burn from spicy tomato sauce. The results found: the following in order of effectiveness:
Whole milk
Kool-Aid
Skim milk
Beer
Cola
Water
Seltzer
Nothing
An unusual case was reported where a woman accidentally inserted a tampon contaminated with pepper spray. She presented to an emergency department in extreme pain. Doctors administered pain relief and removed the tampon. A lidocaine jelly was administered into the vagina using a speculum, followed by a tampon soaked in pasteurised milk. The woman reported a decrease in pain relief within several minutes.
Remember, a little goes a long way. It is always better to start with a small amount of chilli and add more if the heat isn’t strong enough. We find adding half a hot chilli to a curry gives a nice heat, but isn’t too hot. Adding chillies to raw food such as a salad intensifies the heat as it’s not being diluted in any sauce.
Does cooking chilli over a long period reduce the heat?
Cooking over a longer period doesn’t make the heat any less or more intense, however, as noted above, when adding chilli to a cooked meal that contains a sauce, the intensity tends to be less due to the distribution of capsaicin throughout the entire meal. If you are eating a meal with slivers of chilli, such as a cooked pizza, you are more likely to experience the heat from the chilli.
How to reduce the intensity of chilli in food
Look for chillies with a lower Scoville rating such as bishop’s crown, jalapeno, pepperoncini or banana pepper. You can reduce the heat from hotter chilli varieties by removing the placenta and seeds and using only the outer layers. Although noted below, chillies with a rating of 1 million SHU also have capsaicin present elsewhere, and not just the in placenta and seeds.
What is the hottest chilli in the world?
Smokin Ed’s ‘Carolina Reaper’ was officially declared the world’s hottest chilli by Guinness World Records on 17th August 2017. The average Scoville heat unit of the Carolina Reaper is 1,641,183. In second place is the Trinidad Moruga Scorpion.
When handling hot chillies, always wear disposable gloves and glasses. Wash your hands thoroughly afterwards.
Use a knife and fork or food processor when handling chillies to minimize direct contact with your hands.
Wear disposable gloves to avoid getting the oils onto your skin.
Prepare in a well-ventilated area when working with chillies to avoid inhaling the fumes.
Keep a bowl of milk or yoghurt nearby when eating spicy foods to help neutralise the heat.
Avoid touching your eyes, nose or mouth when and after working with chillies.
Wash hands thoroughly after handling chillies.
If you accidentally rub your eyes after handling chilli, flush with sterile eye wash if you have some handy, or plain water. While water is less effective than other methods, it is better than nothing. Do not use milk to flush your eyes. Artificial tears may be used after the eyes have been flushed to relieve pain.
For external exposure, wash the area with shampoo or soap and water (water alone is ineffective). Oil products such as cooking oil or Vaseline will also reduce discomfort.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
As a home gardener with a lot of fruit trees, I have found citrus to be one of the easiest species of fruit tree to grow in our subtropical climate. But, as with all plants, citrus can be affected by pests which can greatly impact their health and reduce fruit quality and quantity.
Citrus pests
African citrus psyllid
Trioza erytreae (African citrus psyllid)
African citrus psyllid (Trioza erytrea) is a sap-sucking insect native to southeastern Africa. African citrus psyllid causes direct damage to the plant and can transmit the lethal Huanglongbing (yellow dragon disease, previously known as citrus greening disease).
Distribution:
Affected regions include sub-Saharan Africa; Saudi Arabia; Yemen; the Indian Ocean islands of Madagascar, Mauritius and Reunion; and the Atlantic Ocean islands of Saint Helena, Madeira, Porto Santo, Tenerife and Gomera.
Life cycle:
Infestation occurs via natural dispersal as well as commercial trade of affected plants. Adult African citrus psyllids are 2.5 – 4mm long, with a brown body, black head and large, transparent wings with clearly defined veins. A female can lay up to 2,000 eggs on the margins of new leaves. Both larvae and adult African citrus psyllids feed on citrus leaves, and as they do, they inject a toxin.
Infestation occurs during spring, and the complete life cycle is over within 45 days. Signs of infestation include galls (pits) on affected leaves, distorted leaf growth, a premature drop of young flowers, stunted growth, and dieback. Psyllids excrete a white sugar-rich sticky substance called honeydew, which may be visible on the leaves and surrounding the tree.
