Plants annual, without rhizomes, forming tufts. Flowering
stems 6–25 cm long, spreading to more commonly erect or ascending, circular in
cross‑section or slightly flattened, glabrous. Leaf sheaths rounded,
glabrous, the ligule 0.5–2.6 mm long, rounded to truncate on the margin. Leaf
blades 1–8 cm long, 0.5–2.5 mm wide, flat or sometimes with the margins loosely
inrolled, glabrous. Inflorescences 2–7 cm long, open, the lowermost branches
single or paired, ascending to spreading or less commonly loosely reflexed.
Spikelets 2.3–4.5 mm long, with 2–6 fertile florets. Lower glume 1.5–2.2 mm long,
lanceolate, sharply pointed at the tip, with broad, thin margins, 1‑nerved,
roughened along the midnerve. Upper glume 1.7–2.6 mm long, narrowly ovate,
sharply pointed at the tip, with broad, thin margins, 3‑nerved, roughened
along the midnerve. Lemmas 1.6–2.6 mm long, elliptic, bluntly pointed at the
tip, 3‑nerved (an additional, very faint pair of lateral nerves sometimes
present), short‑hairy along the nerves and with a tuft of long, cobwebby
hairs at the base. Anthers 0.1–0.3 mm long, included in the spikelet at
maturity. Fruits 1.0–1.2 mm long, brownish yellow. April–May.
Scattered nearly throughout the state, but absent or
uncommon in some parts of northern Missouri (southeastern U.S. north to Delaware and Nebraska, occasionally introduced farther north). Margins and openings of
bottomland and more commonly mesic to dry upland forests, glades, upland
prairies, pastures, margins of crop fields, fallow fields, roadsides,
railroads, and disturbed, open areas, often on acidic substrates.
Poa chapmaniana is very closely related to P. annua. Some authors
combine the two and treat it as a native phase of that species. The two differ
primarily in that P. chapmaniana has lemmas with cobwebby bases and
smaller anthers. The stamens and stigmas usually remain included in the
spikelets during flowering, with the lemmas remaining appressed at maturity,
and the plants thus are nearly obligately self‑pollinated
(cleistogamous). In Missouri, this species is less frequently encountered than P.
annua, but it is probably overlooked by some collectors who mistake plants
of P. chapmaniana for that species.