Black medic, English Trefoil (Quinlivan et al., 1986), yellow trefoil (Duke, 1981).

Medicago lupulina L. (Duke, 1981).

'George' black medic, distributed by Timeless Seeds and released by Montana State University, is the predominant cultivar in the Western U.S.

The black medic variety 'Virgo' outperforms other varieties (Brinton, 1989).

The seeds are small, round or oval, 1 to 2.5 mm long and 0.75 to 1.75 mm wide, and the radicle is longer than half the length of the cotyledons (Quinlivan et al.,1986).

Taylor and Ewing (1996) found that buried hard seed of medics was slower to soften in the upper 2 cm of the soil then were seed of 3 cvs of subclover. Subclover seed remained hard if buried 6-10 cm deep, for 12 years. Softening of subclover seed initially requires high temperature, followed by alternating high and low temperatures.

Annual or perennial herb with stems pubescent, prostrate or ascending, four angled, up to 60 cm tall; leaves pinnately trifoliate; leaflets cuneate-obovate, up to 20 mm long, 12 mm wide, pubescent on both surfaces, denticulate; stipules green. Racemes dense, axillary, 5-50 flowered; corolla yellow, 2.5-3 mm long; and pods 1-seeded (Duke, 1981). The plant surface is for the most part hairy. The leaflets are usually rounded. Petioles in the rosette may be as long as 7 cm, while on the runners they are usually about 1 cm. The flower stalk is as long as the leaf stalk and elongates further in fruit. The flowers are in distinctive, crowded, oblong heads composed of 20 to 50 tiny flowers. The petals are only just longer than the calyx teeth. The fruits are spineless, single seeded, and kidney-shaped or discoid, being coiled on at the end. The pods blacken when ripe (resulting in the name black medic) and may or may not have hairs. The radiating veins on the surface are very clear and appear almost concentric. The species is difficult to classify taxonomically because different strains show some but not all of the features of the genus Medicago, whereas in general appearance the plants are similar to Melilotus spp. (sweetclovers and sourclover) (Quinlivan et al.,1986).

Black medic survives frost once well established (Duke, 1981). This species withstands much greater cold than crimson or red clover and is similar in climatic adaptation to alsike clover; there are many varieties of diverse climatic tolerances, but in general the species grows best in a cool, moist climate (McLeod, 1982).

Duke (1981) states that black medic requires 500-800 mm of annual precipitation but goes on to say that it tolerates from 3.1-17.1 dm/year of precipitation.

Black Medic requires fertile soil and does not tolerate soil acidity (Duke, 1981). Applying lime will help it grow on poor soil (McLeod, 1982).

Range of pH tolerated is 4.5-8.2, with a mean of 48 cases of 6.5 (Duke, 1981). This species is well adapted to all soils that are neutral to slightly alkaline (Finch & Sharp, 1983).

This species is adapted to fertile soils that are not highly acid and can grow on a wide variety of soils having a good lime supply (Duke, 1981). Best growth occurs on calcareous soils (McLeod, 1982), but black medic will not tolerate salinity (Duke, 1981). On poor, mildly-acid soils, bur clover grows better than Black Medic (McLeod, 1982).

Black medic shows poor tolerance to shade (Brinton, 1989).

Black medic does not tolerate salinity (Duke, 1981).

This is generally considered an annual or perennial herb (Duke, 1981), but it has also been termed semi-biennial (McLeod, 1982). In Western Australia, black medic behaves as an annual. In Europe and other Australian states, biennial and perennial forms are also found (Quinlivan et al., 1986). The plant starts growth in the winter but puts most of its growth on during the spring; it is regarded as early maturing (Finch & Sharp, 1983).

Seeding rates are given as 6 lb/acre (Finch & Sharp, 1983), broadcast at 10-15 lb/acre (Duke, 1981; McLeod, 1982), and, when overseeded into standing corn, 15-20 lb/a (Brinton, 1989).

This small seeded legume should be seeded like alfalfa: either drilled or broadcast and cultipacked on a firm seed bed.

Black medic should be overseeded into corn when corn is 8-16" high (Brinton, 1989).

McLeod (1982) suggests sowing in late summer or early fall, whereas Duke (1981) says that the species is usually sown in the spring.

