Soil Temperature for Higher Germination

Soil Temperature for Higher Germination

Soil temperature is just as important as proper moisture to quickly achieve optimal germination rate. Without the right soil temperature range, germination can be delayed or prevented, and the germination rate will decrease. Temperatures below minimum can leave seed vulnerable to mold or hungry wildlife.

Soil temperature generally lags behind air temperature in spring, which may require you to wait longer to sow, consequently eliminating direct-sowing of some longer-season varieties from your garden. For example, some pumpkins take 120 days to mature, but also require soil temperatures of 70°–90°F for germination. If your soil doesn't typically warm in time for a variety to mature, you can start those seeds indoors, essentially extending your growing season by giving plants a head start. Even inside, however, some plants will need additional heating to maintain that ideal soil temperature; for those plants, use a waterproof seedling heat mat. Using a soil thermometer will also give you an advantage towards successful germination, as you can monitor and adjust the indoor environment to reach the optimal temperature. Germination temperature requirements are often higher than what the plant needs to grow, so once germinated, most varieties can be transplanted into cooler soils (after hardening off, and your average last frost dates).

How to use your soil thermometer

A soil thermometer is an easy-to-use, indispensable tool that can make gardening from seed more successful, helping you achieve a great germination rate. Here are some tips for using a soil thermometer to accurately measure soil temperature.

Take soil temperature measurements twice a day for an average, in the early morning and in the afternoon/evening. Taking and recording readings over a couple of days will give you an even more accurate average of your current soil temperature.


  • Place the thermometer 1"–2" in the soil for seeds, and as deep as the pot in the case of transplants.
  • Shade the thermometer if it is in direct sun.
  • Thermometers may read slowly, so wait until the temperature holds steady.
  • Store your soil thermometer indoors, away from moisture.
  • Reference our soil temperature chart below!
Note: A soil thermometer with a metal probe is sturdiest and safest. If your thermometer's probe is glass, create a pilot hole with a tool like a screwdriver that is slightly narrower than the thermometer probe. The slightly smaller hole will ensure the thermometer is still getting good soil contact with ideal conditions.

Download our soil temperature guide for vegetables or reference the chart below!

For more seed starting tips, see our other articles on seed starting.

Ideal Soil Temperatures for Vegetables

Variety Ideal Soil Temperature Range
for Germination (°F)
Variety Ideal Soil Temperature Range
for Germination (°F)
Amaranth 68-75 Leek 60-85
Artichoke 70-80 Lettuce 60-85
Arugula 50-70 Mache 60-70
Bean 70-85 Melon 40-68
Bean, Fava 40-75 Mustard 70-90
Beet 60-85 Okra 60-75
Bok Choy 75-85 Onion 80-90
Broccoli 60-85 Parsnip 60-85
Brussel Sprouts 70-85 Peas 50-70
Cabbage 60-85 Pepper 60-80
Carrots 75-85 Pumpkin 70-90
Cauliflower 60-85 Quinoa 70-90
Celery 70-85 Radicchio 45-50
Collards 70-75 Radish 60-75
Corn 75-85 Rutabaga 65-85
Corn 'Painted Hill' 65-90 Sorrel 60-80
Cucumber 50-90 Spinach 68-86
Edamame 70-90 Squash 50-75
Eggplant 70-85 Swiss Chard 70-85
Endive 80-90 Tomatillo 75-90
Fennel 60-70 Tomato 80-85
Kale 60-75 Turnip 70-90
Kohlrabi 65-85 Watermelon 65-80
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