How to Get Rid of Weeds
Learn how to identify common lawn and garden invaders, then get pro advice on how to eliminate them forever
Weed-free lawns are the stuff of dreams and championship golf courses. In fact, when you consider the tenacity of weeds, it's a wonder any of us win the pitched battles we wage with these pesky invaders. Just one dandelion plant makes up to 15,000 seeds, each of which can survive six years in the soil—creating 15,000 more seeds when it sprouts and matures.
Synthetic herbicides are the usual response to chronic weed problems. But used unwisely, these chemical weed killers can be dangerous to people, pets and turf. And unless you get at the underlying problems that weaken lawns and favor weeds, you might have to apply herbicides frequently.
The best way to control dandelions and other weeds in your yard is to grow a thick, vigorous lawn. Dense grass crowds out weeds and blocks the sunlight their seeds need to germinate. If only a few weeds dot your lawn, changing your maintenance tactics might be all it takes to get rid of them. And if your efforts at hand-to-hand combat haven't worked, take heart. There really is a way to pull out even stubborn dandelions so they don't come back.
No single herbicide, weeding technique or lawn care tactic works against all weeds. How you attack the weeds in your lawn depends on which you have. Lawn weeds fall under three broad categories: unwanted grasses; grasslike plants called sedges; and broadleaf plants. Most are annuals or perennials. Annuals complete their life cycle in one season and reproduce from seeds. Perennials live several years and spread underground as well as by seed, making them harder to control.
The following guide shows examples of the different types of weeds that plague lawns throughout the country. If you're still stumped about whether yellow nutsedge or yellow woodsorrel has invaded your turf, call the extension service in your area for help from experts.
Crabgrass is an annual with branching, spreading stems. Its coarse, blue-green to purplish leaf blades can be smooth or hairy, depending on the species. Flower heads with several fingerlike spikes rise from narrow stems.
Crabgrass thrives in lawns mowed shorter than 2 inches, underfed lawns, and those watered frequently and lightly. Thick, deeply irrigated turf is the best control. Dig crabgrass before it seeds. Preemergence crabgrass herbicides are available; apply in spring before soil temperature reaches a steady 60 degrees Fahrenheit.
Dandelion is a broadleaf perennial recognized by bright-yellow flowers and a large, flat rosette of leaves rising from a long, fleshy taproot. Dandelions favor thin turf.
Pull or dig out young plants before they go to seed. Then cut any regrowth from leftover root pieces. You can also spot-treat weeds with a selective broadleaf weed killer.
White clover is a broadleaf perennial that used to be included in grass seed mixes. Also called white Dutch clover, it's distinguished by three-lobed leaves with a crescent-shaped white band. The plant spreads by creeping stems and thrives in sparse, undernourished turf with excessive moisture.
Control it by watering well, applying nitrogen fertilizer and avoiding excessive applications of phosphorus. Spot-treat with a selective broadleaf weed killer; a second treatment often is needed.
Ground ivy is a broadleaf perennial with square stems and bright-green rounded leaves with scalloped edges. It reproduces by seed and creeping stems that root as they touch the ground.
Also called creeping Charlie, it prefers damp soil and shade. Improve drainage and water less. Pull stems and roots of young plants. Spot-treat with a broadleaf postemergence herbicide.
Yellow woodsorrel is a broadleaf perennial, although it might act as an annual in some regions. Also known as oxalis, it has cloverlike leaves and yellow flowers, each with five petals. Plants spread by roots and seed.
This weed is difficult to control, and does best in thin turf watered frequently and lightly. Water thoroughly and fertilize properly. Dig out small plants or spot-treat isolated ones with a postemergence weed killer. Prevent new weeds with a preemergence herbicide with oxalis on the label.
Quackgrass is a perennial grass with flat light-green to blue-green leaves. It spreads by seeds and aggressive underground stems, called rhizomes.
Thoroughly dig out roots and pointed rhizomes—remaining pieces regenerate new plants. Spot-treat with a nonselective weed killer.
Yellow nutsedge is a grasslike perennial sedge with triangular stems and ¼-inch-wide leaves. Also called yellow nutgrass, it reproduces by seed and tubers that grow at the root tips. Tubers often persist in the soil, making established plants difficult to control.
Mow high in early to midsummer and water infrequently though thoroughly. Spot-treat with postemergence herbicides labeled for nutsedge. As with most weeds, control is easiest when plants are small.
Spotted spurge is a broadleaf annual that grows close to the ground in a fast-spreading mat. Its small leaves are green with a brown-red spot on top. Cut stems exude a milky liquid.
Spotted spurge reseeds heavily. A high-mowed, well-fertilized and vigorous lawn provides tough competition. Pull isolated plants before they seed. Spot-treat with a postemergence weed killer and use appropriate preemergence herbicides to prevent new weeds.
Most lawn weeds are opportunists that take root wherever they can find the space and catch a few rays of sunlight. These interlopers stand little chance of establishing themselves in healthy grass. That's why a sensible lawn care plan will help stop weed problems before they have a chance to start.
Too little fertilizer can lead to sparse lawn that loses the competition with weeds. Too much helps nurture certain weeds, notably annual bluegrass, Bermuda grass and crabgrass. Strike a balance by following the application rates on the package. And use a fertilizer with a high percentage of controlled-release nitrogen, such as sulfur-coated urea, ureaform or IBDU. These provide a slow, steady nutrient supply.
