IUCN threat status:

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Description

General: Grass Family (Poaceae). Bulbous bluegrass is an introduced, short-lived perennial cool-season grass. It is the only grass known to have true bulbs (Halperin, 1933). The bulbs are normally dormant from mid-May through early October. When the weather begins to cool, leaves emerge from the bulbs. Growth is slow during the winter months, and by early March the plant is typically around 3 inches tall. As weather becomes warmer, it grows to a height of 6 to 24 inches. Leaf blades are narrow, flat or loosely rolled, with membranous ligules about 1/8 inch long. Few culms are produced per plant. Flowers are usually modified to bulblets with a dark purple base. The panicle has a plume-like appearance from the long, slender lemma (some refer to them as bracts) attached to each bulblet. The bulblets typically mature around early May, and soon after the grass senesces. The bulblets produced within the inflorescences germinate after a period of dormancy lasting a few months up to 2 years.

The formation of bulblets in bulbous bluegrass is a type of apomictic vivipary. The lowermost floret of the spikelet usually has a developed lemma, but lacks a palea. The lemmas of the second and third florets are long and leaf-like and are attached to a bulblet, which develops from the floral parts (Gould & Shaw, 1983).

Bulbous bluegrass reproduces primarily through asexual means in North America (USDA, 1948; Hitchcock, 1971; Gaines & Swan, 1972; Cronquist, 1977). However, it is believed to reproduce primarily through sexual means in its native habitat of Europe and mid East Asia (Youngner & McKell, 1972). This phenomenon may be explained by differences in climate. Youngner (1960) conducted a study to determine the effects of day length and temperature on reproductive structures of bulbous bluegrass, and found high temperatures (70-80ºF) and long days (16 hrs.) following inflorescence initiation promoted seed production, whereas cool temperatures (68ºF or less) and short days (8 hrs.) promoted bulblet production. Long days and cool temperatures or short days and high temperatures produced panicles with both seeds and bulblets.

Sexual reproduction of bulbous bluegrass may occur more frequently in North America than originally expected. Novak & Welfley (1997) used bulbous bluegrass to evaluate genetic diversity within and among populations of an introduced, vegetatively reproductive species, and found the diversity to be surprisingly high at both the species and population levels. They concluded the diversity likely resulted from a combination of sexual reproduction, the autopolyploid nature of the species, and multiple introduction events.

Bulbous bluegrass was introduced to North America accidentally, as a contaminant of alfalfa and clover seed. The grass was also introduced intentionally, for research purposes. In 1906 the USDA Office of Foreign Plant Introduction received bulblets of bulbous bluegrass from Russia (Vinall & Westover, 1928). The bulblets were grown by the Arlington, VA Experimental Farm in 1907, 1908 and 1909, and at Pullman, WA in 1907. At that time the grass was reported as having no particular promise, and the investigations soon ended.

Bulbous bluegrass was re-evaluated in 1915 after the groundskeepers at the state capitol in Richmond, VA asked the USDA for assistance identifying the grass and determining methods to eradicate it. The groundskeepers considered the grass to be undesirable since it performed poorly in the summer months. The USDA grew the grass in a greenhouse and determined the grass to be Poa bulbosa. They advised the groundskeepers not to eradicate it, but instead manage it as winter grass in combination with Bermuda grass for the summer months (Vinall & Westover, 1928).

In 1916 bulblets of the grass were distributed by the USDA to several experiment stations. Commercial production of the grass followed, and in 1928, Medford, OR was considered the center of production (Vinall & Westover, 1928). During this time, bulbous bluegrass was used to compliment Bermuda grass in pastures and turf, but new evaluations were beginning to demonstrate the grass did not tolerate frequent clipping, and actually outcompeted Bermuda grass when both were grown together.

Bulbous bluegrass was still thought to have value in 1948, when it was recommended to replace cheatgrass on poor condition sites and as an understory species in seed mixtures in southern Idaho (Hull & Stewart, 1948).

The Pullman Plant Materials Center (PMC) evaluated bulbous bluegrass for use in critical area plantings in the 1950's. In 1956, P-4784 was released but the bulblets failed to retain acceptable levels of germination. Consequently, P-4784 was not distributed to growers.

As recently as 1997, the merits of bulbous bluegrass were still being considered, when it was included in a study to determine optimal species for low-input sustainable turf grass in the upper Midwest. The grass performed poorly and was not recommended for this use (Diesburg, 1997).

Distribution: Bulbous bluegrass grows in nearly all temperate and subtropical regions throughout the world. In North America, it inhabits roadsides and hay and crop fields. It tends to be more common in western states than eastern states.

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USDA NRCS Plant Materials Center, Pullman, Washington

Source: USDA NRCS PLANTS Database

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