Smooth vs. Hairy vs. Large Crabgrass

When it comes to the management of weeds, the first step is to always identify the weeds so that you can determine the right control methods.

The most common types of crabgrass are smooth and hairy crabgrass. They are what you may find in your lawns 90% of the time.

Hairy crabgrass is also called large crabgrass or long crabgrass, depending on the the region it stems from. 

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Comparison and Differences

But how can you distinguish smooth crabgrass from large crabgrass? Although they all belong to the same genus, certain distinct features can help you set the two apart.

Their features include:


  • Large/hairy crabgrass

Hairy crabgrass has flat leaves that measure 0.75 to 6 inches long and as much as 0.5 inches wide. It has a prominent midrib that is visible on both sides.

Hairy crabgrass also has a membranous ligule with a characteristic jagged appearance. Its sheath which joins the leaf and the stem is well covered with straight and long hairs.

  • Smooth crabgrass

Smooth crabgrass also has flat leaves which measure 0.75 to six inches long but the width is characteristically shorter – measuring about 0.3 inches. 

Its midrib is also prominent and visible on both sides. The plant also has a membranous ligule, albeit with a smooth appearance unlike the jagged appearance seen in large crabgrass.

Its sheath that connects the leaf and the stem has no hairs.


  • Large/hairy crabgrass

Large crabgrass has a stout stem that usually exhibits a reclining growth pattern. Additional root systems may form at the node regions adjacent to the soil to propagate the growth of the plant.

It has an inflorescent which consists of a panicle of branches laced with small spikes that are arranged in double rows of flattened rachis.

  • Smooth crabgrass

The stem/culm of smooth crabgrass is somewhat slender and exhibits a decumbent/ reclining growth pattern. Just like hairy crabgrass, it may also form additional root systems from nodes that are adjacent to the ground.

These root systems help in propagating the growth of the plant even in the absence of seeds. Unlike hairy crabgrass, smooth crabgrass has an inflorescent which consists of a panicle with digitate branches.

Nevertheless, its small spikes are similarly arranged in double rows of flattened rachis.

Maximum growth height

Hairy crabgrass can grow up to as high as 3.5 feet while the smooth crabgrass grows slightly shorter than hairy crabgrass to a maximum height of 2.5 feet tall.

Growth pattern

Hairy crabgrass and smooth crabgrass are both annual grasses with peak yield during summer. They also thrive well in nutritiously rich sandy or clay soils. Here’s a detailed guide on managing clay soils in your lawn and garden

Seeds begin to sprout during the mid-spring when the soil temperature strikes 55 degrees Fahrenheit. Crabgrass becomes more problematic when summer approaches because these weeds can thrive well in hot and dry weather conditions.

Before the entire plant dies off in the fall, every single crabgrass produces several seeds that eventually germinate into new plants in the following spring climate.

Generally, it suffices to note that hairy crabgrass is almost similar to smooth crabgrass. The exceptional difference is that smooth crabgrass is not as coarse or as tall as hairy crabgrass.

It also has no hairs around the sheath, and neither are the hairs present on the leaves. Smooth crabgrass is also more reddish and sometimes appears purple.

Large crabgrass and smooth crabgrass were initially grown to provide grazing for animals. Others also produced it for human consumption.

However, it turns out that these grasses found their way into people’s lawns and became a nuisance almost immediately.

The differences between hairy crabgrass and smooth crabgrass are somewhat very subtle because the plants exhibit very minimal botanic differences.

What is the significance of these grasses?

Both these kinds of grass pose a very great challenge, especially to corn farmers when they are managed correctly. Some herbicides do not respond well in managing both smooth and hairy crabgrass but you can use Quinclorac Select 75 DF herbicide for effective control. 

Whatever herbicide is being used to manage these grasses should be used under the consultation and approval of a professional. It should also be mixed in the right proportions just to ensure that you do not under-dilute or over-dilute the herbicide.

Nonetheless, spraying these grasses is the chief treatment mechanism for managing the incidence and/or spread of these grasses.

Final Thoughts

The ability to effectively manage these weeds is by first understanding them. Just as their names suggest, they grow to the ground as their stems spread out of the center hence the name crabgrass.

Whether you are using these grasses for food or just eliminating them to clear your lawn, consult intensively with a qualified professional to help you understand these weeds.

Performing any dangerous procedures with no experience does not predispose your lawn to the risk of damage but also puts your health at risk.


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