How to control Poa Annua
Poa Annua – also known as Annual Bluegrass – is an undesirable winter annual grass that germinates in the late summer/early fall once soil temperatures fall below 70 degrees. Seedlings mature in the fall, overwinter in a vegetative state, and flower and produce seed in late spring and early summer.
You can control Poa Annua with a green-up fertilizer plus crabgrass preventer. For effective Poa Annua control, you can apply a pre-emergent in April and end of August. This will keep the Poa Annua seeds from sprouting in the early spring and fall. But keep in mind that Poa Annua seeds are tough and can survive many seasons without germinating. This method will work towards reducing Poa Annua in the lawn over time. You will need to treat your lawn for many seasons in order to rid of this weed completely. The downside to treating with a pre emergent like Green-Up with Crabgrass Preventer is that you cannot seed for 4 months after application.
Tenacity for example. However, keep in mind that this also needs repeated applications over time. Round-Up will also kill Poa Annua, but since it’s non-selective, it will also kill any other plants and desirable grasses that it comes in contact with. Avenger, non-selective organic spray will also kill Poa Annua, but like Round-Up, it will also kill any other plants that it comes in contact with.
Poa Annua Control (Pre Emergent)
Poa Annua Weed Killer (Non-Selective, Post Emergent)
Poa Annua Prevention – Cultural Practices
Poa annua prefers shady and damp areas. If you water deeply and infrequently, its shallow roots won’t be able to reach down to where the moisture is.
Mow Grass Tall
Poa Annua is short. When you mow your grass high, between 3-4 inches, you make it harder for annual bluegrass to survive. Lawns with taller grass tend to have fewer Poa Annua problems.
Lawn Phix Remedy
I first noticed Poa Annua in my lawn in spring of 2018.
In early spring (first week of April before soil temps hit 55 degrees), apply 0-0-7 with 0.37% Prodiamine at 4 lbs. per 1,000. Follow that up with another application in mid-May. Read the label. The maximum annual application rate of this product is 9 lbs. per 1,000 in a calendar year.
In late summer – last week of August – apply Tenacity as a post emergent (with non-ionic surfactant (NIS)) as you prep your lawn for overseeding; follow this up with an application of as a pre emergent (no NIS, and watered-on) when you seed.
With this method, I was virtually free of all Annual Bluegrass in 2019. I hope this works for you, too!