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GRASSES
OF THE COLUMBIA BASIN OF BRITISH COLUMBIA
As well as being the most common genus, it is also one of the most difficult to identify because several species reproduce asexually, that is, without the fusion of male and female gametes. In a few of the species of this genus, only female flowers form and reproduction occurs without pollen. Species resemble one another closely and many of the Poa species are of hybrid origin. There are several key features that help separate Poa species from one another. These include the growth habit, that is whether it is an annual grass or is perennial, the presence of cobwebby hairs along the base of the lemma on the callus, and whether or not the lemma is keeled. The presence of a rhizome is also a key feature. Exact Poa identification sometimes demands a great deal of careful study, because a key feature is the degree of hairiness on the lemma, which requires the use of a dissecting microscope. Kentucky Bluegrass was introduced to the east coast of North America by colonial settlers in 1600, and slowly spread west with settlement. Two species of Poa are the only vascular plant weeds in Antarctica. Many ecologists attribute the practice of seeding pastures with improved species with the decline in native grass species. It would be a mistake to think that Poas are introduced pasture grass only. In Western North America at high altitudes Poa alpina, P. arctica, P. cusickii and Poa glauca ssp. rupicola are important natural forage. Below the treeline Poa secunda (Poa sandbergii) and Poa glauca are very important as natural forage.
Leaves and Stem: The smooth sheaths are open, almost to the base, and persist as obvious white or cream-coloured sheath fragments at the base of the culms. There are no auricles. Blunt ligules are 1-3 mm long and ragged along the edge. Flat leaf blades are 2-4 mm wide and occur mostly at the base of the stem where they form a dense mat. There are small leaves along the stem mostly below the midway point in the stem. The tips of the leaves are boatlike or prowlike. Flowerhead and Flowers: The pyramid-shaped flowerhead is as wide as it is long, (2-6 cm). Spikelets are green to purplish. Two broad, unequal glumes have a wide transparent margin and minute bumps along the mid-nerve. The lemmas are almost as long as the glumes and have coarse hairs along the keel and the edges, but they do not have cobwebby hairs at the base. Similar Species: Alpine Bluegrass resembles Poa grayana, and Douglas et al. (1994) have placed all records for P. grayana in with Alpine Bluegrass. Although Hitchcock et al. (1969) describe P. grayana as having cobwebby hairs, this feature varies a lot and is unreliable as a differentiating factor when separating Alpine Bluegrass and P. grayana.
Leaves and Stem: Spreading and flattened stems root at the nodes from which the flowering branches arch upwards. Sheaths are open for over half of the length, but the margins overlap. Hairless leaf blades are 1-4.5 mm wide and folded in half along the midrib -- especially the leaves toward the base. There are no auricles. The whitish ligule is about 1-2 mm high and clearly visible when you bend back the leaf blade. Flowerhead and Flowers: The pyramid-shaped open flowerhead is 3-8 cm long. Branches are mostly perpendicular to the stem axis. The spikelets are 3-6 mm long and contain three to six flowers each. The two glumes are unequal and much shorter than the spikelet. The flowers are spaced out along the axis so much so that you can see the axis between them. The five-nerved lemmas and the glumes may have purplish margins (especially in young flowers) and be hairy toward the base. Similar Species: The early flowering of Annual Bluegrass (starting in March), its small size, stem rooting habit and open flowerhead should be enough to distinguish this species from other very short grasses such as the hairgrasses (Aira spp.).
Leaves and Stem: The stem curves upwards growing from short rhizomes that could be confused with stolons. Sheaths are open to 1/4 of the length. The brown, dead leaves and sheaths persist around the base of the stem. These are not as creamy white as those of Alpine Bluegrass. The leaves are short and usually inrolled with rough edges. The pointed ligule is 1-3 mm high. There are no auricles. Flowerhead and Flowers: The flowerhead is open and pyramid-shaped. Purplish spikelets contain two to three flowers. The glumes are equal in length and the lemmas are more or less hairy at the base and across the lower back. There is often a tuft of cobwebby hairs at the base of the lemma on the callus. Similar Species: Arctic Bluegrass has two subspecies in British Columbia: lanata and arctica. Subspecies lanata has longer spikelets (> 6 mm) and correspondingly longer lemmas than ssp. arctica. The stem leaf blades are flat and more than 2 mm wide. Subspecies arctica has smaller spikelets and the stem leaf blades are folded or inrolled and less than 2 mm wide. Douglas et al. (1994) note that ssp. arctica is widespread throughout British Columbia, whereas ssp. lanata occurs in northwest B.C.
