Medicago rigidula
rigid or Tifton bur (burr) medic, Tifton burclover, Tifton medick
procumbent to ascending.
blades cuneate to obovate, (4–)6–12 × (3–)4–8 mm, margins serrate on distal 1/2.
1–3(–6)-flowered, racemes.
(3–)4–6(–8) mm;
calyx pubescent, hairs eglandular and/or glandular, lobes shorter to longer than calyx length;
corolla yellow, less than 2 times length of calyx.
with (4–)5–6.5(–7.5) coils, coils weakly to strongly adpressed, usually ovoid, sometimes cylindrical, discoid, or spherical, 5–10(–12) × 5–10(–15) mm, usually pubescent with eglandular and gland-tipped hairs, evident only when young, when glandular, often producing velvety appearance, rarely glabrous, margin prickly, tuberculate, or prickleless, prickles, when present, at different angles to plane of coil, very stocky and difficult to bend, base often round, 2 roots often apparent at maturity;
faces very hard at maturity, coil face with strongly curved radial veins anastomosing somewhat towards coil periphery, veins obscure at maturity from developing spongy tissue.
yellow to yellow-brown, reniform, (2.5–)3–4(–4.5) × (1.3–)1.5–2(–2.5) mm;
radicle 1/2, or slightly less, seed length.
margins dentate to laciniate.
= 14, 16.
Medicago rigidula
Medicago rigidula has been sown for forage only to a limited extent. There are a few forage cultivars, including ‘Laramie’, a self-regenerating pasture species for the Central High Plains of the United States.
The European and African populations of this species complex have been segregated as Medicago rigiduloides E. Small, based particularly on pollen morphology and fruit characters (E. Small et al. 1990). Additional studies confirming separation of these taxa are needed (D. C. Heft and R. W. Groose, http://www.naaic.org/Publications/ 1996Proc/poster_session.htm), before determining their applicability to the plants in the flora area.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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