Annual Blue Grass
Poa annua or annual blue grass is a very common problem in most places in the US. It is very prevalent in the Piedmont North Carolina where we are and is difficult to eradicate. The reason for that is that the seeds germinate in the fall and if you are planting or reseeding a fescue lawn a pre-emergent weed killer will make it difficult to re-seed your fescue. Most pre-emergent weed killlers have a residual that last for 90 days or longer. If you have a healthy strong lawn going into fall, and you keep your grass mowed about 4 inches during the late summer and early fall, you usually can keep the Poa annua from being a problem.
Another reason the Poa is hard to control is that it seed heads never get very high and in general grass mowers don’t cut low enough to cut off the seed head. Seeds remain dormant for many years so if the soil is bare, and especially compacted, you will have Poa annua.
Most pre-emergent will keep Poa annua from germinating as said above, but there is one that appears to be pretty effective. That is ProGrass. Prograss will kill the very young Poa annua, but once the grass matures Prograss does not do much to the mature plant. Prograss is applied in the early fall when Poa annua is starting to germinate, and then again once more mid winter. Another interesting thing is that you can sow or spot seed fescue immediately after treatment with Prolawn. That is what the chemical label says, but that doesn’t make sense to me.
Poa annua thrives in moist cool weather especially in compacted soil that is near the edge of a sidewalk or driveway.
Below are a couple of photos.
The next photo is of a close up of Poa annua close up of seed heads