Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu
We have had a late spring with limited periods where soils were dry enough to plant spring crops. Warmer weather is being forecast for the coming week. However, soil temperatures currently are on the cold side. Cold, wet soils will lead to delays in crop emergence and potential loss of stand due to seed rots, seedling diseases, and insect feeding as fungicide and insecticide seed protectants dissipate. The longer the emergence period, the more risk to the crop.
The following are some guidelines for days to emergence at various soil temperatures for field seeded vegetable crops:
Beans (snap): at 50°F limited germination, at 59°F emergence takes 16 days, at 68°F emergence takes 11 days, at 77°F emergence takes 8 days, at 86°F emergence takes 6 days.
Beans (lima): at 50°F limited or no germination, at 59°F emergence takes 31 days, at 68°F emergence takes 18 days, at 77°F emergence takes 7 days, at 86°F emergence takes 7 days.
Cantaloupe: at 50°F limited or no germination, at 59°F emergence takes 14 days, at 68°F emergence takes 8 days, at 77°F emergence takes 4 days, at 86°F emergence takes 3 days.
Carrot: at 41°F emergence takes 51 days, at 50°F emergence takes 17 days, at 59°F emergence takes 10 days, at 68°F emergence takes 7 days, at 77°F emergence takes 6 days.
Cucumbers: at 50°F limited or no germination, at 59°F emergence takes 13 days, at 68°F emergence takes 6 days, at 77°F emergence takes 4 days, at 86°F emergence takes 3 days.
Lettuce: at 41°F emergence takes 15 days, at 50°F emergence takes 7 days, at 59°F emergence takes 4 days, at 68°F emergence takes 3 days, at 77°F emergence takes 2 days.
Okra: at 50°F no germination, at 59°F emergence takes 27 days, at 68°F emergence takes 17 days, at 77°F emergence takes 13 days, at 86°F emergence takes 7 days.
Onion: at 41°F emergence takes 31 days, at 50°F emergence takes 13 days, at 59°F emergence takes 7 days, at 68°F emergence takes 5 days, at 77°F emergence takes 4 days.
Peas: at 40°F emergence takes as much as 30 days, at 50°F emergence takes 10-14 days, at 59°F emergence takes 9 days, at 68°F emergence takes 8 days, at 77°F emergence takes 6 days.
Spinach: at 41°F emergence takes 23 days, at 50°F emergence takes 12 days, at 59°F emergence takes 7 days, at 68°F emergence takes 6 days, at 77°F emergence takes 5 days.
Sweet Corn: at 50°F emergence takes 22 days, at 59°F emergence takes 12 days, at 68°F emergence takes 7 days, at 77°F emergence takes 4 days, and at 86°F emergence takes 4 days. Sweet corn emergence success in cold soils will vary greatly depending on variety class. Shrunken seed types have low cold tolerance.
Watermelon: at 50°F no germination, at 59°F emergence takes 21 days, at 68°F emergence takes 12 days, at 77°F emergence takes 5 days, at 86°F emergence takes 4 days.
Of course, there are many factors that will modify days to emergence including soil moisture, seed vigor, seed quality, and variety.