Poa Annua, also known as annual bluegrass, is one of the most common grassy weeds in the US. Its seeds can lay dormant in your soil for years, making it especially difficult to control. Treatment and prevention of poa annua rely heavily on grass type. You can get rid of poa annua and prevent poa annua with these tips and product recommendations.
Poa Annua, also known as annual bluegrass, grows during the winter and emerges as temperatures warm. It can be hard to get rid of because the seeds can lay dormant for years before emerging in your lawn.
Therefore, a two-step approach of both pre-emergent herbicides and post-emergent herbicides is needed to effectively prevent and control poa annua in your lawn.
Plant Growth Regulators can also be used to stop the seed head production of poa annua and limit vertical growth of your turfgrass. We recommend this method primarily for cool season turfgrass.
A pre-emergent that contains an active ingredient labeled for your grass type is ideal to prevent poa annua. We recommend using a pre-emergent herbicide that contains pendimethalin, dithiopyr, or prodiamine.
A spring pre-emergent application between late January and early May is ideal before temperatures rise and weeds begin to germinate. You should also apply a fall pre-emergent in late summer or early fall before soil temps fall below about 70 degrees. This will help prevent germination of poa the following winter/spring. Most Pre emergents cannot be applied in the fall if oversetting your turf.
Make sure to do a split application when you apply your pre-emergents. You can learn how to do a split application effectively with our video on split applications. This will help ensure your entire lawn is treated, reducing the amount of spots you may have missed during your initial treatment.
Post-emergents work best in combination with pre-emergents. If you happened to miss any spots during your pre-emergent application, post-emergent herbicides can be used to kill any poa annua that grows in your lawn in the spring.
If you have a warm season lawn, we recommend a selective post-emergent herbicide. The product you choose will depend on the size of your lawn and your grass type.
Since poa annua and cool season grasses are so closely related, there are few products that will kill the poa annua without also harming your cool-season lawn. In this case, spot treating for poa annua with a non-selective post-emergent herbicide may be your best option.
Regardless of your turf type, you should read the label of any herbicide you use to be sure the product is labeled for your grass type and appropriate for your area of application.
Poa annua will die in the summer when temperatures are consistently 85 degrees Fahrenheit and higher. It may leave unsightly brown patches if not treated properly. If the temperatures are forecasted to be high in your area, you may want to wait before applying a spot treatment.
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