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How to Remove Poa annua From Your Lawn

Close Up Of Poa Annua Growing Rock Landscape

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. Poa annua’s color often differs from various turfgrass colors which can contribute to the “patchy-look” in lawns.

Pictured above from left to right: A closeup of Poa annua with its tall seed heads and a photo of what Poa annua might look like in a residential landscape.

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. The amount of seeds produced can make this weed really hard to permanently get rid of.

Poa annua grass 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.

The poa annua 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.

Non-Chemical Control of Poa annua

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. Consider conducting an irrigation audit to provide the different areas in your lawn with the proper amount of water.

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. Check out our care guides on individual grass types for more information.

Weeds will struggle to compete against a maintained, established lawn. Proper fertilization can help it develop a healthy canopy that is thick enough to crowd out weeds. Here are some of our favorite fertilizers. You can learn more about them in Why Use Lawnifi Fertilizer?

Chemical Control of Poa annua

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 method for controlling Poa annua is by using a pre-emergent or post-emergent herbicides.

Chemical control is often the best approach if Poa annua has spread throughout your entire lawn. While there are many herbicide options available, they will typically fall under one of the following categories: pre-emergent herbicides and post-emergent herbicides. Both types are typically necessary for controlling Poa annua since it’s such a tricky weed.

Pre-Emergent Control of Poa annua

A pre-emergent, as its name suggests, controls weeds before they germinate and appear in your lawn. Post-emergents, on the other hand, are products that control currently existing weeds. Pre-emergent herbicides are best for treating Poa annua during the fall when soil temperatures reach 70 degrees Fahrenheit in the fall or less. This should also take place before the first frost. If you live in an area that doesn’t have frost, then just keep an eye on soil temperatures and apply the pre-emergent when they start to drop. To learn more, visit our How to Use a Pre-Emergent Herbicide in the Fall blog.

Make two separate applications of fall pre-emergents spaced 6–8 weeks apart from each other. This helps by eliminating any spots you might miss with one treatment while also lasting longer. Because the two individual treatments last longer, it helps to provide more protection from Poa annua seeds that germinate later in the season.

We also recommend applying a spring pre-emergent herbicide treatment sometime between late January and May before temperatures rise and weeds begin to germinate. Check out this blog for more information on spring pre-emergents and exact times for applications based on where you live.

One pre-emergent control option is Prodiamine 65 WDG, 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. Other effective pre-emergents for Poa annua are Crabgrass Control Plus 0-0-7 with 0.37% Prodiamine, Hi-Yield Atrazine and Dimension 2EW. Tenacity also has a reputation for controlling Poa annua. The neat thing about this herbicide is that it has both pre- and post-emergent properties AND it can either be tank mixed and applied with a spray applicator or used for spot-treating with the small syringe the product comes with.

Note: Atrazine products like Hi-Yield Atrazine and. Spectracide Weed Stop for St. Augustine and Centipede have both pre- and post-emergent properties for St. Augustine and centipede lawns.

Post-Emergent Control of Poa annua

However, if annual bluegrass has already established itself, a post-emergent herbicide will be necessary. A post-emergent option can be found with Hi-Yield Atrazine, Spectracide Weed Stop for St. Augustine and Centipede and TenacityRevolver is also a good option.

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.

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