Melilotus albus Medik. (white sweet clover)
Trifolium
officinalis L.
Pl. 403 a–c; Map 1784
Stems 30–200 cm long. Petioles 1–2 cm
long, the terminal leaflet with the stalk 2–6 mm long. Stipules 5–9 mm long. Leaflets
10–30 mm long, 4–17 mm wide. Inflorescences (2–)4–14 cm long, becoming
elongated at fruiting, the stalk 1–5 cm long. Corollas white, the banner
3.5–5.0 mm long, 2.0–2.2 mm wide, slightly longer than the wings and keel.
Ovary narrowed at the base, but not stalked. Fruits 2.5–4.0 mm long, sessile or
nearly so, the surfaces with a network of raised nerves. 2n=16. June–December.
Introduced, scattered to common nearly
throughout the state, but apparently absent from most of the Mississippi
Lowlands Division (native of Europe, Asia; introduced nearly throughout the
U.S., Canada). Upland prairies, glades, bases, ledges, and tops of bluffs,
banks of streams and rivers, margins of ponds and lakes, and oxbows; also
pastures, old fields, fallow fields, crop fields, levees, lawns, railroads,
roadsides, and open, disturbed areas.
Melilotus
albus
is easily distinguished from M.
officinalis by the white flowers and fruits with a network of raised
nerves. It is very variable in height, thickness of the stems, degree of
branching, period of flowering, shape and size of the leaves, and color of the
seeds (Turkington et al., 1978). The flowers are self-fertile, but need an
insect visitor to trip the pollination mechanism. The species name has been
spelled M. alba in some of the
botanical literature, but according to the International Code of Botanical
Nomenclature Melilotus should be
treated as a masculine word with the appropriate masculine spelling of the
species epithet.