Poa bulbosa

This grass is a short-lived cool-season perennial. From fall to early spring, it consists of a tuft of sprawling basal leaves less than 6" tall. From mid-spring to early summer, leafy culms develop that are 6-20" long; these culms are erect to sprawling. The slender culms are light to medium green, terete, hollow, glabrous, and unbranched. Alternate leaves occur primarily along the lower one-third of each culm. The linear leaf blades are 1-3 mm. across and 1-4" long; they are medium green to grayish blue, glabrous, and either flat or furrowed in the middle; their tips are hull-shaped. The leaf sheaths are medium green, longitudinally veined, glabrous, and rather loose; the upper two-thirds of each sheath are open, while the lower one-third is closed. The nodes are slightly swollen and dark-colored, while the ligules are white-membranous. Each culm terminates in an ovoid to oblongoid panicle of spikelets or aerial bulblets. The typical panicle is 1½-4" long and 1-1½" across; it has a slender central stalk (rachis) and whorls of 2-3 wiry lateral branches that are more or less horizontal below and ascending above. The lateral branches often divide into secondary branches that terminate in either flattened spikelets or clusters of scaly bulblets; both spikelets and bulblet clusters have short pedicels. Individual culms can produce all spikelets, all bulblets, or a mixture of the two. In Illinois, most culms produce only bulblets. When spikelets are produced, they are 4-6 mm. long, consisting of a pair of glumes at the bottom and 2-6 lemmas above that have perfect florets. The glumes and lemmas are arranged into two ranks that are columnar and overlapping. The narrow glumes and lemmas are keeled; the glumes are 2-3.5 mm. long, while the lemmas are 2.5-3.5 mm. long. In each spikelet, one glume is a little longer than the other. Each lemma has a midvein along the keel and 2 marginal veins that are minutely pubescent, at least along the lower half of each vein (requires 10x magnification to see). Individual florets have 3 stamens and a pair of feathery stigmata. The aerial bulblets are about 1/4" long and 1/8" across; they have purple bases and greenish purple or greenish white scales (modified lemmas). At the apex of each bulblet, one or more aerial basal leaves are produced that are green and narrowly linear in shape; they are up to 1" long. Each cluster of aerial bulblets has a pair of glumes underneath that are lanceolate and slightly succulent. When spikelets are produced, the blooming period occurs during late spring or early summer. The florets are wind-pollinated. In Illinois and other areas of North America, relatively few spikelets produce grains. Aerial bulblets also develop during the late spring and early summer; they become mature later in the summer, becoming detached from the mother plant. By forming rootlets in the ground, the bulblets are capable of forming clonal plants. The root system of a plant consists of a terrestrial bulb with secondary fibrous roots below. New bulbs are often produced below ground as vegetative offsets.

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.

Winter bluegrass

Bulbous bluegrass, a native species in southern Asia, Europe, and northern Africa, has established outside cultivation in North America. It is much more common in the western than in the eastern United States [21,24,47,86]. From North Dakota to Oklahoma and westward, bulbous bluegrass is common [10], but in the northeastern United States, bulbous bluegrass is generally restricted to fields, lawns, and meadows [21]. Bulbous bluegrass is also reported from parts of southern Canada [41].

Bulbous bluegrass was likely a contaminant in grass and/or clover seed imported by the United States [80]. Records indicate that in early 1900s bulbous bluegrass was intentionally planted on sites near Arlington, Virginia, and Pullman, Washington [47]. In the Pacific Northwest, bulbous bluegrass dispersal was tracked through the use of herbaria records. Bulbous bluegrass originated near Portland, Oregon, an active shipping port, spread into Washington and progressed eastward to northern Idaho and western Montana between 1891 and 1980 [17]. The distribution of bulbous bluegrass in the United States and southern Canada is available from the Grass Manual on the Web.

The non-native Bulbous Bluegrass is uncommon in Illinois, occurring in widely scattered areas. However, it is likely that this Eurasian grass will become more common in the future. Bulbous Bluegrass was introduced deliberately into the United States to be used as a possible turf grass; it also may have been introduced accidentally as a contaminant in grass and clover seed. Habitats include weedy meadows, lawns, abandoned fields, roadsides, areas near parking lots, thin woodlands, and waste areas. Degraded habitats with a history of disturbance are preferred.

Poa montana Honck.:
Germany (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa montana Cordem.:
Reunion (Africa & Madagascar)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa concinna var. carniolica Hladnik & Graf ex Mutel:
Austria (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa bulbosa subsp. perligulata H. Scholz:
France (Europe)
Greece (Europe)
Italy (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa montana All.:
Italy (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa cephalonica H. Scholz:
Greece (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa bulbosa subsp. pseudoconcinna (Schur) Domin:
Czechoslovakia (Europe)
Greece (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa bulbosa subsp. nevskii (Roshev. ex Ovcz.) Tzvelev:
Russian Federation (Asia)
Tajikistan (Asia)
Turkmenistan (Asia)
Uzbekistan (Asia)
China (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa bulbosa subsp. delicatula (Wilhelms ex Tzvelev) Tzvelev:
Iran (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Poa bulbosa L.:
Austria (Europe)
Afghanistan (Asia)
Albania (Europe)
Argentina (South America)
Australia (Oceania)
Baleares (Europe)
Belgium (Europe)
Canada (North America)
Chile (South America)
Czechoslovakia (Europe)
Denmark (Europe)
Germany (Europe)
Finland (Europe)
France (Europe)
Greece (Europe)
Hungary (Europe)
India (Asia)
Iraq (Asia)
Iran (Asia)
Italy (Europe)
Kriti (Europe)
Kyrgyzstan (Asia)
Kazakhstan (Asia)
Netherlands (Europe)
Norway (Europe)
Nepal (Asia)
Sweden (Europe)
New Zealand (Oceania)
Corsica (Europe)
Pakistan (Asia)
Portugal (Europe)
Poland (Europe)
Russian Federation (Asia)
Romania (Europe)
Sardegna (Europe)
Sicilia (Europe)
Spain (Europe)
Switzerland (Europe)
Tajikistan (Asia)
Turkmenistan (Asia)
Turkey (Asia)
Bulgaria (Europe)
Ukraine (Europe)
United Kingdom (Europe)
United States (North America)
South Africa (Africa & Madagascar)
Yugoslavia (Europe)
China (Asia)
Uzbekistan (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Xinjiang, Xizang [Afghanistan, NW India, Kazakhstan, Kyrgyzstan, Nepal, Pakistan, Russia (Siberia), Tajikistan, Turkmenistan, Uzbekistan; Africa, SW Asia, Europe; introduced in Australia, New Zealand, North and South America, and Pacific Islands].

