Bulbous Bluegrass: Poa Bulbosa L

PNW 467 • July 1994 Bulbous Bluegrass Poa bulbosa L. K. Locke and L.C. Burrill B ulbous bluegrass is an- other example of an introduced European plant that escaped to become weedy. The first reports DATE. of its growth in the United States were experimental plantings at Arlington, Virginia, OF in 1907, and one at Pullman, Washington, at about the same time. It was produced commer- cially in southern Oregon soon after this and was planted with OUT alfalfa, where its presence tended to reduce invasion by weeds. By 1919, it had spread IS over much of southern Oregon. Bulbous bluegrass now is weedy in pastures, grain fields, and roadsides. It has spread over much of the Pacific North- Figure 1.—Bulbous bluegrass. west, across the northern information: United States from Alaska to New York, and south to Califor- spring and matures ahead of The bulbils (small, bulb-like nia, Utah, and Colorado. Bul- other grasses. It often is the first bodies or fleshy, detachable bous bluegrass also is an excel- invading species on shallow buds, borne usually on the lent example of how our trans- soils that are moist only during stem), which are produced in- portation system speeds the the winter and early spring. The stead of seeds, add to the palat- spread of weeds. One may see movement of bulbous bluegrass ability of the dry forage when this plant frequently while trav-currentfrom marginal sites to nearby they are retained on the plant, eling highwaysPUBLICATION across the Pa- deep productive soils then be- as they contain appreciable cific Northwest. comes a matter of time. amounts of starch and some fat. Bulbous bluegrass also has Bulbous bluegrass is quite This makes them attractive to been called winter bluegrass tolerant to drought and is not rodents and birds. because of its tendencymost to grow without merit. On shallow soils, duringTHIS mild winter weather. it stabilizes the site and helps When temperatures do not per- prevent soil erosion early in the mit growth during the winter, season, but the leaves and this grassFor starts its growth stems dry up and blow away by much earlier in the spring than August. It completes its annual Kerry Locke, Extension agent, Kla- most other grasses.http://extension.oregonstate.edu/catalogcycle so quickly that it does not math County, and Larry C. Burrill, When it is adapted, it com- provide much forage to wildlife Extension weed specialist; Oregon pletes its growth cycle in the or livestock. State University. A Pacific Northwest Extension Publication • Oregon • Idaho • Washington Identification Control Bulbous bluegrass is unique Prevent infestations. Use crop because it fails to produce true seed, hay, and straw that is free seeds. This perennial grass re- of bulbous bluegrass bulbils. produces vegetatively in two Clean equipment before mov- ways. ing from a site infested with It grows from basal bulbs to bulbous bluegrass. form closely clustered bunches Bulbous bluegrass frequently of stems up to 2 feet tall. The moves into fields from adjacent bulbs multiply by sending new road shoulders, fence lines, and bulbs out laterally. other poorly vegetated areas. In addition, the flowers pro- Controlling this and most other duce bulbils rather than seed. weeds in these areas is the best The dark purple bulbils contain method of preventing weeds a rudimentary plant that does from infestingDATE. cropland. not develop until after an ex- Bulbous bluegrass is not an tended dormant period. Fields aggressive competitor in good of mature bulbous bluegrass OFstands of perennial crops such have a dark purplish cast. The as pastures and alfalfa. Estab- heads droop over with their lishment of a competitive pe- heavy load of bulbils. rennial grass in uncropped land The leaf blades are narrow, or rotation from annual crops to hairless, flat or loosely rolled, OUT permanent pasture or alfalfa with membranous ligules about will help prevent spread and is 1 ⁄8 inch long. A thick stand of IS a good management strategy bulbous bluegrass has a bright, Bulbous bluegrass and bulbil for an existing population. light green appearance in the In areas where the weed has spring. The inflorescence is a already become established, it is moderately dense panicle of important to stop production of awnless spikelets. new bulbs and bulbils. Heavy grazing, tillage, and selective information:herbicides are effective control methods. Seed new crops in the spring when possible to allow Photograph provided by Larry Burrill, Extension weed specialist, Oregon State University. The black-and-white illustration was reproduced, with permission, from La Rea Dennis, destruction of the bulbous blue- Gilkey’s Weeds of the Pacific Northwest (Corvallis, OR, Oregon State University, 1980); © La Rea grass plants that start in the fall J. Dennis. and winter. Pacific Northwest Extension Publications contain material written and produced for public For chemical control distribution. You may reprint written material, provided you do not use it to endorse a recommendations, refer to the commercial product. Please reference by titlecurrent and credit Pacific Northwest Extension Pacific Northwest Weed Control Publications. To reproducePUBLICATION material used with permission on page 2 in this publication, please contact the original source. Handbook, an annually revised Pacific Northwest Extension publications are jointly produced by the three Pacific Northwest Extension publication available states—Oregon, Washington, and Idaho. Similar crops, climate, and topography create a from the Extension bulletin natural geographic unit that crosses state lines. Since 1949 the PNW program has published offices of Oregon State more than 450 titles. Jointmost writing, editing, and production have prevented duplication of effort, broadened the availability of faculty specialists, and substantially reduced the costs for University, Washington State participatingTHIS states. University, and the University Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, of Idaho. by the Oregon State University Extension Service, O.E. Smith, director; Washington State University CooperativeFor Extension, Harry B. Burcalow, interim director; the University of Idaho Cooperative Extension System, LeRoy D. Luft, director; and the U.S. Department of Agriculture cooperating. The three participatinghttp://extension.oregonstate.edu/catalog Extension Services offer educational programs, activities, and materials—without regard to race, color, national origin, sex, age, or disability—as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. The Oregon State University Extension Service, Washington State University Cooperative Extension, and the University of Idaho Cooperative Extension System are Equal Opportunity Employers. Published July 1994. 50¢/50¢/50¢.

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