Leaves and Stem: Stem bases sometimes develop a narrow, bulblike form surrounded by old, dry leaf sheaths. Sheaths are open nearly to the base. The soft leaf blades are 1 mm wide, flat to folded and wither away. Leaf tips are not really prowlike. Ligules are 1.5-3.0 mm long and have a smooth to slightly jagged margin with the highest point in the middle. You can see the ligules easily with the naked eye. There are no auricles. Flowerhead and Flowers: The leafy flowerhead is 10 cm long, may have an open or narrowed form that has branches with several spikelets. The spikelets are 3.5 mm long and crowded with purplish, bulbous mini-plants, which may be up to 2 cm long. The purple base of the mini-plant extends into green, hairlike leaves. The glumes are 2-3 mmlong, nearly equal and much shorter than the flowers. Normal non-bulbil lemmas (when you can find them) are small, prominently keeled and have a cobwebby base. Similar Species: Leafy flowerheads combined with bulbous leaf bases distinguish Bulbous Bluegrass from other blue grasses especially the somewhat similar Fowl Bluegrass (Poa palustris).
Leaves and Stem: Plants grow from a strong rhizome system and may sometimes produce stolons. The stems are strongly flattened with two edges. Sheaths are open nearly to the base. The flat to folded leaf blades are 2-4 mm wide and have a prowlike tip that is sharply pointed. Leaf blade edges are slightly rough. Slightly hairy ligules are 0.5-1.5 mm long and have a smooth margin. There are no auricles. Flowerhead and Flowers: The flowerhead is compact, narrowed and 3-12 cm long. Spikelets have mostly three to six flowers held inside two, nearly equal glumes. The glumes are about half as long as the spikelet. Flowers contain both male and female parts, and have strongly keeled lemmas, which may have webbing at the base. Similar Species: Canada Bluegrass resembles other bluegrasses, but in B.C. it is distinguished at first sight by the flattened stems.
Leaves and Stem: The leaf sheaths are closed to almost half their length and the dead sheaths persist at the base of the living leaf sheaths. The leaves are 0.5-1 mm wide, mostly basal and inrolled, and may feel rough. The ligules are 1-3 mm high and pointed, but the edge may be jagged so the point may be hard to distinguish. There are no auricles. Flowerhead and Flowers: The flowerhead is 2-9 cm long, narrow and compact. It has an oblong shape, rather than the pyramidal shape of many Poa species. The slightly keeled glumes are unequal and shorter than the spikelet. The keeled lemmas have five prominent nerves with short, rough hairs on the keel. The back of the lower half of the lemma may sometimes be rough. There is no webbing at the base. Similar Species: All of the plants of this species complex in the Columbia Basin are female. Consequently, there are no anthers or they are non-functional. Wheeler's Bluegrass (Poa wheeleri) is similar to Cusick's Bluegrass, but Wheeler's Bluegrass has a more closed flowerhead, thinner ligules than and has no rhizome. In British Columbia there are three subspecies of Poa cusickii: pallida, epilis and cusickii. Within ssp. epilis there has been one variety described: var. purpurascens. The table below is an outline of the major differentiating characters of Cusick's Bluegrass subspecies. For more detail, Soreng (1991) has provided a key to the subspecies in the Epiles group, which is a group within Poa.
Leaves and Stem: The height varies between the two subspecies -- one is a dwarf alpine form. The hairless sheaths are closed only at the base. Stems and leaves are hairless except that the stem has a rough patch just below the flowerhead. The ligules are 0.5-1.5 mm high, variable and may be blunt to rounded with a slightly jagged margin. The leaf blades are short, stiff, 1-1.5 mm wide and folded rather than inrolled. There are no auricles. Flowerhead and Flowers: The narrowly lanceolate flowerhead has rough branches. Glumes are sharp and lance-shaped. Keeled lemmas are rough textured. Sparsely spaced hairs occur along the keel and the edge nerves. There are no cobwebby hairs at the base of the lemma. Similar Species: Soreng (1994) includes Poa interior in the description of Glaucous Bluegrass and describes form Poa interior Rydb. as having true green -- rather than bluish green -- leaves, short hairs on the lemma keel and nerves at the edge of the lemma. Hitchcock et al. (1969) also describe Glaucous Bluegrass as having longer ligules than Poa interior. Glaucous Bluegrass has two subspecies in British Columbia: Poa glauca ssp. rupicola, which is the dwarf alpine form, has densely short hairs between the keel and the nerves at the edge of the lemma. There are no cobwebby hairs on the callus. The other subspecies, Poa glauca ssp. glauca, has lemmas that are covered in short hairs throughout.
