Does Frost Kill Carrots?

Planting Date

• Carrot seeds tolerate a soil temperature as low as 40 degrees Fahrenheit. You can plant them directly into the garden as soon as you can work the soil in the spring and they will germinate in seven to 21 days. Plant seeds about three weeks before the last spring frost date and cover with only 1/2 inch of soil, as seeds are tiny and often germinate unevenly. Carrot seeds will germinate at a temperature of 40 degrees Fahrenheit, but will appear through the soil surface in about one week at a temperature of 75 degrees Fahrenheit.

Soil Conditions

• Carrots prefer cool soil at planting time. They are not bothered by a light frost, but roots develop best in a soil temperature of 60 to 70 degrees Fahrenheit. Mulching, particularly in areas where summer temperatures are consistently above 80 degrees Fahrenheit, not only helps to control weeds but also keeps the soil cool and moist. Carrots deprived of sufficient moisture, especially during hot dry periods, will not develop properly and be fibrous and bitter-tasting. An extended soil temperature of 55 degrees Fahrenheit or lower may produce carrots that are longer, thinner and not as brightly colored as they should be.

Carrots and Frost

• According to the National Snow & Ice Data Center, a frost occurs when air temperature drops to 32 degrees Fahrenheit, creating ice on plants that kills the most tender ones first. A freeze is a prolonged event and is rated on how low the temperature drops, with a light freeze occurring at a range of 29 to 32 degrees Fahrenheit. Temperatures of 25 to 28 degrees Fahrenheit indicate a moderate freeze that heavily damages vegetation including semi-hardy plants. A severe freeze occurs when temperatures fall to 24 degrees Fahrenheit or lower and heavily damages most crops. Frost damage to above-ground plants depends on its duration, as many plants recover from the effects of a light frost if the temperature rises during the day.

Frost Protection

• Leaving carrots in the garden until the soil temperature drops to about 24 degrees Fahrenheit improves their flavor and sweetness and makes them better candidates for long-term storage, as this gives them time to develop a thick outer skin. Putting down at least 12 inches of mulch, such as straw, hay or leaves, creates a barrier between the cold air and the soil surface that effectively insulates the soil around the carrots. A light or moderate freeze will kill their green tops, but the thick mulch will protect the roots until the soil temperature drops to below 24 degrees Fahrenheit.