Got weeds? Get the dirt on natural weed controls.
I've been weeding the last few days, crawling between perennials to remove the latest crop of weeds that have appeared after 15 straight days of rain. Yanking seedlings and digging taproots makes me wax philosophical (likely due to altered blood flow), which is probably why my thoughts turned to Ben Franklin as I wriggled beneath an elderberry to grab some weeds. Franklin coined the infamous saying that nothing is certain in life but death and taxes. I’d say his assessment fell just a little short: He should have included weeds.
Getting the upper hand on weeds mostly takes persistence. Shortcuts sound tempting, and many natural weed control recipes promise fast results. Learn what works—and how to use it effectively.
Salt is a common ingredient in natural weed killers. Concoctions may call for amounts from a few tablespoons to 1 pound per gallon of water. Recipes may recommend rock salt, table salt or water softener salt. Salt is salt, and it works by drying out leaves and stems. It’s most effective on young seedlings.
Use caution pouring salt onto planting areas because it kills indiscriminately. If you apply it heavily, it can move through soil and affect plants you love. Get enough salt in soil, and nothing will grow. The best place to use salt is in areas not near desired plants, including gravel areas or driveways or sidewalk cracks.
Household vinegar, which contains 5 percent acetic acid, is probably the most touted natural weed killer. An acid kills plants by removing water from leaves and stems. Vinegar doesn’t usually kill plant roots, except on seedlings.
You may find stronger vinegar concentrations sold as horticultural vinegar. Ten percent seems to work well in killing weeds in a single spray, although perennial weeds do regrow from the root. Be careful using higher strength vinegar. First, because vinegar kills indiscriminately—both good and bad plants. Second, higher concentrations can cause skin irritation, damage eyes and burn mucus membranes. Wear eye protection when spraying vinegar. You may want to stick with household strength vinegar and simply plan on repeated sprays to kill mature weeds completely.
Some of the best places to use vinegar are on gravel areas or paver paths or patios—places you don’t want anything growing—provided you can protect nearby plants from spray drift.
Many weedkiller brews call for soap, meaning liquid dish detergent (not what you put in the dishwasher). Soap helps kill weeds by breaking down the waxy covering that forms on weed leaves. Soap also makes water “stick” to leaves better by breaking the water’s surface tension.
A high concentration of soap alone could kill plants, but most often it’s used in combination with other ingredients, like vinegar and/or salt. Soap is also an effective control for soft-bodied insects, like aphids, caterpillars or beetle larvae.
Some gardeners swear by pouring boiling water on weeds. I’ve done this on weeds in a gravel driveway and path. It works wonderfully on young seedlings. On more mature weeds, results can be iffy. Multiple treatments are the secret to eventual success. Be sure to wear closed toe shoes (no flip flops) when pouring boiling water on weeds. It’s also an indiscriminate killer, so it’s best used on paths or driveways where you don’t want anything growing.
Smothering weeds with newspaper is a tried and true method for starting new beds and maintaining weed-free planting beds. A few layers of newspaper (no slick inserts) topped with mulch is the preferred technique. Be careful using newspaper on heavy clay soil that doesn’t drain well. The paper can reduce air flow to soil and create low oxygen conditions that help un-healthy soil microbes to grow, the kind that produce a stagnant water odor. Avoid using cardboard to smother weeds—it’s the equivalent of junk food for termites.
The Bottom Line
No matter what method you try, there is no “natural” silver bullet to kill weeds. Most natural weed controls kill plants indiscriminately, so use them carefully around plants you want. Many natural weed controls kill the green parts of plants and have little effect on roots. That works great on weed seedlings or young annual weeds. With established perennial weeds like dandelions or burdock, repeat applications every 7 to 10 days until roots stop sending up new growth. Once weeds are gone, add mulch to planting areas to cover soil and help suppress future weed outbreaks.
When you’re battling perennial weeds, you may find that the most reliable eradication comes by digging them out. Wait for rain to soften soil, then grab your favorite weeding tool, strap on a pair of knee pads and start crawling. You’ll be waxing philosophical in no time.