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To help kill weeds, cover the soil with a clear plastic sheet. The sun’s rays pass through the plastic causing temperatures near the surface to soar, reaching over 140 degrees 4 inches deep.

The hot summer sun can be used to your advantage to help get rid of weeds in your garden.

Weeds are an inevitable part of gardening. A while back I wrote about using mulch and herbicides to control weeds. We are now in a season when another option arrives, that being harnessing the heat of the blazing summer sun.

In July and August our vegetable gardens shrink in size to a few crops that can survive the scorching heat. We can take advantage of this “time out” and enlist the summer sun in our war against weeds.

You know how hot a car can get as the sun bakes down through the windshield into the interior. We can use this same principle to help control weed seeds, soil borne diseases, insects and nematodes which cannot survive high temperatures over a period of time.

The soil is covered with a clear plastic sheet. The sun’s rays pass through the plastic causing temperatures near the surface to soar, reaching over 140 degrees 4 inches deep.

Research at the University of California has shown that “bad” microorganisms are killed by solarization, while most beneficial microbes withstand the heat and survive. Earthworms move down into the soil until the temperatures cool off again. Trials have even shown an increase in plant growth and yield in solarized plots.

To use solarization in your home garden select a full sun location and follow these steps:

Rototill the plot to break up clods and blend the soil. You won’t want to disturb the soil after solarizing to avoid bringing weed seeds and other targeted problems to the surface. So do your soil preparation now for planting later. Beds or garden plots to be solarized should be slightly mounded in the center to allow rainfall (hey, I’m an optimist) to drain off and not form cooling puddles.

Water the area well to soak the soil thoroughly. Moist, evenly tilled soil maximizes heat transfer. Large areas are more effectively solarized than long narrow areas since the cooler soil alongside the solarized bed works against your effort to maintain high soil temperatures for an extended period of time.

Spread a sheet of clear plastic over the plot. Black plastic will absorb rays and will not allow as much heat to pass through into the soil. Thin plastic sheets work fine although thicker sheets are sturdier and less likely to puncture. Most hardware stores and large do-it-yourself centers carry wide rolls of clear plastic.

Plastic sheets should be 3 feet longer and wider than area to be covered. Place the edges of the plastic sheets in a shallow trench and cover them with a little soil to hold them firmly in place and prevent hot air from escaping. You can also use bricks or other weights to hold down the edges but the better you seal the edges the less heat can escape from beneath the plastic.

Watch and wait. It should take 3-6 weeks to do the job, depending on the weather. Hot, sunny days are best. Rain and cloudy conditions cool the soil, delaying the process. If it does rain, remove any puddles from the plastic with a power blower.

Sit in the shade with a glass of iced tea imagining that you can hear the tiny screams of millions of tiny broiling weed seeds, squash vine borer pupae and other notorious soil dwellers.

I usually mulch the bare soil surface after solarizing to protect it against crusting and erosion. This also helps keep the soil moist and cooler so when it is time to plant, the seeds or transplants have an easier time establishing.

Another way to put the summer sun to work for you is through summer tillage. I first observed this technique at a peach orchard where a field of bermudagrass was mostly destroyed with summer tillage in preparation for planting the following winter.

Rototilling the soil in summer heat kills some of the bermudagrass, Johnsongrass and other such perennial weeds by bringing underground storage structures to the surface where they desiccate in the hot, dry conditions. Weeds not killed will remain viable beneath the surface. After 10 to 14 days, rototill again and allow the drying to continue. If you repeat this process and the weather remains hot and dry, these perennial invaders will be significantly reduced, making subsequent control efforts much easier.

Gardeners wishing to avoid herbicide use may find summer tillage a way to create a garden spot in an area where bermudagrass is present. Summer tillage only minimally affects weed seeds although a light irrigation to induce weed sprouting before another rototilling can increase the effectiveness.

Robert “Skip” Richter is the Texas A&M AgriLife Extension horticulture agent for Brazos County. For local gardening information and events, visit brazosmg.com. Gardening questions? Call Skip at 823-0129 or email rrichter@ag.tamu.edu.

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To help kill weeds, cover the soil with a clear plastic sheet. The sun’s rays pass through the plastic causing temperatures near the surface to soar, reaching over 140 degrees 4 inches deep.

The hot summer sun can be used to your advantage to help get rid of weeds in your garden.

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