Is there really such a thing as a nontoxic organic weed killer?
Fortunately for all of us, the quest to find safer green alternatives instead of poisoning the earth with chemicals, has led to the discovery of quite a few ways to kill weeds.
Boiling water is by far the safest, most effective weed killer. The only problem is boiling all that water if you have a lot of weeds to kill. Time to charge up the barbecue.
Indiscriminately scattering chemicals around our yards affects everything: birds, bees, butterflies, pets, children, soil and water. So how do we kill insects that threaten the plants we want?
The latest research is on using natural predators for specific targets. More are discovered every year. Bacillus thuringiensis var. Kurstaki, known as Btk is one such predator. Currently being used in Shady Cove to attack gypsy moths, these bacteria produce a toxin that kills certain caterpillars, but does not harm anything else.
Pouring salt on weeds, an old folk standby, will cause them to curl up and die. Unfortunately, so will good insects and microbes in the soil. Better tools exist today.
One option is to use the sun’s heat to fry unwanted plants. This only works where you want to create a weed-free bed before planting. Cover the area with black plastic and weight it down. Depending on the weather, everything under the plastic should die in one to eight weeks, including the weed seeds in the top couple inches of soil.
Vinegar works well enough that many railroads use it to keep down weeds along their tracks. Some gardeners use grocery store vinegar, but the 20 percent concentration forms work better and do not require repeat applications. Be sure to follow directions with this strong acid, available in hardware stores and garden centers, and keep pets and children away until the liquid dries.
Heard of corn gluten meal? Different than corn meal, this byproduct of the corn milling process prevents seeds from germinating. Food grade, it can be used safely around all plants. Because it only affects seeds, you can put it on the lawn to kill weedy interlopers with no harm to the grass. This stuff doesn’t kill existing weeds, and shouldn’t be used anywhere you want seeds to grow.
“Seeds just don’t sprout when you sprinkle this on them,” says Pam Rouhier, garden clerk at the South Medford Grange Co-op. “It isn’t harmful to birds or the microbes in the soil.”
Our experts also suggested some of the newly formulated organic weed killers, such as BurnOut, Weed Zap, Matran II, Green Match and Worry Free Weed & Grass Killer. These all have various formulas of citrus, cinnamon, thyme or clove oil, some with added vinegar.
“These must be used when the temperature is 70 degrees or better, and best used on smaller plants with new leaves that are small and tender,” says Ajit Singh, manager and plant scientist at Phoenix Organics in Phoenix. “They are all good if you use them properly. They’ll kill annual [weeds] within hours, but you may have to repeat the dose for woody perennials.”
“The smaller the plant, the better chance of killing the whole plant,” says Rouhier. “Plants have wax on their leaves so they breathe only through the pores. The oils take the wax off so they transpire all moisture and dry up. What’s nice is they smell good — no chemical smells, and you don’t have to worry about them around pets and children.”
With so many healthy alternatives there really isn’t any reason to resort to harsh chemicals. Maybe this is the year to try going green.