Treatment:
Contact your local government authority if you suspect your citrus has African citrus psyllid. They will be able to confirm the presence of African citrus psyllid and provide guidance on how to manage the infestation.
Asian citrus psyllid
Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae). Macro
The Asian citrus psyllid (Diaphorina citri) is similar to the African citrus psyllid, as a sap-sucking insect and vector for Huanglongbing.
Distribution:
Native to Asia, the Asian citrus phyllid is now found in the Middle East, South and Central America, Mexico, and the Caribbean.
Life cycle:
Adult Asian citrus psyllids are approximately 4 mm in length with a mottled brown body, light brown head and mottled wings. A waxy secretion covers the body.
Larvae and adults feed on the sap of young citrus leaves and shoots, during which, they produce honeysuckle, which coats the leaf which blocks sunlight and encourages sooty mould.
Treatment:
Contact your local government authority if you suspect your citrus has Asian citrus psyllid.
Citrus leaf miner
Moth Citrus Leafminer (Phyllocnistis citrella). Development stages and damaged citrus leaf.
Citrus leafminers (Phyllocnistis citrella) are the larvae of a small silvery-white nocturnal moth native to southern Asia. The adult moth doesn’t damage the citrus tree, only the lavae pose a risk. Infestations are most common in late summer.
Distribution:
Citrus leafminers can be found in Asia, Australia, north and south America, Africa and the Mediterranean basin.
Life cycle:
Adult moths lay their eggs on the underside of citrus leaves. Once hatched, larvae tunnel under the surface of young citrus leaves, forming shallow channels, causing distortion of the leaves and stunted growth. Larvae go through three larval stages (instars) before they pupate inside a citrus leaf by folding it over. Pupation takes 1 – 3 weeks before the adult moth emerges.
Treatment:
Remove any affected leaves, place them in a plastic bag and dispose of them in the garbage. Do not place in compost, which will allow the larvae to pupate. Products containing neem oil can disrupt the life cycle of citrus leafminer, and products with the active ingredient spinetoram can kill larvae within the leaf.
Citrus fruit borer
Also known as citrus pulp borer, citrus fruit moth and lemon fruit borer, the citrus fruit borer (Citripestis sagittiferella) is a subtropical and tropical species of snout moth native to Indonesia, Malaysia, Singapore, Vietnam and Thailand. The adult moth is 10mm long brown/grey with brown forewings and translucent hindwings.
Distribution:
Indonesia, Malaysia, Singapore, Vietnam and Thailand.
Life cycle:
The adult moth lays her eggs in clusters on the surface of citrus fruit. Once the eggs hatch, they burrow into the rind, and after the first moult, they dig into the pith and through to the pulp, causing rotting and fruit drop. Once they have reached their final moult, the 16mm long larvae leave the fruit and pupate in the soil.
Treatment:
Contact your local government authority if you suspect your citrus has citrus fruit borer.
Citrus mealybug (Planococcus citri) are one of the most common insects to infest citrus trees. Native to Asia, these small, flat, segmented insects. The body of the female mealybug is covered in a white powdery wax material, extending into filaments (spines) along the body margin.
Distribution:
Worldwide.
Life cycle:
The adult mealybug lays her eggs covered in sticky wax ovisac (an envelope made of silk that encloses the eggs) on the trunk and stems of citrus trees. Nymphs (known as crawlers) hatch from the eggs within a week. Adult females and nymphs feed on sap with their piercing mouthparts, which damages the plant and causes chlorosis (yellowing) of the foliage, as well as leaf drop, stunted growth and reduced crop yields. As the female and nymphs feed, they secrete honeydew, which can lead to sooty mould, a fungus that feeds on honeydew.
Treatment:
Maintaining beneficial insects such as the mealybug ladybird (Cryptolaemus montrouzieri), lacewing larvae (Oligochrysa lutea) and parasitic wasp, Leptomastix dactylopii. Keep ant populations down as they feed on the sugar-rich honeydew and in return protect citrus mealybug.
Mealybugs can be difficult to control with chemicals due to their resistance, waxy coating and their natural tendency to hide.
Queensland fruit fly
The Queensland fruit fly is a species of fly in the family Tephritidae in the insect order Diptera. B. tyroni is native to subtropical coastal Queensland and northern New South Wales.
