Trifolium arvense L. (rabbit’s foot clover)

Pl. 408 a, b; Map 1809

Plants annual, taprooted. Stems 5–40 cm long, erect or ascending, not rooting at the nodes, often much-branched, with dense, appressed to spreading, silky hairs. Leaves petiolate toward the stem base to nearly sessile toward the tip, the longest petioles to 15 mm, shorter than the leaflets. Stipules longer than the associated petiole, narrowly lanceolate, the fused basal portion short and broad, the elongate free portions narrowly long-tapered at the tips, membranous between the veins, the margins usually entire. Leaflets 5–20 mm long, 2–4 mm wide, all sessile or nearly so, linear to narrowly lanceolate, angled at the base, angled to a sharply pointed tip, sometimes abruptly short-tapered to a minute sharp point, the margins with relatively few, minute, very inconspicuous, blunt teeth (sometimes visible only with magnification), the surfaces finely pubescent with long appressed to loosely appressed hairs. Inflorescences 8–30 mm long (usually elongating with age), 8–10 mm wide, ovoid to cylindric dense spikes, the stalk (1–)5–30 mm long. Flowers 10–150, sessile, spreading in various directions at fruiting. Calyces 4–7 mm long, the tube 1.5–2.0 mm long, long-hairy, often silvery to pinkish- or purplish-tinged, the teeth 1.5–2.0 times as long as the tube, equal or subequal, slender and long-tapered, plumose, lacking a prominent network of nerves and not becoming inflated at fruiting. Corollas 3–4 mm long, shorter than the calyx lobes, pale pink (white elsewhere), the banner outcurved, narrowly oblong, rounded to bluntly and broadly angled at the tip, faintly to moderately nerved, especially with age. Fruits 1.2–1.5 mm long, ovoid, sessile, the outer wall membranous to papery, 1-seeded. Seeds 0.9–1.3 mm long, more or less globose, pale yellow to pale yellowish green, shiny. 2n=14, 16, 28. May–October.

Introduced, widely scattered, mostly in the Ozark and Ozark Border Divisions (native of Europe, Africa, Asia; introduced widely in the U.S. and Canada). Pastures, old fields, fallow fields, railroads, roadsides, and open disturbed areas.

Rabbit’s foot clover is naturalized in many areas of the world and throughout much of North America. It sometimes is cultivated as a winter annual (Henson and Hollowell, 1960). It is adapted to infertile, dry, often sandy soil such as that found on roadsides, where is makes an attractive, silvery-pink display when in flower, and rose to buff when in fruit. It also has been called hare’s foot, stone clover, old-field clover, and pussies.

Zohary and Heller (1984) tentatively recognized two varieties, which were said to differ somewhat in habit and pubescence density. Missouri specimens are all var. arvense. White-flowered plants, which have yet to be found in Missouri, have been called f. albiflorum Sylvén.