The 10 Worst Garden Weeds

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by Pixabay/photoAC

Weeds are an inevitable thorn in every gardener’s side. While some weeds offer benefits, such as the edible greens of young dandelions and the nutritious roots of burdock, many quickly become a frustrating, ongoing struggle if you don’t spot them early. Garden weeds can steal water, sunlight and soil nutrients from food crops, and some even release toxic chemicals into the soil that inhibit the growth of other plants.

To find out which garden weeds pose the biggest problems in gardens throughout the United States and Canada, MOTHER EARTH NEWS surveyed more than 2,000 gardeners. We asked respondents to rate which weeds were the worst in their gardens, and to tell us about their best organic weed control methods. They also rated the effectiveness of specific mulch types, organic herbicides and tools used to cope with garden weeds.

Two thousand gardeners can’t be wrong — the best tools for keeping ahead of weeds include several types of hoes (see Hard-Working Garden Hoes), a good garden fork, a garden knife, a dandelion puller (some use an old screwdriver or butcher knife instead), and a high-quality pair of gloves.

Grasses took the cake among the top 10 worst weeds in home gardens with four representatives: crab grass, Bermuda grass, quack grass and Johnson grass. Dishonorable mentions included docks, lamb’s-quarters, knotweed and poison ivy. Hand weeding and mulching heavily with organic matter were far and away the control measures that received the most praise, and nothing beats frequent monitoring and early intervention for protection against serious infestations.

The illustrations in the Image Gallery above will help you with early identification of the 10 worst weeds. Plus, download a free poster to help you ID the 22 worst weeds (including 12 not discussed here).

1. Crab Grass

Aliases: crowfoot grass, finger grass, pigeon grass, polish millet

This super-fast-growing annual is the worst weed plaguing veggie gardens. Thriving in nearly every U.S. state and southern Canada, it makes crabby cursers out of gardeners from California to the Carolinas. “Is there a way to win with this monster?” an Ontario gardener with more than 20 years of experience asked. Many simply pleaded, “Help!”

Yes, there is a way to win! Knowing how to spot crab grass is key. Study the crab grass illustration in the free poster, and hoe or pull up the hand-like seed heads throughout summer. This weed is hard to deal with partly because it tends to wait for warm days to sprout, which is likely after you’ve finished your spring weeding and mulching routines and your crops are already coming up. When the weather turns hot, crab grass goes into overdrive, sending out long stems that grow so fast they may flower and go to seed before you even notice them among your carrots. If you do notice them, you may pull what you think is the plant but fail to notice that you left behind some stems that had rooted at the nodes (where secondary stems sprout off from the main stem), perhaps a foot or two away from the main crown. Unnoticed, those pieces will grow and set seeds, and next summer you’ll have even more sneaky crabbies sprouting.

If you learn how to spot crab grass and remove it all each summer, you can prevent it from becoming a huge problem. Hand weeding and hoeing were rated as effective control measures, and mulching will help, as long as you spot and remove any seedlings that sneak up through the mulch. Crab grass grows best in acidic soil, so if you’re having trouble with it, test your soil’s pH and add lime to reduce the acidity if needed.

2. Dandelion

Aliases: lion’s tooth, blowball, cankerwort

Dandelion sprang in at the No. 2 spot, but — wait! — before any dandelion lovers get up in arms about this perennial plant making our worst weeds list, let’s fully acknowledge its benefits. Numerous survey respondents waxed poetic about enjoying all parts of dandelion: tender young leaves for salad greens, flowers for wine, roots for flavoring herbal vinegar, roasted roots for a coffee substitute, and other uses. Many reported feeding dandelions to their rabbits, chickens, ducks and geese, or letting them flower to serve as food for bees and other beneficial insects.

But for those of you who do want to control dandelions, our respondents reported several effective methods. Dandelions have one thick taproot that can extend more than a foot into the ground. The fluffy seed heads of dandelions appear from March to fall frost, so getting these weeds before the seeds float all over your garden is crucial.

A Washington gardener (more than 20 years of experience) reported paying neighborhood kids to dig up dandelions, including the roots. Pulling without removing some of the taproot is futile, as plants can endure their leaves being plucked several times. “This is a weed that needs the roots dug up, or it must be covered thickly so it can’t come up. Light organic mulches won’t stop it” (Oklahoma gardener, more than 20 years of experience). Others reported success with specialized tools such as a dandelion puller.

