What Does Crabgrass Look Like?

Lawns accentuate your home’s exterior and provide a ground for recreation. Maintaining the yard could be the most cumbersome task lawn keepers face — from endless mowing, dethatching, fertilizing, aerating, and watering. Weeds encroachment (dandelions, crabgrass, dallisgrass, and ground ivy) on the property destroys the yard’s ambiance and may take over if not controlled.

Quick identification of crabgrass weed on your lawn allows you take most effective preventative solutions for it. Crabgrass has coarse textured green or yellow green leaves that can be hairy or hairless. The crabgrass stem is prostrate and has roots in the internodes and thrives at temp above 55oF.

I’ll dive deep to know crabgrass’ features and characteristics.  You’ll also get tips on keeping the weed at bay from your yard.

What does crabgrass look like + Pictures

Crabgrass (Digitaria spp.)  is an annual warm-season weed native to Eurasia and Europe. It is prevalent in the northern lawns, where they thrive during summer when cold season grasses are stressed and dormant.

Crabgrass has a prostrate growth habit. It lies low on the ground and survives 1 ½ inch mowing height. Its leaves are coarse-textured, lime-green, or yellowish-green. The seedheads are fingerlike and have racemes or spikes that emerge from different points at the tip of the stem.

Crabgrass has a rolled vernation. The leaf sheaths and leaves of crabgrass can be hairy or hairless. You can also identify crabgrass’s large, membranous, and toothed ligule. The ligule is toothed, membranous, and large. Additionally, it has no auricles.

Crabgrass has numerous varieties. Smooth crabgrass and hairy crabgrass are the most common.

Smooth crabgrass (Digitaria ischaemum), also called small crabgrass, is more prevalent than large crabgrass. Its leaves and leaf sheath have no hairs, although the lower part of the stem has few hairs. The base of its stem is purplish. Smooth crabgrass lies lower to the ground than large crabgrass.

Meanwhile, large crabgrass (Digitaria sangunalis), also called hairy crabgrass, has hairs on its leaves’ surface and the leaf sheath. Large crabgrass seedlings appear light green and are more upright than smooth crabgrass seedlings.

Crabgrass seeds’ germination highly depends on the soil temperature. The crabgrass seeds germinate in spring when the temperature for four to five consecutive days is above 55oF. Vegetative growth is rapid from early to mid-summer. Late summers have short days. Therefore, vegetative growth slows.

The weed enters its reproductive stage in late summer, producing numerous seeds on the lawn. The plant dies at the first fall frost, leaving seeds that remain dormant in the ground for several years only to regrow in favorable temperatures. 

Crabgrass poses a perennial problem yearly because of its long-lasting seeds. Knowing how to identify, help to get rid of crabrass from your lawn.

How do I know if I have crabgrass?

You’re more likely to notice you have crabgrass in summer. It grows faster in hot weather when cool-season grass growth is suppressed. Crabgrass has coarse-textured, lime green conspicuous leaves, easily noticeable when growing among dark green turf on the lawn. The stem is prostrate and has roots in the internodes. Some crabgrass varieties form clumps. 

Crabgrass is an opportunistic, competitive weed that grows when the turf is thin, and there are empty spots on the lawn. Understanding these features will help you know when to apply crabgrass preventer.

 When the turf is mowed too short, crabgrass seeds will germinate in favorable temperatures and thrive on the lawn. The weeds are low growing and tolerate a short mowing height of less than 1 ½ inches.

Less competitive grasses like annual ryegrass are more vulnerable to crabgrass invasions because crabgrass grows faster than them.

When the grass is under fertilized, it becomes thin and less competitive. Underfertilized lawns present the optimum space for diseases, pests, and weeds like crabgrass.

When annual winter grasses like annual bluegrass and ryegrass die, they leave bare spots on the lawn, providing space for crabgrass to grow.

In the hot summer months, cool-season grasses get stressed because of the extreme temperatures. They, therefore, become dormant and thin. Crabgrass spreads fast and takes over the yard. These features will also help differentiate between quackgrass vs. crabgrass for easy and quick management.