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Distribution: Pakistan (Baluchistan, N.W.F.P., Gilgit & Kashmir); Europe, South-west and Central Asia.

Widespread in N. hemisphere.

Bulbous bluegrass is best adapted to areas that have dry summers, mild winters, and winter rainfall. It is typically found within the 12" – 40" precipitation zones.

More info for the terms: bulb, bulbil

This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [12,21,30,31,41,56,76]).

Aboveground description: Bulbous bluegrass is a nonnative tuft- or sod-forming grass [26,56]. It is described as a perennial [26,29,66], an annual [38], and as an annual with "perennial tendencies" [36]. Because bulbous bluegrass grows new roots each season [63,81] and has a relatively short life span [61,86], its life history is easily confused. Bulbous bluegrass stems and culms are erect, attach to bulbous bases, and measure 6 to 28 inches (15-70 cm) tall [29,31,76,86]. Culms are hollow and smooth [25]. Basal leaves are flat to involute, 1 to 3 mm wide, and 2 to 6 inches (5-15 cm) long [31,41,67].

The aboveground pear-shaped bulbs are approximately 1 cm long [86] and consist of a thick, solid internode that is surrounded by scale-like leaves [26]. Studies of bulbous bluegrass in its native habitats showed that bulbs were common in regions that experienced a periodic dry season but not in moist areas. When bulbous bluegrass was planted in moist areas, basal bulbs were not produced. The researcher indicated that although bulbous bluegrass basal bulbs were structurally similar to those of lilies and irises, they stored primarily water and not starch or sugar [32].

On its 1- to 4.5-inch (3-12 cm) long, one-sided panicle, bulbous bluegrass produces 2 types of spikelets: one typically has 3 to 6 normal florets; the other is a viviparous bulbil or bulblet without pistils or stamens [26,31,41,51]. Bulbils are more common than true florets in most US populations [28,29,31,56,86]. However, plants with both bulbils and true florets do occur [26,67]. Bulbils are transformed florets with all the necessary tissue to propagate a new plant, and measure 5 to 15 mm long [26,67].

Belowground description: 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 (1-10 cm) long and support numerous, short, thread-like rootlets about 1 mm long [26]. On disturbed sites in Utah, bulbous bluegrass roots formed mycorrhizal associations [62].

Perennials, Terrestrial, not aquatic, Bulbs present, Basal sheaths fibrous, old leaves p ersistent at base of plant, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems swollen at base, tuberous, cormous or bulbous, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, In florescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence with 2-10 branches, Inflorescence branches more than 10 to numerous, Flowers bisexual, Flowers replaced by bulbils, Spikelets pedicellate, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 2 florets, Spikelets with 3-7 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes shorter than adjacent lemma, Glumes keeled or winged, Glumes 1 nerved, Glumes 3 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 5-7 nerved, Lemma body or surface hairy, Lemma apex acute or acuminate, Lemma awnless, Lemma margins th in, lying flat, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Lemma with long cobwebby white hairs, Palea present, well developed, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Plants sterile, few or no mature seeds produced, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Tufted perennial; culms 15–40cm high, erect or geniculately ascending, clothed at the base with the hardened remains of old leaf-sheaths forming a bulbous swelling. Leaf-blades flat or folded, mostly basal, 2–10cm long, (0.5–)1–2 mm wide, abruptly contracted to a hooded tip, smooth or scaberulous; ligule acute, 1-3mm long. Panicle ovate, 2–6(–9)cm long, compact; branches paired, ascending, scabrid. Spikelets 2–6–flowered, ovate-oblong, 3–6mm long, often tinged with purple; glumes subequal, broadly ovate, 2–3mm long, the lower 1–nerved, the upper 3–nerved; lemmas oblong–lanceolate in side-view, 2.5–3.5mm long, acute, ciliate on the keel and marginal nerves or sometimes ± glabrous, usually densely woolly at the base; palea almost as long as the lemma, scabrid along the keels; anthers 1–1.5mm long.

Perennials, densely tufted; shoots with bulbous bases. Culms erect or geniculately ascending, (9–)15–55 cm tall, base with bulbous withered leaf sheaths, nodes 2 or 3, exserted. Leaf sheath smooth, uppermost culm sheath closed for 1/4 of length, tiller sheaths usually less than 1/15–1/7(–1/5) length of blades; blades flat or folded, thin, soon withering, mostly basal, 2–10 cm, 0.5–2(–2.5) mm wide, surfaces smooth, margins scabrid, not cartilaginous; ligule hyaline or milky-white, 1–2(–3.5) mm, apex acuminate. Panicle contracted (looser in viviparous inflorescences), oblong to ovate, 2–8 cm; branches obliquely ascending, 2–4 per node, scabrid, longest to 2 cm. Spikelets purple tinged, 3.5–5(–7.5) mm, florets 2–6 (when normal); vivipary commonly present; rachilla smooth, glabrous; glumes subequal, ovate, 3-veined, 2–3 mm, keel sparsely scabrid; lemmas normal or viviparous, lower 1 or 2 normal, (2.5–)3–3.5 mm, apex acute, keel villous to 2/3 of length, marginal veins to 1/2, area between veins glabrous, often glabrous throughout in viviparous spikelets; callus webbed, hairs moderately dense, commonly glabrous in viviparous spikelets; palea keels scabrid. Anthers (1–)1.4–1.6 mm, usually abortive in viviparous spikelets. Fl. and fr. May–Jul. 2n = 14, 28, 39, 42, 45.

4200 m

More info for the terms: bulb, cover, serpentine soils

Bulbous bluegrass is primarily described in disturbed, dry to moist habitats throughout its range. Low- to mid-elevation pastures, abandoned fields, and roadsides near low elevation chaparral, oak, sagebrush, pinyon-juniper, mixed conifer, meadow, and streambank communities are typical bulbous bluegrass habitat [25,28,56,66,86]. Growth is considered best on sites with moderately fertile soils that experience cool, moist growing seasons [81].

