Row covers

Use row covers to protect squash and pumpkin vines from borer moths, ensuring the plants stay healthy without the use of insecticides.

There are a number of gardening tools I’ve come to treasure over the years. An unbreakable, hand-forged trowel from a Maine craftsman, long out of business, is definitely on the list, as is a Tina-brand German carbon-steel gardener’s knife that is easy to sharpen, yet holds an edge well. I’d certainly include my two-wheel Italian BCS tractor, which can power attachments as varied as a rototiller, a brush mower and a snowblower. Less exotic in origin, but equally versatile and useful in their applications, are the floating row covers that I buy every spring by the roll.

This material is a gauzy strip of polypropylene cloth that typically measures 4 to 10 feet wide and 50 feet long. It’s so light that you can lay it down right over seedlings or a bed of plants without damaging them. You can also buy wire hoops to stick in the soil under the fabric to create low tunnels.

The uses of this material seem to be limited only by the gardener’s imagination. In the spring, for instance, I lay down a strip of row cover over a freshly planted bed of seeds to keep the soil moist and enhance germination. Depending on the grade of row cover — it comes in varying thicknesses — it allows anywhere from 50 to 85 percent of the light to pass through it, so it does not shade the emerging seedlings significantly or cause them to stretch.

The partial shade that floating row covers provide and their ability to trap moisture beneath them also benefit newly transplanted seedlings such as the lettuces and cabbages I set out in the spring and again about now at mid-summer. The combination of shade and enhanced humidity really minimizes the trauma of transplanting. Because the cloth is so porous, it doesn’t block water, so I’m able to keep the seedlings irrigated as needed.

When I lay down a strip of floating row cover, I weight down the edges with stones or scrap lumber. This keeps the cloth from blowing about in the wind and also provides a seal to keep insects away from the plants underneath it. This ability to bar insects can be used to provide effective, toxin-free insect control.

Squash vine borer moths, for example, whose larvae tunnel into squash and pumpkin vines causing the plants to wilt, typically emerge just as the wild chicory, a blue-flowered, roadside weed, blooms in late June or early July. Cover your squash plants with row covers just before the chicory flower buds open and the squash vine borer moths won’t be able to get to your plants to lay their eggs on them. Leave the covers in place for three weeks and you will have a slightly delayed crop (the row covers will shut out pollinating insects as well), but one that remains healthy without the use of insecticides. Do, however, make sure to plant your squashes in a different spot each year as the squash vine borers overwinter in the soil and if you replant in the same spot as last year, your row covers may trap emerging moths in with your plants rather than keeping them out.

One final use for row cover is for frost protection in the fall. When the first frost is predicted, my wife, Suzanne, and I will cover our fall crops, cool-adapted greens and annuals, with row covers. By trapping the heat rising from the soil, the row covers can ward off several degrees of frost, helping to extend the harvest season, often by a couple of weeks. One use of the row covers I’ve heard recommended, but have yet to try is to cover cold hardy crops, such as leeks and kale with wire-supported tunnels, as described at the beginning of this column. Such tunnels can keep these frost-tolerant crops flourishing, I am told, right into late fall even in the North Country.

Be-a-Better-Gardener is a community service of Berkshire Botanical Garden in Stockbridge. Thomas Christopher is a volunteer at Berkshire Botanical Garden and is the author or co-author of more than a dozen books His companion broadcast to this column, Growing Greener, streams on, Pacifica Radio and NPR and is available at his website,