Putting Poa Annua in its Place

Putting Poa Annua in its Place

Sod University

Putting Poa Annua in its Place

A weed that can easily be mistaken for Kentucky bluegrass is known as Poa annua, or annual bluegrass. This grassy weed is extremely common throughout the United States and is well adapted to various locations, conditions and maintenance practices making it a weed that can be tough to get rid of. Perhaps the easiest way to identify this light green invader is by its tall seed head which produces tassels and rises above the typical home lawn, resulting in unsightly patches as seen in the images below.

A single Poa annua plant can produce hundreds to thousands of seeds, which can remain dormant in the soil for years and will typically germinate during the late summer to early fall. Poa annua germinates in the fall when soil temperatures drop below 70 degrees. Once the germination process begins, the weed will continue to grow throughout the spring, and will then flower and die off in the summer. When the weed dies off from the heat of the summer, it leaves behind unattractive brown or bare patches in the lawn. This weed can also continue to grow in the winter when most home lawns go dormant and will thrive in areas of the lawn that are damp, shady and compact due to its shallow rooting system.

Poa Annua Prevention and Non-Chemical Control

Before moving to chemical controls, there are a few preventative maintenance practices homeowners can implement to allow their lawn to outcompete the annual bluegrass. Due to its shallow rooting system, the weed will thrive in areas of the lawn that are overwatered; therefore, homeowners should attempt to water deeply and infrequently so that the shallow rooting system is unable to obtain the water it needs. It can also be beneficial to raise the mowing height for the lawn, as Poa annua is a shorter plant, which gives the lawn a chance to choke out the weeds. Creating a lawn that is dense and healthy can prevent weed problems from occurring. This includes maintaining a proper mowing, irrigation and fertilization schedule to meet the needs of the turf so that thin or diseased patches that are more susceptible to weeds do not have the chance to develop. Weeds will struggle to compete against a maintained, established lawn. Visit Lawnifi.com to learn more about how Lawnifi™️’s proper fertilization schedule will help your lawn become nourished and strong. Our Fall Fertilizer Box contains one bottle of Boost, Maintain and Recover, which work together to help your lawn get over the stressful heat of the summer as well as prepare for winter dormancy. Lastly, apply a pre-emergent in the late summer or early fall to prevent Poa annua from germinating. As previously mentioned, Poa germinates in the fall when soil temperatures drop below 70 degrees. To learn more, visit our Fall Weed Control: Apply Your Pre-Emergent Now blog.

Poa Annua Chemical Control

If you have identified the problem early on and only a few weeds are present, Poa annua can be pulled by hand and may not grow back again. However, if Poa annua turns into a recurring problem or is too extensive to pull by hand, there are many chemical options that can control this issue. One pre-emergent control option is Scotts WeedEx Prevent with Halts (active ingredients 2,4-Penanediol, 2-menthyl-, pendimethalin, and titanium oxide), which comes in a granular form and should be applied in the late summer or early fall to prevent the weed seed from germinating. Another pre-emergent is Quali-Pro Prodiamine 65WDG (active ingredient prodiamine), which can provide control for up to six months and can result in 70 percent of better control of Poa annua in just one application. However, if annual bluegrass has already established itself, a post-emergent herbicide will be necessary. A post-emergent option can be found with Revolver (active ingredient foramsulfuron), which selectively removes cool season grasses from warm season grasses and can be applied as a spot application or to an entire lawn.

Please read the label carefully before applying to ensure that the chemical will not hurt your lawn. When Poa annua cannot be controlled by maintenance practices alone and a chemical must be applied, make sure to read the label carefully to ensure that it will not cause any damage to your lawn and is compatible with your type of grass. This weed is very similar to some grasses commonly found in home lawns and many chemical products can cause damage if the label is not checked before application.

For more information on weed control, click here. To learn more about applying a fall pre-emergent, read our previous blog on Fall Weed Control: Apply Your Pre-Emergent Now.

Want to learn more about achieving a great lawn? Check out our other Sod University tips here.

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