Climate: Bulbous bluegrass tolerates drought and cold [82] and grows best in climates with dry summers and mild, moist winters. Big sagebrush-bluebunch wheatgrass communities in Grant County, Washington, where bulbous bluegrass occurs, experience a semiarid climate. Annual precipitation averages 8 inches (203 mm), and most precipitation comes in the fall and winter [46]. Near Pocatello, Idaho, bulbous bluegrass occurs in big sagebrush/mixed grasslands that average 10.9 inches (276 mm) of precipitation annually, most of which is delivered as snow in the winter and rain in the spring [68]. In bulbous bluegrass habitats in Tooele County, Utah, average annual precipitation was 12.9 inches (328 mm) for a 30-year period. In the same period, the maximum annual precipitation was 19 inches (483 mm), and the minimum was 6.8 inches (173 mm). Temperature extremes for the 30-year period were 102 °F (39 °C) and -22 °F (-30 °C) [19].

Available moisture can affect bulbous bluegrass abundance. In big sagebrush- and low sagebrush-dominated communities in Washington County, Idaho, bulbous bluegrass cover averaged 23% to 37% during a cool, wet spring and summer. When conditions were hot and dry in the spring and summer months, bulbous bluegrass cover averaged 13% to 22% [71].

Summer dormancy/drought avoidance: Bulbous bluegrass avoids drought conditions by senescing roots and green tissue. Tissues regrow from the bulb when growing conditions are favorable. Experiments conducted in Davis, California, revealed that bulbous bluegrass exhibited summer dormancy even when supplied with summer moisture [45]. Volaire and Norton [83] determined that summer dormancy was triggered by increasing day lengths and temperatures and that mature tissues within the bulbs remain dormant for at least 4 weeks. Regrowth from bulbs was rapid.

Elevation: Based on plantings of bulbous bluegrass in the Intermountain Region, Plummer [63] indicates that bulbous bluegrass establishes well in the lower foothills but typically does not survive at "high" elevation sites. Elevational tolerances in other western US habitats are provided below.

Elevational tolerances for bulbous bluegrass by state or region State/region Elevation California below 6,600 feet [29] southern California below 5,000 feet [56] northern Colorado 5,000-8,000 feet [28] Nevada 4,300-7,200 feet [38] Utah 3,000-7,000 feet [61] Intermountain West low to middle elevations [10]

Soils: Bulbous bluegrass occurs on sandy, gravelly, silty, loamy, and clayey soils and tolerates salty, shallow, and low-fertility conditions [61,82]. Bulbous bluegrass is adapted to shallow, coarse-textured soils in northeastern Oregon [87]. Bulbous bluegrass is also common on shallow scabland soils with cheatgrass (Bromus tectorum) [24]. In a 320,000-acre (130,000 ha) study area that included parts of Napa, Lake, and Colusa counties in California, bulbous bluegrass occurred on nonserpentine but not on serpentine soils [20]. On Fire Island in Suffolk County, New York, bulbous bluegrass was rare and occurred on dry, ruderal sands [13].

Disturbed sites, roadsides, and abandoned fields are common bulbous bluegrass habitats. In the western
United States, it occurs in perennial and annual grasslands, chaparral, pinyon-juniper
(Pinus-Juniperus spp.) woodlands, riparian communities, sagebrush (Artemisia spp.)-
steppe vegetation, and openings in coniferous forests. Bulbous bluegrass has been used to seed disturbed
sites throughout the United States [54,61] and is possible in any disturbed area or opening near
seeded sites. Species commonly associated with bulbous bluegrass include brome grasses (Bromus spp.),
wheatgrasses (Agropyron spp.), bluebunch wheatgrass (Pseudoroegneria spicata), Kentucky
bluegrass (Poa pratensis), big sagebrush (A. tridentata), low sagebrush (A. arbuscula),
mountain-mahogany (Cercocarpus spp.), oaks (Quercus spp.), ponderosa pine (P. ponderosa),
Douglas-fir (Pseudotsuga menziesii), and quaking aspen (Populus tremuloides).

The non-native Bulbous Bluegrass is uncommon in Illinois, occurring in widely scattered areas. However, it is likely that this Eurasian grass will become more common in the future. Bulbous Bluegrass was introduced deliberately into the United States to be used as a possible turf grass; it also may have been introduced accidentally as a contaminant in grass and clover seed. Habitats include weedy meadows, lawns, abandoned fields, roadsides, areas near parking lots, thin woodlands, and waste areas. Degraded habitats with a history of disturbance are preferred.

Plains, sandstone slopes, desert grasslands, river shores, wastelands near fruit gardens; 700–4700 m.

This species is not recommended for seeding.

 Insects that feed on bluegrasses (Poa spp.) include Leptoterna dolobrata (Meadow Plant Bug) and other plant bugs, the planthopper Delphacodes campestris, Schizaphis graminum (Greenbug), and other aphids. Many grasshoppers eat the foliage of bluegrasses; they include Aeropedellus clavatus (Club-Horned Grasshopper), Arphia sulfurea (Sulfur-Winged Grasshopper), Eritettix simplex (Velvet-Striped Grasshopper), Melanoplus foedus (Striped Sand Grasshopper), and Melanoplus sanguinipes (Migratory Grasshopper). Other insect feeders include the caterpillars of the butterflies Cercyonis pegala (Common Wood Nymph) and Megisto cymela (Little Wood Satyr); also the caterpillars of several skippers, including Amblyscirtes hegon (Pepper-and-Salt Skipper), Amblyscirtes vialis (Common Roadside Skipper), Poanes hobomok (Hobomok Skipper), and Polites peckius (Peck's Skipper). Moth caterpillars that feed on bluegrasses include Feltia jaculifera (Dingy Cutworm), Nephelodes minians (Bronze Cutworm), Parapediasia teterrella (Bluegrass Webworm), Pediasia trisecta (Sod Webworm), Phalaenostola larentioides (Black-Banded Owlet), and Thioptera nigrofimbria (Black-Bordered Lemon Moth). Among these moth species, caterpillars of the Black-Banded Owlet feed on dead leaves. Because the aerial bulblets of Bulbous Bluegrass contain abundant starch and some fat, they are a useful source of food to many vertebrate animals, including elk, deer, sheep, upland gamebirds, deer-mice, and ground squirrels. Young foliage of Bulbous Bluegrass is palatable to rabbits and hoofed mammalian herbivores during the spring.

Foodplant / parasite
Blumeria graminis parasitises live Poa bulbosa

There is little information regarding the effects of fire on bulbous bluegrass. Additional studies of fire in bulbous bluegrass habitats are needed before recommendations regarding fire effects on this species are warranted.