3. Bermuda Grass

Aliases: wire grass, scutch grass, devil grass

This perennial grass was a devil for 51 percent of respondents. Not only is it incredibly difficult to kill, but its roots actually give off chemicals that harm other plants (a phenomenon called allelopathy). When we asked gardeners how they handled this weed, one respondent said frankly, “It handles me.” After the weather warms up, this grass grows rapidly: A single sprig can expand to a 10-foot-wide plant in just a few weeks, and the creeping stems quickly develop a massive root system. The grass sprouts from rhizomes (pieces of root) that break off if you try to dig out the plants. Because of this, tilling tends to make a Bermuda infestation even worse.

If you’re dealing with Bermuda grass, mulch heavily. Even though this grass will probably still run above and below your mulch, the mulch will make it easier to pull. You could also try laying plastic or wooden boards over the top of the area where the grass is growing. An Arkansas gardener with more than 20 years of experience offered this tip: “Hand pulling and digging the roots is the only thing that works, and keeping the grass out by digging a moat around the garden is effective after you’ve dug out all you can.” Solarizing affected areas may also help weaken the plant (see “Organic Weed Control: What Works, What Doesn’t” near the end of this article for instructions on how to solarize).

4. Bindweed

Aliases: woodbine, lady’s nightcap, wild morning glory, creeping Jenny, hedge bells, possession vine

Bindweed, a perennial cousin to the sweet potato, got no sweet comments from the 46 percent of respondents who were dealing with it in their gardens. Many bindweed-battlers noted this weed’s persistence, and one even called it a “zombie plant” because it’s so difficult to kill. Bindweed can sprout, resprout and resprout from wide, spreading roots that can reach as deep as 30 feet underground! And, if you let this weed’s flowers go to seed in your garden, watch out: The seeds can stay viable for up to 50 years. You must dig or pull all bindweed shoots when they first appear, and keep pulling. Repeated pulling will weaken the roots until — hopefully — they die out. If you let bindweed get established, you may never be able to eliminate it.

A few respondents had tried bindweed mites with some success. A Colorado gardener said free mites can be obtained from the state insectary (a program of the Department of Agriculture) and worked best in non-watered parts of the garden. A New Mexico gardener with three to five years of experience said, “This darn weed seems to ignore herbicides, and tilling just spreads the plants around. Judicious hand weeding is the only way I have found to keep this prolific weed out of my garden.” Use a fork instead of a hoe to dig up bindweed, as you’ll leave fewer fragments behind, and dig after a rain or heavy watering when the roots are less brittle.

5. Chickweed

Aliases: starweed, satin flower, tongue grass, passerina, clucken wort, skirt button

Rather than fighting it, several gardeners used chickweed as an edible green (one gardener tosses its leaves with honey and lemon juice to make a tasty salad) and take advantage of its medicinal properties (some make it into a salve to soothe skin irritation).

­­Chickweed is a low-growing, c­old-tolerant annual that takes off in early winter. If you notice it then, turn it over with a fork and leave it in the garden. If you don’t get to it until early spring, switch to careful-hand-pulling-and-raking mode.

“Chickweed is the worst for me. It grows so quickly! If you pull it at the wrong time, the seeds pop out everywhere — argh! I hand pull early, then use fabric mulch to cover the spot” (Maryland gardener, 11 to 20 years of experience).

Several gardeners commented on how quickly this winter annual goes to seed. Seeds can germinate after being in the soil for up to 10 years, so if you have a major chickweed problem, stay on top of it before your plants set seed, and don’t compost chickweed plants no matter what stage of growth they’re in (chickweed seeds can continue to mature even after you pull the plant).

One respondent reported that this is the worst weed around perennial crops such as strawberries. It requires intensive hand weeding, but its roots are shallower and thus easier to handle than others that made our worst weeds list. Plus, it’s called chickweed for a reason: Many love feeding this weed to their poultry. “Just pull up the clumps and toss them to your ducks — they love it!” (Virginia gardener, more than 20 years of experience).

6. Ground Ivy

Aliases: creeping Charlie, cat’s foot, field balm, dollar weed

This creeping perennial had crept unwelcomingly into the gardens of 38 percent of survey respondents. Common in the eastern half of the United States, ground ivy roots at the nodes and rapidly creates an expanding, densely matted plant. Many gardeners reported that persistence was key with this weed. “Just keep pulling it out, year after year. If you keep on it, it will recede” (New York gardener, 11 to 20 years of experience). Another said, “Hand weeding does the trick, but by God it’s tedious and requires an almost vicious persistence” (Illinois gardener, 11 to 20 years of experience). Many reported that watering the affected area one hour before a thorough hand weeding session made the job easier. Tackle this task before the plants have developed seed.

