Poa trivialis is a perennial cool-season grass that’s typically considered a weed. It can resemble patch diseases in lawns, making it difficult to identify and control. This blog post will address these issues.

Poa trivialis sometimes make its way into lawns through seeding projects. Cheaper seed typically contains a higher content of “weed seed” or “noxious weeds,” as designated on the label. State laws determine if Poa trivialis falls into one of these categories and, if so, which one. 

Beware of weed seed in your purchases—you’ll probably get what you pay for. Some shade mixes of seed actually include Poa trivialis as a desired grass, but the University of Minnesota cautions against these mixes except for use in full-shade environments.

According to the PennState Extension, Poa trivialis prefers soil with high moisture content. It prefers shade but can survive in sunny environments with enough moisture. Poa trivialis produces seedheads in early summer but spreads significantly via stolons. These stolons can remain viable in the soil for years before germinating.

We typically refer to Poa trivialis by its scientific name, but it’s also known as roughstalk bluegrass. This nickname comes from the rough texture of its blades, which are covered with small hairs. Poa trivialis leaves have a light green, shiny surface.

As you could probably guess from the “Poa” part of its name, this plant is a bluegrass with some similar characteristics to Poa annua and even Kentucky bluegrass (Poa pratensis). These similarities include “boat-shaped” leaf tips and open panicle seedheads. Poa trivialis is larger than Poa annua and has a lighter color than Kentucky bluegrass, though. 

Despite these similarities with other weeds, lawn care professionals sometimes mistake Poa trivialis for something altogether different: a patch disease. Poa trivialis has a low tolerance for drought and heat. When these stressors set in, the grassy weed begins to turn red or purplish. It may even go dormant in the summer, slowing growth and turning brown to conserve energy. These discolored patches resemble patch diseases, which can lead to the application of the wrong product.

If Poa trivialis is misdiagnosed as a patch disease, control attempts will likely be ineffective. But even a proper diagnosis doesn’t guarantee an easy solution to Poa trivialis. Because of its resilient stolons that can survive from year to year, this weed is notoriously difficult to manage.

According to Purdue University, glyphosate and glufosinate are post-emergent options for Poa trivialis, though even these chemistries will likely require multiple applications. And because glyphosate and glufosinate are both non-selective herbicides, they require precise applications to protect any surrounding desired turfgrass.

Aside from purchasing quality seed to prevent Poa trivialis infestation in the first place, be careful not to spread the weed from one property to the next via equipment. Clean your equipment regularly to prevent spread, and pay attention to the weed history of any site where you source soil to minimize the risk of contamination.

If you want a second set of eyes on what you think may be Poa trivialis in a lawn you treat, reach out to your ATS rep. We can help you make an accurate diagnosis and plan your control approach from there.