More info for the terms: cover, fire severity, frequency, prescribed fire, severity, wildfire

There are very few studies that compare bulbous bluegrass abundance on unburned and burned sites. Of the
few fire studies available, most fail to provide prefire or unburned comparison data and/or fire season
or severity information. While bulbous bluegrass is often present on burned sites, without more
information on postfire recovery, inferences regarding the effects of fire season and severity on bulbous
bluegrass abundance are difficult to make. Discussion of bulbous bluegrass's response to fire is also
made difficult because of its often low frequency and/or cover and patchy distribution relative to
disturbed sites. Without prefire data and land use history on burned and unburned sites, the validity of
comparisons is unknown.

Bulbous bluegrass is often present on recently burned sites [44,52,62]. Three to four years after a
wildfire in a forage kochia (Bassia prostrata)-dominated community near Ephraim Canyon in central
Utah, researchers indicated that bulbous bluegrass was "not materially affected by fire". The
assessment was based on transect data from burned and adjacent unburned sites, but abundance of bulbous
bluegrass was not reported [52]. In the fourth postfire growing season after a severe sagebrush-mixed
grass fire on West Mountain in Utah, bulbous bluegrass cover averaged 4.5% on the burned site but was
absent from the unburned site [62]. Bulbous bluegrass was present only on early-spring grazed and burned
sites when burned and unburned, summer and spring grazed purple needlegrass (Nassella pulchra)
grasslands at the Jepson Prairie Preserve in Solano, California, were compared. "High intensity,
short duration" grazing by domestic sheep occurred in March to early April or in August from 1988
to 1990. The fire burned in September when temperatures were 75 to 82 °F (24-28 °C), relative humidity was
47% to 61%, and wind speeds were 10 to 25 km/hour with gusts of up to 40 km/h [44].
While some report increased bulbous bluegrass abundance with time since fire [68], others report that
time since fire may not affect abundance [11,23,46]. It is likely that postfire growing conditions
and/or fire severity would affect recovery over time. Bulbous bluegrass cover averaged 6.7% on burned
sagebrush-grasslands southwest of Pocatello, Idaho, and cover was significantly (P=0.001) greater
in the 2nd postfire growing season than in the 1st. The fire burned in August in an area free of domestic
grazing for more than 35 years. No unburned or prefire data were reported, and neither
burning conditions nor fire behavior was described [68]. While bulbous bluegrass cover greatly increased after a fire
in bluebunch wheatgrass/Sandberg bluegrass (Poa secunda) grasslands near Lewiston, Idaho, cover
in the 2nd and 3rd postfire years was relatively unchanged. The fire was low severity and burned in August.
Average bulbous bluegrass cover before the fire was 0.09%. In the 2nd and 3rd postfire years, bulbous
bluegrass cover was 1.11% and 1.04%, respectively [23]. Bulbous bluegrass occurred on 1 of 6 plots before
a prescribed fire and 1 of 6 plots 1 and 2 years after a prescribed fire in big sagebrush-bluebunch
wheatgrass vegetation on the Columbia National Wildlife Refuge in Grant County, Washington. Sites burned
previously in 1993 before the early October 2002 prescribed fire. The 2002 fire was a flanking fire although
some back and head fire behavior occurred [46]. When 2- to 3-year-old and 5- to 6-year-old burned Wyoming
big sagebrush (Artemisia tridentata ssp. wyomingensis)-dominated vegetation in southern Idaho
were compared, bulbous bluegrass cover averaged 0.16/m² on both sites. Both
sites burned in August. Prefire or unburned bulbous bluegrass cover was not reported [11].
The following Research Project Summaries provide information on prescribed
fire and postfire response of many plant species including bulbous bluegrass:

• Effects of fall and spring prescribed burning in sagebrush steppe in Oregon
• Changes in grassland vegetation following fire in northern Idaho

More info for the terms: fire severity, litter, severity

Based on studies and literature from the Mediterranean Region, bulbous bluegrass may sprout vegetatively after fire [57], but regeneration methods in nonnative US habitats have not been described (2007). Postfire sprouting may depend on fire season since roots shrivel and disappear during the summer dormant period. Survival of basal bulbs and bulbils on the soil surface is likely dependent on fire severity. Buried bulbils may survive fire, and consumption of litter and humus layers may uncover bulbils enough for successful germination. (See discussion on Depth of burial). Dispersal of bulbils from adjacent unburned sites or unburned refugia into burned areas is probable.

Although immediate fire effects are not described in the literature, bulbous bluegrass is likely top-killed or killed by fire.

More info for the terms: graminoid, ground residual colonizer, initial off-site colonizer, secondary colonizer, tussock

POSTFIRE REGENERATION STRATEGY [75]:
Tussock graminoid
Ground residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Secondary colonizer (on-site or off-site seed sources)

More info for the terms: fire regime, fire severity, fuel, litter, low-severity fire, mesic, natural, presence, severity, shrub, shrubs

Fire adaptations: A review of studies and literature from the Mediterranean Region suggests that bulbous bluegrass may sprout vegetatively after fire [57]. The postfire regeneration methods for North American bulbous bluegrass populations have not been described, but inferences based on its reproductive biology are possible. Postfire sprouting may depend on fire season since roots shrivel and disappear during the summer dormant period. Survival of basal bulbs and bulbils on the soil surface is likely dependent on fire severity. Buried bulbils may survive fire, and consumption of litter and humus layers may uncover bulbils enough for successful germination. (See discussion on Depth of burial). Dispersal of bulbils from adjacent unburned sites or unburned refugia into the burned area is probable.

FIRE REGIMES: In native bulbous bluegrass habitats, the prevailing fire regime in which the species evolved is unknown. It is also unclear how the presence of bulbous bluegrass may affect FIRE REGIMES in its nonnative US habitats. Kartesz [38] suggests that bulbous bluegrass may pose a fire risk when dry; however, Plummer and others [65] suggest that bulbous bluegrass establishment in cheatgrass-dominated areas may decrease fire risk. Because stems and culms often shrivel and detach from basal bulbs during drought conditions, bulbous bluegrass establishment in cheatgrass-dominated areas can break up the continuity of available fine fuels. Decreased fuel availability could lead to decreased ignition and/or fire spread potential.

The distribution of bulbous bluegrass in the western United States is described, while its distribution throughout the rest of the United States is not. Below is a list of habitats containing species that bulbous bluegrass is associated with in the West. For information on communities not listed below, see the complete FEIS Fire Regime Table.

