Have you ever seen rogue, grass-like weeds on your lawn? You are not alone. Grassy weeds like crabgrass plague the landscapes of many homeowners.
Knowing how to identify and control grassy weeds can be challenging because, for one, they look a lot like turfgrass, and they can be hard to identify.
The other challenge is finding weed control methods that will kill grassy weeds but not the grass you want to keep. This how-to guide will help you identify grassy weeds and determine the best method of weed control for your lawn and garden.
What are grassy weeds?
As their name implies, grassy weeds are unwanted plants that look like grass. In fact, many of them belong to the family Poaceae, commonly known as true grasses.
When comparing grassy weeds to broadleaf weeds, grassy weeds have the characteristics of monocots, including:
- Long, narrow leaves similar to blades of turfgrass
- Alternating leaves
- Hollow, rounded stems with hard, closed nodes
- Small, thin root systems (also known as fibrous roots)
Grassy weeds vs. turfgrass: weed identification
Identifying grassy weeds from turfgrass can be difficult because they are both types of grass. However, you can identify many grassy weeds by comparing them to your turfgrass. Some characteristics to take note of are:
- Leaf blades
- Seed heads
- Colors
- Flowers
- Root system
- Growth habit
- Growing season
Common grassy weeds
Here are some common grassy weeds that you might find in your lawn and their defining characteristics:
Annual bluegrass (Poa annua)
Often contaminating Kentucky bluegrass seed packets, annual bluegrass is a European native that grows throughout the United States. Like Kentucky bluegrass, it is a cool-season grass. However, it is annual with a short lifespan, only living for 12 months at most.
Annual bluegrass has a shallow root system and thrives in moist areas with regular irrigation, although it will grow pretty much anywhere. It’s also quite a nuisance on golf courses.
- Life cycle: Winter annual
- Spreads through: Seeds
- Growing season: Germinates in the late summer or early fall, grows in the winter, and typically dies during the summer heat.
- Distinct characteristics:
- Leaves: Smooth and bright green with two lines and inward-curling leaf tips, similar to a canoe or a boat
- Seed head: White, pyramid-shaped
Other weed grasses belong to the Poa genus. Some of these are rough bluegrass (P. trivialis) and bulbous bluegrass (P. bulbosus). There’s also a perennial variant of annual bluegrass that looks quite similar. It lives longer and is more difficult to get rid of.
Crabgrass (Digitaria spp.)
Several crabgrass species terrorize lawns all over the United States. They’re one of the most common lawn weeds. These European summer annual grasses favor thin, weakened turfgrass and they get their name from the branches they form as they grow, which look like crab legs.
It is an aggressive grower that will choke out any other plants and eventually take over your yard. Once it gets a foothold in your lawn, getting rid of crabgrass is difficult. The weed produces up to 150,000 seeds which can lie dormant for years.
It is important to prevent this sun-loving grass from resprouting even if you don’t see any living plants left. Common crabgrass species that invade lawns include large or hairy crabgrass (Digitaria sanguinalis) and small crabgrass (D. ischaemum).
- Life cycle: Summer annual
- Spreads through: Seeds
- Growth season: Germinate when soil temperatures reach 55 degrees Fahrenheit, which is usually in the early spring or late summer.
- Distinct characteristics:
- Leaves: Smooth crabgrass has wide and short leaves, while large crabgrass has longer ones. The leaves are yellow-green to blue-green.
- Stems: Large crabgrass has hairy stems. Sometimes, the stems are purplish.
- Flower spikes: Two to five finger-like branches
- Growth pattern: Tufted, upright growth habit, meaning it spreads along the ground and its leaves spread outwards.
Goosegrass (Eleusine indica)
Because it looks similar to crabgrass, goosegrass is also called silver crabgrass, white crabgrass, and wiregrass. You can differentiate this Eurasian summer annual from crabgrass by its white or silver-colored base stem.
Often found in disturbed areas, goosegrass grows in a wide variety of conditions. However, it is not cold-resistant.
- Life cycle: Summer annual
- Spreads through: Seeds
- Growth season: Germinates in the late spring and grows during the summer.
- Distinct characteristics:
- Leaves: A darker green than crabgrass.
- Stems: White or silver-colored at the base and flat, letting it survive low mowing heights
- Seed head: Has three to seven spikes. The seeds are arranged in two rows that look like a herringbone pattern.
