Bulbous bluegrass

Poa bulbosa

Keys to Identification

  • Stems are bulblike at the base
  • Flowers are purplish leafy bulblets
  • Only grass known to produce bulblets

Family

Poaceae – Grass family

USDA Code

POBU

Legal Status

Colorado Noxious Weed List C

Identification

Lifecycle

Short-lived perennial

Growth form

Tuft or sod forming grass. Plants are 6-24 inches tall

Flower

Flowers are arranged in 2-5 inch long panicles. Flowers develop as leafy bulblets with a dark purple base, 4-6 bulblets on each spikelet. May-June

Seeds/Fruit

Bulbous bluegrass produces asexually in the US, though in Europe it produces seeds

Leaves

Leaves are narrow and 2-6 inches long, flat or loosely rolled and keeled at the base

Stems

Stems are flattened near the base, upper stems are round

Roots

Fibrous roots regrow each season and have a relatively short lifespan

Seedling

Early season

Similar Species

Exotics

Kentucky bluegrass

Natives

N/A

Impacts

Agricultural

Bulbous bluegrass outcompetes desirable vegetation and offers little biomass as forage. Invades degraded rangelands and pastures

Ecological 

Mature plants are palatable to rodents and birds due to high starch and fat content

Habitat and Distribution

General requirements

Found in disturbed sites, roadsides, hay fields, and rangeland. Typically found in areas that receive 12-40 inches annual precipitation

Distribution 

Reported in western and Front Range counties in Colorado. Found throughout the western and mid-Atlantic regions of the US

Historical 

From Europe, Asia, and North Africa. Introduced accidentally to the US in the early 1900’s when it was being evaluated for turf, erosion control, and pasture

Biology/Ecology

Life cycle

Short-lived perennial

Mode of reproduction

Reproduces asexually in the US and asexually or by seed in its native range.  Bulblets may germinate immediately or stay dormant up to 2 years

References

Weed Control in Natural Areas in the Western United States. University of California Weed Research and Information Center. Pg 316-317 USDA. (2020). Bulbous Bluegrass.

USDA. (2019). Bulbous Bluegrass. USDA NRCS Plant Guide

Montana State University – http://msuinvasiveplants.org/extension/2014_june.html

Invasive Plant Atlas – https://www.invasiveplantatlas.org/subject.html?sub=6212

EddMaps – https://www.eddmaps.org/distribution/uscounty.cfm?sub=6212

 

Back to Weed List
Bulbous bluegrass