Plants might benefit from physical protection in the summer months for several reasons: cold weather, hot weather, insect pests, small mammals, wind damage. We have tried various shade cloths and row covers, and methods of fastening them, some more successful than others.
What and How
Shade cloth is available in many widths and different densities of shade. We generally use 45-60% shade cloth to cool crops such as lettuce growing in summer. We also have a short roll of very dense (80 or 90%) shade cloth which we use to cover harvested produce as we gather a load to move to the refrigerator. And we have a giant piece of shadecloth that goes over our hoophouse mid-May to early-September. Shade cloth is available woven or knitted, polypropylene or polyethylene. It’s usually black, sometimes green.
White polypropylene row cover is available in lightweight forms for insect protection in summer. We have found it very fragile, easily torn, and so we often use thicker row cover, even in summer. If you have a serious insect problem and don’t mind single-use plastics, lightweight row cover might suit you fine.
In the United Kingdom, Carrot Rust Fly/Carrot Root Fly is a big pest, and prior to the invention of row cover, organic growers made 3-foot high, insect-proof fencing around carrot beds, usually of polyethylene sheeting. This worked because the Carrot Rust Fly flies in close to the ground. It had the additional benefits of wind protection and a mini-greenhouse effect, but was more work than floating row cover.
This season we will be trialing a small roll of Enviromesh Insect Netting which I brought back from the U.K. I haven’t found it available for sale in the US yet. It is a white, woven small mesh. I wonder if a shadecloth is available with a small enough mesh to do the same job? I wonder if window screen fabric would work, and whether it would hold up to intense sunlight, or disintegrate? Farmtek now has an insect screen fabric for doors, vents and hoophouses.
Details of When
Row cover can be used to extend the season at both ends, providing protection against cold weather. It can also be used at any time of year against insect pests and small rodents. Rabbits, though, are smart enough and big enough to chew out the squares between the reinforced grid of Agromesh type reinforced row cover, if they are hungry! We use row cover against cucumber beetles when we transplant early summer squash, cucumbers and melons, and on most direct sown cucurbits throughout the season. We keep the row cover on until the crop is flowering, then pack it away, so that the flowers can be pollinated. By then the bigger plants are better able to resist the pests. We don’t cover winter squash, as it would be so much work, and many varieties are resistant to cucumber beetles. (We don’t suffer badly from Squash Vine Borers or Squash Bugs.) It does mean we forgo Hubbard Squash, the favorite of the beetles. Hubbard squash is suggested as a trap crop for cucumber beetles, in a row beside a plot of summer squash. Here the Hubbard seedlings barely make it out of the ground before they are devastated by the beetles, and there is then nothing left to trap anything!
We use row cover in late July/early August on our broccoli and cabbage transplants, to protect against Harlequin bugs, and to help the plants recover from the transplant shock. We keep it on for about 3 weeks, then pack away the cover and cultivate, undersowing with clover. We also use row cover on eggplant to protect against flea beetles, until the plants are larger.
We keep the seedlings covered in the cold frame, and then do our best to get the transplants covered promptly after setting them out. Sometimes we have someone hose the plants with a jet of water to dislodge any flea beetles already there, and have the row cover-spreading people follow immediately behind. By the way, a fact not everyone knows is that brassica flea beetles and nightshade (eggplant) flea beetles are not the same species, and don’t care for each others’ food, so don’t worry about setting out eggplant next to broccoli.
Details of What and How
Row cover: we think polypropylene row cover lasts longer and is tougher than polyester (Reemay). Our favorite is Typar, which is very durable and lasts us six years or more. It weighs in at 1.25 oz./sq. yd. and is made of spunbonded polypropylene. It transmits 75% of the light. We buy from Seven Springs Farm. We have also liked Agribon 17 (or 19), spunbonded polypropylene, which weighs 0.55 oz./sq. yd., transmits 85% of sunlight, and offers 4 degrees of frost protection for winter use. It is usually available in 83” width from Johnny’s, Peaceful Valley and many other suppliers. I’ve never tried the Tuffbell, sold by Peaceful Valley.
Hoops: For warm weather use, we usually drape the row cover directly on the plants, without hoops. (In winter we use double hoops to keep the row cover above the foliage and reduce frost damage and abrasion.). If making your own hoops, use 10-gauge wire or thicker. We sometimes use the spring steel hoops sold for setting out by machine. They are easy to use and easy to store as they spring back, more or less, to straight lengths and don’t get tangled. Their disadvantage is that they seem to come in just one length – 64” - which is fine for a single row of plants, but less good for our 48” beds with multiple rows. We bought ours from Nolt’s. It’s possible that spring hoops could be cut from high-tensile fence wire, but I haven’t tried that yet. Seven Springs Farm in Floyd, Virginia, has started selling fiberglass rods to use with row cover, and these too, store as straight lengths.
