Annual bluegrass (Poa annua) and rough bluegrass (Poa trivialis) are becoming common weeds in lawns and athletic fields, though they have been a problem on golf courses for a long time. Both of these grasses are very visible right now because they are lighter-colored than Kentucky bluegrass and perennial ryegrass. Both weeds tend to thin and die out during the heat and drought of August in Indiana. Poa annua is especially noticeable in May and June because of it’s prolific seedhead production (photos). Poa trivialis, on the other hand, rarely produces a seedhead when mowed (photos). Control of Poa annua and Poa trivialis in lawns is difficult, if not impossible and it may not be economically feasible or practical. Control of Poa trivialis is most effective with a non-selective herbicide followed by reseeding. Poa annua on the other hand, can be killed with drought stress, and then germination can usually be minimized with a preemergence herbicide applied around Labor Day and again in the early spring. More information is on our web page under “Publications” in AGRY-98-02: Control of Poa annua and Poa trivialis in Lawns and watch for a brand new extension publication on this topic coming in the next few weeks.
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