In one respect, plants are similar to cold-blooded animals like frogs and turtles. The speed of their respective metabolisms matches the temperature; when it’s hot, both plants and cold-blooded animals grow fast and need a lot of water and nutrients. Conversely, in cold weather, they slow down and may come to a complete stop if it’s cold enough.
We can speed up the metabolism of annual vegetables in cool weather by covering them with floating row covers, (Reemay is a well-known brand name.) which act as small greenhouses, or baby greenhouses. Row covers are porous modern fabrics, light enough to lay on a crop, which allow light, rain and air to reach the plants. The key is securing the edges so the wind can’t blow under the fabric. If the edges are secured with soil, landscape staples or other means, they’ll hold heat from the sun, raising the temperature and boosting the metabolism of annual crops. By holding in the heat, these fabrics act like a baby greenhouse, but they won’t overheat like a large greenhouse, because they are porous.
As an organic farmer in the ’80s, I used Reemay to cover part of a spinach crop. The uncovered spinach plants were the size of buttons when the covered plants were large enough to harvest.
Try some floating row cover with your early spring crops, like lettuce or carrots, but leave a few plants uncovered so you can see the difference.
For more information on small greenhouses, visit Small-Scale Greenhouses.