Varieties of crabgrass

There are about 35 crabgrass varieties, with smooth and hairy crabgrass as the most prevalent in North America. Other than the most common crabgrass, Blanket crabgrass, southern crabgrass, India crabgrass, and tropical crabgrass are the other varieties found on lawns and gardens.

  • Smooth or small crabgrass: Has no hairs on the leaves and the leaf sheath. Their leaf blades are more expansive than large crabgrass.
  • Large or hairy crabgrass: Has dense hairs on leaf surfaces and the leaf sheath. Large crabgrass has broader leaves and appears taller than smooth crabgrass.
  • Blanket crabgrass (Digitaria setorina): Has creeping stolons with short, hairy leaf blades. The leaf blades crowd on the creeping stem. Blanket crabgrass has a longer lifespan than other types of crabgrass, thus called annual summer perennate weed.
  • India crabgrass (Digitaria longifora):  India crabgrass is mat-forming and lives longer than blanket crabgrass. India crabgrass has no hairs on the leaf sheaths. Its ligule is membranous. India crabgrass has a creeping stem and spreads by stolons and seeds.
  • Southern crabgrass (Digitaria ciliaris): Forms clumps and has branched stems. Its leaf blades have no hairs. Its seedhead rises from different spots along the stem.
  • Tropical crabgrass (Digitaria bicornis): Has long leaves with hairs on the surfaces. The ligule is membranous and visible from the base of the leaf blades. Tropical crabgrass has a creeping growth habit.

How does crabgrass spread

Crabgrass is an annual weed that spreads through its numerous seeds. It has no rhizomes or stolons. The seeds germinate around spring when the average temperature is above 55oF for four to five consecutive days. 

In early summer and mid-summer, the weed grows vegetatively until the days become shorter. In late summer, crabgrass enters the reproductive stage, producing numerous seeds in the yard. The plant dies in the first frost of fall.

The seeds remain dormant throughout winter until spring when temperatures become favorable again to promote their germination. The seeds grow, and the cycle continues for several years, as long as the seeds remain on the lawn.

The best way to keep crabgrass seeds from germinating on the lawn is by applying pre-emergent herbicides. Because the seeds develop when the average soil temperature is above 55oF for four consecutive days, apply the herbicide before the temperatures reach 55oF. Several applications are needed to kill the seeds from the lawn altogether.

If crabgrass has already grown on the lawn, wait till the first frost of fall. They will automatically die. Later, kill their seeds as earlier directed. Otherwise, use post-emergent herbicides such as Tenacity and MSMA to kill the crabgrass. Be careful not to destroy your turf grass, as most post-emergent herbicides are non-selective.

What’s the best way to keep crabgrass from regrowing?

The best way to keep crabgrass from regrowing after killing their seeds is proper turf management to promote healthy, competitive grass. These practices include:

  • Mowing the lawn higher: Cutting grass taller blocks sunlight from reaching the ground to favor crabgrass seeds germination. Raise your mower deck higher when mowing.
  • Fertilizing the grass: Fertilizers provide nutrients to grass to grow them healthy and dense, thus becoming more competitive than crabgrass. Apply fertilizers when the grass is actively growing.

Slow-release fertilizers are recommended to feed the turf longer. Remember to apply the recommended amount of fertilizer to avoid burning the grass.

  • Fill bare spots on lawns– Bare spots create spaces that allow crabgrass to grow—Overseed bare spaces with new grass seeds to prevent the weeds from growing.
  • Grow more competitive grass species– Tall fescues and Kentucky bluegrass are more competitive than annual ryegrass and bluegrass because they are perennial grasses. Plant more competitive grasses like fescues to discourage crabgrass from growing.
  • Eliminate pests and treat diseases: Pests and diseases thin grasses and make them susceptible to weed invasion. Use recommended fungicides to treat diseases and remove pests from the lawn.

Here is the best crabgrass killer that won’t kill grass on your lawn.

References

  1. University of Maryland Extension: Crabgrass.
  2. University of California Agricultural & Natural Resources: Crabgrass Management.

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