Fire regime information on vegetation communities in which bulbous bluegrass may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models [43]. These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the .pdf file linked from each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model. Pacific Northwest California Southwest Great Basin Northern Rockies Pacific Northwest

• Northwest Grassland
• Northwest Shrubland
• Northwest Woodland
• Northwest Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Northwest Grassland Bluebunch wheatgrass Replacement 47% 18 5 20 Mixed 53% 16 5 20 Idaho fescue grasslands Replacement 76% 40     Mixed 24% 125     Northwest Shrubland Wyoming big sagebrush semidesert Replacement 86% 200 30 200 Mixed 9% >1,000 20   Surface or low 5% >1,000 20   Wyoming sagebrush steppe Replacement 89% 92 30 120 Mixed 11% 714 120   Low sagebrush Replacement 41% 180     Mixed 59% 125     Mountain big sagebrush (cool sagebrush) Replacement 100% 20 10 40 Northwest Woodland Western juniper (pumice) Replacement 33% >1,000     Mixed 67% 500     Oregon white oak-ponderosa pine Replacement 16% 125 100 300 Mixed 2% 900 50   Surface or low 81% 25 5 30 Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     Oregon white oak Replacement 3% 275     Mixed 19% 50     Surface or low 78% 12.5     Northwest Forested Douglas-fir (Willamette Valley foothills) Replacement 18% 150 100 400 Mixed 29% 90 40 150 Surface or low 53% 50 20 80 Ponderosa pine (xeric) Replacement 37% 130     Mixed 48% 100     Surface or low 16% 300     Dry ponderosa pine (mesic) Replacement 5% 125     Mixed 13% 50     Surface or low 82% 8     Douglas-fir-western hemlock (dry mesic) Replacement 25% 300 250 500 Mixed 75% 100 50 150 Douglas-fir-western hemlock (wet mesic) Replacement 71% 400     Mixed 29% >1,000     Mixed conifer (southwestern Oregon) Replacement 4% 400     Mixed 29% 50     Surface or low 67% 22     Mixed conifer (eastside dry) Replacement 14% 115 70 200 Mixed 21% 75 70 175 Surface or low 64% 25 20 25 Mixed conifer (eastside mesic) Replacement 35% 200     Mixed 47% 150     Surface or low 18% 400     California

• California Grassland
• California Shrubland
• California Woodland
• California Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) California Grassland California grassland Replacement 100% 2 1 3 California Shrubland Chaparral Replacement 100% 50 30 125 Montane chaparral Replacement 34% 95     Mixed 66% 50     California Woodland California oak woodlands Replacement 8% 120     Mixed 2% 500     Surface or low 91% 10     Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     California Forested Mixed conifer (North Slopes) Replacement 5% 250     Mixed 7% 200     Surface or low 88% 15 10 40 Mixed conifer (South Slopes) Replacement 4% 200     Mixed 16% 50     Surface or low 80% 10     Aspen with conifer Replacement 24% 155 50 300 Mixed 15% 240     Surface or low 61% 60     Southwest

• Southwest Grassland
• Southwest Shrubland
• Southwest Woodland
• Southwest Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Southwest Grassland Desert grassland with shrubs and trees Replacement 85% 12     Mixed 15% 70     Plains mesa grassland with shrubs or trees Replacement 76% 20     Mixed 24% 65     Montane and subalpine grasslands Replacement 55% 18 10 100 Surface or low 45% 22     Montane and subalpine grasslands with shrubs or trees Replacement 30% 70 10 100 Surface or low 70% 30     Southwest Shrubland Low sagebrush shrubland Replacement 100% 125 60 150 Mountain sagebrush (cool sage) Replacement 75% 100     Mixed 25% 300     Gambel oak Replacement 75% 50     Mixed 25% 150     Mountain-mahogany shrubland Replacement 73% 75     Mixed 27% 200     Southwest Woodland Pinyon-juniper (mixed fire regime) Replacement 29% 430     Mixed 65% 192     Surface or low 6% >1,000     Ponderosa pine/grassland (Southwest) Replacement 3% 300     Surface or low 97% 10     Southwest Forested Riparian deciduous woodland Replacement 50% 110 15 200 Mixed 20% 275 25   Surface or low 30% 180 10   Southwest mixed conifer (warm, dry with aspen) Replacement 7% 300     Mixed 13% 150 80 200 Surface or low 80% 25 2 70 Southwest mixed conifer (cool, moist with aspen) Replacement 29% 200 80 200 Mixed 35% 165 35   Surface or low 36% 160 10   Stable aspen without conifers Replacement 81% 150 50 300 Surface or low 19% 650 600 >1,000 Great Basin

• Great Basin Grassland
• Great Basin Shrubland
• Great Basin Woodland
• Great Basin Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Great Basin Grassland Great Basin grassland Replacement 33% 75 40 110 Mixed 67% 37 20 54 Mountain meadow (mesic to dry) Replacement 66% 31 15 45 Mixed 34% 59 30 90 Great Basin Shrubland Basin big sagebrush Replacement 80% 50 10 100 Mixed 20% 200 50 300 Wyoming big sagebrush semidesert Replacement 86% 200 30 200 Mixed 9% >1,000 20 >1,000 Surface or low 5% >1,000 20 >1,000 Wyoming big sagebrush semidesert with trees Replacement 84% 137 30 200 Mixed 11% >1,000 20 >1,000 Surface or low 5% >1,000 20 >1,000 Wyoming sagebrush steppe Replacement 89% 92 30 120 Mixed 11% 714 120   Mountain big sagebrush Replacement 100% 48 15 100 Mountain big sagebrush with conifers Replacement 100% 49 15 100 Mountain sagebrush (cool sage) Replacement 75% 100     Mixed 25% 300     Mountain shrubland with trees Replacement 22% 105 100 200 Mixed 78% 29 25 100 Black and low sagebrushes Replacement 33% 243 100   Mixed 67% 119 75 140 Black and low sagebrushes with trees Replacement 37% 227 150 290 Mixed 63% 136 50 190 Curlleaf mountain-mahogany Replacement 31% 250 100 500 Mixed 37% 212 50   Surface or low 31% 250 50   Great Basin Woodland Juniper and pinyon-juniper steppe woodland Replacement 20% 333 100 >1,000 Mixed 31% 217 100 >1,000 Surface or low 49% 135 100   Ponderosa pine Replacement 5% 200     Mixed 17% 60     Surface or low 78% 13     Great Basin Forested Interior ponderosa pine Replacement 5% 161   800 Mixed 10% 80 50 80 Surface or low 86% 9 8 10 Ponderosa pine-Douglas-fir Replacement 10% 250   >1,000 Mixed 51% 50 50 130 Surface or low 39% 65 15   Great Basin Douglas-fir (dry) Replacement 12% 90   600 Mixed 14% 76 45   Surface or low 75% 14 10 50 Aspen with conifer (low to midelevation) Replacement 53% 61 20   Mixed 24% 137 10   Surface or low 23% 143 10   Douglas-fir (warm mesic interior) Replacement 28% 170 80 400 Mixed 72% 65 50 250 Aspen with conifer (high elevation) Replacement 47% 76 40   Mixed 18% 196 10   Surface or low 35% 100 10   Stable aspen without conifers Replacement 81% 150 50 300 Surface or low 19% 650 600 >1,000 Northern Rockies

