Crop Covers Better Than Plastic Bags

Q. With cooler weather here I was wondering if it is safe to cover frost sensitive vegetables with every day trash bags. I would cut some vent holes in the bags so these vegetables don’t overheat. I would not keep them covered except the coolest evenings. I have used burlap but sometimes it is difficult to keep it on some larger plants.

A. Warm season vegetables and herbs like tomatoes, basil and peppers get chilling damage below 45F. It isn’t just freezing temperatures that could be a problem, but “refrigerator temperatures” could be as well.

Crop covers give about 5 or 6F added protection during freezing weather. And they breathe. And they let in light. And they protect from insects. And.......

            Plastic bags won’t give the plants enough protection from these types of temperatures. Row crop covers (frost covers, frost blankets) that are draped over the entire row and in contact with the soil are a better choice. Unlike trash bags, they can be left on top of the plants for several days at time. Use row crop covers that weigh about 1 ounce per square yard. They can be used for three or four years, “breathe”, and transmit at least 50% of the sunlight.

            Row crop covers keep temperatures under the cover about 5 to 6° warmer than the outside temperature. Plastic bags won’t do this. Make sure row crop covers cannot be blown off the plants or the row. Tack or peg the edges to the soil. Cover the edges with soil.

            The added benefit from row crop covers is protection from insects OUTSIDE the cover. If insects are trapped under the cover that won’t help protect plants and fruits from being devoured or attacked.

            If using some form of pest control, apply it and then cover these plants soon after the application. Warm temperatures under crop covers help cool season types of vegetables (lettuce, spinach, broccoli, carrots) grow a bit faster and protects them from wind damage as well.