How cold can you go?
Horticluture Extension Educator
Mother Nature can play cruel tricks on gardeners and homeowners. This last stretch of cold weather and snow has made many of us aware that cold weather and freezes are still very possible through April, and into mid to late May in western Nebraska. With this cold reminder in our minds, how do vegetable and bedding plants tolerate the cold?
Vegetable and bedding plants are arriving in retail stores now. It is very tempting to purchase these plants, and plant them outside, hoping that warm weather will allow them to grow and thrive. With the weather’s ability to still provide cold weather and freezes, protecting these plants is very important to avoid cold damage or freezing.
Before any seeds or plants are planted in the garden or flower bed, monitor the soil temperature first. A minimum soil temperature of 40 degrees Fahrenheit is needed for most plant roots to grow and function. Soil temperature thermometers can be purchased through garden supply catalogs and garden centers at a reasonable price.
The following information from Fall Vegetable Gardening, written by Dale Lindgren, from the University of Nebraska-Lincoln Extension, illustrates the cold tolerance ranges for various vegetable crops.
Crops that can withstand several freezes, but are not killed when temperatures drop near 20 degrees Fahrenheit include cabbage, carrots, broccoli, cauliflower, rutabagas, Brussels sprouts, and kale.
Crops that withstand a light frost between 30 and 32 degrees Fahrenheit include beets, mustard, Chinese cabbage, radishes, collards, spinach, potatoes, Swiss chard, Bibb lettuce, green onions and leaf lettuce.
Warm loving crops that do not tolerate frost and temperatures very well include tomatoes, peppers, sweet potatoes, okra, eggplant, cucumbers, and summer squash. Watermelon, cantaloupe, pumpkin, corn, peppers and eggplant are also very sensitive at this temperature, often resulting in plant damage or death. Young plants in the garden from this group can be damaged or killed at temperatures around 32 degrees Fahrenheit.
As tempting as it is to buy vegetable plants or plant seeds in the garden early, cold weather can, and probably will return to western Nebraska before mid May. Protect tender, young plants by bringing them out of the cold weather. These plants can be placed outside and out of the wind during the day when the air temperature reaches 50 degrees Fahrenheit to go through the hardening process two weeks prior to planting. Until then, protect most young garden plants and seeds until warmer temperatures establish themselves for the spring growing season.
Copies of garden planting guides are available at your local University of Nebraska-Lincoln Extension Office. Please contact them to receive a copy. This guide can help gardeners decide when to plant those young vegetable plants and seeds.