• Northern Rockies Grassland
• Northern Rockies Shrubland
• Northern Rockies Forested

Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean interval
(years) Minimum interval
(years) Maximum interval
(years) Northern Rockies Grassland Northern prairie grassland Replacement 55% 22 2 40 Mixed 45% 27 10 50 Mountain grassland Replacement 60% 20 10   Mixed 40% 30     Northern Rockies Shrubland Riparian (Wyoming) Mixed 100% 100 25 500 Wyoming big sagebrush Replacement 63% 145 80 240 Mixed 37% 250     Basin big sagebrush Replacement 60% 100 10 150 Mixed 40% 150     Low sagebrush shrubland Replacement 100% 125 60 150 Mountain shrub, nonsagebrush Replacement 80% 100 20 150 Mixed 20% 400     Mountain big sagebrush steppe and shrubland Replacement 100% 70 30 200 Northern Rockies Forested Ponderosa pine (Northern Great Plains) Replacement 5% 300     Mixed 20% 75     Surface or low 75% 20 10 40 Ponderosa pine (Northern and Central Rockies) Replacement 4% 300 100 >1,000 Mixed 19% 60 50 200 Surface or low 77% 15 3 30 Ponderosa pine (Black Hills, low elevation) Replacement 7% 300 200 400 Mixed 21% 100 50 400 Surface or low 71% 30 5 50 Ponderosa pine-Douglas-fir Replacement 10% 250   >1,000 Mixed 51% 50 50 130 Surface or low 39% 65 15   Western redcedar Replacement 87% 385 75 >1,000 Mixed 13% >1,000 25   Douglas-fir (xeric interior) Replacement 12% 165 100 300 Mixed 19% 100 30 100 Surface or low 69% 28 15 40 Douglas-fir (warm mesic interior) Replacement 28% 170 80 400 Mixed 72% 65 50 250 Douglas-fir (cold) Replacement 31% 145 75 250 Mixed 69% 65 35 150 *Fire Severities: Replacement=Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Surface or low=Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area.
Mixed=Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects [27,42].

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More info for the terms: cover, frequency, shrub

In its native habitats, bulbous bluegrass occurs in both early- and late-seral habitats, but in the United States, it is most typical of disturbed sites and early-seral communities.

Native habitats: Bulbous bluegrass dominated late-seral pastures within open woodland habitats north of Madrid, Spain, and was not listed as a common species in early-successional pastures dominated by annual grasses [49]. In Israel, bulbous bluegrass was associated with closed and semi-open maquis vegetation and oak woodlands. In western Spain, bulbous bluegrass occurred on ploughed dehesas and persisted in later-seral shrub-dominated communities [34].

Shade tolerance: Open sites and canopy openings are preferred bulbous bluegrass habitat. Bulbous bluegrass cover and herbage production were greater in the openings than in the shrub understory in seeded sites within shrub/bunchgrass communities in south-central Idaho [54].

Disturbance-related succession: Most research and studies suggest that bulbous bluegrass establishment requires some type of disturbance. In Oregon and Washington, bulbous bluegrass is characteristic of overgrazed or disturbed western juniper/curlleaf mountain-mahogany (Juniperus occidentalis/Cercocarpus ledifolius) and riparian habitats [8,9]. In southeastern Oregon, bulbous bluegrass occurs on "severely degraded" riparian sites [15]. On the Fitzner-Eberhardt Arid Lands Ecology Reserve in Washington, bulbous bluegrass frequency was 40% to 60% in 57-year-old abandoned fields but was absent from adjacent uncultivated big sagebrush/bluebunch wheatgrass vegetation [73]. However, in bluebunch wheatgrass-dominated canyon grasslands near Lewiston, Idaho, bulbous bluegrass occurred in communities classified as early-, mid-, and late-seral. Bulbous bluegrass abundance increased after fire in all seral stages [23].

While the introduction of bulbous bluegrass is typically associated with disturbances, it established in never tilled, native shrub-steppe communities in Methow Valley, Washington. A comparison of tilled and untilled sites revealed that bulbous bluegrass abundance increased with increased time since abandonment, and cover increased over time in untilled, native shrub-steppe communities. Tilled sites spanned a 52-year chronosequence. Bulbous bluegrass cover was significantly greater on tilled than untilled (P<0.05) communities, averaging 6.6% on old fields and 1.3% in never tilled communities. Bulbous bluegrass cover was greater in untilled areas adjacent to older tilled fields than those adjacent to younger tilled fields [39].

Grazing: Bulbous bluegrass often increases on grazed sites. Bulbous bluegrass is classified as an invader of grazed sites, as its total annual production typically increases as range site conditions deteriorate, or as site dominance changes from late-seral to early-seral species [40]. In the Trout Creek Mountains of southeastern Oregon, bulbous bluegrass was typical of "severely degraded" riparian sites that received high animal use. Researchers considered bulbous bluegrass an "aggressive colonizer" [15]. Bulbous bluegrass cover typically increased as bunchgrass cover decreased with trampling and use by domestic and native grazers in Idaho fescue (Festuca idahoensis)-bluebunch wheatgrass-lupine (Lupinus spp.) and oatgrass-Wasatch desertparsley (Danthonia spp.-Lomatium bicolor var. leptocarpum) communities in eastern Oregon's Blue and Ochoco mountains [35]. In crested wheatgrass (Agropyron cristatum) communities in Tooele County, Utah, bulbous bluegrass frequency increased after sites were grazed for 10 years. Before grazing, bulbous bluegrass occurred on 16% of the study plots. After grazing, bulbous bluegrass occurred on 39% of plots. Bulbous bluegrass often grew adjacent to or within crested wheatgrass crowns. Cattle grazing treatments included all possible combinations of 3 intensities (50%, 56%, and 80% utilization) and 4 systems (continuous, continuous delayed start, continuous early removal, and rotation) [19].

