Annual Bluegrass (Poa Annua) Control

Annual bluegrass is a tough yearly weed winter in residential turf. The leaves have coarser textures and produce unsightly seedheads, making them an eyesore to behold. Spread by seed, Annual bluegrass (Poa annua) is a cool-season annual grass. It has a bright green leaf color and fine texture.

The Annual bluegrass seeds mature in the fall, it grows during the winter, produces seed in the spring, and usually dies in the summer months. The heat brought on by summer puts stress on it and it will help kill it all but not completely eliminate it. When soil temperatures fall below 70° F, Annual bluegrass seed germinates in late summer/early fall. It may remain dormant in the soil for a long time before germinating.

What you apply and when you apply certain herbicides is very important to control your population. Overall, we recommend pre-emergent herbicides in the late summer and early fall months and post-emergent herbicides during the rest of the year (See list below for recommendations to determine which are safe for your turf type).

Characteristics

Poa.annua_seed
  • Bright green leaf with boat-shaped tip

  • Leaf has a smooth texture

  • Low growing and tends to grow in bunches winter annual weed

  • Likes to grow in compact and moist areas

  • Seed heads are greenish to white/off-white color

Annual Bluegrass (Poa Annua) Control

Treatment With Selective Herbicides

When starting a weed control program, homeowners should realize that complete eradication of annual bluegrass (or any other type) from the landscape isn't practical. A more realistic approach is to manage weeds by reducing their infestation levels to tolerate them.

The most effective method in knocking down your Poa Annua population is though the use of selective herbicides. These herbicides are specifically designed to target your Poa Annua and not the surrounding vegetation. Selective herbicides for Poa Annua control tend to be more on the expensive side, so figuring out which is best for you and your lawn is very important. As of recent, Poa Annua has developed resistance to some herbicides so long term control may involve rotation of herbicides. Here are some tips for selecting the right product:

  • Identify what kind of grass you have in your lawn. Some products are not safe for sensitive grasses such as St.Augustine so this will help narrow your search.
  • Many of the chemicals are limited to warm season grass such as zoysiagrass, bermudagrass, centipede, and St. Augustine. Care should be taken with cool season grasses such Kentucky Bluegrass and Fescue grasses. Use Tenacity herbicide on cool-season turf as a pre-emergent and it will not effect over-seeding.
  • Determine the scope and severity of your Poa Annua infestation. If you have a small lawn and a light infestation, that $300 bottle may not be for you.

Recommended Selective Herbicides

Non-Selective Herbicides

  • A non-selective herbicide will kill any vegetation that it touches.
  • Apply ONLY when your surrounding turf grass is dormant (all green is gone) and spot treat trouble areas.
  • Apply when there is a low chance of rain to avoid runoff of chemical to other vegetation.
  • Recommended ProductsGly Pho-Sel Pro Dry 75 SGEraser Max, and Alligare Glyphosate 5.4 

Key Takeaway

Poa annua is a winter annual weed. It dies off every summer. Seeds sprout in the fall and winter to replace it.

Applying pre-emergent herbicides in the late summer or early fall will greatly reduce the amount of Poa annua in your turf.

There are several good choices for killing Poa annua and not killing your lawn.

Prevent Annual Bluegrass (Poa Annua)

  • Application of pre-emergent herbicides is the most effective way to control annual bluegrass.
  • The first application needs to happen in late fall/early winter before the seed germinates.
  • Apply when the soil temperature reaches around 70 degrees.
  • A second application is recommended for seeds that germinate late.
  • Pre-emergent herbicides only prevent germination. They do not get rid of an established population.
  • Recommended Products:  Prodiamine 65 WDG, Dithiopyr 40 WSB, and Hi-Yield Turf & Ornamental Weed & Grass Stopper  
  • Tenacity Herbicide (Use as an pre-emergent on Kentucky Bluegrass and Fescue grasses)