DIY Network

Organic Ways to Manage Weeds

Master gardener Joe Lamp'l, host of Fresh from the Garden, provides tips for controlling weeds through organic methods.

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Acetic acid (vinegar) works, but common household vinegar is not effective for mature weeds. Minimum concentrations above 7 percent are needed to manage tougher weeds, and multiple applications may be necessary with tap-rooted weeds.

Weed out those 'plants out of place' organically

By Joe Lamp'l

July 16, 2007 — So how do you know if that plant you are looking at is really a weed? Pull it up. If it comes out easily, it wasn't a weed!

Although that's not really the true definition, it seems to be the case, more often than not. So just what is a weed anyway? The most widely accepted definition is simply "a plant out of place."

I get many questions about how to control weeds in lawns and gardens organically and selectively. Honestly, that presents a challenge, but with a little patience and dedication, satisfactory results are achievable.

First, the best defense is a good offense. Take lawns for example. Other than manual methods, such as hand-pulling, once weeds are present, organic controls are unavailable to selectively eliminate the weeds. Promoting the health and vigor of the lawn is the best way to starve off, shade out and out-compete the weeds.

When you're ready to manage weeds with organic controls, there are several options. The following is a listing of some of the most popular eco-friendly choices.

Manual Controls

• Hand-pulling. This, to me, has an element of satisfaction that no other weed-control method can offer. It's also one of the few ways for selective control. Hand weeding is easiest after a soaking rain. With tap-rooted weeds, make sure to get the entire root! Otherwise, any remaining piece will provide sufficient energy for it to regenerate a new plant.

• Mulch. A layer of mulch two to four inches thick is a very effective organic means of preventing most weeds from germinating.

  If you want to know that the bagged mulch you buy is free of potentially harmful contaminates such as arsenic from treated wood, be sure each bag has the certification seal of the Mulch and Soil Council. (www.mulchandsoilcouncil.org)

Sprays and Drenches

These methods affect plants on contact by burning or desiccating the cell structure. As a contact herbicide, they are most effective on young annual weeds.

• Boiling Water. This works well at killing most weeds with one application. Some weeds, especially those with tap roots such as dandelions may need multiple applications. Use caution, keep the water as close to the weed as possible to avoid splashing yourself or other desirable plants.

• Acetic Acid (vinegar). Works, but common household vinegar is not effective for mature weeds. Minimum concentrations above 7 percent are needed to manage tougher weeds, and multiple applications may be necessary with tap-rooted weeds. Use caution when using acetic acid, as it can burn skin and eyes on contact. Approved sources for herbicide use can be found online or at farm-supply stores.

• Plant-based ingredients such as citric oil, clove oil and garlic are non-selective post-emergent herbicides. Use caution, as they will injure or kill all vegetation they touch. Tougher weeds usually require multiple applications for complete control. Ready-to-use products are available through organic gardening-supply sources online and in some garden centers.

Granular Pre-emergent

• Corn Gluten is a granular corn-based product that is used as an organic pre-emergent control in lawns. Although effective, it takes several seasons for results comparable to synthetic options. Corn gluten has the added benefit of containing 10 percent nitrogen by volume for natural fertilization as well. It is becoming more popular but is not yet widely available in retail garden centers. It is readily available online.

• Flame weeders are devices that use the intense heat of a concentrated flame to destroy the cell structure of the plant. Typically powered by a propane canister, they are portable and effective. Simply pass the flame over the weed for several seconds. It is not necessary to visibly burn the weed. A few seconds of intense heat is all that is necessary.

  Like the other methods listed above, because the roots are unaffected, the toughest weeds may require multiple applications. Use extreme caution when working with this tool.

Prevention is the best way to reduce the weeds from spreading next year. Although they will still come into your yard through other means, eliminating weeds on your property before they go to seed or have a chance to spread will save you many hours of work next year and beyond.

(Joe Lamp'l, a master gardener, hosts DIY's Fresh from the Garden as well as a gardening radio show. For more information, visit www.joegardener.com. Distributed by Scripps Howard News Service.)

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