Leaves and Stem: The smooth stems often recline or lie on the ground and occasionally have stolons. Smooth or slightly rough leaf sheaths are closed to almost half their length. The flat and lax leaves have a prowlike tip and are 1-4 mm wide. The liguleis 1.5-2 mm high and blunt. There are no auricles. Flowerhead and Flowers: The open flowerhead has paired branches and a droopy appearance, because long, thin branchlets carry the spikelets. The flowerheads are often purplish. Glumes have sharp points and both glumes are keeled and slightly rough along the keel. Lower glume has one vein. The lemmas have a strong keel and a broad, transparent margin. The keel and lemma edges are covered with dense, long silky hairs. Lepto is Greek for fine, and coma is Latin for hair in reference to these hairs. The lemmas are cobwebby at the base. Elsewhere, except on the keel and the marginal nerves, the lemmas are hairless. Similar Species: Cody (1996) placed Bog Bluegrass and Western Bluegrass together as Bog Bluegrass. Douglas et al. (1994) distinguished these two species in their key. Bog Bluegrass has a longer flowerhead than Western Bluegrass (4-15 cm compared to less than 7 cm) and rough branchelets. The first glume of Bog Bluegrass has one nerve rather than one- to three-nerved in the Western Bluegrass. The glumes of Bog Bluegrass are awl-shaped rather than broadly lance-shaped. For the purpose of this work we have combined Bog Bluegrass and Western Bluegrass.
Leaves and Stem: Stolons may be present. The sheaths are closed for less than a quarter of the length, and there are no auricles. The blunt and very short ligules are 0.3-0.6 mm long. The flat or inrolled leaf blades are 1.5-3 mm wide. Flowerhead and Flowers: The erect to drooping flowerhead is narrow and 8-20 cm long. The spikelets are strongly flattened. The unequal glumes are sharp pointed and shorter than the spikelet. Lower glume has 3 veins. The lemmas are hairy on the keel and about 3 mm long. The lemma has a cobwebby base, but you may have to look at several spikelets to see this character. Similar Species: Poa nemoralis and Poa interior are considered by several authors to be the same species. Douglas et al. (1994, p. 136) describe the similarities under the P. glauca description and suggest that "this species (Poa nemoralis) should include P. glauca since nearly continuous variation occurs between them with P. interior". Hitchcock et al. (1969) describe P. interior as a separate species from P. nemoralis and differentiate the two based on smaller spikelets in P. interior and glumes that are shorter and less acuminate than those of Poa nemoralis. Hitchcock et al. (1994) go on to say that P. interior, as well as P. rupicola, could be treated as races of P. glauca. In this treatment we have included P. interior as part of P. nemoralis, but we have treated P. glauca as a separate species.
Leaves and Stem: The lower parts of stems lay upon the ground and root at the nodes like stolons. Stem bases are purplish. The sheaths are open and overlapping to the node below. The leaf blades are flat to folded, up to 20 cm long, 1.5-3 mm wide, droopy and end in prow-shaped tips. Ligules are 2-5 mm high and the margin is wavy or jagged. There are no auricles. Flowerhead and Flowers: The flowerhead is 10 -30 cm long, open and loose, with whorls of four to six branches at the widely separated lower nodes. Spikelets contain two to four flowers. The nearly equal, narrow glumes reach half way up the spikelet. The strongly keeled lemmas have masses of webbed hairs at the base and up the keel. Similar Species: Fowl Bluegrass is similar to Bulbous Bluegrass, but Fowl Bluegrass is distinguished by its large, open flowerhead and lack of purplish plantlets in the spikelets.
Leaves and Stem: The leaves are thin, up to 30 cm long, have inrolled margins and are typically a mass at the base of the smooth stems. Sheaths are closed for about half of their length. The leaf blades of the stem are mostly 2-4 mm wide, flat to folded and end in the distinctive prow-shaped tip. Ligules are 1-3 mm long with entire to slightly irregular to rough margins. There are no auricles. Flowerhead and Flowers: The narrowed but moderately loose flowerhead ranges from 3-15 cm long and has three to five branches per node (lower ones). The form is weakly pyramidlike, but the branches may droop or sweep to one side especially with age. The strongly flattened spikelets are three to five flowered. One glume is slightly smaller, and both have well-developed keels. Flowers extend beyond the glumes. Lemmas are strongly keeled and cobwebby at the base. Similar Species: This species has several subspecies in British Columbia. Some of these are introduced from Europe (ssp. pratensis, ssp. irrigata and ssp. angustifolia) and there are three native subspecies (ssp. agassizensis, ssp. alpigena and ssp. colpodea). For greater detail and a key of these subspecies consult Douglas et al. (1994).
