BLACK MEDIC OR YELLOW TREFOIL
Medicago lupulina L., family LeguminosaeBlack medic or yellow trefoil, a near relative of alfalfa and burclover, is widely distributed in the South but is seldom abundant in one location.
Plant:
The annual or biennial plant that reseeds readily has slender, finely pubescent, procumbent stems from a few inches to two feet long, with hairy leaflets l/4 to 3/4 inch long. It is an introduced yellow-flowered European legume that has escaped in waste places throughout the country (Graham 1941*, Martin and Leonard 1949*).
Inflorescence:
Black medic bears small, bright-yellow flowers in dense heads, l/2 inch or less in length. The mechanism of the small (2 mm) flower is similar to that of alfalfa. An insect visit causes the sexual column to trip, but, unlike the alfalfa sexual column, it does not return to its original position in the keel when the pressure is removed.
Pollination Requirements:
Bohart (1960*) stated that black medic is self-fertile and self- pollinating and thus has no need for pollinating insects.
Knuth (1908*, p. 279 - 280) also stated that automatic self- pollination takes place readily, but that it is far less productive than cross-pollination. Apparently, like ball and crimson clover, black medic will set seed in selfed flowers, but more seeds will set if crossing occurs. Todd (1957*) listed black medic as a crop whose seed production is increased by bees.
Hartwig (1953) stated that florets were more likely to be fertilized if visited by insects.
Pollinators:
Honey bees are the chief visitors to black medic flowers. They visit a few flowers on an inflorescence then move to other inflorescences, thereby increasing possible crossing. Many other bees are of some value as pollinators.
Pollination Recommendations and Practices:
No recommendations have been made for use of insect pollinators on black medic; however, the meager data available indicate that many bees are needed for maximum seed production.
LITERATURE CITED:
HARTWIG, H. B.
1953. LEGUME CULTURE AND PICTURE IDENTIFICATION. 42 pp. M. S. Hartwig, Ithaca, N.Y.