Previously, black medic seed was more readily available than that of burr clover (Finch & Sharp, 1983). In 1997, however, in California and most of the U.S., imported burr clover varieties 'Serena', 'Circle Valley', and 'Santiago' are more abundant and readily available than black medic.

Quinlivan et al. state that the crop is late maturing. According to Finch & Sharp (1983), seed maturity is in mid-April to May.

Black medic is a reliable reseeder (Finch & Sharp, 1983).

Seed remains viable for a relatively long time (McLeod, 1982).

This species branches profusely at the base, the stems lay flat, and they attain a height of about 6-10 inches (Finch & Sharp, 1983).

According to Finch & Sharp (1983), maximum height is around 6-10 inches, but Duke (1981) says 60 cm (23.6 inches).

Black medic roots extend to a depth of 3-5 ft (Brinton, 1989).

Black medic germination is rapid (Brinton, 1989).

Duke (1981) notes that most black medic stands are volunteer, that no special cultural procedures are needed to maintain such stands, and that black medic has been noted for tolerance of bacteria, high pH, limestone, low pH, mycobacteria, slope, virus, and weeds.

Goldstein and Young (1987) compared a conventional winter wheat-spring barley-winter wheat-spring peas rotation to low-input rotation of peas+black medic-medic-wheat rotation for the Palouse region of Washington state. The latter is termed a "perpetuating-alternative-legume-system" (PALS), because the medic will reseed and reestablish. Based on results from field trials, PALS generated higher net returns when market prices were used, but the converse was true when government target prices were employed.

Black medic is useful for forage and green manure (McLeod, 1982). Its use and management are the same as for bur clover, and the species is well adapted to all orchard & vineyard soils (Finch & Sharp, 1983). McLeod (1982) recommends that where clovers fail, black medic should be tried.

Goldstein and Young (1987) compared a conventional winter wheat-spring barley-winter wheat-spring peas rotation to low-input rotation of peas+black medic-medic-wheat rotation for the Palouse region of Washington state. The latter is termed a "perpetuating-alternative-legume-system" (PALS), because the medic will reseed and reestablish. Based on results from field trials, PALS generated higher net returns when market prices were used, but the converse was true when government target prices were employed.

McLeod (1982) suggests that black medic should never be sown alone but in mixtures with clovers and grasses; however, it does not grow well with red clover. Black medic competes little with standing corn into which it has been overseeded, but does give "fair" soil coverage (Brinton, 1989).

In replicated pot and field trials, wheat was grown with undersown black medic, Medicago lupulina L., Persian clover, Trifolium resupinatum L., and various associated weeds. In both pot and field trials, biomass of weeds alive at the time of harvest was reduced substantially (50% or more reduction). The field trials showed reduction of wheat yield, as well, for black medic and Persian clover, but a non-significantly-increased yield when white clover, Trifolium repens, was used (Hartl, W. 1989).

No precise figures were documented in the literature, but Brinton (1989) stated that black medic shows "good" nitrogen fixation.

In Sweden, Marstorp and Kirchmann (1991) reported the following values for stems and leaves of several legumes harvested from the field 100 days after emergence. and later used as green manure:

Like most annual legumes, black medic enriches the fertility of soil over time.

Black medic overseeded into standing corn gives "fair" soil coverage (Brinton, 1989).

Black medic is not very palatable to livestock, yet it is nutritious (McLeod, 1982). It is said to give good color and flavor to butter (Duke, 1981).

Less susceptible to the Sclerotinia fungus than red clover (McLeod, 1982). Duke (1981) lists 30 fungi, 1 virus (Common Pea mosaic), 1 parasitic plant (Orobanche purpurea), and 6 species of plant-parasitic nematode as attacking black medic.

Black medic overseeded into standing corn gives "fair" weed suppression (Brinton, 1989). In replicated pot and field trials, wheat was grown with undersown black medic, Medicago lupulina L., Persian clover, Trifolium resupinatum L., and various associated weeds. In both pot and field trials, biomass of weeds alive at the time of harvest was reduced substantially (50% or more reduction). The field trials showed reduction of wheat yield, as well, for black medic and Persian clover, but a non-significantly-increased yield when white clover, Trifolium repens, was used (Hartl, 1989).