Curbing lawn weeds naturally is a challenge

If you want a sure way to drive yourself crazy, take on Mother Nature, especially in the lawn-weed department. It is a contest you won’t win.

Better we learn to work with her and eventually realize that the best we can do sometimes is drop back and punt.

Take the desire to have a weed-free lawn, for example. Even though there is no shortage of chemicals to kill weeds in the lawn, there are a few environmentally friendly steps to reduce the weed population without resorting to potent synthetic herbicides.

Weed-control products are classified into two broad categories: pre-emergence and post-emergence.

Pre-emergence

Pre-emergence weed-control products inhibit development of the germinating weed seeds.

Success depends on the timing of the application. Most weed seeds germinate when soil temperatures reach a certain level. Therefore, the pre-emergence product must be in place before the temperatures arrive. Apply pre-emergence control in late summer or early fall for cool-season annual weeds and again in late winter for warm-season weeds.

Corn gluten has gained popularity as a natural alternative to synthetic pre-emergence herbicides. Perhaps its best attribute, though, is as a natural fertilizer since it contains about 10 percent nitrogen content by weight.

But there are some challenges to using corn gluten as a weed control. First, it is pricy. A 25-pound bag costs about $30. It’s also important to pay attention to timing and application rates (no less than 20 pounds per thousand square feet) for best control.

Doing the math, a quarter acre lawn (a little more than 10,000 square feet) would need about 200 pounds — a $250 investment at least.

Consistent applications over several years are necessary to approach the effectiveness of synthetic herbicides. This sounds daunting, but it’s the only option to curb weeds before they gain traction.

Post-emergence

Post-emergence weed control is the other tactic. These products kill established broadleaf weeds. Read the label; using a product not made for your grass type could inadvertently kill it, too.

Until recently, all organic solutions to post-emergence weed control have been non-selective — meaning, they kill whatever they contact (weeds, grass and more).

For the most part, these options are effective at burning down top growth. However, long-term control varies depending on the weed and the extent of the root system. Deep “tap-rooted” weeds such as dandelions and wild onions are very difficult if not impossible to control with one application.

Ready-to-use products on the market typically incorporate one or more of the following ingredients: clove oil, thyme oil and citric acid. A popular do-it-yourself option is horticultural-grade vinegar (acetic acid, 20 percent concentration).

Don’t use vinegar if there is a risk it might come in contact with frogs, toads, lizards or any amphibious creature. The vinegar at this concentration is lethal to them.

Another option is boiling water. It’s effective in killing annual weeds and with repeated use will also kill a number of perennial weeds. Use caution and pour the water from just a few inches above the plant.

Recently a chelated-iron selective post-emergence herbicide has been introduced. I haven’t used the product yet, but online reports show promising levels of effectiveness on common weeds. To find where to buy products with this active ingredient, search online for “iron-based organic weed control.”

Perhaps the best organic approach to weed control is to manage the soil conditions of your lawn. Several factors are involved in creating the ideal environment for promoting grass vs. weed growth. Those include proper mowing height, minimizing soil disturbance, overseeding bare spots and remaining vigilant to prevent weeds from spreading through spot treatment using natural products or manual extraction. In fact, cultivation by hand or tools is still the most effective “selective” method of control and the one I opt for whenever possible.

Joe Lamp’l is the host and executive producer of Growing a Greener World on national public television.