A couple of gardeners reported that using raised beds to keep the soil a bit drier, plus removing all of the underground runners, had helped. As with many weeds on our list, gardeners said tilling made ground ivy come back even more vigorously, as tilling spreads root fragments around and exposes dormant seeds to water and light.

7. Canada Thistle

Aliases: creeping thistle, small-flowered thistle, green thistle

Handling this prickly summer perennial requires heavy leather gloves and strong determination. From an Ontario gardener with more than 20 years of experience: “This is hands down my biggest problem. I’ve tried everything, but it only seems to provoke this plant. I’m at my wits’ end and considering an herbicide as this weed is now costing me money in my 6-acre market garden. Help!”

Several gardeners reported getting control of Canada thistle by chopping down the plant before it went to seed and then pouring vinegar, salt, or a mixture of vinegar and salt water down the stem area. Repeat this process until you exhaust the roots. Vinegar is a broad-spectrum herbicide, and even though it’s water-soluble and will wash away after a heavy rain, avoid spraying it on weeds on windy days or pouring it right next to crops, or you could harm them, too (see “Organic Weed Control: What Works, What Doesn’t” near the end of this article for more on vinegar and other organic herbicides).

Many found success using a fork or narrow shovel to dig deep around the plants (target the mother plant, which is generally taller than others nearby), getting the whole root system, because any root fragments left in the ground will sprout into more plants. Do this when the ground is saturated so the roots will be easier to separate from the soil. Like the other worst weeds, controlling Canada thistle when it first appears is crucial. Neglect it, and you will soon have a serious problem. Some gardeners reported that their goats loved eating Canada thistle, and others said that, instead of fighting it, they used the fibers in the stems of these plants to make rope.

8. Burdock

Aliases: clotbur, wild rhubarb

Some gardeners controlled biennial burdock by pouring vinegar down the stem on hot days. One offered this tip: “The key to getting rid of burdock is to till the ground between rows or plants every 10 days in the spring and early summer, which halts the weed’s growing cycle” (Tennessee gardener, six to 10 years of experience). This makes sense, as burdock can take over in areas that aren’t worked much. This weed has a deep taproot similar to that of dandelion. Take the time to dig out the taproot of established plants when you can, as this plant “doesn’t much care whether you mulch it — it’s so vigorous, it just pushes right back up!” (Michigan gardener, more than 20 years of experience).

Some beneficial uses of this plant include eating the roots (one respondent pickles them) and using it medicinally for conditions from arthritis to sore throat. Or, you could harvest burdock leaves for composting: “The deep taproots bring up many beneficial nutrients. If you want extra material for your compost pile, purposely plant a few seed balls in rows a foot apart. Keep cutting all but two leaves off and put them in the compost bin. This will provide a nearly endless, fast-growing supply” (Michigan gardener, three to five years of experience).

9. Quack Grass

Aliases: couchgrass, quitchgrass, creeping wheat

Perennial quack grass — which one respondent called “the worst menace” — spreads primarily via thin, creeping underground rhizomes that release chemicals that inhibit the growth of other plants. “This weed requires that you remove the runner roots. A garden fork is essential for loosening the soil, followed by a rake, cultivator or CobraHead hoe to lift out the roots” (Wisconsin gardener, more than 20 years of experience). Quack grass roots break easily as you handle them, so go slowly and take care to remove root fragments as you dig up the grass clumps.

“This is the worst weed! It took three years for my wife and me to get it out of the display beds at our garden center. Dig all the roots out, and repeat often until all the bits are gone. A local church that was helping a woman weed her garden used quite a few of the youth to help, and they loved my suggestion to see who could dig the longest quack grass root” (Alberta gardener, 11 to 20 years of experience). When you or anyone helping you pulls quack grass, let it dry fully in the sun before you compost it.

Many respondents warned against tilling this weed, as doing so will make it “spawn many children.” Some reported success with cover crops such as field peas, buckwheat or crimson clover, which outcompete quack grass. This weed is common pasture grass in some areas, so if you’re buying hay mulch or composted manure (quack grass seeds aren’t phased by the digestive tracts of grazing animals) from somewhere this plant is common, make sure you’re not getting a product rife with quack grass seed.

