HPIPM:Bulbous bluegrass

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Lilianae
Order	Poales
Family	Poaceae
Genus	Poa

Scientific Name

Poa bulbosa

Common Name

bulbous bluegrass

Bulbous bluegrass (Poa bulbosa)

Compiled by Jane Mangold, Montana State University

and Marjolein Schat, Montana State University from the following sources:

http://extension.oregonstate.edu/catalog/html/pnw/pnw467/

http://plants.usda.gov/java/profile?symbol=POBU

Gucker, Corey L. 2007. Poa bulbosa. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/plants/graminoid/poabul/all.html [2008, October].

Identification and Life Cycle

Bulbous bluegrass (Poa bulbosa) is an introduced tuft forming grass in the family (Poaceae). Bulbous bluegrass is also called winter bluegrass. It is described as a perennial, an annual, and as an annual with "perennial tendencies". Bulbous bluegrass stems and culms are erect, attach to basal bulbs, and measure 6 to 28 inches tall. Culms are hollow and smooth. The leaf blades are narrow, approximately 2 to 6 inches long, hairless, flat or loosely rolled, with membranous ligules about 1/8 inch long. A thick stand of bulbous bluegrass has a bright, light green appearance in the spring. The inflorescence is a moderately dense panicle of awnless spikelets. Bulbous bluegrass produces 2 types of spikelets: one typically has 3 to 6 normal florets; the other is a viviparous (produces seeds that germinate on the parent plant) bulbil or bulblet without pistils or stamens. Bulbils are more common than true florets in most US populations. Bulbous bluegrass develops a fairly limited root system. Five to twenty roots attach to the basal bulb. These roots range from 0.4 to 4 inches long and support numerous, short, thread-like rootlets about 1 mm long. The aboveground pear-shaped bulbs are approximately 0.4 inches long and consist of a thick, solid internode that is surrounded by scale-like leaves.

Habitats

It often is the first invading species on shallow soils that are moist only during the winter and early spring. Bulbous bluegrass is quite tolerant to drought and is not without merit. Bulbous bluegrass is weedy in pastures, grain fields, abandoned fields, and roadsides. Bulbous bluegrass has been used to seed disturbed sites throughout the United States and is possible in any disturbed area or opening near seeded sites.

Impacts

Bulbous bluegrass is weedy in pastures, grain fields, and roadsides.

Biology and Ecology

Bulbous bluegrass does not produce true seeds. This perennial grass reproduces vegetatively in two ways. It grows from basal bulbs to form closely clustered bunches of stems up to 2 feet tall. The bulbs multiply by sending new bulbs out laterally. In addition, the flowers produce bulbils rather than seed. Bulbils attached to the plant that make contact with the soil can root and grow immediately without a dormancy period. Bulbils detached from the panicle lie dormant for 3 to 6 months before germinating. It completes its growth cycle in the spring and matures ahead of other grasses. Animals, wind, and gravity are all possible dispersers of bulbous bluegrass. Small mammals cache and disperse bulbils.

Management Approaches

Bulbous bluegrass frequently moves into fields from adjacent road shoulders, fence lines, and other poorly vegetated areas. Controlling the source populations to prevent spread into cultivated fields is a preferred management approach.

Biological Control

There is currently no biological control available for bulbous bluegrass.

Mechanical and Cultural Control

Bulbous bluegrass is not an aggressive competitor in good stands of perennial crops such as pastures and alfalfa. Establishment of a competitive perennial grass in uncropped land or rotation from annual crops to permanent pasture or alfalfa will help prevent spread and is a good management strategy for an existing population. In areas where the weed has already become established, it is important to stop production of new bulbs and bulbils. Heavy grazing, tillage, and selective herbicides are effective control methods.

Chemical Control

There are a number of chemical control options available for bulbous bluegrass. For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Examples of herbicides that can be used to manage bulbous bluegrass

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Herbicide Active Ingredient trade name	Mode of Action	Product per Acre	Application Time or Growth Stage
Alfalfa
Pronamide	Microtubule assembly inhibition
*Kerb 50-W		1 to 4 pounds	Apply during the fall or winter months. Applications may be made postemergence to established, actively growing or dormant forage legumes or to new plantings after the legume has reached the trifoliate leaf stage. In established forage legume stands, applications should be made after the last cutting when the weather and soil temperatures are cool.
Barley and Winter Wheat
Metribuzin	Photosynthesis inhibitor (Photosystem II)
*Sencor		1 to 4ounces	Apply when crop is in the 2 leaf to 2 tiller stage. See label for list of tolerant winter wheat and barley varieties.
Potato
Glyphosate	Inhibition of EPSP synthase
*Roundup Original		16 ounces	Apply pre-crop emergence when bulbous bluegrass is less than 6 inches tall.
Grass Grown for Seed – Montana and Wyoming only
Metribuzin	Photosynthesis inhibitor (Photosystem II)
*Sencor		0.5 pounds	Apply only to established grasses that are at least one year old and have been harvested for seed at least once Apply when the crop is dormant and prior to active spring growth. Allow at least 120 days between application and seed harvest.
Conservation Reserve Acres; Established Grasses
Pronamide	Microtubule assembly inhibition
*Kerb 50-W		0.4 pound	Apply between mid- October and mid- December.
Conservation Reserve Acres; Fallow Land
Pronamide	Microtubule assembly inhibition
*Kerb 50-W		0.5 - 1 pound	Apply between mid- October and mid- December prior to soil freeze-up.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=bulbous%20bluegrass