Queensland fruit fly (Bactrocera tryoni) is a wasp-like fly, with brown and yellow markings. Native to subtropical coastal Queensland and northern New South Wales, the Queensland fruit fly is responsible for significant crop losses across a wide range of fruits. Adult fruit flies are most active in humid conditions and after rain.
Distribution:
Eastern Australia.
Life cycle:
There are four stages to the Queensland fruit fly life cycle, egg, larvae, pupae and adult. Adult Queensland fruit flies are most active from October to May. The adult female has an egg-laying organ known as an ovipositor, which she uses to dig a 3 mm deep chamber into the outer layer of ripe fruit, in which she will lay her eggs. After 2 – 4 days, larvae emerge and eat their way towards the inside of the fruit, leading to rot. Eventually, the larvae crawl out of the gruit and burrow into the ground where they develop into pupae. After several weeks, the fruit fly emerges from the ground as adult flies.
Treatment:
Monitor: Hang sticky traps to monitor and catch adult fruit flies.
Lure and kill: A method that uses bait to attract adult fruit flies which are then killed with insecticides or traps.
Exclusion: Use a fine mesh net as a physical barrier against Queensland fruit flies. Either the entire tree is covered, or individual fruit. Organza gift bags make an ideal cover to protect the fruit.
Insecticides: Use an approved insecticide.
Red scale
Also known as California red scale, red scale (Aonidiella aurantii) is a sap-sucking scale insect and one of the most common types of scale to infest citrus trees. The light brown, shield-shaped insect is completely unable to move and is attached to the tree by a leathery protective scale. As they feed, honeydew drips from the body, resulting in sooty mould.
Distribution:
Red scale is believed to have originated in China but is now present in all countries where citrus grows.
Life cycle:
The male has four life stages while the female has five. The adult female gives birth to 2-3 live ‘crawlers’ per day over a 6 – 8 week period. The yellow crawlers emerge from the mother’s scale, settle nearby, and use its mouthparts to attach to a leaf, shoot or fruit. During this stage, they go through several moults. The males emerge as tiny winged insects, while the females remain in their protective covering.
Treatment:
Parasitic wasps (Aphytis lignanensis and Aphytis melinus), ladybirds, chilocorus beetles and predatory mites are used to control red scale populations. Parasitic wasps are commercially available. Sticky traps with synthetic red scale pheromones can be used to monitor for the presence of flying red scale. Movento is an insecticide produced by Bayer that is effective against red scale.
Citrus rust mite
Citrus rust mite on lime fruit, cause damage of fruit
Also known as silver mite, citrus rust mite (Phyllocoptruta oleivora) is a microscopic mite that infests leaves, fruit and twigs of citrus trees in humid regions, causing damage, especially to fruit which occurs to the outside of the fruit, impacting its appearance. If damage occurs early in the season, damage to the peel is referred to as russeting, and takes on a bronze appearance. Infestation also causes a silvering of the peel in lemons and grapefruit, reduced fruit quality and increased fruit drop.
Distribution:
Asia, Africa, North, South and Central America, the Caribbean, Europe and Oceania.
Life cycle:
The female lays her eggs in pits on fruit, or on leaves and cracks in the bark. Eggs hatch into nymphs within three days, with a similar appearance to the adult, only smaller, a second nymph molt occurs two days later, and finally the adult mite emerges. Adults are so small they are invisible to the human eye.
Mites are present year-round, but are in their highest populations are present in early to mid-summer.
Treatment:
Mind infestations can be managed with predatory mites (Amblyseius species). Heavy infestations may benefit a white oil/dishwashing solution diluted in water, lime sulphur (polysulphide sulphur) or wettable sulphur.
Citrus snow scale
Citrus snow scale (Unaspis citri) is a species of armoured scale insect native to Asia, that predominantly lives on the trunk of citrus trees, although heavy infestations can involve the twigs, leaves and fruit. The female has a brown oyster like appearance, is 2mm long. She may not be noticeable on the trunk of the affected tree due to her colour. Adult females insert their mouth parts into the tree, form their protective cover and become sessile (fixed). The male is smaller, at 1mm long, and is white, hence the name ‘snow scale’.
