Plant Row Covers for Insect Protection

Tropical plants covered with foil

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Row covers sometimes referred to as floating row covers, are lightweight spun-bonded synthetic fabrics that are laid over plants for protection against pests and temperatures. They are light enough to rest on the plants and allow light, water, and even fertilizer to get through.

Different Types

Most row covers sold to homeowners are made of either spun-bonded polyester or polypropylene. Row covers generally come in different weights, usually somewhere between 0.5 ounces per square yard and 2.0 ounces per square yard. The heavier the fabric, the more frost protection. Lighter fabrics don’t trap as much heat inside in summer months and allow more sun and water to permeate. However, they are all light enough to not need support and are allowed to ‘float’ on top of plants.

The lighter covers are used primarily as an insect barrier during the warmer growing months. Heavier fabrics are used for frost protection. The heaviest fabrics are used only in the evenings and are removed during the day to allow more light and heat access.

Frost Protection

Row covers will give your plants about two to four degrees of frost protection in the spring and a bit more in the fall because the soil is warmer in fall. That means that your plants will be protected from frost damage down to about 24 to 28 degrees F, depending on the fabric. You could also double the fabric, for additional protection when a frost is forecast. The row cover package should tell you what the frost protection for that product is.

Insect Protection

All weights of row cover work well for insect protection. But to keep pests out, you really need to seal or weight down all the edges and be especially careful that you don’t trap insects inside the cover. They’ll be fat, dumb and happy in there, munching on your plants in a warm, cozy environment. Check underneath periodically, to be sure nothing has hatched.

Installation Tips

  • For low growing crops, you simply need to unfurl the cover over the row and secure the edges. Secure the edges of the fabric with pins or some type of heavy objects like rocks or mounded soil.
  • Don’t stretch the cover tightly over the row. Allow some room for the cover to expand as the plants grow, by pleating or folding slightly as you lay it down.
  • If the garden is in an especially windy spot, consider weighting down the center of the cover, to prevent billowing that could uplift your edges.
  • For taller plants, like tomatoes and eggplants, it’s sometimes easier to install row covers over hoops.

Row Covers to Check Out

  • Lightweight all-season pest control: A fabric like Summerweight Weight Fabric for Pest Control is thick enough to prevent easy tearing but light enough to prevent overheating. It's nice for use over problem crops like cabbage and potatoes. It can also be used over tough crops, like eggplant, that needs insect pollination, once the fruits have been formed. It is listed as letting 85 percent of sunlight through to your plants and providing frost protection down to 28 F.
  • Frost protection season extender: A slightly heavier cover, like the All-Purpose Garden Fabric, has better tear-resistance. Since it only lets in 70 percent of sunlight and traps more heat, this weight is best used as a season extender, rather than all-season pest control. Also protects against frost down to 28 degrees F.
  • Heavy-duty insulation: The word quilt should give it away here. We’re talking about keeping your plants insulted from early and late frosts, as well as in high wind areas. At 1.25 oz., the GardenQuilt is on the heavy side of row covers. Light transmission is 60 percent and frost protection is listed as down to 24 degrees F. This weight fabric makes a nice substitute for a cold frame, to harden off tender plants in spring and to keep greens growing a little longer in the fall.