How To Identify & Control Crabgrass

Understanding Crabgrass In Your Lawn

Crabgrass is one of the most notorious weeds worldwide, but many homeowners either overlook it or mistake it for regular grass. If you miss the warning signs of a crabgrass invasion, this aggressive plant can overrun your lawn and steal valuable nutrients and resources from your grass, not to mention the damage crabgrass does to your lawn’s curb appeal.

The professionals at Merrill Landscape Services are here to share our expertise so you can effectively manage and prevent crabgrass infestations. Let’s learn a bit more about this common lawn invader!

Recognizing crabgrass involves looking for specific characteristics that set it apart from your lawn’s grass species. Crabgrass appears as clusters of narrow, light green blades that contrast with the darker green of your turf. The leaves are typically 1/8 inch wide and range from 2 to 6 inches in length, though they can extend up to a foot under the right conditions. The blades have smooth surfaces but may feature tiny serrations along the edges. They grow in opposite pairs along the stem, with noticeable thickened joints that feel spongy to the touch.

During late spring and early summer, crabgrass produces seed heads that resemble thin, elongated spikes, often compared to a string of beads. These seed heads contain numerous tiny seeds that can persist in the soil for up to five years or more, making crabgrass a long-term problem once established. 

What To Look For:

• Flat, wide leaves
• Long stems
• Low, prostrate growth
• Pinkish or white color at the base
• Bunch-type growth pattern
• A lighter green shade 

Crabgrass is classified as a grassy weed or grass-like weed due to its invasive nature and rapid spread. This opportunistic plant thrives in weak or sparse lawns, forming thick mats that choke out healthy grass. With its low-growing, sprawling habit, crabgrass takes advantage of any bare spots in your lawn and can quickly dominate the landscape.

One of the key reasons crabgrass is such a persistent problem is its shallow root system. Unlike deep-rooted grasses that anchor into the soil, crabgrass roots stay near the surface, making it easy for the plant to spread but difficult to eradicate completely. Because it grows in clusters and lacks a strong root structure, crabgrass is widely regarded as an unwanted nuisance in lawns.

Crabgrass belongs to the Digitaria genus, with the two most common species being hairy crabgrass (Digitaria sanguinalis) and smooth crabgrass (Digitaria ischaemum). Hairy crabgrass (pictured above) is the more aggressive variety, frequently invading lawns and spreading rapidly. Smooth crabgrass, while less aggressive, often appears in gardens and other cultivated spaces. Though hairy crabgrass can appear in lawns in every region, smooth crabgrass is actually more widespread and common throughout the country.

The main way to tell these species apart is by their texture; hairy crabgrass has tiny, bristly hairs covering its leaves and stems, whereas smooth crabgrass lacks this feature. Smooth crabgrass also tends to grow closer to the ground and has smaller leaves than its hairy counterpart.

A single crabgrass plant has the potential to generate up to 150,000 seeds in a single season, making it one of the most prolific weed species. Even a minor infestation can rapidly escalate into a full-scale takeover of your lawn.

Complicating matters, crabgrass seeds can remain dormant in the soil for several years before germinating. This means that even if you eliminate all visible crabgrass now, seeds from past seasons could still sprout in the future. Crabgrass is notorious for its ability to regrow after being pulled, thanks to its resilient root system that can regenerate new plant growth.

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. Once germinated, 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. 

Spring (Germination & Early Growth):

• Crabgrass seeds begin germinating when soil temperatures reach 55-60°F for several consecutive days.
• Seedlings emerge and start establishing roots in bare or weak areas of the lawn.
• Growth remains relatively slow until temperatures rise.

Summer (Rapid Growth & Seed Production):

• Crabgrass grows aggressively in hot, dry conditions, often outcompeting stressed turfgrass.
• Plants develop long, sprawling stems that spread outward.
• Seed heads begin forming in mid-to-late summer, with each plant producing thousands of seeds.

Fall (Seed Drop & Decline):

• As temperatures cool, crabgrass plants begin to die off, leaving behind bare patches in the lawn.
• Mature seeds drop into the soil, where they remain dormant until the next growing season.
• Seeds become part of the persistent seed bank, ready to sprout when conditions are right.

Winter (Dormancy & Seed Persistence):

• The adult plants die completely, leaving only seeds behind.
• Seeds remain viable in the soil for several years, waiting for warm temperatures to trigger germination.
• The cycle often starts again in late winter during unseasonable warmth.

Once crabgrass takes hold in your lawn, eliminating it can be challenging. The best strategy is prevention and maintaining a healthy, dense lawn that reduces the opportunities for crabgrass to establish itself. Because crabgrass thrives in thin, stressed, or sun-exposed lawns, ensuring your grass is thick and robust is the first line of defense.

One simple yet effective method is adjusting your mowing height. Since crabgrass grows low to the ground, taller grass can shade it out, reducing its ability to germinate and spread. Raising your mower blade by an inch or two can significantly limit crabgrass growth. While hand-pulling can help manage small patches, complete removal is difficult, as any remaining root fragments can lead to regrowth. You can use the following techniques to combat crabgrass:

• Apply a pre-emergent herbicide formulated for crabgrass prevention.
• Overseed and fill in bare patches to promote a thick lawn.
• Keep your grass at least 3 inches tall to discourage crabgrass growth.
• Water deeply but infrequently to encourage strong turfgrass roots.
• Remove young crabgrass plants before they have a chance to produce seeds.
• Completely uproot crabgrass clumps, ensuring no root fragments are left behind.

If you need weed control services in Champaign, Illinois, Merrill Landscape Services is here to help! Our team has served Illinois communities for over 20 years, and we have the local expertise needed to get your lawn and yard weed free!