Medicago
sativa L.
Standardized Common
Name: Alfalfa
Other Common Name: Lucerne
Family: Fabaceae
(Leguminosae)
Taxonomy: Medicago
comprises about 83 species of legumes, including some two dozen species
previously placed within Trigonella, which are frequently used as animal
fodder or forage. The taxonomy of these species, which are native primarily to
Europe, Southwest Asia, and Africa, is difficult. Medicago sativa L. is
a diverse polyploid hybrid complex, widely cultivated and naturalized in
Europe, Asia and North America, that may be divided into about five subspecies.
The most important of these are subsp. sativa (the most widespread
cultivated and feral subspecies), subsp. falcata (L.) Arcangeli (a
cold-resistant plant of Eurasian origin), and subsp. ×varia (Martyn)
Arcangeli (the hybrid of the previous two, often cultivated). Subsp. falcata
is distinctive, having yellow flowers and straight or falcate (curved) legumes,
and is still treated by some authors as a separate species, M. falcata
L.
Description: Perennial herb with
woody roots, to 1 m tall; stems branching with numerous short lateral branches
in upper part, more or less short-pubescent. Leaves alternate, stipulate,
trifoliolate; leaflets narrowly oblong to obovate; margins denticulate near
apex. Inflorescences lateral, racemose. Calyx campanulate, 5-lobed, 4.0–5.5 mm
long. Corolla 5-petaled, bilaterally symmetrical, 6–12 mm long; single standard
petal outermost, 2 keel petals fused with small apical notch at juncture; color
variable from purple to bluish, purple and yellow, yellow or cream. Stamens 10,
with 9 forming a single group with attached filaments, 1 separate. Gynoecium of
1 carpel with short style and blunt stigma. Fruit a legume, indehiscent,
somewhat flattened, several-seeded, usually coiled for (1–)2–3(–4) turns
forming a bur 4–6(–9) mm in diameter, or 5–10 mm long, sickle-shaped or rarely
nearly straight in subsp. falcata.
Parts
in Commerce:
Leaves
Identification:
- Trifoliolate
- Central leaflet
borne on longer petiolule than lateral leaflets
- Texture thin
with thin weak petiole
- Pale or clear
green
- Leaflets 1.0–3.5
cm long (usually 0.5–1.2 cm in subsp. falcata, very rarely to 5.0
cm in subsp. sativa), narrowly oblong-oblanceolate to obovate or
rarely elliptical or narrowly lanceolate
- Margins with a
few small teeth near apex, otherwise entire
- Apices rounded
to rounded-truncate with a small tooth extending from midrib (mucron),
sometimes shallowly emarginate (centrally notched)
- Bases tapering,
cuneate to somewhat rounded
- Both surfaces
glabrous
- Venation
pinnate, secondary veins very weak and inconspicuous, at acute angle to
midrib and pointing toward apex
- Odor
characteristic (at least when fresh)
- Taste mild,
grassy, pleasant
References:
Gunn CR, Skrdla WH, Spencer HC. Classification of
Medicago sativa L. Using Legume Characters and Flower Colors.
Washington, DC: United States Department of Agriculture, Agricultural Research
Service; 1978. Technical Bulletin No. 1574.
Isely D. Native and Naturalized Leguminosae
(Fabaceae) of the United States (Exclusive of Alaska and Hawaii). Provo,
UT: Monte L. Bean Life Science Museum; 1998.
Small E. Morphological differentiation in Medicago
sativa s.l. in relation to ploidy. Canad J Bot. 1984 [publ.
1985];63:1747–1752.
Small E, Jomphe M. A synopsis of the genus Medicago
(Leguminosae). Canad J Bot. 1989;67:3260–3294.
Figure 45: a–b, Medicago sativa inflorescence and leaf.
