Plants with short rhizomes, forming loose tufts, green or
dark green. Flowering stems 60–130 cm long, usually dark purple at the base.
Leaf sheaths open nearly to the base, roughened, persistent or sometimes
rupturing between the veins, the ligule 0.5–1.2 mm long. Leaf blades 10–30 cm
long, 3–7 mm wide, flat, without auricles, roughened along the margins and
veins. Inflorescences 10–25 cm long, open, the branches loosely ascending,
spreading, or sometimes drooping at maturity, the lowermost branches with
clusters of 3–6 mostly strongly overlapping spikelets toward the tip. Spikelets
8–11 mm long, 2–4 mm wide, lanceolate before flowering (narrowly ovate to
obovate at maturity), with 3 or 4(5) florets. Lower glume 3–4 mm long, narrowly
lanceolate, sharply pointed at the tip. Upper glume 4.5–6.0 mm long,
lanceolate, sharply pointed at the tip, 3‑nerved. Lemmas 5–9 mm long,
lanceolate, tapered to a sharp point or an awn 0.3–1.0 mm long at the tip, not
toothed, 5‑nerved, the lateral nerves sometimes faint, roughened. Anthers
1.8–2.3 mm long. Fruits 3.5–4.2 mm long, reddish brown. 2n=28. April–May.
Known only from a single historical collection from Jasper County (Utah, Colorado, Arizona, and New Mexico; disjunct in Missouri). Dry, rocky
ledges.
The identity of the single Missouri specimen was determined
by Susan Aiken (Canadian Museum of Nature), who also provided a detailed
morphological analysis of this and related taxa to the author. The occurrence
is more than 1,100 km to the east of the main distribution of this relatively
uncommon species and also at a much lower elevation. Its presence in the state
cannot be explained easily, but examination of the field notebooks of its
collector, E. J. Palmer, preserved at the University of Missouri’s Dunn‑Palmer
Herbarium, indicates that the specimen was not mislabeled. Unfortunately, most
of the area around Carthage, where the plant was collected, was subsequently
impacted heavily by lead mining, and it seems unlikely that the species is
extant in Missouri.
Festuca sororia resembles F. subverticillata in general aspect but
differs most noticeably in its larger spikelets in denser clusters toward the
branch tips. It also has the rachillas densely roughened, vs. glabrous in F.
subverticillata.