Crabgrass is a problematic summer annual weed that can quickly take over lawns. With its spreading stems and coarse texture, this opportunistic grass thrives in the hot, dry conditions of mid to late summer. Homeowners often struggle to discern crabgrass from desirable lawn grasses, leading to confusion about the best control methods. By learning the identifying traits and life cycle of crabgrass, you can better understand why it’s so invasive and how to banish it from your yard.
Appearance and Growth Habits That Set Crabgrass Apart
Crabgrass gets its name from its low-growing, sprawling stems that resemble crab legs radiating out from a central base. Unlike upright, clump-forming perennial grasses, crabgrass forms a flat, spreading mat that hugs the ground. Other distinctive physical characteristics include:
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Blade texture Broad, coarse blades with slightly wavy, jagged edges The blades are often compared to pencils in width
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Color Light green or yellow-green color that contrasts with surrounding lawn grass
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Height and density: Grows low, from 2 to 6 inches tall. Forms patches and bare spots rather than an even, dense turf.
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Stems: Sturdy, smooth, often reddish stems that root at nodes where they touch the ground.
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Seed heads: Bushy panicles that resemble crab claws appear in late summer.
How Crabgrass Grows and Spreads
Crabgrass is an annual weed, meaning it completes its entire lifecycle in one growing season. Here is how it typically progresses:
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Spring: Begins germinating when soil temperatures reach 55°F for 4-5 consecutive days. Emerges in early summer.
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Summer: Grows rapidly and produces extensive roots and stems during summer heat. Spreads through ground-rooting stems.
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Fall: Forms seed heads by late summer, then dies after first frost. Each plant can produce 150,000 seeds!
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Winter: Seeds lie dormant through winter and re-emerge the following spring.
Why Crabgrass Is Such a Nuisance in Lawns
Unlike perennial lawn grasses, crabgrass sprouts from seeds each year, so it thrives in thin or bare lawn areas where it has room to establish. A healthy, dense lawn will crowd out crabgrass and prevent seeds from germinating. But once crabgrass takes hold, it can be a challenge to control for several reasons:
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Aggressive spreading habit quickly overtakes desirable grass.
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Broad leaves and low growth allow it to evade mower blades.
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Extensive root system makes manual removal difficult.
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Prolific re-seeding leads to recurrent infestations.
Distinguishing Crabgrass from Look-Alike Grasses
Crabgrass is often confused with coarse perennial grassy weeds as well as grassy annual weeds like foxtail. Observing texture, color, growth habits, and time of emergence can help confirm an accurate identification.
Perennial Grass Weeds
Tall Fescue – Unlike the annual crabgrass, clumps of coarse bladed perennial fescue will persist year-round. It has a darker green color and faster vertical growth habit compared to crabgrass.
Nimblewill – This perennial grass has thin, bluish-green leaves and looks dried out in winter in cold climates when crabgrass dies back. It also lacks the spreading crab-like growth habit.
Quackgrass – Quackgrass shoots up in bunches rather than spreading out like crabgrass. Its long, vertical leaves have a prominent whitish midrib lacking on crabgrass.
Annual Grass Weeds
Foxtail – Unlike crabgrass, foxtail has a bushy, bristly seed head resembling its namesake. The leaves are longer, narrower, and lack the crabgrass’s wavy margins.
Goosegrass- Goosegrass emerges earlier than crabgrass and has a more upright, bunch-forming growth habit compared to the crab-like spreading stems of crabgrass. The leaves are finer textured as well.
Timing, Prevention, and Control
One of the best ways to identify crabgrass is by getting familiar with its typical emergence timing. In most regions, it will begin to sprout in early to mid spring and will be noticeable by early summer if conditions are favorable.
Putting down a pre-emergent herbicide in early spring before soil temperatures reach 55°F is an effective preventive strategy. Promoting lawn health through proper mowing, irrigation, and fertilization is also key to deny crabgrass the bare, thin spots it needs to establish. Post-emergent herbicides specifically targeting crabgrass, along with hand weeding, can help manage spot infestations.
Adult Japanese beetle damage Japanese beetles damaging an apple tree. Japanese beetle damage on a rose.
Adult Japanese beetles feed on the leaves, flowers and fruits of many different plants. Preferred plants include rose, grape, linden, apple, crabapple, cherry, plum and related trees, birch, elm, raspberry, currant, basil, Virginia creeper, hollyhock, marigold, corn silks and soybean.
They skeletonize leaves by feeding on tissue between the major veins giving them a lace-like appearance. Damaged leaves turn brown and may fall off. Japanese beetles on raspberries.
Adult Japanese beetle damage usually affects only the appearance of plants.
- Healthy, mature trees and shrubs can tolerate a lot of feeding without significant, long-term injury.
- Young or unhealthy plants may be stunted, injured or even killed from severe, persistent feeding.
- Healthy flowering plants such as roses can survive Japanese beetle feeding. But the blossoms are often ruined by the insects.
- Fruits, vegetables and herbs can tolerate limited leaf feeding, but severe damage may affect plant growth and reduce yield.
- Regular harvesting during July and August can decrease feeding on edible parts of the plant.
Damage caused by Japanese beetles
Japanese beetles are a serious pest of flowers, trees and shrubs, fruits and vegetables, field crops and turf. Adults feed on more than 300 plant species, whereas the grubs feed mainly on the roots of grasses.
Identify Crabgrass In ANY Lawn In Just 3-Steps
FAQ
How do I get rid of crabgrass on my lawn?
Use a post-emergent herbicide labeled for crabgrass. If you already have a crabgrass infestation, then a chemical treatment may be necessary to tackle the problem. All lawn weed herbicides are not made the same. Some will kill your regular grass and other common weeds.
What grass is mistaken for crabgrass?
Often mistaken for its annual lookalike, crabgrass, quackgrass spreads through extensive underground networks of rhizomes as well as seeds. The easiest way to tell whether you have quack grass or crabgrass is to examine the leaves.
What does full grown crabgrass look like?
Crabgrass is a light green, grass-like weed that appears in summer, rapidly forming low-growing mats in lawns or in cracks in the sidewalk or driveway. Wide, coarse leaf blades grow out from the center in a star-shaped pattern that makes the rounded mats look a bit like a bunch of crab legs, hence the name.