How to Know the Difference Between Common Grass Species

Compared to broadleaf weeds, various grass species can be difficult to distinguish. After all, many have a similar shape and size. 

Even so, there are some telltale signs that can help crop scouts make a proper identification. That’s an important step when setting up an integrated weed management (IWM) approach. IWM is the sustainable use of all available methods to reduce weed pressure without reducing farm income and damaging the environment. 

Here’s what to look for the next time you spot a common grass weed in your fields: 

Fall Panicum. At the seedling stage, fall panicum is easily mistaken for barnyardgrass, johnsongrass and green foxtail. A primary identifying characteristic is its zigzag growth pattern, which causes the plant to bend at the nodes of its large, round, smooth sheaths.  

Barnyardgrass. Look for plants with thick stems that can grow up to 5 feet tall. Barnyardgrass is one of the few grass weeds that lacks ligules (a strap-shaped scale found on the inner side of leaf sheaths where they join the blade).  

Johnsongrass. This prevalent weed is also vigorous, with plants that can grow as tall as 9 feet. Look for leaf blades without hairs on both sides. Plants also feature ligules that are 3 to 4 millimeters long and often toothed at the end, a feature that distinguishes it from fall panicum and barnyardgrass. 

Shattercane. This weed species is often mistaken for johnsongrass, and it can even hybridize with cultivated johnsongrass. However, it features hairless leaves that have a distinct midvein. The seedhead is also more compact than johnsongrass, with a ligule that is about half as long. 

Foxtails. As its name suggests, this weed species produces seedheads that resemble a fox’s tail. Also look for long, silky hairs at the base of leaf blades. The stems are upright, hairless and often flattened with a reddish tint at the base. 

Goosegrass. This grass species hugs the ground with flattened stems that spread outward from its distinctive white or silver center. It is often mistaken for smooth crabgrass, but look for leaves that are folded in the bud, rather than rolled in the bud. 

Crabgrass. There are two species of note – smooth crabgrass and large crabgrass (sometimes also called hairy crabgrass). Look for leaf blades that have a fold line down the middle, a plant that grows out in a star pattern, and develops side shoots. Crabgrass sends out runners quickly. Leaves can be between 2 and 8 inches long may have a reddish tint at the base especially near maturity. 

Worried about other grass weed species? There are several free online resources to help identify weeds, including digital guides from the University of Missouri and the University of Wisconsin. 


Photo Credit: ©2013 AgStock Images / Wolfgang Hoffmann

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