Poa annua is a prolific seed producer at any height of cut. The grass’ ability to seed contributes to its spread, and the seedheads can affect putting green smoothness in spring. Poa plants are also noticeable on bermudagrass fairways that are starting to green up. The Poa plants grow quickly, making them very noticeable within the much shorter bermudagrass.
Managing seedheads is necessary in many cases, especially on putting greens. Suppression of seedheads is possible with properly timed growth regulator applications. If your course is like many others in the Northeast, seedheads have already emerged. Once that occurs, suppression is no longer possible. Fortunately, some seedheads can be removed mechanically. Some of the most popular and effective methods to mechanically remove seedheads are brushing, verticutting or grooming. However, it is important to be careful with aggressively brushing or grooming grass that is not yet growing rapidly. Although these procedures will help remove seedheads, if performed too often or too aggressively, they can hurt the desired grass and slow spring development.
Several herbicides are labeled for selective control of Poa annua and broadleaf weeds in bermudagrass tees and fairways. It is important to control the plants with postemergence herbicides so that seeds do not spread with mowing and increase the population, making control more difficult next year.
If you aren’t on a preventive program for Poa seedhead control, perhaps it is time to consider one. For putting greens, ongoing research suggests that preloading Poa with a late fall application of the growth regulator Proxy® can help suppress seedheads. Timing is variable, but the most recent research shows good results with the following program:
- One application after the last mowing in the fall
- An initial spring application between 200 and 500 growing degree days with a base of 32 degrees Fahrenheit
- A final application three to four weeks after the initial spring application
On bermudagrass, applying a preemergence herbicide in late summer to early fall will control the emergence of Poa plants from seed in the soil. The University of Tennessee have examined several products for preemergence control of Poa. This summary video is a helpful resource for determining optimal treatments for Poa control in warm-season grasses. If plants still germinate, waiting until the bermudagrass is dormant and applying a nonselective herbicide will clean the rest of the plants up.
Poa annua is a frustrating plant to control because it is so prolific. That doesn’t mean that suppression isn’t possible or warranted in various instances, especially on putting greens if the desired grass is something other than Poa. Continue to mechanically remove seedheads this spring and plan for preventive programs this fall and winter.
Northeast Region Agronomists:
David A. Oatis, regional director – email@example.com
Adam Moeller, director, Green Section Education – firstname.lastname@example.org
James E. Skorulski, agronomist – email@example.com
Elliott Dowling, agronomist – firstname.lastname@example.org
Paul Jacobs, agronomist – email@example.com