- Growth pattern: Clumping, upright
Sandbur (Cenchrus spp.)
Also known as sandspur, sandbur gets its name from its spiky seed heads (burs). These prickly and weedy grasses thrive in sandy soils but can grow elsewhere.
Common sandbur varieties include southern or spiny sandbur (C. echinatus) and the perennial common sandbur (C. spinifex, also known as coastal sandbur or stickyweed).
- Life cycle: Summer annual or perennial grass (depending on species)
- Spreads through: Seeds
- Growth season: Germinates in the late spring and flowers in the late fall.
- Distinct characteristics:
- Leaves: Sandpaper-like texture
- Seed head: Produces burs that are thorny and painful to the touch
Foxtail (Setaria spp.)
Foxtail is a summer annual weed grass that gets its name from its spiked seed heads, which look like a drooping fox’s tail. There are many species of foxtail, but the most common species are the yellow foxtail (Setaria pumila), green foxtail (S. viridis), and giant foxtail (S. faberi).
These common weeds can survive in many different environments but often grow on disturbed sites. They are a nuisance for homes with pets, as their barbs are dangerous to dogs and cats.
- Life cycle: Summer annual
- Spreads through: Seeds
- Growth season: Germinates in the late spring, grows during the summer, and dies in the fall.
- Distinct characteristics:
- Leaves: Coarse, yellow-green to blue-green. Around 12 inches long and ½ inch wide
- Seed head: Cylindrical, 2 to 3 inches long. Looks like a fox’s tail.
Nimblewill (Muhlenbergia schreberi)
Unlike most of the other grassy weeds on this list, nimblewill is a warm-season perennial weed. Often mistaken for Bermudagrass, nimblewill spreads through stolons and forms mat-like patches in your turfgrass.
Its blue-green color, coarse-textured leaves, and a tendency for early dormancy make Nimblewill stick out in most cool-season lawns but blend in easily in warm-season lawns.
- Life cycle: Perennial
- Spreads through: Seeds and stolons
- Growth season: It germinates in the spring and flowers from August through October.
- Distinct characteristics:
- Leaves: Tan when dormant, blue-green to blue-gray otherwise
- Seed head: Has long “hairs”
Dallisgrass (Paspalum dilatatum)
Related to Bahiagrass, dallisgrass is another warm-season perennial grassy weed. Originally from South America, dallisgrass migrated to the U.S., and you can find it throughout the southern half of the country.
In lawns, dallisgrass is often mistaken for Bahiagrass. While it’s young, it also resembles crabgrass.
- Life cycle: Perennial
- Spreads through: Seeds and rhizomes
- Growth season: It is dormant during the winter, but it returns in the spring. It grows for most of the year, from the spring to the fall.
- Distinct characteristics:
- Leaves: Wider than most turfgrasses
- Growth pattern: Clumping
- Stems: Hairy with a purple-red base
Quackgrass (Elymus repens)
A European native, quackgrass thrives in moist or disturbed soils, though it isn’t picky and can grow in most soil types. This cool-season grass is blue-green, forming dense patches. Its seeds can stay dormant for two to three years before germinating, making it resilient and hard to control.
If not mowed regularly, quackgrass can grow very tall, up 4 feet. Quackgrass, also known as twitch grass and couch grass, plagues weak and unhealthy lawns.
- Life cycle: Perennial
- Spreads through: Seeds and rhizomes
- Growth season: Germinates in the spring or fall and flowers during the early summer. It grows until late summer or early fall.
- Distinct characteristics:
- Leaves: Smooth and flat
- Growth pattern: Dense clusters
- Clasping auricles: One of the distinguishing features of quackgrass is its clasping auricles (small projections resembling clasped hands that extend upwards on its stem).
How to control grassy weeds
There are several ways to control existing grassy weeds.
Hand-pulling
If you already have grassy weeds on your lawn, hand-pulling can work, but only if your infestation is very small. It is also worth noting that this method does not work for grassy weeds that spread through stolons or rhizomes.
