Optimal Soil Temperature For Flower Seed Germination

Seeds are in a dormant state until the right conditions occur which triggers the end of dormancy. There are a number of critical factors that determine when a seed will germinate including moisture, oxygen and the right soil temperature. Some seeds also require a period of cold, known as cold stratification. This mimics the normal winter a seed would usually experience before germinating once temperatures warm up in spring.

We recommend gardeners purchase a soil temperature thermometer to check soil temperature before sowing seeds. These are available from most nurseries or online.

Celsius

Fahrenheit

Stratification?

African daisy (Arctotis stoechadifolia)18 – 2165 – 70No
African daisy (Osteospermum spp.)21 – 2470 – 75No
Alyssum (Lobularia maritima)12 – 2355 – 75No
Amethist flower (Browallia spp.)18 – 2165 – 70No
Aster (Aster spp.)18 – 2365 – 75No
Baby’s breath (Gypsophila spp.)15 – 1860 – 65No
Balloon flower (Platycodon grandiflorus)16 – 2060 – 68No
Bear’s breeches (Acanthus mollis)18 – 2165 – 70No
Bee balm (Monarda didyma)16 – 2160 – 70No
Begonia (Begonia spp.)18 – 2165 – 70No
Bellflower (Campanula spp.)21 – 2370 – 75Yes
Bells-of-Ireland (Moluccella laevis)13 – 1855 – 64Yes
Black-eyed Susan (Rudbeckia hirta)18 – 2165 – 70Yes
Bleeding heart (Dicentra spectabilis)4 – 1240 – 55Yes
Boltonia (Boltonia spp.)18 – 2165 – 70No
Borage (Borago officinalis)18 – 2965 – 85No
Bugle flower (Ajuga spp.)10 – 1550 – 60No
Bugloss (Anchusa capensis)18 – 2165 – 70No
Butter daisy (Melampodium
paludosum
)
18 – 2165 – 70No
Butterfly flower (Schizanthus spp.)18 – 2265 – 71No
Butterfly weed (Asclepias tuberosa)18 – 2465 – 75Yes
Calendula (Calendula officinalis)18 – 2165 – 70No
Californian poppy (Eschscholzia californica)12 – 2155 – 70No
Candytuft (Iberis spp.)23 – 2975 – 85No
Canterbury bells (Campanula medium)18 – 2165 – 70Yes
Cape jewels (Nemesia strumosa)13 – 1855 – 65No
Carnation (Dianthus spp.)15 – 2160 – 70No
Catnip/catmint (Nepeta spp.)18 – 2165 – 70No
Chamomile (Matricaria chamomilla)18 – 2165 – 70Yes
Chilean bellflower (Nolana paradoxa)20 – 2268 – 72No
Chinese aster (Callistephus chinensis)20 – 2368 – 73No
Chinese forget-me-not (Cynoglossum amabile)18 – 2065 – 68No
Chinese lantern (Physalis alkekengi)16 – 2160 – 70No
Chrysanthemum (Chrysanthemum spp.)18 – 2365 – 75No
Clematis (Clematis spp.)20 – 2268 – 73Yes
Cliquefoil (Potentilla spp.)19-2167-70No
Cohosh (Cimicifuga spp.)18 – 2165 – 70No
Columbine (Aquilegia spp.)10 – 1250 – 55Yes
Common rockrose (Helianthemum nummularium)21 – 2470 – 75No
Common sneezeweed (Helenium autumnale)19 – 2265 – 73No
Coral bell (Heuchera spp.)18 – 2165 – 70No
Corncockle (Agrostemma githago)15 – 2160 – 70No
Cornflower (Centaurea cyanus)15 – 2160 – 70No
Cosmos (Cosmos bipinnatus)21 – 2570 – 77No
Cup and saucer vine (Cobaea scandens)21 – 2370 – 75No
Cupflower (Nierembergia spp.)21 – 2370 – 75No
Cupid’s bow (Achimenes spp.)21 – 2370 – 75No
Cupid’s dart (Catananche caerulea)20 – 2368 – 75No
Cyclamen (Cyclamen spp.)18 – 2065 – 68No
Dahlberg daisy (Dyssodia tenuiloba)18 – 2165 – 70No
Dahlia (Dahlia spp.)21 – 2370 – 75No
Delphinium (Delphinium elatum)15 – 2059 – 68Yes
Echinacea (Echinacea spp.)18 – 2165 – 70Yes
Edeiweiss (Leontopodium alpinum)18 – 2165 – 70Yes
English daisy (Bellis perennis)18 – 2165 – 70No
Evening primrose (Oenothera spp.)21 – 2670 – 80No
Everlasting (Helichrysum bracteatum)21 – 2470 – 75No
False sunflower (Heliopsis spp.)21 – 2370 – 73No
Fan flower (Scaevola aemula)20 – 2268 – 71No
Firecracker flower (Crossandra infundibuliformis)21 – 2770 – 80No
Flax (Linum usitatissimum)18 – 2165 – 70No
Fleabane (Erigeron spp.)18 – 2165 – 70No
Floss flower (Ageratum houstonianum)24 – 2975 – 85No
Forget-me-not (Myosotis spp.)18 – 2165 – 70No
Foxglove (Digitalis spp.)15 – 1860 – 65No
Garden heliotrope (Heliotropium spp.)18 – 2165 – 70No
