Does Frost Kill Seeds?

Prolonging Seed Germination

• Frost will not harm seeds as long as they haven't sprouted. However, frosts cools down the soil, which makes germination difficult. All plants need a certain soil temperature to germinate. While frost will not kill your seeds, it will prolong their germination. Gardeners can prevent exposing their seeds to frost by seeding after the frost date for their area and sowing their seeds in the correct soil temperature for their type.

Last Frost Dates

• Gardeners must check the last frost date for their region; there is not one set day for the United States. For example, the last frost date for Tampa, Florida is January 28, while the last frost date for Denver, Colorado is April 30, according to the Farmer's Almanac. You can check with your local cooperative extension office to find out when your seeds are safe from the dangers of frost. Also, checking your soil temperature provides an accurate reading.

Soil Temperatures

• It is best to follow your plant seed's recommended sowing temperature for optimal germination rates. For instance, lettuce seeds must be planted when soil temperatures are above 40 degrees Fahrenheit, beans need soil temperatures 60 degrees Fahrenheit and above and annual bluegrass turf needs soil temperatures between 68 to 86 degrees Fahrenheit. Throwing seeds onto soil that hasn't warmed up yet won't kill them, but you will have a reduced chance of seed germination.

Measuring Soil Temperature

• Measure your soil temperature with a soil thermometer. Make a pilot hole 6 inches deep in the soil with a screwdriver. Place a soil thermometer inside the hole. Take a reading in the morning and afternoon. If you are reading the soil temperature in a sunny area, place your hand over the thermometer to prevent skewing the results. Calculate the average of both temperatures to obtain an accurate reading.