Weed of the month for January 2014 is Annual Bluegrass
Annual Bluegrass
Identification: Annual bluegrass is an upright, clump-forming grassy weed that expands through the development of aggressive tillers. It is generally identifiable by its light green leaf blades that are smooth on both surfaces, have two distinct, clear lines on each side of the midrib, and a boat-shaped leaf tip. Annual bluegrass also has a slightly pointed, membranous ligule. One of the factors that makes annual bluegrass so difficult to control is its ability to produce a large amount of seedheads, even at putting green mowing heights. These seedheads can be observed as a greenish to white, open, pyramid-shaped panicle. A single annual bluegrass plant is capable of producing up to 360 viable seed that have the ability to lie dormant in the soil for many years before finally germinating.
Annual bluegrass is a prolific seed producer |
Annual bluegrass membranous ligule |
Boat-shaped leaf tip |
Annual bluegrass seedhead |
Prolific seedhead production |
Bunch-type growth habit |
Light-green annual bluegrass color in a cool-season lawn. Notice it is growing in a trafficked, compacted area. |
Light green color and prolific seedhead production at low mowing heights |
Annual bluegrass invading a creeping bentgrass putting green. |
Annual bluegrass produces seedheads even at putting green heights |
Light green color and prolific seedhead production in a golf course putting green |
Cultural control: The use of cultural practices to increase the competitive growth and development of the desired turf over annual bluegrass is one of the limited options for cultural control. However, annual bluegrass’ ability to tolerate extremely low mowing heights and prolific production of viable seed severely limits a professional turf manager’s ability to control the weed using cultural methods.
Biological control: No consistently effective biological control for annual bluegrass although previous research has examined some options.
Chemical control: There are options for controlling bluegrass through the use of herbicides; however, those options are generally specific to the species of the desired turf and the use of the area which is being treated (i.e. home lawns, golf course, sports turf, etc.). One could literally write a book on how to control this species.
To keep annual bluegrass out of your home lawn.
To keep annual bluegrass out of your home lawn.
- Do not over-water yours lawns as annual bluegrass likes moist areas.
- Do not compact your soil through traffic where possible and aerify your lawn to reduce soil compaction as annual bluegrass grows well in thin, compacted areas.
- Maintain dense turf through fertilization, overseeding, and weed control (crabgrass and broadleaf weeds).
- Mow your lawn at higher heights of cut (>2.5 inches) as annual bluegrass is less competitive at a higher cutting height.
For professionals, more information on annual bluegrass control is available in Turfgrass Weed Control for Professionals Publication.
For archives of past weed of the month postings, visit our Weed of the Month Archive.
Aaron Patton, Turfgrass Extension Specialist
Leslie Beck, Postdoctoral Research Associate
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