In New Hampshire, the growing season is relatively short with an average of barely four months of frost free weather. Finding ways to extend the growing season can mean the difference between an ordinary yield and a harvest that will get you through the winter. One of the best ways to extend the growing season is through the use of row covers.
The slide show at the left side of the page provides step by step instructions for building row covers using things you’d find around your yard and a piece of sheet plastic. The only tools you’ll need are something to cut the plastic and something to cut branches and twigs.
Row covers extend the growing season by allowing you to start your plants earlier and letting them survive and grow deeper into the fall. They provide a variety of different protections for seedlings.
First, row covers protect sensitive plants from frost that would otherwise kill them. Frost occurs when moisture precipitates out of the cooling night air and freezes on exposed surfaces. If the plants are covered, then the precipitating moisture falls on top of the row covers and not on the delicate leaves sheltered beneath.
Row covers also act to trap heat. The ground changes temperature very slowly, and once it is warm enough to bring most vegetable seeds out of dormancy (about 50-55 degrees), it doesn’t cool down very much until late autumn. When row covers are in place, the relatively small amount of air inside the cover is heated by the warmth of the ground so that it stays warm when New England’s spring nights send the mercury plummeting.
If you start seedlings indoors, then row covers can help harden them off until they are strong enough to withstand the summer sun. By opening the row covers for a gradually increasing amount of time each day, the young plants can build up a tolerance to the sun’s harsh rays. Start with an hour or two of morning sunshine and work up to midday sun over a period of several weeks.
While it may be true that April showers bring May flowers, soggy soil during the rainy season can rot seeds in the ground and suffocate developing roots. Row covers can help control the amount of moisture in the soil especially if raised beds are used. By closing the row covers during heavy or sustained rains, much of the water can be shunted off the garden so the soil doesn’t become over-saturated.
The air inside the row covers will be warmer and more humid than the outside air providing a mini-greenhouse environment for your garden plants and accelerating their growth. Care must be taken, however, to make sure that it doesn’t get too damp under the covers or mold and fungus may become a problem especially if they aren’t opened up to allow direct sunlight.
While most remove row covers entirely once all danger of frost is past, some leave them in place to protect tasty vegetable plants from being eaten by birds, deer, free-range chickens and many varieties of insects.
At the end of the season, many vegetable plants take their cue from the amount of daily sunlight. They will stop fruiting or ripening whether or not they are protected from the cold unless artificial light is used to extend the daylight hours for the plants. Other plants are less sensitive to the amount of daylight and may produce as long as they and the soil around their roots are kept warm.
By using row covers to start spring planting early and using successive plantings that produce well into the late fall, northern gardeners can increase their yields and maximize the production of their available garden space each year.