Information from Colorado State University Cooperative Extension
Fickle spring weather leaves gardeners frustrated. Warm, sunny days promise of good growing weather, but a frosty night and a snowstorm puts reality into thoughts of fresh tomatoes by the 4th of July.
Anxious gardeners needn't wait for the last frost before to plant vegetables. In a normal year, garden soil has warmed enough by late March to plant cool season crops such as beets, broccoli, cabbage, lettuce, spinach, peas, potatoes, onions and radishes. Should the weather remain unusually wintry, planting still can proceed with the aid of cold frames or floating row covers.
A cold frame essentially is a miniature, unheated greenhouse. A wooden or metal frame is covered with glass, clear plastic or fiberglass, allowing the sun's warm rays to heat plants or soil inside. To warm the soil in advance, place the cold frame directly over the area to be planted a week or two before seeding. Once seedlings have emerged, leave the frame in place to protect tender plants on frosty nights. On warm, sunny days, you may need to prop the top open to prevent over-heating.
Floating row covers are spun-bonded fabrics designed especially for crop protection. They are porous enough to allow sunlight, water, and some air through for ventilation, but they still provide several degrees of frost protection. Heavy wire or PVC pipes can be used to support row covers, but their light weight allows them to be used with no supporting structures.
By using cold frames and floating row covers, vegetable planting and harvest season can be advanced by as much as three weeks.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010