10. Johnson Grass

Aliases: Egyptian grass, Morocco millet, false guinea grass

One gardener battling Johnson grass referred to this noxious perennial as “Bermuda grass on steroids.” If you want to beat this weed, dig out an entire clump and lay it gently in a wheelbarrow or on your sidewalk without trying to knock off the soil. After it’s out of your garden, start removing the roots from the soil, taking care to get every last fragment. Set the dug-out clumps in a pile and let them rot for several months before tossing the whole lot into your compost pile.

“Johnson grass is very serious for me. It has taken over my strawberries and asparagus beds. We’ve tried to dig up the roots, but they’re an extensive, interlocking system” (Pennsylvania gardener, 11 to 20 years of experience). If Johnson grass has taken over perennial beds, your best bet may be to move your crops to a new location during their dormant season, then plant a cover crop that will suppress the remaining grass. One respondent had success defeating Johnson grass by setting up a chicken house over the affected area, letting the birds eat the sprouting grasses every time they surfaced. Eventually, the rhizomes weakened and died.

Organic Weed Control: What Works, What Doesn’t

In our comprehensive Worst Garden Weeds Survey, gardeners rated several mulch types and organic herbicides based on their effectiveness in controlling weeds. Out of those who’d tried each type, here’s how the methods ranked, including the percentage of respondents who found each effective.

Top-Rated Mulch Types

1. Paper or newspaper (80 percent)
2. Black plastic (76 percent)
3. Straw or hay (69 percent)
4. Shredded wood or bark (65 percent)
5. Grass clippings (63 percent)
6. Living mulch (45 percent)
7. Clear plastic (21 percent)

Top-Rated Organic Herbicides

1. Vinegar (72 percent)
2. Herbicidal soap (68 percent)
3. Neem oil (57 percent)
4. BurnOut Weed & Grass Killer (42 percent)
5. Weed Prevention Plus (29 percent)
6. Weed Pharm Organic Weed Killer (23 percent)
7. Cinnamon bark crab grass killer (17 percent)

Seize the Sun. More gardeners reported success with mulches than with herbicides. As you evaluate your mulch options, keep in mind that clear plastic — the lowest-ranking mulch type — will only work to kill weeds if it’s used in summer and pulled tightly over soil, creating a hot environment weeds can’t tolerate. This method of capturing radiant heat from the sun under clear plastic is often called solarization. To solarize a bed, water areas of bare soil, and then cover the areas with clear plastic. Dig a trench and bury the edges of the tightly pulled plastic in the trench so the heat will build up, and keep the plastic cover on the garden bed for three to six weeks.

Mulches Are Strong Medicine. Several gardeners said the most successful mulch strategy was to use newspapers and/or cardboard under a thick layer of organic mulch, such as grass clippings, shredded leaves, straw, hay or a combination of these (wet your newspapers so they don’t fly around as you try to lay them down).

The tips most often cited were to do a couple of good hand weeding sessions early in the growing season before laying down mulch, and to keep reapplying organic mulches as they decompose throughout the season. Grass clippings will block weed growth better than the same thickness of hay or straw, but will usually not last as long. Grass also releases more beneficial nitrogen than hay, straw or leaves. Start your mulching regimen early, before weeds get a foothold, and don’t be shy about applying a lot — if you can, mulch 6 to 8 inches deep with hay, straw or leaves, or 2 to 3 inches deep with grass clippings. Organic mulches are a quadruple win because they suppress weeds, build fertility, retain moisture and are often free. Simply gather grass clippings and leaves from your property, or get them from friends or neighbors who don’t use lawn herbicides.

Many respondents commented that black plastic mulch is effective because it blocks light from weeds, but it can leave a mess of fragments in your garden when it eventually deteriorates. Others noted the usefulness of landscape fabric laid beneath a layer of straw for keeping weeds out of paths.

Organic Herbicides. Almost all of the gardeners who commented on organic herbicides said the ones that work only offer a temporary fix. Many said store-bought options aren’t worth the money. Many gardeners considered vinegar an effective herbicide option if applied directly to weeds on a sunny day. If you’re cautious about protecting the soil food web in your garden, note that vinegar can do minor harm to soil microorganisms.

Shelley Stonebrook is MOTHER EARTH NEWS magazine’s main gardening editor. She’s passionate about growing healthy, sustainable food and also runs Stonegrass Farms Soap Co. in her spare time. Follow her on Twitter and Pinterest.