Agrostis exarata
Agrostis mertensii
bentgrass, spike bent, spike bent grass
agrostide de Mertens, Merten's bentgrass, northern bent, northern bentgrass
8-100 cm, erect or decumbent at the base, sometimes rooting at the lower nodes, with (2)3-6(8) nodes.
(5)10-40 cm, erect, with 2-4 nodes.
mostly cauline;
sheaths smooth or slightly scabrous;
ligules (1)1.7-8(11.2) mm, dorsal surfaces scabrous, apices truncate to obtuse, lacerate to erose;
blades 4-15 cm long, 2-7 mm wide, flat.
mostly basal or basal and cauline, basal leaves persistent;
sheaths smooth or scabrous;
ligules 0.7-3.3 mm, scabridulous or smooth, usually rounded, sometimes acute or truncate, erose, sometimes lacerate;
blades 2.5-13 cm long, 0.5-3 mm wide, usually flat, occasionally involute or folded.
(3)5-30 cm long, 0.5-4 cm wide, contracted, spikelike, oblong, or lanceolate, usually dense, rarely more open, sometimes interrupted near the base, bases usually exserted, rarely enclosed by the upper sheaths at maturity, lowest node with 1-5 branches;
branches scabrous, ascending to appressed, spikelet-bearing to or near the base, usually hidden by the spikelets, spikelets crowded, lower branches 1-2(4) cm;
pedicels 0.2-4.3 mm.
(2)3-10 cm long, (0.5)1.5-5 cm wide, widely ovate to lanceolate, usually open, exserted from the upper sheaths at maturity, lowest node with (1)2-5 branches;
branches erect, not capillary, readily visible, smooth or sparsely scabridulous, branched above midlength, spikelets in the distal 1/2 or beyond, lower branches (1.5)2-4 cm;
pedicels 0.4-6.4 mm.
lanceolate to narrowly ovate, greenish to purplish.
lanceolate to narrowly ovate, dark brown or purplish.
subequal to equal, 1.5-3.5 mm, scabrous on the midvein and sometimes on the back, 1(3)-veined, acute, elongate-acuminate, with an awnlike tip to 1 mm;
callus hairs to 0.3 mm, sparse to abundant;
lemmas 1.2-2.2 mm, smooth, translucent to opaque, 5-veined, veins prominent distally or obscure throughout, apices acute, entire or toothed, teeth no more than 0.12 mm, unawned or awned from above midlength, awns to 3.5 mm, straight or geniculate;
paleas absent or to 0.5 mm;
anthers 3, 0.3-0.6 mm.
subequal, 2-4 mm, elliptical to lanceolate, midveins scabrous to scabridulous, at least distally, 1-veined, acute;
callus hairs to 0.4 mm, sparse;
lemmas 1.6-2.6 mm, smooth or scabridulous, translucent to opaque, 5-veined, veins prominent to obscure, apices acute, entire or erose, awned from just below midlength, awns (2)3-4.4 mm, geniculate, exserted, persistent;
paleas absent, or to 0.1 mm and thin;
anthers 3, 0.5-0.8 mm, usually shed at anthesis.
0.9-1.2 mm;
endosperm solid or soft.
1.4-2 mm;
endosperm solid.
= 28, 42, 56.
= 56 [reports of 2n = 42 are for Agrostis scabra].
Agrostis exarata
Agrostis mertensii
Agrostis exarata is common and widely distributed in western North America, usually growing in moist ground in open woodlands, river valleys, tidal marshes, and swamp and lake margins; it also grows in dry habitats such as grasslands and shrublands. It extends from Alaska into Mexico, and is also found in Kamchatka and the Kuril Islands. Eastern North American records probably reflect introductions. It readily colonizes roadsides and bare soil, and exhibits ecological and developmental flexibility. Agrostis exarata is recognized here as a single, variable species that includes what others have treated as distinct species or varieties. Cytotaxonomic study might clarify the basis of the observed variation. Agrostis exarata appears to be related to A. densiflora (see below).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Agrostis mertensii grows on banks and gravel bars in river and lake valleys, and on open grasslands and rocky slopes of mountains and cliffs. It has a circumboreal distribution. In the Flora region, it extends from Alaska across Canada to Newfoundland and Greenland, south in the mountains to Wyoming and Colorado in the west, and West Virginia, Tennessee, and North Carolina in the east. It also grows in arctic Europe, Scandinavia, the mountainous regions of Mexico, and northwestern South America, where some unusually robust specimens have been somewhat dubiously referred to this species.
Agrostis mertensii is frequently confused with dwarf, awned forms of A. scabra (p. 646), but has larger spikelets, more culm nodes, larger anthers, slightly wider, flatter leaves, and panicles that are less expanded and less than lh the culm length. Agrostis mertensii is also often confused with A. idahoensis (p. 649), but A. mertensii tends to grow in better-drained habitats. Agrostis mertensii differs from A. anadyrensis (see next) in being less robust, having narrower, less abundant basal leaves, smaller panicles, and minor differences in the insertion of the awns on the lemmas. In addition, the panicle branches are smooth to weakly scabrous, contrasting with the branches of A. anadyrensis, which are strongly scabrous, with long acicules throughout their length.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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