By Darrell Blackwelder
For the Salisbury Post
A home gardener called one morning this week asking if it was OK to go ahead and plant his early tomatoes. He had heard it was the time to go ahead and plant.
My immediate answer was no, it’s still too early and there is still an outside chance of a late frost.
Warm spring days and retail outlets offering tender plants make the purchase tempting. Normally the last frost-free date in this area is April 15, but many people take a chance and plant tomatoes and other tender perennials and get by with little or no damage.
Commercial tomato producers are gearing up to plant tomatoes for the early market. Commercial tomato producers have the ability to frost-protect early crops with overhead irrigation. Irrigation systems spray a fine mist of water over tender plants when temperatures dip to 32 degrees at night, forming a thin layer of ice on the plant.
The irrigation mist must be continuous until melting, usually the next morning. Continuous freezing keeps the tomato and other susceptible plants at a constant 31 degrees, just warm enough to prevent damage to tender plant tissue. The mist must be continuous. If it stops for any reason, the temperature will go below the critical temperature stage and the plant will be damaged.
Obviously, this type of frost protection practice is geared for commercial producers and not recommended for home gardeners. Washing off frost from tomato plants early in the morning is ineffective frost protection.
Home gardeners gambling against late frosts can use alternative and less expensive methods. Using an old sheet or bedspread as a temporary cover often protects tender annuals. Some use buckets, cans or anything to cover the plants.
Many garden shops and retail outlets have spun fiber row covers designed for home garden frost protection. Commercial strawberry producers implement spun fiber row covers with remarkable success with limited use of irrigation frost protection.
Retail outlets may also offer plastic bags filled with water that surround tender plants, shielding them from frost. The water adsorbs heat during the day and acts to insulate the plants at night when frost is most likely to occur.
Avoid using sheets of plastic to protect tender plants. Foliage is often burned when plastic touches the plants.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener Web site at www.rowanmastergardener.com, e-mail Darrell_ Blackwelder@ncsu.edu; 704-216-8970.