Trifolium campestre
Trifolium stoloniferum
field clover, hop clover, hop trefoil, low hop-clover, pinnate hop clover
running buffalo clover
erect to ascending, branched.
creeping, branched, rooting at nodes.
pinnate;
stipules ovate-lanceolate, 0.5–0.8 cm, margins entire, glandular, apex acuminate;
petiole 0.3–2 cm;
lateral leaflet petiolules 0.5–0.6 mm, terminal leaflet stalk 3–5 mm;
leaflets 3, blades rhombic to obovate, 0.4–1.5 × 0.4–0.8 cm, base cuneate, lateral veins prominent, ± parallel, ascending, margins denticulate distally, apex truncate or retuse, surfaces strigose adaxially.
palmate, opposite or subopposite on erect stems;
stipules lanceolate (on prostrate stems) or ovate (on erect stems), 1–2 cm, margins entire or shallowly serrate, apex acuminate;
petioles 6–15 cm on prostrate stems, 0.5–4 cm on erect stems;
petiolules 1 mm;
leaflets 3, blades broadly ovate or obcordate, 1–2 × 0.5–2.5 cm, base broadly cuneate to rounded, veins fine, margins serrate, apex emarginate or rounded, surfaces glabrous.
axillary, 30–60-flowered, globose or broadly ovoid, 0.8–1.5 × 0.7–1 cm;
involucres absent.
terminal, single or paired at tip of upright stem, 15–30-flowered, globose, 2–3.5 × 2–3.5 cm;
involucres absent.
1.5–3.5 cm.
2–7 cm.
reflexed, 0.7–1.2 mm;
bracteoles a fringe of red setae.
elongated and strongly reflexed in fruit, 2–5 mm;
bracteoles lanceolate, 2 mm.
4.3–5 mm;
calyx campanulate, strongly bilabiate, 1.3–1.5 mm, glabrous, veins 5, tube 0.3–0.6 mm, lobes unequal, adaxial deltate, very short, lateral and abaxial linear-subulate, each tipped with 1 or 2 stiff hairs, orifice open;
corolla yellow becoming brown, 3.5–6 mm, ribbed, banner persistent, obovate, enveloping other petals, boat-shaped, 4.3–5 × 2.8–3.2 mm, apex broad, acute.
9–15 mm;
calyx campanulate, 4–7 mm, glabrous or sparsely pubescent, veins 10, tube 1.3–3.3 mm, lobes subequal, subulate, orifice open;
corolla white, veins often pinkish, 8–14 mm, banner ovate or oblong, 8–14 × 4–5 mm, apex rounded or emarginate.
stipitate, oblong, 2–2.5 mm.
oblong, 2.5–3 mm.
1 or 2, yellow, ellipsoid, 1–1.5 mm, smooth, lustrous.
1 or 2, tan to brown, reniform, 1.3–2 mm, smooth.
= 14.
= 16.
Trifolium campestre
Trifolium stoloniferum
Trifolium filiforme Linnaeus and T. procumbens Linnaeus are rejected names that were used historically for T. campestre (J. E. Dandy 1958; N. J. Turland et al. 1996).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Trifolium stoloniferum was thought to be extinct but was rediscovered in the early 1980s (R. L. Bartgis 1985). It is now known from extant populations scattered throughout much of its original range, in five of the original eight states in which it was found historically (D. J. Crawford et al. 1998); it was discovered in Greene County, Pennsylvania, in 2017, but appears to be extirpated in Arkansas, Illinois, and Kansas. R. J. Hickey et al. (1991) examined genetic diversity of T. stoloniferum populations using allozymes and found low diversity, with some populations appearing genetically uniform. Molecular studies using RAPDs (Crawford et al.) indicated somewhat higher genetic diversity, even in relatively small populations.
Trifolium stoloniferum is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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