Optimal temperature for seed germination

Soil Temperature For Vegetable & Herb Seed Germination

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Soil temperature is one of the most important factors in seed germination. Too cold or too hot and the seeds may not germinate. Seeds are dormant, and germination occurs when outside factors are optimal for the plant’s survival. When the time is right, the seed germinates. Knowing the preferred soil temperature for common vegetables and herbs will increase the germination rate.

The gardener should be familiar with the requirements of each type of seed. Some require cold stratification, or seed scarification to mimic what would happen to the seed in its natural environment. Most garden centres sell soil thermometers for gardeners to monitor soil temperature.

Celsius

Fahrenheit
Anise 16-18 60-65
Arnica 16-21 60-70
Artichoke 20-21 70-80
Asparagus 16-29 60-85
Basil 18-30 64-86
Beetroot 7-25 45-77
Bergamot 16-21 60-70
Bok choy 24-29 75-85
Borage 18-21 65-70
Broad beans 15-25 59-77
Broccoli 16-29 60-85
Brussels sprouts 7-29 45-85
Cabbage 7-35 45-95
Calendula 16-18 60-65
Capsicum (pepper) 21-32 18-35
Caraway 18-21 65-70
Carrots 7-29 45-85
Cauliflower 12-26 55-80
Celery 16-21 60-70
Chervil 12-18 55-65
Chilli 22-26 71-79
Chives 16-21 60-70
Cicely 12-18 55-65
Collards 24-29 75-85
Comfrey 20-26 68-80
Coriander 15-22 59-71
Corn 16-35 60-95
Cucumber 16-24 60-95
Dill 16-21 60-70
Eggplant (aubergine) 24-32 75-90
Endive 15-25 59-77
Fennel 16-24 60-75
Kale 16-29 60-85
Leek 16-29 60-85
Lemongrass 20-23 68-75
Lettuce 16-23 60-75
Melons 24-35 75-95
Mint 12-18 55-65
Mustard 12-18 55-65
Okra 29-35 85-95
Onion 10-35 50-95
Oregano 18-21 65-70
Parsley 21-26 70-80
Parsnip 10-21 50-85
Peas 4-24 40-75
Pumpkin 21-32 70-90
Radicchio 16-24 60-75
Radish 7-32 45-90
Rocket 15-20 59-68
Rosemary 27-32 80-90
Sage 15-21 60-70
Spaghetti squash 15-18 60-65
Spinach 7-24 45-75
Spring onion 20-35 68-77
Squash 21-32 70-90
Swedes 7-25 45-77
Thyme 15-24 59-75
Tomato 21-35 70-95
Turnip 7-29 45-85
Watermelon 21-32 70-90
Zucchini (courgette) 25-35 68-95