When pulling weeds, make sure to get as much of the roots as possible. Hand-pulling works best if you stay on top of the task, so stay vigilant and pull weeds as soon as you spot them in your yard. Here are a few simple tips to help you stay on top of your weed infestation:
- Remove weeds while they are young before they have bloomed or developed complex root systems
- Be sure to remove the entire weed, including roots, bulbs, or tubers
- Use a screwdriver or dandelion fork to help remove weeds with a taproot, like dandelions or spotted spurge
Pre-emergent herbicide
Hand-pulling is the cheapest way to get rid of weeds, but it is time-consuming. Sometimes, an herbicide application is necessary, especially for grassy weeds with stolons or rhizomes.
Pre-emergent herbicides prevent weed seeds from germinating and are safer for your turfgrass. While they won’t do anything against existing weeds, they prevent weed sprouts from popping up in the first place.
Pro tip: Before applying herbicides, read the label instructions and any warnings on the product.
Post-emergent herbicide
Post-emergent herbicides target existing grassy weeds. Look for a selective herbicide that specifically targets the variety of weeds growing in your yard. Here are some helpful tips:
- For a crabgrass killer, look for herbicide products with MSMA or DSMA.
- Quinclorac 75 DF works against most grassy weeds.
- Glyphosate is another effective post-emergent grassy weed killer.
In the worst-case scenario, you should remove your turfgrass and start from scratch for severe infestations or a weak lawn.
Pro tip: When your lawn is over 50% weeds, use a non-selective herbicide (with caution). This method will kill the weeds and your grass. Overseed with new grass seed or install new sod after weed eradication.
Homemade weed killer
If you prefer a more environmental approach and aren’t afraid of a little DIY project, consider homemade weed killers. Just beware, these homemade solutions are non-selective and will harm healthy turfgrass and landscape plants. Many also require multiple treatments for complete weed elimination.
How to prevent grassy weeds
The adage “an ounce of prevention is worth a pound of cure” is true when it comes to controlling grassy weeds. In other words, keeping a healthy lawn is the best way to control grassy weeds. Healthy turf will outcompete weeds—grassy or otherwise.
Fertilize properly
When you fertilize your lawn in the right amounts at the correct time of year, it provides your lawn with nutrients to grow strong. Improper fertilization can injure or kill your lawn grass.
Mow frequently
Mowing your grass isn’t just about preventing snakes from getting into your yard or keeping your grass at a manageable length; it is important to its health as well. Conversely, frequent mowing can also injure grassy weeds.
Make sure to mow your lawn to the proper height. Take off no more than one-third of the grass’s height each time, and be careful not to scalp your lawn. Longer grass shades the soil, discouraging weed seeds from germinating. However, cutting your grass short exposes the soil to the sun, providing excellent conditions for weed growth.
Water appropriately
Water your lawn with 1 to 1 ½ inches of water per week–no more and no less.
Too little water will dry out your lawn and weaken it, leaving it defenseless against weeds. However, too much water feeds weeds, helping them grow. And remember, many grassy weeds thrive in moist environments.
FAQ about grassy weeds
Can turfgrasses ever be classified as weeds?
By definition, weeds are unwanted plants. Some lawn grass types are desirable in one area but considered an aggressive weed in others. Here are some turfgrasses that are considered grassy weeds by some homeowners:
● Bermudagrass
● Zoysiagrass
● Creeping bentgrass
● Tall fescue
● Carpetgrass
Is nutsedge a grassy weed?
Although nutsedge (also called nutgrass) looks like grass and is often considered a grass-like weed, it belongs to a different category, sedges.
Unfortunately, sedges can be even more difficult to get rid of when compared to typical grassy weeds, so it’s important to make the distinction and identify nutsedge and other invasive sedges.
What are other common types of weeds?
Grassy weeds aren’t the only unwanted invaders in your yard; broadleaf weeds will often come to invade your lawn too. In addition to grassy weeds, some of the most common lawn weeds include:
- Chickweed
- Clover
- Dandelion
- Dollarweed
- Ground ivy
- Lambsquarter
- Oxalis
- Ragweed
- Spotted spurge
- Thistle
When to look for professional weed control services
If you’re still unsure about what grassy weeds are growing on your lawn, it’s time to call in the experts. Weed control professionals have the knowledge and expertise to identify and control your weed problem, no matter if your weeds are grassy or broadleaf.
Let Lawn Love connect you with a local landscaping pro who can help you control your weeds and transform your turfgrass into a healthy, and vibrant landscape.
Main Photo Credit: Linnaea Mallette | PublicDomainPictures | CC0
