What Is Crabgrass?

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Crabgrass is a common grassy weed that has a knack for infiltrating lawns, disrupting the carefully nurtured greenery you work so hard to establish. As a homeowner, you must know how to spot and deal with crabgrass on your property as quickly as possible. Even one single crabgrass plant emerging in your lawn could spell disaster for the rest of your yard if it is not dealt with promptly and properly. 

Let's get down into the weeds about what crabgrass means for the health of your lawn and yard, and be sure to check out CPM for more information!

Identifying Crabgrass

One key characteristic of crabgrass is its growth habit, as crabgrass typically forms low, spreading clumps that grow from a central point. The prostrate growth habit that stems from the center of the plant is often described as a star-shaped pattern when viewed from above. The leaves are light green and have a coarse texture, with blades that are wide and flat. Upon closer inspection, crabgrass can also be identified by its slightly rolled stems that will typically appear white or faint pink at the base. It is often said that viewing crabgrass from above can reveal a crab leg-like appearance due to the weed's long, sprawling stems, especially when a pink hue is present.

Another distinguishing factor is the presence of finger-like spikes at the leaf junctions, known as ligules. Crabgrass produces seed heads that are long and thin, kind of like fingers. They can be anywhere from 6 to 24 inches long, and they often have a reddish color at the tips. These seed heads appear in late summer or early fall, and they're one of the ways that crabgrass spreads itself so quickly and easily. Crabgrass tends to thrive in areas with poor lawn density or bare soil, making regular lawn maintenance essential to prevent its establishment. 

What To Look For:

  • Faint green leaves
  • Flat, wide leaves
  • Coarse texture
  • Rolled stems
  • Occasional hairs on sheaths
  • Low, star-shaped growth
  • Finger-like seed head
  • Shallow, fibrous roots

Types Of Crabgrass

Large/Hairy Crabgrass (Digitaria sanguinalis): Hairy crabgrass (pictured above) is often referred to as large crabgrass, and both nicknames are clues on how to differentiate this species from smooth crabgrass. This variety is more common in the northern United States, while smooth crabgrass is more prevalent in the South. Its leaves tend to grow longer than those of small crabgrass, reaching maximum lengths of up to 3.5 feet. One of the quickest ways to identify hairy crabgrass is by finding small hairs growing on the sheaths of leaf blades, which are not present on smooth crabgrass. The leaves of large crabgrass are also typically wider than the leaves of small crabgrass, but height and hair are always your most obvious signs. Usually, but not always, hairy crabgrass stems will have a more white color near the base.

Small/Smooth Crabgrass (Digitaria ischaemum): This species is the most common variety of crabgrass in the United States. As you can probably guess from the "small" nickname, this species develops smaller leaves and grows lower to the ground than large crabgrass. Typically, smooth/small crabgrass does not exceed 2-2.5 feet in length (in ideal conditions), and the individual blades of grass are slightly less wide than those of hairy crabgrass. This weed is also referred to as smooth crabgrass because the sheath and leaves of this species do not have any hairs, unlike its aforementioned counterpart. You may also be able to identify small crabgrass by a faintly red or pink stem that is observable when viewed from above.

Life Cycle Of Crabgrass

The life cycle of crabgrass follows an annual pattern, beginning with seed germination in the spring. Crabgrass is a warm-season annual weed that grows best in full sun and well-drained soil. It typically germinates in late spring, when soil temperatures reach 55-60 degrees Fahrenheit, and it thrives in areas with bare soil or thin grass cover. Once germination occurs, young crabgrass plants develop rapidly, taking advantage of available sunlight and nutrients. As temperatures rise, crabgrass enters its rapid growth phase during the summer months, with the plants spreading through tillering and producing additional shoots. Crabgrass will continue to grow and spread throughout the summer months. In late summer or early fall, the plant will produce seed heads and then die off with the first frost.

The reproductive stage of crabgrass usually commences in mid-summer when the plants start forming seed heads. These seed heads contain many small seeds that are dispersed by wind, water, or human activity, contributing to the weed's prolific nature. As fall approaches, mature crabgrass plants begin to decline, and the first frost signals the end of their life cycle. However, the cycle continues as the dispersed seeds overwinter in the soil, lying dormant until the following spring when conditions become favorable for germination once again.

How Does Crabgrass Spread?

Crabgrass is known for its efficient and prolific means of invasion, primarily relying on seed dispersal for its spread. A single plant can produce up to 150,000 seeds per season, which means that one crabgrass plant can quickly turn into a full-blown infestation. The seeds can remain viable in the soil for an extended period, waiting for favorable conditions to germinate. Crabgrass seeds can remain dormant in the soil for several years before germinating. This means that even if you're able to get rid of all the crabgrass plants in your lawn today, there's a good chance that the weed will come back next year or even several years from now.

Crabgrass weeds also spread by rhizomes, which are horizontal stems that grow just below the surface of the soil. These rhizomes can extend up to 2 feet from the main plant, and they enable crabgrass to quickly fill in any gaps in your lawn. This is also the means by which crabgrass manages to appear all over cracks in the pavement. Crabgrass is particularly opportunistic in areas with bare soil or thin grass cover, where the absence of competition allows it to establish and spread rapidly. The weed's ability to colonize disturbed areas, coupled with its adaptable nature, contributes to its invasive tendencies, making prevention and early intervention crucial in managing crabgrass infestations.

How To Prevent & Control Crabgrass

The best way to prevent crabgrass is to have a healthy, thick lawn that crowds out the weed before it has a chance to take root. Once crabgrass emerges in your lawn and throughout your yard, it can be difficult to remove. Crabgrass is notorious for its shallow, fibrous roots that are very invasive and aggressive. The roots of your lawn will struggle to develop as crabgrass roots spread, so controlling the weed is crucial to your lawn's success. Keep the following tips in mind for a lush lawn that is free from crabgrass this season, and call Coastal Property Maintenance today for even more help!

  • Pull Immature Crabgrass: Removing crabgrass before it develops a seed head is the best way to prevent an infestation in the following year.
  • Dig Out Roots: Established crabgrass will have roots that are slightly stronger, so digging down and around the fibrous roots is best.
  • Apply Pre-Emergent: Early spring is the best time to apply a pre-emergent weed killer, which prevents seedlings from being able to emerge.
  • Overseed In Fall & Spring: Keeping your lawn lush and thick is key to choking out crabgrass, and seeding is effective when crabgrass seeds are germinating.
  • Mow High: Prostrate growth and high sunlight requirements cause crabgrass to struggle in taller lawns, which also means deeper and healthier grass roots.
  • Use Grassy Weed Killers: If all else fails, small bunches of mature crabgrass can be removed by directly applying grassy weed killers, but professional help is always best due to the non-selective nature of these chemicals.