The oldest public wildflower garden in the United States
Black Medick (Hop Clover)
Medicago lupulina L.
Early Summer to Autumn
Black Medick is an introduced sprawling to erect annual (biennial in some areas) whose stems are from less than a foot to two feet long. Second year plants develop a taproot, quite large for the size of the plant. The entire plant is generally procumbent with branching from the stem base with shorter branches and flowering branches held erect. Stems are 4-angled and have fine whitish hair.
Leaves are tri-foliate, the terminal leaflet is stalked and the laterals are not. Leaflet shape is obovate with a rounded tip, but usually with a shallow but broad notch at the tip with an abrupt point in the notch from the termination of midrib vein. There can be fine teeth in the upper margins of the leaflets, which are seldom more than one half inch long. Both sides have hair, the underside densely. The leaf stalk is rather long for such a short plant, is hairy and ends in a pair of stipules.
The inflorescence is a dense head no more than 1/2 inch long and 1/4 inch thick on a long hairy stalk rising from the leaf axils. Large heads can contain up to 50 tiny 2-3 mm flowers.
Flowers have bright yellow corollas composed of typical pea family structure - a banner petal, which is quite large (compared to the other 4 petals - but this is a tiny flower), with two forward projecting lateral petals with the two keel petals between them. The keel petals are fused on top and contain the reproductive parts which here, are two groups of stamens with yellow anthers and a style rising from a green ovary. The large banner petal is upright, usually folding back and with a vertical fold line in the middle. The flower calyx is short-stalked, hairy with 5 long-pointed tips. Each flower is subtended by a very small bract.
Seed: Flowers mature to a kidney shaped thin-skinned pod, black at maturity, ridged and slightly twisted, containing one seed.
Habitat: Black Medick grows in disturbed places, roadsides, lawns and fields. It needs full to at least partial sun, but moisture conditions can vary from moist to dry. It spread by reseeding and can form large colonies of plants if not disturbed. Vigorous growth of larger plants will crowd them out. The root is nitrogen fixing. This is a plant found world-wide.
Names: The genus name Medicago if from the Greek mēdike a classical name for a crop plant, in this case, Alfalfa, which has the same genus name and was thought to have been introduced to the world from the old near east land of Media. The species, lupulina, used for a number of different plants, means 'hop-like' but to understand that we need to go back to Carl Linnaeus who started this mess: lupulina literally means 'wolf-like' referring to the name of the wolf - Canis lupus. Picture a wolfs head from the front and you have a rounded-at-the-top cone shape, which is the shape of the common hop plant seed cluster, hence 'hop-like' and hence the alternate common name for this plant of Hop Clover as the general shape of the mature flower cluster resembles that of red or white clover.
We can thank Linnaeus for that logic. It would be simple if every plant had a unique species name but think of all the names one would have to remember. The author name for the plant classification 'L.' refers to that same Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Similar plant or comparisons:: The leaf structure resembles clover plants such as the white and red clover but their flower heads are much larger and not yellow. Another plant with leaves in three parts growing in similar places with a yellow flower is Yellow Woodsorrel (Oxalis stricta). The flowers are small, but open face with 5 petals and not clustered in heads. See comparison photo below.
See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.
Above: An erect stem section with several inflorescence. Drawing courtesy Kurt Stüber's Online Library.
Below: 1st photo - the dense heads are only up to 1/2 inch long. The upright banner petal dwarfs the other 4 petals. 2nd photo - the green calyx of each flower is densely hairy as is the flower stalk.
Below: 1st photo: Stems have 4-angles, fine hair. The leaf underside is densely hairy. 2nd photo - a long taproot develops, usually in the second year plants.
Below: Each leaflet has a rounded top with a broad shallow notch with a projecting point of the midrib in the center of the notch.
Below: Stems typically sprawl across the ground with the flowering portion held erect.
Below: Kidney shaped seeds of Black Medick. Photo courtesy Steve Hurst, USDA-NRCS Plants Database
Below: A comparison of the leaves with Yellow Woodsorrel.
Notes: It is not known when Black Medick first appeared in the Garden but being an adventitious plant it may have arrived when the Upland Garden space was added in 1944. Martha Crone listed it on her 1951 plant census. There are only five of Minnesota's 87 counties where the DNR plant survey has not found it, but it might be in those also. The only other species of Medicago found in Minnesota is Alfalfa, M. sativa.
In North America Black Medick is found everywhere from the lower Canadian provinces southward and also in Alaska and Hawaii, as well as most of the temperate areas of the globe. It was imported into North America for grazing animal feed. Ada George (Ref. #6b) reported a century ago that cattle readily eat the plant and it makes good pasture as it is nitrogen fixing. She also noted that unscrupulous seed dealers would adulterate the more expensive Alfalfa seed with Black Medick seed.
References and site links
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"