Frost Date Math

Soil Temperature for Vegetable Seed Germination

By Tam Vu · Updated

On this page
  1. Soil temperatures for germination
  2. Soil temperature is not transplant timing
  3. Sources

Air temperature is not the same as seed-bed temperature. Alabama Cooperative Extension's table lists minimum, optimum-range, optimum-point and maximum soil temperatures for germinating 27 vegetables. Use the values as a reference for germination; the table does not provide a complete outdoor planting calendar for every region.

Soil temperatures for germination

All values are °F. “Minimum” and “maximum” are the table's limits, while the range and point show the listed optimum conditions.

Vegetable Minimum Optimum range Optimum point Maximum
Asparagus 50 60–85 75 95
Lima bean 60 60–85 85 85
Snap bean 60 65–85 80 95
Beet 40 50–85 85 85
Cabbage 40 45–95 85 100
Carrot 40 45–85 80 95
Cauliflower 40 45–85 80 100
Celery 40 60–70 70 85
Swiss chard 40 50–85 85 95
Corn 50 60–95 95 105
Cucumber 60 60–95 95 105
Eggplant 60 75–90 85 95
Lettuce 35 40–80 75 85
Muskmelon (cantaloupe) 60 75–95 90 100
Okra 60 70–95 95 105
Onion 35 50–95 75 95
Parsley 40 50–95 75 95
Parsnip 35 50–70 65 85
English pea 40 40–75 75 85
Pepper 60 65–95 85 95
Pumpkin 60 70–90 90 100
Radish 40 45–90 85 95
Spinach 35 45–75 70 85
Squash 60 70–95 95 100
Tomato 50 70–95 85 95
Turnip 40 60–105 85 105
Watermelon 60 70–95 95 105

The Alabama Extension publication says soil temperature is critical to germination and that measuring it with a thermometer can help gardeners compare the seed bed with the crop's range. It also notes that field soil temperature can be affected by planting date and practices such as mulch. The table is reproduced as published; its source note does not identify the origin of each crop's temperature values.

Soil temperature is not transplant timing

These numbers are for seed germination in soil. For starting transplants indoors, University of Idaho Extension separately lists soil germination temperatures, germination days and weeks indoors for selected crop groups. Its timing guidance for moving broccoli, onions, tomatoes and peppers outdoors is linked to the average last frost, not to the table above.

See cool-season vs warm-season vegetables for a smaller comparison and the seed-starting calculator for indoor timing based on a frost date.

Sources