Robin's Outdoors

Robin Follette
Copyright 2006
Originally published in Farm & Garden

Floating row covers serve several purposes. They’re an important tool for the family gardener. Gardeners have a lot of options available. We can purchase row covers or raid the linen closet. Row covers will keep heat in and insects out. They protect soil and our plants and give us extra time at the beginning and end of the growing season.

Spring Planting

Floating row cover is the simplest cover to use. It doesn’t need to be supported on a frame. It’s so light weight the plants will lift it as they grow. You can start using a floating row cover in the spring. They provide a few degrees of frost protection allowing you to plant a little earlier. Some covers are thick enough to keep seedlings protected from frost down to 24°. The down side of heavier covers is that let only 50% of sunlight through instead of the typical 85%. You should switch to a lighter cover as soon as possible. Gardeners might not agree on what fertilizer to use or where to buy their seeds or who grows the best tomatoes. We do all agree that the sooner we’re in the garden the happier we are and we’ll take one or two extra weeks in the spring. Place the row cover over the row and weight it down on the ends. You can purchase U clips to push through the cover and into the soil, use odd pieces of lumber (which will also make picking up slugs and other pests simple each morning) or use simply rocks. Any heavy object will do.

Row covers also aid in seed germination. It helps the soil stay moist. Tiny seeds, such as petunias or carrots, can dry out quickly and die. Moist soil protects against crusting, something that happens when the soil dries out and becomes hard and thick at the surface. Larger seeds might be able to push themselves up through the crust or even lift the crust off the softer soil below. Small seeds seldom stand a chance.You can avoid a problem with spring pests by using row cover as an insect barrier. You have to the sides and ends to block the insects from climbing under the barrier edges. Look for pests that have emerged from the soil underneath the barrier. You don’t want to trap in what you’ve worked to keep out. If you find pests you can pull back the barrier, remove the pests, apply the appropriate insecticide, and replace the barrier. Be sure to check again the next day and continue to check while the row cover is being used.

Summer Use

I use floating row cover to control cabbage worms (broccoli, cauliflower and cabbage), carrot weevils, Colorado potato beetles, cucumber beetles, flea beetles (not as much of a problem in summer as in spring), leafhoppers, leaf miners, squash vine borers, birds, rabbits, woodchucks and even an occasional goat that has escaped through the pasture fence. You need to continue to check for insects trapped under the row cover. Avoid a heavy row cover that will hold in too much heat during the summer. Stick with a light weight spun bonded polypropylene.

If you use a heavier row cover like slitted plastic you need to check the temperature under the plastic daily. Even heat-loving plants can get too hot under cover.

Fall Protection

Row covers will keep plants and soil warmer during the fall. When the temperature is over 60° I recommend pulling the sunny side of the row cover up to allow for air circulation and avoid over heating the plants. When the temperatures rise to 80°, such as during an Indian Summer, push the row cover all the way off to one side for the hottest part of the day. If it’s windy you should tack the cover down in a few places. A flapping cover can do a lot of damage in a short time. Replace the cover in late afternoon so that the ground stays warm. I use row covers in the fall on lettuce, peppers, bush beans, squash, pumpkins and other plants that appreciate the extra warmth. For a little extra radiant heat, add some large rocks and let them absorb heat during the day.

Frost protection is very important once the night time temperatures start dropping. It won’t hurt to cover your flowers and vegetables “just in case” there might be a frost. If you don’t hear a frost warning until the 6 o’clock news don’t worry. Grab your extra sheets! They’ll fit over tomatoes in cages, patches of squash and pumpkins and actually, just about anything else you might need to cover. Save your covers for the frost sensitive plants. You don’t need to cover broccoli, cauliflower, cabbage, Brussels sprouts, turnip, kale, spinach, rutabaga, carrots and other cold hardy plants. They’ll take a light frost, and sometimes a heavy killing frost, without being damaged. Root vegetables usually taste better after being chilled by frost.

You can delay the ground from freezing by using row covers to trap heat. This will give you more time to dig your root crops.

After the frost melts and the air starts to warm you can remove the cover but it might not be necessary. If the cover is light weight and allows sun and water through, and the temperature isn’t going to be too warm, you can leave the cover on.

Low Tunnels

You might have heard of high tunnels being used by commercial flower, fruit and vegetable growers. Backyard gardeners often use another version called low tunnels. They’re usually around three feet wide. A low tunnel is a mini greenhouse over the soil.

I use slitted row cover in late spring into fall. Slitted cover is heavy weight plastic that has pre-cut slots. It’s supported by No. 9 wire cut to the appropriate length. I cut mine five to six feet long depending on how high and/or wide I need the low tunnel. Each end of the wire is pushed into the ground to form the hoop. The slitted cover is stretched out the width of the row plus an additional three feet on each end. Cover one side with soil, rocks, boards or something else to hold the plastic down. Stretch it out over the hoop and cover the other side. Close in the ends. As the plastic warms and becomes more flexible the plastic between the slots will relax, opening the slots. Heat is released through the slots. If the temperature rises too much you need to either open the end to increase circulation or lift one side of the plastic. You can clip the plastic onto the wire with clothes pins.

Low tunnels are particularly helpful with heat-loving plants like tomatoes and okra. Keep in mind that slots don’t close completely. A lot of heat is lost through the top during the night. If it’s going to be too cold over night you should use an unslitted cover on top of the tunnel. It doesn’t have to cover the entire tunnel. You can cover six inches below the slots. Again, clothes pins will attach the second cover for the night.

Cucumbers, melons and squash can be transplanted into the soil and covered with a low tunnel to give them an early start in the spring. These are plants that don’t like cold feet. The soil temperature needs to be warm enough to keep them happy before you transplant the seedlings. You can warm the soil by spreading strips of clear plastic over the row and anchoring it down tightly. Clear plastic allows sunlight through to warm the soil faster than black plastic. Black plastic absorbs the sun’s heat then warms the soil. When the soil has warmed you can roll your plastic up and store it for next year’s use. Make your low tunnels and transplant your seedlings at the same time you remove the plastic.

If you need pest protection but not additional heat you can use a light weight floating row cover over the wire hoops. As with row cover on the ground, check for pests that emerge from the soil so that you don’t trap them in instead of out.

Don’t be intimidated by low tunnels. They’re simple, low maintenance, and you’ll get a lot of use out of them.

At End of Season

At the end of the growing season you should look your row covers over carefully. Cuts in plastic covers can be repaired with greenhouse patch tape. A rip or hole in a long length of row cover can be cut out with scissors. You’ll have a shorter piece of row cover but you’ll be able to save and reuse it next year. If mice are a problem you should store spun bonded polypropylene in hard plastic containers.

If I’ve removed a row cover from diseased plants I throw it away. I’d rather replace a cover than take a chance of introducing the disease next year.

Some row covers are compostable. The information that came with your covers should tell you if this is so. I add mine to the compost pile while I’m building the pile.

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