Gardener: Natural control of lawn weeds – Sacramento Bee

If you want a sure way to drive yourself crazy, take on Mother Nature, especially in the lawn weed department. It’s never a contest you will conquer. Better we learn to work with her, and eventually come to realize that the best we can do sometimes is drop back and punt. The sooner we learn the rules of the game, the saner we’ll be.

Take the desire to have a weed-free lawn for example. Even though there is no shortage of chemicals to kill them, there are a few environmentally friendly steps we can take to reducing the population, without having to resort to potent synthetic herbicides.

Weed control products are classified into two broad categories:

PRE-EMERGENCE

Pre-emergence weed control products are designed to inhibit development of the germinating weed seeds from establishing in your lawn. 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 these temperatures arrive. Apply pre-emergence control in the 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. In all fairness, there are some challenges to using corn gluten as a weed control. First, it’s pricy. A 25-pound bag costs about $30 when you can find it. 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 over 10,000 square feet) would need about 200 pounds; a $250 investment at least.

Consistent applications over several years are necessary to get closer to the effectiveness of synthetic counterparts. I realize I’m not painting the most-compelling case for taking this route, but to my knowledge it’s the only option when it comes to taking on weeds before they gain any 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 dandelion and wild onion are very difficult if not impossible to control with one application. Multiple applications will be likely for effective control.

Ready-to-use products on the market typically incorporate one or more of the following ingredients: clove oil, thyme oil and citric acid. Another popular DIY option is horticultural grade vinegar (acetic acid � 20 percent concentration). Personally, the vinegar option is one I advise against whenever there is a risk it may 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 we’ve seen the introduction of a chelated-iron selective post-emergence herbicide. I have not used this product yet but online reports show promising levels of effectiveness on common lawn weeds. To find product names and where to buy products with this active ingredient, search online for “iron based organic weed control.”

Perhaps the best organic approach though 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, over seeding bare spots and ongoing vigilance 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, and the founder of The joe gardener� Company, devoted to environmentally responsible gardening and sustainable outdoor living.

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