The frequency and timing of your fertilizing efforts are also crucial to healthy lawns. Both vary depending on your lawn type and the length of your growing season. Most northern lawns need only one or two applications of fertilizer annually—once in fall and sometimes a second time in spring. Southern grasses might require three feedings—early to midspring just after the grass greens up, early summer and again in early fall.
Frequent, light watering causes shallow roots and helps annual bluegrass, crabgrass, chickweed, sedges and other weed seeds germinate. If you water too little, the lawn suffers while spotted spurge, Bermuda grass, quackgrass and other weeds adapted to drier soil thrive. Instead, provide your lawn with infrequent, deep soakings. Lawns need about 1 inch of water per week. Set an empty tuna can on the lawn to determine when you have applied 1 inch of water.
Mowing too low weakens turf by reducing the ability of a grass leaf to produce enough nutrients. It also lets light hit the soil surface, which helps crabgrass and goosegrass seeds sprout and grow. Check with your local extension service for the recommended range of mowing heights for your grass type. Then mow at the highest level—usually between 2 and 4 inches.
Sometimes weeds are a clue to soil or site problems. Correct them so your landscape favors lawn grasses and discourages weeds. For example, ground ivy grows best where the soil surface remains damp. It also thrives in areas too shady for good grass growth. So consider improving soil drainage by aerating—removing small cores of soil—if ground ivy is a problem. And, to allow more light to reach the surface of the soil, selectively remove tree branches in shady areas.
Growing a healthy lawn with proper mowing and watering can keep weeds from sprouting. Here's how to go after the weeds you have:
Hand-weeding is still the best defense on small lawns where the number of weeds isn't overwhelming. It's most effective against annual broadleaf weeds. Pulling them while they're young—before they flower and seed—is the simplest way to prevent them from spreading.
Catching perennial weeds early is crucial. Dandelions, for example, develop deep taproots that are hard to pull once they mature. Yank the entire plant, including the root—any root pieces left underground will grow new plants. If new sprouts grow, pull them repeatedly to eventually starve and kill the weed.
Weeding is easiest when the soil is moist. Tools like the dandelion digger help get at the root by probing deep into the soil. Once the weed is out, promptly reseed the bare spot; otherwise, new weeds will fill it in.
Perennial weeds such as dandelions should be pulled when they are young. When soil is moist, push a sharp spade or dandelion digger into the soil, angled downward toward the center of the plant, and loosen the soil around it.
Use the tool to pry the weed upward while pulling it; try not to break off the roots.
Once the weed and roots are out, smooth the soil, work in some compost, and patch the area with lawn seed. Keep the soil evenly moist until the grass is 1 inch high.
Use herbicides as a last resort—when nothing else works on a particular weed or when your lawn is completely overrun. And follow directions carefully. Used incorrectly, herbicides can injure or kill turf and other desirable plants.
If you use an herbicide, choose one that's labeled as safe for the type of turf you're growing and effective against the weeds you've got. The label states when and in which conditions to use the product. Some herbicides work only within a certain temperature range; others work only when applied at a specific time of year.
Herbicides fall into three major categories: preeemergence herbicides, postemergence herbicides and weed-and-feed products.
Preemergence herbicides kill germinating seeds before seedlings break through the soil. Crabgrass is the primary target. The most common preemergence herbicides are synthetic. Natural, nontoxic preemergence herbicides made from corn gluten are safer, though you might have to apply them for several seasons for them to be fully effective. Three quality products are Concern Weed Prevention Plus, WOW! and WeedzSTOP. A drawback to these and most other preemergence herbicides is that they kill germinating lawn seed. Check product labels carefully.
Postemergence herbicides kill existing weeds that are actively growing. These come in two basic forms: contact and systemic. Contact herbicides kill only the part of the plant they touch. Most act quickly and work best against annual weeds. Systemic herbicides circulate inside the plant, killing the whole thing. They're more effective than contact herbicides on perennial weeds, though repeat treatments might be needed.
You also need to choose between selective and nonselective versions of systemic herbicides. Selective herbicides kill only certain weeds, while nonselective herbicides kill any green, growing plant, whether it's a weed or not. Most broadleaf herbicides, including products like Weed-Away and Weed Warrior, are systemic and selective to kill broadleaf weeds only. They won't kill weedy grasses. Glyphosate—the active ingredient in Roundup and other products—is an example of a systemic, nonselective herbicide that kills broadleaf weeds and weedy grasses. But because it also kills turf and other desirable plants, it's safest to use it on your lawn when you want to kill an entire section and then replant it. Finale, in which the active ingredient is gluphosinate ammonium, is another nonselective used for this purpose.
When using any postemergence herbicide, don't apply them over your entire lawn, if possible. Instead, spot-treat isolated weeds or weedy patches.
Weed-and-feed products combine fertilizer and herbicides to do two jobs at once. But their promised labor savings can backfire if the recommended time for weed control doesn't coincide with the best time and rates for fertilizing. Most also pose an herbicide-overdose risk when used for follow-up fertilizing. Corn gluten with added organic fertilizer is the safest weed-and-feed.
Whichever herbicide you use, follow the directions. Address the causes of weeds at the same time to keep new ones from growing. And reseed the bare spots left by dead weeds. The bottom line in the war against weeds: Care for your lawn and apply only what it needs—and only when necessary.