Festuca perennis (L.) Columbus & J. P. Smith, perennial rye grass (including annual rye grass or Italian rye grass). Annual to perennial herb, fibrous–rooted, 1—many–stemmed at base and clump–forming, ascending to erect, 25—90 cm tall; shoots with 2—7 leaves, blades folded or rolled in bud, glabrous; adventitious roots at buried nodes
Stems (culms) cylindric, 1—3 mm diameter, tough, green aging tannish with dark purplish red nodes, straight or bent at swollen nodes, internodes 10—85 mm long increasing upward, smooth, glabrous; internodes hollow.
Leaves alternate distichous, simple with sheath; sheath open, 35—160 mm long, striped, with or without lobes (auricles) at top, auricles clasping or descending, acute, to 2 mm long, light green to pale green, diminutive auricle = convex widening of leaf base; ligule membranous, transverse to oblique truncate, 0.4—3 mm, dark tan at base to whitish to light tan at tip; blade linear, 25—300 × 1.7—8 mm, the widest near base, flat, minutely toothed on margins near base to tip, parallel–veined but lacking a midrib, upper surface smooth and glossy, lower surface smooth or rough.
Inflorescence spikelets on a terminal, unbranched, spikelike panicles, panicle 70—310 mm long, with 12—40+ regularly spaced, vertically oriented, sessile spikelets arranged alternate distichous along rachis, 2–ranked, spikelet with 4—15 florets, bracteate, glabrous, awned or lacking awns; peduncle cylindric or somewhat compressed, 60—330 mm long, < 1.5 mm diameter at top, striped, smooth or finely scabrous, hollow; rachis with spikelets partially sunken edgewise into concave niche, scabrous on edges of concavity.
Spikelet ellipsoid to narrowly oblong strongly compressed side–to–side, 5—19 × 1.5—5 mm, spreading to 7 mm at anthesis, with florets decreasing in length distally, breaking above glume and between florets; rachilla 0.7—1.5 mm long, strongly flattened, glabrous; glume 1 = upper glume on outer side (lower glume present on terminal spikelet), linear–lanceolate, 4.8—11.5 mm long increasing in fruit, stiff, green aging tannish, 5—7–veined with the outermost veins commonly short and faint, narrowly membranous and incurved on margins, tapered to an acute or narrowly rounded tip, the tip stiff (± chartaceous); lemma mostly awned, lanceolate, in range 5—7 × 0.8—2.5 mm decreasing along spikelet, acute to slightly 2–toothed at tip, generally 5–veined, glabrous, awn 0—7.5 mm long, attached 0.2—0.4 mm below tip, light colored or purplish red at base; palea ± as long as lemma, 2–veined, 2–keeled, membranous and green along each vein, densely short–ciliate along keels.
Flower bisexual; perianth (lodicules) 2, ± obovoid–shaped to oblong teardrop–shaped or ± sickle–shaped, 0.6—1 × 0.3—0.5 mm, bulbous at base, translucent, with a membranous, lateral lobe; stamens 3, free, exserted or exposed by spreading lemma and palea; filaments threadlike, 1.5—3+ mm long, white; anthers basifixed, dithecal, linear, 2.6—4.5 mm long, light yellow to greenish yellow or purplish to raspberry red, longitudinally dehiscent; pollen light yellow to pinkish; pistil 1; ovary superior, ± heart–shaped to broadly obovoid, 0.4—0.8 × 0.6—0.9 mm, glossy greenish white to whitish, glabrous, 1–chambered with 1 ovule; styles 2, 1.2—2 mm long, translucent, erect at base above sharply bent and spreading, densely feathery (plumose) base to tip or nearly so, the plumose stigmatic hairs ascending, ± 0.5 mm long.
Fruit achene (caryopsis), firmly enclosed within palea and lemma, obovoid to oblong, 2.5—4 × 1.5—1.6 mm, dull dark brown to black, rounded at base, rounded to truncate at tip with flap of ovary tissue, flat next to palea and convex next to lemma, glabrous.
A. C. Gibson & B. A. Prigge