Trifolium reflexum L. (buffalo clover)
Pl. 410 a, b; Map 1817
Plants annual or
more commonly biennial, taprooted. Stems 20–50 cm
long, loosely to strongly ascending, not rooting at the lower nodes, unbranched or few branched toward the base, glabrous to
densely short-hairy. Leaves long-petiolate toward the
stem base, somewhat reduced toward the tip, the longest petioles to 65 mm long,
3–4 times as long as the leaflets. Stipules shorter than the associated
petiole, broadly ovate, fused nearly to the midpoint and somewhat sheathing the
stem, the free portions angled or tapered at the tips, herbaceous and leaflike, the margins entire or toothed. Leaflets
10–30(–45) mm long, 6–20(–25) mm wide, all sessile or nearly so, ovate to obovate, angled at the base, broadly rounded to sharply
pointed at the tip, the margins sharply toothed. Inflorescences
20–35(–40) mm long and wide, dense globose umbels,
the stalk 20–60(–80) mm long. Flowers 10–40, the stalk 4–8 mm long at
flowering, elongating to 7–12(–15) mm and becoming sharply reflexed at
fruiting. Calyces 4–9 mm long, the tube 1.0–1.5 mm long, glabrous to densely
hairy, the teeth narrowly triangular to linear, 3–5 times as long as the tube,
nearly equal, lacking a prominent network of nerves and not becoming inflated
at fruiting. Corollas 8–14 mm long, longer than the calyx lobes, white to
cream-colored or occasionally deep pink, the banner outcurved,
oblong to elliptic, bluntly and broadly pointed to rounded or shallowly notched
at the tip and with an entire or more commonly somewhat irregular margin,
finely but relatively strongly parallel-nerved with age. Fruits 3–5 mm, ovoid
to oblong-obovoid, minutely stalked, (1)2–4-seeded.
Seeds 1.0–1.5 mm long, more or less globose, pale
yellow, sometimes with darker mottling, dull and finely pebbled. 2n=16. May–August.
Scattered widely in the state, but
absent from most of the Mississippi Lowlands Division and most of the western
portion of the Glaciated Plains (eastern U.S. west to Nebraska and Texas;
Canada). Upland prairies, glades, openings and edges of bottomland to mesic and dry upland forests, savannas, banks of streams,
and margins of ponds, lakes, and oxbows; also pastures, ditches, and roadsides.
Populations of this species often
appear at sites after a burn, heavy logging, or some equally severe
disturbance, and they also occur along logging roads. Without continued
disturbance, plants usually disappear after a few years, but remain in the soil
seed bank. According to N. L. Taylor et al. (1994), although plants are
routinely visited by bees and other insects, buffalo clover is mostly self pollinated.
Steyermark (1963) and some
other authors have recognized two varieties (the hairy var. reflexum, and the more glabrous
var. glabrum
Lojac.), but the pubescence character is variable,
with the more glabrous forms most common in the northeastern part of the range.
Both types of plants, as well as apparent intermediates, are present in
Missouri, and glabrous and pubescent plants may grow intermingled in some
populations.