Weedy Bluegrasses Found in Lawns.
Annual bluegrass and roughstalk bluegrass are both very obvious in many lawns right now. Both of these grassy weeds are very common in residential and commercial turfgrass and are a problem because there is no adequate control for them in the Kentucky bluegrass/Tall Fescue lawns that comprise most Baltimore area lawns.
Annual bluegrass (Poa annua) is a cool season annual grassy weed that starts germinating in late summer or fall, as temperatures fall, and continues to germinate throughout the winter into early spring. Because of this growth habit, it is more competitive than other turf cultivars during the cool season, accounting for the spring annual bluegrass invasion.
Annual bluegrass has light green flattened stems and silvery-colored seed heads that cause yellow or light green patches in lawns. It is especially noticeable in April and May. Annual bluegrass is able to survive low mowing heights of less than 1 inch and still reseed. It tends to die out in hot summer weather.
Roughstalk bluegrass (Poa trivialis) is an undesirable perennial turf species that do well in moist, shaded areas but lacks heat and drought tolerance. It is considered short-lived but can persist in Baltimore area lawns. It is characterized by a mid/light-green leaf coloration that browns out quickly above 80 degrees, resulting in distinct dense, patchy growth where other grasses tend to be absent. Roughstalk bluegrass is noticeable in the spring with its lime-green color and in the summer when it goes brown and dormant under heat stress. Rough bluegrass favors light, frequent irrigation, moist/wet soils, low mowing heights and/or high fertility. Dormant Roughstalk bluegrass is sometimes misdiagnosed as grub injury in late summer, because of its shallow root system.
Roughstalk bluegrass in a lawn in the spring
No Easy Control Procedure
Mark Schlossberg is the President of ProLawnPlus in Baltimore, MD. He graduated from the University of Maryland in 1977 with a B.S. in agronomy. He is the President of the Maryland Association of Green Industries, and past president of the Maryland Turfgrass Council.