Leaves and Stem: Mostly leafless purplish stems arise from a mass of basal leaves. Sheaths are closed for about 1/6 of their length. Very narrow leaf blades are inrolled or folded, almost never flat, 0.5-1.5 cm wide, 2-3+ cm long. Ligules of stem leaves are 1.5-3 mm long. There are no auricles. Flowerhead and Flowers: The flowerhead is 3-10 cm long, narrowed to somewhat open and has erect to ascending branches. The purplish spikelets are three- to five-flowered and 0.5-0.8 cm long. Slightly unequal glumes are 1/2 to 1/3 the length of the spikelet. Lemmas are about 4 mm long, convex or rounded on the back and there are no cobwebby hairs at the base. The lemmas are not prominently keeled like other bluegrasses. Similar Species: This "species" includes a complex of different types that need a systematic study. Generally, members of this group are distinguished from other Poa species by their bunchgrass habit, narrow dense flowerheads, non-flattened spikelets and lemmas without cobwebby hairs at the base. Soreng (1991) has grouped together a number of taxa in this species (P. ampla, P. canbyi, P. gracillema, P. incurva, P. juncifolia, P. nevadensis, P. sandbergii, and P. scabrella). P. juncifolia, P. sandbergii, and P. scabrella were well recognized as individual species before Soreng's treatment.
Leaves and Stem: The smooth sheaths are closed at the base for about 1-2 cm. The 1-3 mm high ligules are sharply pointed and have rough hairs. Leaf blades are 1-2 mm wide, inrolled to flat and lax not stiff. There are no auricles. Flowerhead and Flowers: The open, drooping, flowerhead reaches 7-15 cm long. There are two to three branches per node at the base of the flowerhead. The three-nerved glumes are unequal in length and extend about ½ the length of the spikelet. Strongly keeled lemmas have long hairs at the base and along the edge of the lower portion but they do not have a cobwebby callus below the base of the lemma. Similar Species: Narrow-flowered Bluegrass resembles Bog Bluegrass. It is easy to mistake the two. Look carefully at the base of the lemma because Narrow-flowered Bluegrass does not have a cobwebby base, whereas Bog Bluegrass does.
Leaves and Stem: The slightly roughened sheaths are open and may appear to overlap. The drooping, flat leaf blades are 15-20 cm long by 2-4 mm wide. Tips are only slightly prowlike. The prominent pointed ligules are 3-7 mm high. There are no auricles. Flowerhead and Flowers: The open flowerhead is 8-15 cm long with as many as five branches at the lower nodes. Spikelets have two to three flowers. The two nearly equal, sharply pointed glumes reach slightly more than half the height of the spikelet. Lemmas are smooth except for the short scattered hairs along the keel. There are long, tangled cobwebby hairs at the base. Habitat: The typical environment for Rough Bluegrass includes moist disturbed woods and wet sites. It occurs in the Columbia Basin region at Mount Morrissey. Similar Species: Rough Bluegrass may at first appear to have a rhizome, but on closer examination it is obvious that the rhizome is a stolon that roots at the nodes. Rough Bluegrass may also look like Fowl Bluegrass, but the nerves on the longer lemmas are more pronounced in Rough Bluegrass. The ligules are longer (3-7 mm long for Rough Bluegrass vs 2-5 mm long for Fowl Bluegrass).
Leaves and Stem: The leaf sheaths are open 1/3 to 2/3 their length. The lower end of the sheaths have dense, short hairs that are curved backwards and the collar of the sheath is short hairy to rough, but does not have long hairs. The blunt or rounded ligules are 0.5-2 mm high. The soft to firm leaf blade can be flat or folded, but generally the stem leaf blades are inrolled and have a finely hairy upper surface. There are no auricles. Flowerhead and Flowers: The open to oval-shaped flowerhead is 5-12 cm long. Its spreading branches are sparse and threadlike. Pointed glumes are shorter than the first flowers. The blunt to rounded lemma is smooth to sparsely hairy or rough. There are only female flowers without anthers because this species reproduces apomictically. Similar Species: Wheeler's bluegrass is very similar to Coastal Bluegrass (Poa nervosa). In fact, some people consider it a variety of P. nervosa. The two species are separated, in part, by geographic range. Wheeler's Bluegrass occurs east of the Coast-Cascade mountains, whereas Coastal Bluegrass is found only west of the Coast-Cascade mountains. There is also a difference in the length of the lemma (3-6.5 mm for Wheeler's Bluegrass compared to 2.5-3.5 mm for Coastal Bluegrass). The lower culm sheaths of Wheeler's Bluegrass are hairy with short backward-facing hairs, whereas the lower culm sheaths of Coastal Bluegrass are rarely hairy. Wheeler's Bluegrass also resembles Cusick's Bluegrass in that they both have only pistillate flowers. However, Wheeler's Bluegrass has a more-open panicle and has a rhizome, whereas Cusick's Bluegrass has creeping stolons and no rhizome.
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