A heavy infestation can lead to leaf drop, twig dieback and a splitting of the trunk, which exposes it to other pathogens. The saliva injected into the tree is toxic, producing necrotic areas around the site, dieback of twigs and eventual death of the branch.
Distribution:
Citrus snow scale is found in North, Central and South America, Africa and Oceania.
Life cycle:
Citrus snow scale can produce between 3 – 6 generations a year. The adult female lays round, orange eggs, which hatch into instars and move to other crevices on the tree, forming a protective scale over their body. Females moult four times, compared to males who only moult twice.
Treatment:
Natural predators include wasp species Aphytis lingnanensis and Aspidiotiphagus lounsburyi and in Australia, the predatory caterpillar, Batrachedra spp.
Stink bugs
A Brown Marmorated Stink Bug with his distinctive striped antennae crawling along a light piece of green leaves.
Stink bugs are insects that belong to the family Pentatomidae which is made up of 4,700 species of six-legged, flat-bodied insects. They are known for the unpleasant odour they emit when threatened or disturbed. These sap-sucking plant-feeders and are considered agricultural pests, as they feed on the sap of young shoots and flower stems causing them to die. They have a shield-shaped body and can vary in colour, but are typically green or brown.
Distribution:
Stink bugs are native to Asia, but are widespread throughout the world including Oceania, Europe, and North and South America.
Life cycle:
The stink bug life cycle is made up of three stages: egg, nymph, and adult. Stink bugs mate in spring, as the weather warms up. The eggs are usually laid in clusters on the undersides of leaves, and hatch into nymphs within a week. Nymphs resemble small versions of adult stink bugs, but do not have fully developed wings. They undergo several molts as they grow, and eventually become adults. The entire life cycle from egg to adult can take anywhere from 4 to 6 weeks, depending on the species and environmental conditions. Adult stink bugs can live for several months.
Treatment:
The simplest and most environmentally friendly way to kill stink bugs is with hot water and washing detergent. It is important to wear protective clothing (long sleeves and pants), gloves and eyewear as stink bugs spray a corrosive substance.
Resources
For Australian readers, Bugs for Bugs sell a large number of predatory insects to control pests on citrus trees. Where possible, look for non-chemical methods before reaching for insecticides, which can harm helpful insects, which include bees.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Also known as kaffir lime, makrut lime (Citrus hystrix) is a citrus species native to Laos, Indonesia, Malaysia and Thailand. The fragrant leaves are a key ingredient in Thai cuisines, such as tom yum soup and green curry. The rind is typically used in marinades, dressings and salads. Makrut lime is also popular in Cambodia, Vietnam, Malaysia and Indonesia.
In addition to its widespread culinary use, makrut lime has been employed in traditional medicine to treat coughs, period pain, foot odour, wound healing, and skin and hair care. Makrut lime shows promise in the medical field for its antibacterial, antifungal, anticancer properties and antioxidant activity.
How does makrut lime get its citrus scent?
The leaves contain secretory cavities known as ‘schizogenous secretory cavities, leaf pellucid glands, or pellucid dots‘. These glandular cavities produce, store and release the essential oils responsible for the fresh lemony scent of makrut lime. Secretory cells produce volatile compounds, and the subcuticular space stores them. A cuticle surrounds the secretory cells to protect them and prevent essential oils from being released until they are damaged or disturbed.
The essential oil within the pellucid dots performs several functions, including defence against herbivory, protection against pathogenic organisms, insect repellent and attracting pollinators.
Pellucid dots are visible on citrus leaves in bright light. Here is a makrut lime leaf placed in front of a torch, which clearly shows the yellow pellucid dots.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Citrus trees add an attractive feature to decks and gardens. Their shiny evergreen leaves, scented flowers and fruit make an appealing feature to any patio, deck or balcony. A number of dwarf and semi-dwarf varieties are available, that are suitable for pots and small spaces. It is important to note that growing citrus in a pot will reduce the yield compared to growing it in the ground.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
Julia is a writer and landscape consultant from Wollongong with a love of horticulture. She had been an avid gardener for over 30 years, collects rare variegated plants and is a home orchardist. Julia is passionate about learning and sharing her knowledge of plant propagation and plant toxicology. Whether it’s giving advice on landscape projects or sharing tips on growing, Julia enjoys helping people make their gardens flourish.
