Different Types of Crabgrass With Pictures to Identify Each

Crabgrass is a common sight in lawns and gardens across the Americas, but did you know there are several varieties of this tenacious weed? From the smooth and flat-lying crabgrass to the tall and spiky species, each type of crabgrass presents unique challenges for gardeners and landscapers.

In this blog post, I’ll explore the most common varieties of crabgrass found in the Americas and learn what makes each type so distinctive. So, whether you’re a seasoned gardener or just starting out, get ready to identify crabgrass types and expand your knowledge of these pesky yet fascinating plants.

With over 33 types of crabgrass found worldwide, this ‘weed’ is part of the Digitaria family. Interestingly, not all Digitaria family plants are weeds; some are grasses that help feed some animal populations such as cattle.

Here is a list of the most common and some less common varieties of crabgrass found in the Americas:

Smooth Crabgrass (Digitaria ischaemum)

This is the most common type of crabgrass and is recognizable by its smooth, flat, glossy leaves. It spreads quickly through seeds and is often found in disturbed soils, such as bare spots in lawns or along roadsides.

Large Crabgrass (Digitaria sanguinalis)

Also known as hairy crabgrass, this species is easily recognized by its larger, hairy leaves and seed heads. It is commonly found in gardens and landscaped areas and is often considered a weed because it can outcompete desirable plants. It is also a late-season growing weed, so pre-emergents put down in the spring may not be effective against it.

Southern Crabgrass (Digitaria ciliaris)

This species is commonly found in the southern United States and is recognized by its hairy leaves and seed heads that are slightly smaller than those of large crabgrass. It grows in a dense, bushy form and is often used as forage for livestock.

Slender Crabgrass (Digitaria filiformis)

This species is native to the southern part of the USA and is recognized by its fine, finger-like leaves and seed heads. It is commonly found in disturbed soils in grasslands and fields and is known to be very invasive, quickly spreading and out-competing desirable plants.

Asian Crabgrass/Finger Grass – (Digitaria bicornis)

Digitaria bicornis, also known as smooth crabgrass, is a species of crabgrass that is native to tropical and subtropical regions of the world. Here are some key characteristics that can help you identify this type of crabgrass:

1. Leaf blade: The leaves of Digitaria bicornis are thin and have a smooth or hairless surface. They are typically 2-10 cm long and 5-15 mm wide.
2. Stems: The stems of Digitaria bicornis are typically 10-50 cm long and are erect, branching, and hairless or nearly so.
3. Flowers: Digitaria bicornis produces distinctive, spike-like inflorescences that are 2-8 cm long. The inflorescences contain small, spikelet-like flowers that are usually yellow to purplish in color.
4. Seeds: Digitaria bicornis produces seeds that are small, reddish-brown to brown, and somewhat flattened. They are typically less than 2 mm in length.
5. Habitat: Digitaria bicornis is a tropical and subtropical weed that prefers warm, moist soil and is often found in disturbed areas such as gardens, lawns, and fields.

Less Common Varieties of Crabgrass Include:

Jumbo Crabgrass (Digitaria horizontalis) – This species is native to tropical regions and is recognizable by its large leaves and seed heads.

Narrow-leaved Crabgrass (Digitaria compacta) – This species is native to tropical regions and is recognizable by its narrow, pointed leaves and seed heads.

Flat Crabgrass (Digitaria platyphylla) – This species is native to tropical regions and is recognizable by its flat leaves and small seed heads.

Woolly Crabgrass (Digitaria eriantha) – This species is native to South America and is recognizable by its dense, woolly seed heads and leaves. It is considered a weed in many parts of the world because it quickly invades disturbed soils and displaces native vegetation.

These are some of the most common and less common varieties of crabgrass found in the Americas. Understanding the characteristics of each species can help gardeners and landscapers better manage these persistent weeds.

How To Identify Crabgrass

Crabgrass can be identified by its distinctive growth habit and leaf structure. Here are some key features to look for:

Prostrate growth habit

Crabgrass typically grows close to the ground and spreads outward in a flat, mat-like manner.

Leaves

Crabgrass leaves are usually smooth and flat, with a glossy appearance. They are typically broader at the base and narrow at the tip.

Seed heads

Crabgrass produces spikes of seed heads that are usually several inches long. The seed heads are composed of tiny seeds that are easily spread by wind or transported on clothing or animal fur.

Leaf-sheaths

The base of each crabgrass leaf is wrapped in a sheath attached to the stem of the plant. This distinctive characteristic of crabgrass can be used to differentiate it from other types of grasses or weeds.

By looking for these key features, you can quickly identify crabgrass and take the necessary steps to control it in your lawn or garden. Additionally, you can consult a reference guide or seek help from a local garden center or extension office to confirm crabgrass identification.

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How To Control Crabgrass

Here are some strategies that can help control crabgrass growth:

1. Cultural control: Maintaining a dense and healthy turf is one of the best ways to control crabgrass. Regular mowing, watering, and fertilization can help keep the grass healthy and reduce the chances of crabgrass taking hold.
2. Pre-emergent herbicides: Applying a pre-emergent herbicide to the soil in the spring before crabgrass seed germination can effectively prevent crabgrass growth. Some popular preemergent herbicides include Prodiamine, Pendimethalin, and Isoxaben.
3. Post-emergent herbicides: Once crabgrass has emerged, it can be controlled using post-emergent herbicides such as Quinclorac, sethoxydim, or glyphosate. These products can be applied directly to the crabgrass plants to kill them.
4. Mulching: Mulching can be used to prevent crabgrass seeds from germinating. Applying a layer of organic mulch over the soil surface can help suppress crabgrass growth and conserve moisture in the soil.
5. Hand-pulling: Hand-pulling crabgrass can be an effective way to control it for small areas. This method is labor-intensive but can be done without the use of chemicals.

References:

• https://www.semanticscholar.org/paper/Genetic-diversity-among-crabgrass-weed-ecotypes-in-Fontana-Agostinetto/1ba21e47a696718af3a2ddd6050274378ff69077/figure/1
• https://ag.umass.edu/turf/fact-sheets/biology-management-of-crabgrass
• https://extension.tennessee.edu/publications/Documents/W146.pdf