Gay feather (Liatris spp.)18 – 2165 – 70Yes
Gazania (Gazania spp.)15 – 1860 – 65No
Gerbera (Gerbera spp.)21 – 2370 – 73No
Geum (Geum spp.)18 – 2165 – 70No
Globeflower (Trollius spp.)18 – 2165 – 70Yes
Glory of the snow (Chionodoxa spp.)10 – 1550 – 59Yes
Gloxinia (Sinningia speciosa)19 – 2166 – 70No
Goldencup (Hunnemannia fumariifolia)19 – 2166 – 70No
Goldenrod (Solidago spp.)20 – 2268 – 71Yes
Goldentuft (Aurinia saxatilis)15 – 2159 – 70No
Hellebore (Helleborus spp.)18 – 2165 – 70Yes
Hibiscus (Hibiscus spp.)21 – 2670 – 75No
Hollyhock (Alcea rosea)15 – 2160 – 70Yes
Iceland poppy (Papaver nudicaule)18 – 2465 – 75Yes
Impatiens (Impatiens spp.)21 – 2370 – 73No
Jacob’s ladder (Polemonium spp.)18 – 2165 – 70No
Laceflower (Trachymene coerulea)18 – 2165 – 70No
Ladys purse (Calceolaria spp.)21 – 2370 – 73No
Larkspur (Consolida ambigua)10 – 1250 – 55Yes
Lavender (Lavandula spp.)18 – 2165 – 70No
Leopard plant (Ligularia spp.)18 – 2165 – 70No
Linaria (Linaria spp.)12 – 1855 – 65Yes
Lisianthus (Eustoma grandiflorum)22 – 2372 – 73No
Livingstone daisy (Dorotheanthus
bellidiformis
)
18 – 2465 – 78No
Lobelia (Lobelia spp.)18 – 2365 – 73No
Love-lies-bleeding (Amaranthus caudatus)20 – 2868 – 82No
Lupine (Lupinus spp.)12 – 2155 – 70Yes
Madagascar periwinkle (Catharanthus
roseus
)
24 – 2775 – 80No
Marigold (Tagetes spp.)21 – 2370 – 73No
Marshmallow plant (Althaea officinalis)15 – 2160 – 70Yes
Mexican creeping zinnia (Sanvitali procumbens)18 – 2165 – 70No
Mignonette (Reseda odorata)12 – 1453 – 57No
Monkey flowers (Mimulus spp.)15 – 2160 – 70No
Monk’s hood (Aconitum spp.)12 – 1555 – 60Yes
Morning glory (Convolvulus spp.)
20 – 2168 – 70No
Nasturtium (Tropaeolum majus)15 – 1860 – 65No
Nemesia (Nemesia spp.)12 – 1855 – 65No
Nemophila (Nemophila spp.)12 – 1555 – 60No
Nigella (Nigella damascena)15 – 1860 – 65No
Obedient plant (Physostegia virginiana)18 – 2165 – 70No
Pansy (Viola tricolor var. hortensis)15 – 2360 – 73No
Pearly everlasting (Anaphalis margaritacea)18 – 2165 – 70No
Persian violet (Exacum affine)21 – 2470 – 78No
Petunia (Petunia spp.)18 – 2365 – 73No
Phlox (Phlox spp.)15 – 1860 – 65No
Poppy (Papaver spp.)15 – 2060 – 68Yes
Portulaca (Portulaca spp.)21 – 2670 – 80No
Pride of Madeira (Echium candicans)15 – 2060 – 68No
Primrose (Primula spp.)15 – 1860 – 65Yes
Purple rock cress (Aubrieta deltoidea)18 – 2165 – 70No
Queen Anne’s lace (Daucus carota)16 – 1860 – 65No
Rock cress (Arabis spp.)18 – 2165 – 70No
Rudbeckia (Rudbeckia spp.)21 – 2370 – 73No
Salvia (Salvia officinalis)21 – 2370 – 73No
Satin flower (Clarkia amoena)21 – 2370 – 73No
Shooting star (Dodecatheon meadia)18 – 2165 – 70Yes
Sea holly (Eryngium spp.)18 – 2365 – 73Yes
Shasta daisy (Leucanthemum x superbum)18 – 2165 – 70No
Snapdragon (Antirrhinum majus)18 – 2365 – 73Yes
Snow-in-summer (Cerastium tomentosum)18 – 2165 – 70No
Speedwell (Veronica spp.)18 – 2465 – 75No
Spider flower (Cleome spinosa)21 – 2370 – 73Yes
Statice (Limonium sinuatum)15 – 2060 – 68No
Stock (Matthiola incana)15 – 1860 – 65No
Stoke’s aster (Stokesia laevis)21 – 2470 – 75No
Sunflower (Helianthus spp.)21 – 2370 – 73No
Swan river daisy (Brachyscome iberidifolia)21 – 2470 – 78No
Sweet pea (Lathyrus odoratus)12 – 1855 – 65No
Trumpet flower (Incarvillea spp.)18 – 2165 – 70No
Tweedia (Oxypetalum coeruleum)18 – 2165 – 70No
Twinspur (Diascia spp.)15 – 1860 – 65No
Verbena (Verbena spp.)18 – 2365 – 73No
Viola (Viola spp.)18 – 2365 – 73No
Virginian stock (Malcolmia maritima)18 – 2365 – 73No
Wallflower (Erysimum cheiri, syn. Cheiranthus cheiri)15 – 1860 – 65No
Wild indigo (Baptisia spp.)18 – 2165 – 70No
Wishbone flower (Torenia fournieri)21 – 2370 – 75No
Xeranthemum (Xeranthemum annuum)24-3575 – 95No
Yarrow (Achillea spp.)18 – 2165 – 70Yes
Yellow lotus (Nelumbo lutea)21 – 2470 – 78No
Zinnia (Zinnia spp.)21 – 2370 – 73No

Optimal soil temperature for flower germination PDF