We are using a lot of row cover in the field here and can be kept covered for months at a time without any worry. Most crops it is no hoop just tuck it in and let them push it up as they grow. In the farm greenhouse, we also use row cover over seedlings on a cold night, and yes it's best to remove it in the day time if it gets hot. But it isn't too deadly because it does help to retain moisture too, and yet it breathes, unlike plastic which will really cook your seedlings if the sun strikes in.
I've tried plastic vs row cover for early tomatoes in my greenhouse... row cover was better. The worst feature of plastic was the tendency for condensation to form on the surface and make the plants wet and more prone to frost damage. There is a tradeoff with the weight of the cover - light cover allows more light but provides fewer extra degrees of warmth, vs heavier cover which is warmer but blocks too much light, especially in our climate where it's often overcast as well as cold.
For any cover, the downside is the labor involved in covering and uncovering. I've tried some different approaches - hoops over young plants; or attaching and draping over cages. Then I tried a different thing - hanging row cover around the perimeter of my rather small greenhouse and using a different piece to cover the top of the plants at night. The perimeter cover could be left up during the day, and honestly, it did continue to make a difference to the temperature without seriously blocking the light. I could use the warmer stuff around the sides and the lighter stuff on top which could be left on if we had several cold days in a row. Using heavy row cover around the perimeter would likely help to reduce your heating costs. I used clothespins to hang mine from a wire, hanging at the point where about 6- 7 ft height to the ceiling about the width of the row cover roll and a few feet back from the glazing.
|