Cover and aboveground production of bulbous bluegrass were not significantly (P<0.05) different between an exclosure and a grazed site in the Case Creek Drainage of south-central Idaho. Before a fire in the area, sites were dominated by mountain big sagebrush (Artemisia tridentata subsp. vaseyana), antelope bitterbrush (Purshia tridentata) and mixed bunchgrasses. After the fire, the area was seeded with desert wheatgrass (Agropyron desertorum), tall oatgrass (Arrhenatherum elatius), smooth brome (Bromus inermis), bulbous bluegrass, yellow sweetclover (Melilotus officinalis), and antelope bitterbrush. In 1981, cover and production were compared on unprotected sites and sites within the exclosure, constructed soon after seeding in 1942. Bulbous bluegrass cover and production were slightly greater in the exclosure [54]. Bulbous bluegrass "production and vigor" were not affected by domestic sheep grazing at an average utilization intensity of 61% in crested wheatgrass pastures near Ephraim, Utah. Grazing occurred for 7 years [3].

More info for the terms: bulb, bulbil, culm, frequency, perfect, serpentine soils

Although bulbous bluegrass produces true florets as well as bulbils, seeds are rare [30,47,80]. Bulbous bluegrass regeneration is almost exclusively through asexual means including bulbil production [10,47], basal bulb production [47], and sometimes through culm rooting [12].

Reproduction through true floret and seed production does occur in bulbous bluegrass's native habitats. Some bulbous bluegrass populations reproduce primarily by seed, while in others reproduction is dominated by basal bulb growth and/or bulbil production. Researchers found a significant negative linear relationship (r=-0.596, P=0.02) between percentage of flowering plants and mean annual precipitation of habitats when plants were taken from field sites and grown in controlled conditions [59].

Pollination: When true florets are produced, they are wind pollinated [60].

Breeding system: Spikelets are perfect [53]. Although asexual regeneration is predominant, researchers found "surprisingly high levels of genetic diversity at the species and population level" when bulbous bluegrass bulbils were collected and grown from 10 populations in Idaho, Oregon, and Washington. An average of 26 plants were grown from each population. Researchers concluded that bulbous bluegrass was an autopolyploid and that the high levels of diversity resulted from multiple introductions and/or some past sexual reproduction [58].

Seed production: Through controlled experiments on bulbous bluegrass strains from Turkey and Afghanistan, Youngner [88] determined that floret and bulbil production were controlled by day length and temperature. Plants grown under high temperature (70-81 °F (21-27 °C)) and long day (16 hours of light) conditions produced normal florets. Plants produced bulbils when grown at lower temperatures (68 °F (<20 °C)) and exposed to shorter days (8 hours of light). Plants exposed to long day and low temperature or short day and high temperature conditions produced panicles with both florets and bulbils. The researcher recalled observations of bulbous bluegrass plants near Los Angeles, California, producing normal florets in late March, when day length exceeded 13 hours [88].

Seed dispersal: Animals, wind, and gravity are all possible dispersers of bulbous bluegrass. Small mammals cache and disperse bulbous bluegrass bulbils [24]. Because leaves and roots senesce with the dry season, it is possible that basal bulbs may be moved by wind (Sowerby cited in [26]). However, this method of dispersal is not described elsewhere, and Halperin [26] indicates he never observed this type of dispersal.

Roadsides are important dispersal corridors for bulbous bluegrass. The frequency of bulbous bluegrass was compared on sites with serpentine and nonsepentine soils at 30, 300, 3,000 feet (10 m, 100 m, and >1,000 m) from paved or improved roads. Bulbous bluegrass did not occur on serpentine soils but had 9.6% and 9.2% frequency on nonserpentine soil sites 30 feet (10 m) and 300 feet (100 m) from roads, respectively. Bulbous bluegrass was not found 3,000 feet (1,000 m) away from roads [20].

Seed banking: Studies regarding the longevity of bulbous bluegrass bulbs or bulbils are lacking. 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 [88]. Basal bulbs may live dormant for "several" years [24]. Basal bulbs can dry to below 10% moisture yet maintain growth potential for "extended periods" [83]. Depth of burial affects bulbous bluegrass emergence; for more on this topic, see the Depth of burial discussion.

Germination: Several studies of bulbous bluegrass germination under controlled conditions suggest that germination is best when temperatures are cool 41 to 64 °F (5-18 °C) for at least part of the day [36,58] and when seeds are uncovered or only shallowly covered with soil [63,81]. Bulbous bluegrass bulbils collected from populations in Oregon, Washington, and Idaho usually germinated within 24 hours after being chilled for 4 to 5 days at 41 °F (5 °C) [58]. Germination was 98% to 99% for bulbils collected from Moscow, Idaho, exposed to cool (50 to 64 °F (10-18 °C)) 8-hour days and cold (38 °F (3.5 °C)) nights. No bulbils germinated when exposed to 14-hour warm (79 °F (26 °C)) days and warm nights (68 °F (20 °C)). When day length was shortened to 11 hours under the warm day and night treatments germination was 18% [36].

Bulbous bluegrass bulbils from Intermountain seed suppliers germinated best under fluctuating greenhouse temperatures that ranged from 50 to 100 °F (10-40 °C), averaged 57 °F (14 °C), and closely approximated outdoor early spring conditions. Fluctuating greenhouse temperatures produced 98% germination in 14 days. Room temperature conditions that averaged 70 °F (21°C) and ranged from 66 to 73 °F (19-23 °C) produced 91% germination after 19 days. Germination was only 1% after 24 days at a constant temperature of 86 °F (30 °C) [63].

Depth of burial: Shoot emergence was delayed and reduced as bulbous bluegrass bulbil planting depths increased. Bulbils were kept moist in a greenhouse where temperatures averaged 64 °F (18 °C) and ranged daily from 54 to 90 °F (12-32 °C). Just 8% of seedlings emerged after 30 days when bulbils were planted 1.5 inches (3.8 cm) deep. Emergence was more rapid and more successful when seeds were left of the soil surface or shallowly planted. Researchers indicated that field conditions may not provide adequate moisture for successful germination of uncovered bulbils. A summary of the findings is provided below [63].

