Scientific Name
Poa bulbosa L.
Common Name(s)
Bulbous bluegrass
Tribe / Family Name
Poeae
Flowering Period
May to June
Symbol
POBU
Description
Bulbous bluegrass is an introduced cool-season perennial bunchgrass. Culms range from 15–60 cm in height and contain bulbous bases. Its inflorescence is a contracted to open panicle 3–12 cm long and often nodding. Unmodified spikelets rare, but when present about 5-flowered, distinctly keeled, pubescent on the nerves, and webbed at the base. Modified spikelets usually produce bulblets with dark purple bases extending into foliaceous linear tips up to 20 mm long; each bulblet has the ability to form roots once it falls to the ground and asexually produce new plants. Awns are absent on unmodified spikelets, but the modified spikelets have awn-like foliaceous linear tips. Sheaths are closed about a 1/4 of their length and glabrous. Ligules are up to 3 mm long, membranous, obtuse to acute, entire or occasionally erose, and puberulent abaxially.
General Info
This short-lived species can be found along roadsides, sidewalks, trails, pastures, and other disturbed sites; and in open dry sites, foothills, plains, and montane areas.
Similar Species
Bulbous bluegrass may look similar to other bluegrass (Poa) species, which all have keeled (boat-shaped) leaf tips, panicle seed heads, and mainly basal leaves. To distinguish it from other bluegrasses, look for its dark purple bulblets with extending foliaceous linear tips and bulbous base stems. After it scenesces and drops its bulblets, it may look more silimilar to other bluegrasses, especially Sanberg bluegrass (Poa secunda).
Picture of growth habit.
Close-up picture of contracted to open panicle inflorescence.
Close-up picture of transformed vegetative bulblet extending into foliaceous linear tips.
Close-up picture of unmodified spikelet.
Close-up picture of membranous ligule.
Close-up picture of bulbous base.
Illustration of bulbous bluegrass. USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. <i>Manual of the grasses of the United States</i>. USDA Miscellaneous Publication No. 200. Washington, DC.
Distribution map of bulbous bluegrass. USDA PLANTS Database, 2022.