1. Opuntia humifusa (Raf.) Raf. (eastern prickly pear)
O. compressa (Salisb.) J.F. Macbr.
Pl. 329 f–c; Map
1400
Plants prostrate
or less commonly forming low mounds, the main roots sometimes tuberous-thickened.
Pads 4–8(–12) cm long, obovate to nearly circular, dark or bright green, often
somewhat shiny at maturity, often somewhat glaucous when young. Areoles mostly
10–30 mm apart, 2–4 mm in diameter, oval to circular. Glochids 2–3 mm long,
yellowish brown to orangish brown. Spines absent or 1(–3) per areole, often
restricted to near the margin of the pads, 1–5 cm long, spreading or deflexed,
straight, not flattened, white to gray or brown, often purplish toward the
base. Tepals to 3 cm long, the petaloid ones yellow, sometimes orange or
pinkish-tinged toward the base. Stigma lobes white or pale yellow. Fruits 2–5
cm long, the surface with glochids but no spines, the areoles sometimes
restricted to the apical rim, remaining fleshy with age, green, sometimes
becoming reddish- or purplish-tinged with age. Seeds 3.5–4.5 mm long, the
raised rim relatively short (extending about 0.5 mm beyond the seed body) and
smooth. 2n=22, 44. May–July.
Scattered nearly
throughout the state (eastern U.S. west to South Dakota and New Mexico,
disjunct in Montana; Mexico). Rocky areas of upland prairies, sand prairies,
glades, tops and exposed ledges of bluffs, and rocky stream terraces; also
pastures, roadsides, railroads, and open, disturbed areas.
Benson (1982)
treated O. humifusa as comprising three varieties, the widespread var. humifusa
and the southeastern Coastal Plain endemics var. ammophila (Small) L.D.
Benson and var. austrina (Small) Dress. Many subsequent authors have
rejected the last two as mere morphological variants within the species that
tend to differ in their more upright growth form and longer, narrower pads.
These taxa require further study. For a discussion of difficulties in
separating O. humifusa from O. macrorhiza, see the treatment of
that species.