Trifolium pratense L. (red clover)
Pl. 410 i, j;
Map 1816
Plants perennial,
with a short stout rootstock. Stems 20–60(100) cm tall, erect or ascending,
much-branched, glabrous or with appressed to
spreading hairs. Leaves long-petiolate toward the
stem base to nearly sessile toward the tip, the longest petioles to 80 mm, 3–4 times the length of the leaflets. Stipules much shorter than
to about as long as the associated petiole, ovate to lanceolate,
fused more than 2/3 of the way to the tips, the free portions short-tapered to
long slender tips, pale with dark green to red veins, the margins usually
entire. Leaflets 10–30(–50) mm long, 7–15(–25) mm wide, all sessile or nearly
so, ovate to elliptic or obovate, broadly angled at
the base, rounded or rarely minutely notched at the tip, usually with a minute
broad tooth at the very tip, the margins minutely irregular or inconspicuously
and broadly scalloped or toothed, often only near the tip, the surfaces
glabrous or sparsely to moderately appressed-hairy. Inflorescences 10–30 mm long and wide, dense globose
to ovoid headlike spikes, sessile or the stalk 1–4 mm
(closely subtended by a pair of bractlike leaves).
Flowers 40–150, sessile, ascending to spreading at fruiting.
Calyces 5–8 mm long, the tube 2.5–4.0 mm long, sparsely to moderately hairy,
the teeth narrowly triangular to nearly linear, unequal, the lowest tooth about
as long as the tube, the others nearly equal and much shorter, moderately
hairy, lacking a prominent network of nerves and not becoming inflated at
fruiting. Corollas 11–18 mm long, longer than the calyx lobes, reddish purple
or rarely white, cream-colored, or pale pink, the banner outcurved,
oblong-oblanceolate, shallowly notched at the tip,
inconspicuously nerved. Fruits 2–3 mm long, oblong-obovoid,
sessile, the outer wall membranous below a well-defined somewhat hardened shiny
apical region, 1(2)-seeded. Seeds 1.5–2.0 mm long, ovoid to
slightly kidney-shaped, tan to brown, dull. 2n=14, 28, 56. April–October.
Introduced, common nearly throughout
the state (native of Europe, Asia; introduced nearly worldwide). Upland
prairies, glades, banks of streams and rivers, and margins of ponds, lakes,
marshes, sloughs, and oxbows; also pastures, old fields, fallow fields,
quarries, lawns, levees, ditches, roadsides, railroads, and open disturbed
areas.
Red clover (also called purple clover)
is grown in more areas of the world than any other species of Trifolium (N. L.
Taylor, 1975; R. R. Smith et al., 1985), and it has been in cultivation since
the third and fourth centuries, probably beginning in Spain, from where it
spread to Holland and Lombardy, then to Germany. The species was introduced
into England about 1645, from where it was brought to the New World by 1663 (N.
L. Taylor and Quesenberry, 1996). It is a very
important forage crop, but may also cause bloating in animals that overindulge
in its young growth; a diet high in red clover also may cause infertility in
sheep (N. L. Taylor and Quesenberry, 1996). Red
clover has been used in a tea and to flavor vinegar (Coon, 1980), as well as
medicinally as an ingredient in herbal cough syrup (Coon, 1980; Gibbons, 1962)
and as a salve to treat eye and skin diseases (Reader’s Digest Association,
1984). There are even claims that red clover can be used in cancer treatments
(Duke, 1985; Ritchason, 1995). The young growth can
be cooked as a vegetable (Coon, 1980). Dried flower heads have been ground and
used in breads during times of famine (Millspaugh,
1974).
Trifolium pratense is morphologically very variable, and many infraspecific names have been published. Zohary and Heller (1984) recognized six varieties that
differ in a confusing array of characters of the habit, stipules, calyces, and
pubescence patterns. Missouri collections are most similar to var. pratense and var.
sativum Schreb.,
but there is much intergradation in North American populations of the species.
Rare white-flowered plants have been called f. leucochraceum Asch. & Prantl.
Trifolium hirtum All. (rose clover), an
annual species resembling red clover, has been reported from nearby states and
may be found in Missouri, especially as it is an occasional component of
roadside seed mixtures. It differs from both T. incarnatum and T. pratense in its stipules, which have a
long-tapered, slender, free apical portion.