Control Annual Bluegrass Vs Rough Bluegrass
Q: What is the difference between annual bluegrass and rough bluegrass?
A: Annual bluegrass, Poa annua, is a very common grassy weed in local
lawns. It is a lighter green than fescue and really stands out against the brown
of dormant bermuda grass. Clumps are usually covered with hundreds of
Rough bluegrass, Poa trivialis, is a perennial weed.
Both grasses fade away in May, leaving dead spots in your lawn, but rough bluegrass returns in September. Annual bluegrass can be controlled with pre-emergent herbicide applied in September but controlling rough bluegrass is limited to two methods: dig up the clump or spray it with glyphosate (Roundup, etc).
Replanting your desired grass is necessary with whichever control you choose.