Percentage shoot emergence 5 to 30 days after planting at depths of 0 to 1.5 inches [63]   Days after planting Planting depth (inches) 5 7 9 11 13 15 30 surface 26 64 85 90 93 95 96 0.25 0 6 47 71 83 87 90 0.50 0 2 26 60 68 73 77 0.75 0 0 15 49 58 62 64 1.0 0 0 0 5 15 22 28 1.5 0 0 0 1 2 5 8

Seedling establishment/growth: Bulbous bluegrass plants produced the most growth in late April and May and senesced by 6 June in a mountain brush field nursery site in the Intermountain Region. The nursery occurred at 5,375 feet (1,638 m) on deep clay loam soils. Bulbils were sown in late fall, and root and shoot development was monitored periodically from 22 March to 6 June. Root and shoot growth was underway in early April. By mid-May there were 70 roots that penetrated 4.7 inches (12 cm) and spread 3.5 inches (9 cm), and shoot height reached 18 inches (46 cm). By 6 June, the approximate start of summer drought conditions, bulbous bluegrass was senescing [63].

Bulbous bluegrass root and shoot growth over the growing season [63]

Sampling date

April 5 April 12 April 18 April 25 May 2 May 9 June 6 Root length (cm) 10 10 14 30 41 73 9 Shoot length (cm) 5 6 10 16 21 46 0 Number of roots 9 9 28 35 37 70 6 Number of leaves 2 3 3 7 9 18 0 Root penetration (cm) 4 4 5 6 8 12 0 Root spread (cm) 2 2 3 7 6 9 0

Vegetative regeneration: Asexual or vegetative regeneration is the primary means of reproduction in US bulbous bluegrass populations. Bulbils produced in the panicle through the transformation of flowers and lemmas germinate to produce new individuals [10,22,47]. Basal bulbs that multiply and grow laterally lead to vegetative spread [47,64]. Vegetative regeneration is also possible through the rooting of decumbent culms [12].

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More info for the terms: chamaephyte, hemicryptophyte

RAUNKIAER [69] LIFE FORM:
Chamaephyte
Hemicryptophyte

More info for the term: graminoid

Graminoid

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More info for the term: bulbil

Bulbous bluegrass begins growth in the fall, winter, or early spring, produces bulbils by spring or early summer, and senesces before the summer drought period. Development and maturation are rapid [47,80]. Bulbous bluegrass is typically dormant through the summer and resumes growth in the fall or winter before or after freezing conditions persist [24]. Typical timing of flower and/or bulbil production is provided below. Timing of bulbous bluegrass bulbil and/or flower production by state or region State/region Date of bulbil/flower production California spring [29] southern California April-July [56] Carolinas April [67] Nevada April-July [38] New York, Fire Island, Suffolk County June [13] Intermountain West April-July [10]

Fl. & Fr. Per.: April-July.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 9
Specimens with Barcodes: 22
Species With Barcodes: 1

Information on state-level noxious weed status of plants in the United States is available at Plants Database.

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: GNR - Not Yet Ranked

Consult the PLANTS Web (http://plants.usda.gov) site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).

More info for the term: natural

Impacts: There was little literature devoted to the impacts or control of bulbous bluegrass in native plant communities, suggesting that to date (2007) bulbous bluegrass impacts are small and/or unnoticed. In a ranking of nonnative plants' "invasiveness" in Eastern Region National Forests, bulbous bluegrass was categorized as a "common" nonnative species that is restricted to disturbed sites. It was considered "not especially invasive in undisturbed natural habitats" [78].

Control: There are few recommendations for bulbous bluegrass control in the available literature. Prevention of dispersal by cleaning equipment when moving between infested and uninfested sites, planting seed free of bulbous bluegrass, and maintaining perennial and native species were suggested as control methods by Locke and Burrill [47]. On Curlew National Grasslands, fall burning, deep plowing, disking, and drill seeding were used to control bulbous bluegrass, but when treatment areas were visited 9 years later, the researcher suggested that control treatments were "questionable at best" [85].

The Pullman Plant Materials Center (PMC) evaluated bulbous bluegrass for several years in the 1950's. P-4784, an ecotype collected near the Washington-Idaho state line exhibited very robust late maturing growth. It was released in 1956 in cooperation with the Idaho Agricultural Experiment Station. The Pullman PMC grew P-4784 for several years but the bulblets failed to retain acceptable levels of germination. Consequently, P-4784 was not distributed to growers. All seed stock of P-4784 was destroyed in 1976 based on its poor seed storage characteristic and its weedy nature. Currently no seed is commercially available.

No biological controls are known.

There is a wide range of chemicals available to control bulbous bluegrass. Contact your local agricultural extension agent or county weed specialist to learn what products work best in your area and how to use them properly. Always read and follow label and safety instructions.

Infestations can be prevented by using crop seed, hay and straw that is free of bulbous bluegrass bulblets or seed. In addition, cleaning equipment before moving from a site infested with bulbous bluegrass and controlling weeds along fence rows and roadsides will prevent its spread.

Within crop fields where bulbous bluegrass has established, it can be controlled by rotation with a spring crop or to permanent pasture or alfalfa. In uncropped areas, bulbous bluegrass can be managed by establishing a stand of competitive perennial grass.

Intensive spring grazing can reduce bulbous bluegrass populations providing that intensive grazing is applied over a period of several growing seasons. Consult with the NRCS or a Certified Rangeland Management Specialist to determine if this practice could adversely impact other grazing plants and/or soil conditions.

Spring tillage is very effective in controlling bulbous bluegrass. Fall tillage is less effective. Haying and mowing are not effective because the seed heads are frequently shorter than the cutting height. Burning is not effective because it rarely reduces the number of bulblets in the soil.

Bulbous bluegrass is often the first invading species on disturbed shallow soils that are moist during the winter and early spring (Locke & Burrill, 1994).

The grass is known to move from marginal sites to nearby fields of crop and hay. It is easily controlled with early season cultivation using implements such as a spiketooth harrow or viber shanks and herbicides for grass control.

Full sun to light shade, moist to dry conditions, and soil containing sand, loam, clay, or gravel provide acceptable conditions for growth and development, which occur primarily when the weather is cool during the spring and fall. When the weather becomes hot and dry during the summer, this grass becomes dormant and turns brown, but it will revive with the return of cool moist conditions.

Cultural:Bulbous bluegrass is currently considered to be a weedy species, but was used in the mid 1900's as a grass for turf, pasture and erosion control.

Grazing: In early spring, when lush and green it is thought to be a desirable forage species. However, it matures quickly and does not provide a significant amount of forage for livestock.

Wildlife: The bulblets of bulbous bluegrass contain high levels of starch and fat, and therefore are attractive to rodents and birds (Locke & Burrill, 1994).