The moment weeds like dandelions, chickweed, crabgrass and purslane pop up in the grass, you likely dig them up or douse them with a spray bottle full of Roundup or another weed killer. But hold back on your trigger finger and do your homework first. Identifying the weeds growing in your yard could provide important clues about soil health
Before you kill your lawn weeds, Debbie Dillon, a horticulture extension agent at North Carolina State University, suggests identifying the species of weeds growing in your lawn and using them as a tool to learn more about your soil.
Common lawn weeds are called “indicator plants,” she explains. Their presence indicates that certain soil conditions are present.
Weed identification can tell you what conditions are in your soil, allowing you to identify the right weed control measures.
“A soil test will give you the basics about pH and soil fertility, but the weeds in your garden can give you even more information,” Dillon says.
These common weeds can alert you to problems in the soil or in your lawn care habits.
First introduced in the late 1800s, bindweed has become one of the worst invaders in Western states. This perennial weed has many names, including perennial morning glory, creeping jenny, bellbine, sheepbine, and cornbind. Once established, its roots can reach 20 feet.
What bindweed is telling you: You may not be watering enough. It outshines almost all other plants in tolerating drought and seldom thrives in wet or waterlogged soils.
This late spring-flowering plant has many benefits but detracts from the look of a uniform lawn. The most-common variety, white clover, was a common lawn seed ingredient until the introduction of broadleaf weed-killers.
What white clover is telling you: Yards with compacted soil, acidic soil and low nitrogen levels are prime sites for clover to pop up. Clover is drought tolerant and thrives in drought-stressed lawns. It also provides some benefits: The extensive root system and drought tolerance help provide resources to the organisms living in the soil that contribute to a healthy lawn.
“Beekeepers love clover and have been educating people about the benefits and a lot more people are open to having clover in their lawns,” Dillon says. “If you have a moist area, you might try planting white clover.”
The winter annual weed germinates in the fall and spreads its seeds in the spring.
What chickweed is telling you: Chickweed in your turfgrass indicates that you have moist or poorly-drained soil. Dillion suggests cutting back on irrigation and adding organic matter to make the soil more porous, improving drainage. Aerating the lawn also helps reduce compaction and allows air, water and fertilizer to penetrate the soil, which helps reduce the number of weeds. If you have chickweed or other weeds that are signs of soggy soil, you may also consider removing the grass and planting a rain garden, says Dillon. The common chickweed is very similar in appearance to its cousin, the mouse-ear chickweed.
It’s a low-growing, fast-spreading grassy weed. It’s most vigorous in taller grass.
What crabgrass is telling you: A lawn filled with crabgrass could indicate high soil fertility.
“High soil fertility could be a sign that you are over-fertilizing and putting too much nitrogen on your lawn,” Dillion says. “You should test your soil to see what nutrients it needs.”
Pre-emergent herbicides, applied in early spring before the soil temperature rises and seeds start germinating in late spring to early summer, is the most common and effective treatment.
Bright green leaves with scalloped edges mark the creeping Charlie. The “creeping” part comes in from its growth pattern: It relies on above-ground runners called stolons.
What creeping Charlie is telling you: Because it likes shaded areas with damp, fine soils, eliminate those conditions. Trim back the shade and cut back the moisture where either of those is possible. Amend the soil to reduce the fineness of its texture so it can’t creep so easily.
Dandelions are opportunist broadleaf weeds whose yellow flowers mature to puffable white balls, and, Dillion says, it will be a continual battle to control them.
What dandelions are telling you: Acidic soils with low calcium levels and excessive potassium allow dandelions to thrive. Test soil pH to see if your lawn is too acidic. You can add limestone (calcium carbonate), bone meal or crushed oyster shells to help reduce the acid in the soil and make it more alkaline, which will make it less hospitable to the ubiquitous yellow weeds.
There are more than 130 species of the fast-spreading summer annual.
What knotweed is telling you: Knotweed thrives in compacted soils and often pops up along well-worn paths created by heavy foot traffic.
“Aerating the soil and following up with topdressing with compost can help loosen the soil,” Dillon says. “Adding organic matter [with compost] acts as a slow-release of nutrients and the earthworms and beetles will help mix it into the existing soil.”
Description: Cotton, hibiscus and okra are members of the same family of plants. One variety even contributed a key ingredient to marshmallow. But for regular homeowners, the common mallow in the lawn is just a crinkly leafed weed. This annual (or biennial) develops a deep taproot that makes it tough to pull.
What mallow is telling you: You’re not looking over your lawn or garden enough. The plants begin growing with the first rains of the fall, but become woody and tall if they’re allowed to take root.
Stiff, grass-like blades wider than most other turfgrasses mark nutsedge. It’s often called nutgrass but is a true sedge. Once established, it is drought tolerant and tough to kill, spreading by underground runners (rhizomes) that are can reach a foot or more in length.
What nutsedge is telling you: You water too much on poorly draining soil. Amend the soil with sand to help it drain faster.
This common weed, also known as wood sorrel, produces small pink, yellow or white flowers.
What oxalis is telling you: Similar to common chickweed, oxalis is an indicator of moist, poorly drained soils. Oxalis growing in your lawn is also a sign the soil is low in calcium and high in magnesium.
Replacing turf with a rain garden is one option to improve drainage. Drain tiling, which involves installing a series of perforated pipes to redirect water and remove moisture and help water drain, is another — but Dillon warns that it’s expensive.
Plantain weed is never hiding — this perennial’s big broad leaves, 2-6 inches in length, and thick stalks make it easy to spot. Both the common broadleaf plantain and buckhorn plantain varieties were introduced from Europe, and have some medicinal applications. But unless you’re growing them to cure respiratory ailments, they’re just weeds.
What plantain is telling you: You have damp and compacted soil. Aerate your soil, avoid overwatering. Mowing your grass to the proper height also helps by removing any seedheads before they germinate. All these good lawn care techniques will encourage a healthier lawn that should “shade out” plantain seedlings.
This fast-growing, drought-tolerant plant will outcompete just about any other weed. It forms dense mats on red stems. Edible varieties are coveted in some high-end restaurants, but for most of us, it’s just an obnoxious pest.
What purslane is telling you: You may be doing things right. While an opportunist, purslane does best in well-draining soil with a lot of sand and loamy organic material —exactly what you’re supposed to create as the soil for an ideal lawn. It prefers new lawns and poorly maintained lawns, so if that includes you, get out the hoe, the herbicide or both.
A low-spreading summer annual that forms a dense mat that sends shoots in all directions from a single point and hugs the ground.
What spurge is telling you: You don’t have enough grass in your lawn. Most weedy spurges don’t like competition, so they burst forth in bare patches. Aerate and overseed to create a healthy lawn that will outcompete spurges.
You’ll know when you have thistle. Its spiny leaves and stalk will introduce you if you brush against it. If a new plant is left on its own, it can grow up to 6 feet tall. Don’t let it get to that stage: Root systems of a mature thistle can reach 10 feet.
What thistle is telling you: You may have slacked off in your basic lawn care, especially if it has been a cool, wet summer and falls — those are the times when thistle seed production shoots up. If you see them, your lawn wasn’t healthy enough to have out-competed the thistle. Hand-remove them and overseed.
Reading Your Weeds
Reading your weeds can provide important clues about your lawn but the best defense against weeds is a healthy lawn.
Dillion recommends choosing the right types of grass cool season or warm season species depending on your location, aerating the lawn, letting the grass grow a little longer to promote healthier roots and fertilizing at the correct times (and with the right levels of nutrients) can contribute to a healthier lawn and fewer weeds.