Ropes: for our fall broccoli and cabbage, we support row cover on ropes above the crop. The 83” width row cover will cover two rows at 34” spacing. Johnny’s now sells squarish hoops with special loops at the top to hold twine to support row cover.
Shadecloth: Until this year we bought woven polypropylene 50% shade cloth for the beds, and hemmed the ends on a domestic sewing machine using nylon thread. The piece for the hoophouse is knitted, black, 50% shade, UV stabilized polyethylene. Knitted shadecloth is much more flexible/drapeable and will not unravel when cut. Polyethylene is the usual material for knitted shadecloth. This year we’re trying knitted shadecloth for the vegetable beds. We like to hold the shadecloth above the plants on the spring hoops, to improve airflow and let the plants grow unimpeded. Some people clip the shadecloth almost horizontal above the crop and leave the sides open for the best airflow. We’ve bought from Gemplers, Wood Creek and Peaceful Valley. Gemplers has a wide range of knitted black shadecloth, from 50-80% shade, in small to huge pieces. Wood Creek has DeWitt knitted polyethylene shadecloth, in 60% shade, black or green, 6 ft or 12 ft wide, in 100 ft rolls. Peaceful Valley has 72” width black woven polypro, sold by the foot, in 30% ,47%, 63% and 80% shade. Their general field guidelines are: use 30% shade cloth in areas with very hot summers for vegetables such as tomatoes and peppers; for cool weather crops such as lettuce, spinach and cole crops, use 47% in hot areas, 30% in cooler climates. The 63% is for shade-loving plants, and the 80% is often used over patios and skylights to cool people as well as plants. Farmtek has 30, 50, and 70% knitted polyethylene.
For small areas, such as a lettuce nursery seedbed, we use scraps of window screen, old tent mesh windows, etc. Once when desperate, we covered a row of lettuce transplants with a collection of onion and cabbage nets for a few days. They were certainly better than nothing!
Sticks: We hold the edges of our row cover down with 5’ oak sticks which are reject hammock spreader bars from our hammock business (we sometimes jokingly wonder how people who don’t have a hammock business manage without scrap rope and reject spreader bars!). With row cover we roll the edge of the row cover under (not over), around the stick and set the stick up on the edge of the bed. This leaves the path free for us to walk in, and drag hoses, and the rolling under makes the system “self-locking”, in that if the stick starts to roll, it tightens the row cover rather than loosening it.
Pins: We’ve found some very good plastic clothes pins to hold shadecloth onto hoops, and to join short lengths of row cover at a hoop. They are also from the U.K., described as Hurricane Grip Pegs, and come in hard-to-lose shades of yellow, purple and turquoise! They are made of a single piece of plastic (no metal), with an integral spring and a lock. They do break down in sunlight after a couple of years, but last outdoors a lot longer than the standard wooden kind, and don’t get tangled in the fabrics. If you can’t justify a shopping trip to the U.K., they are available wholesale from Jarden Home Products. For summer lettuce, we use one of these clothespins at each spring hoop, space the hoops about 8’ apart, and dispense with sticks to hold the shadecloth down. Because shadecloth lets air through better than row cover, it’s less likely to blow away. We keep the shadecloth on our lettuce for 2 or 3 weeks after transplanting, then pull up the hoops with the shadecloth still attached, and move it (like a giant accordion) on to the next planting. a
Seven Springs Farm: http://www.7springsfarm.com/ Typar and Covertan rowcovers, fiberglass rods, DeWitt shadecloth.
Nolts: 152 North Hershey Ave, Leola, PA 17540. Phone (717) 656 9764. (No website). Shadecloth, knitted 50% and woven in a range of densities, Typar and Agribon rowcovers, spring steel hoops.
Peaceful Valley: http://www.groworganic.com/default.html Agribon and Tufbell rowcovers, wire for hoops.
Wood Creek Farm: http://www.woodcreekfarm.com/ De Witt shadecloth, Typar and Covertan rowcovers.
Gemplers: http://www.gemplers.com/ Wide range of shade cloth.
Farmtek: http://www.farmtek.com Knitted polyethylene shadecloth in bulk, or precut panels, 30-80% shade.
http://www.jardenhomebrands.com/toothpicks.html (scroll past the toothpicks!) firstname.lastname@example.org. Contact them to ask for a retailer in your region.
Johnny’s: http://www.johnnyseeds.com/catalog/category.aspx?category=292 Typar and Agribon rowcovers, loop hoops.
Biointensive IPM info:
Biointensive Integrated Pest Management
Pam Dawling manages the vegetable gardens at Twin Oaks Community in central Virginia. The gardens supply the 100 residents with almost all of their fresh and processed vegetables.