Poa annua, also called annual bluegrass, is that small green weed with white seed heads that appears in your warm season turf in the late winter. Poa can always be a problem in lawns that are heavily compacted. Heavily maintained lawns, such as reel mowed lawns, are even more heavily compacted.
Once compacted the pre-emergent weed control cannot move into the root zone to prevent the poa from germinating thus you get the early flush of Poa before the turf has greened up in the Spring. These lawns must be aerated once per year at the minimum, if not twice per year, to reduce the compaction.
Proper aeration to reduce compaction and proper fertility will greatly reduce Poa activity when on a lawn care program but in some lawns due to sub-standard growing conditions poa can be a recurring problem.
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