Killing weeds with soil solarization
Elbow grease - the new pesticide
DAVID MINK GateHouse Plus

Nobody looks forward to planting a garden full of weeds. Yet year in and year out, gardeners who toil to plant and foster their precious petunias, hydrangeas, tomatoes and honeysuckles end up spending more time cultivating weeds then enjoying the fruits of their labors.

If you're like everyone else, you're considering the same old solutions: a healthy dose of herbicide before the plant, and then some good old-fashioned weed pulling as needed. Herbicide can be costly, however, and it can also lead to decreased production in your fall crop (on top of the fact that it's not good for the environment). And who wants to pull weeds all summer long?

If you're looking for a new option, though, you can always consider soil solarization.

Soil solarization is a method of controlling soilborne pests, weeds and weed seedlings by pulling them to the surface and then exposing them to long periods of extreme heat. It leaves no toxic residues that can damage later crops and pollute ground water. It also improves soil structure and increases the availability of nitrogen and other nutrients.

Solarization incorporates the use of polyethylene tarps to trap in heat and UV rays. Gardeners lay the tarps over smoothed, well-turned soil (which has brought most weeds roots and weed seedlings to the top), and lay the clear tarps over the turned soil. The tarps are left in place for four to six weeks, effectively killing any disease-causing organisms, nematodes and weeds through the use of heat.

Solarization can be incorporated into garden use in a number of ways. It is best employed during the summer months of June and July, when heat and UV rays are at their highest. Gardeners can choose to blanket their garden in tarps, or they can solarize only the strips between their crop rows. Either way, solarization is a simple and safe - albeit workintensive - way to rid your garden of those pesky weeds.

Begin the process by disking, rototilling or turning the soil by hand. Break up any clods and remove any weeds, large rocks or other debris that may puncture the tarp. After sufficiently turning the soil, smooth it down to a consistent level. You'll want the tarps to lay as evenly across the surface as possible.

Once the soil is smooth, sufficiently wet the area. Heat travels more efficiently in wet soil than it does in dry soil. The soil should be saturated to about 70 percent in the upper layers and moist to a depth of 24 inches to be efficient.

Now lay down the tarps. You can anchor them using large rocks or some other heavy weights, or you can secure them by burying the edges in shallow trenches around the treated area. If you're working with a large surface area, overlap the tarps and cover the meeting ends with a mounded strip of dirt. Remember, however, this dirt will be untreated and could contaminate the treated soil after the tarps are removed. After solarization is complete (about four weeks), you can remove the tarps or leave them as a mulch for the next following crop.

Just transplant plants through the plastic. Paint clear plastic white or silver to reflect heat, cool down the soil and repel flying insects. Leaving the plastic may cause some problems next year, however, as it may degrade and become hard to remove. Treated soil can be left to sit until the next growing season. Be careful if you plan on tilling the soil again, however. If you plan on tilling more than two inches, you could move new, viable weed seedlings to the top and negate all the work you just did.