Alfalfa is an introduced perennial forb with 4-angled erect to ascending slender stems, reaching up to 40 Inches in height. Stems are much branched above the base and have fine whitish hair. Mature plants will produce multiple stems from its slender root crown.
Leaves are tri-foliate with leaflets oblong to obovate, the terminal leaflet is stalked and the laterals may have a very short stalk or be sessile. Margins in the upper half of the leaflet can have sharp teeth, the apex is rounded and can have a pointed projection of the midrib vein. Leaflet bases taper to a narrow wedge shape. Leaflets are rarely longer than 1 inch. The leaf is long-stalked with fine hair on the stalk and stipules at the base.
The inflorescence is a compact dense raceme, up to 2 inches long, with up to 40 violet or blue short-stalked flowers rising from the leaf axils. (Yellow flowers in subsp. falcata.)
Flowers have five petals with the larger 1cm long banner petal upright to curved backward and with deeper colored veining. The two lateral petals project forward but do not enclose the 2 smaller keel petals, which contain the reproductive parts - 2 groups of 5 stamens each and a style from a green ovary. Petals may be violet or bluish-lavender. The flower calyx is green, short stalked, with five long pointed lobes, with or without fine hair. Each flower is subtended by a small pointed bract.
Seed: Flowers mature to a coiled pod twisting into 2 or 3 spirals. The pods typically have fine hair and turn black at maturity when they can release several kidney shaped seeds.
Subspecies: Two are accepted - subsp. falcata, which is yellow flowered with flatter seed pods and subsp. sativa which is blue to violet colored. Both are listed by the Minnesota DNR on their plant survey but not tracked by specific county.
Habitat: Outside of agricultural use, Alfalfa can be found along roadsides, railroad rights of way, fence rows and is sometimes planted for ground cover and erosion control as its deep taproot anchors the ground around it. It needs full sun for flowering and adequate moisture but not saturated soils.
Names: The genus name Medicago if from the Greek mēdike a classical name for a crop plant - Alfalfa. The species sativa means "cultivated", referring to a plant which is grown for a specific use. The author name for the plant classification 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Above: A typical Alfalfa plant. Drawing courtesy of Kürt Stuber's Online Library
Below: Alfalfa flowers in violet colors. The banner petal is wide and erect. The two laterals (best seen in the lower left of 1st photo) project forward but do not hide the two small keel petals.
Below: 1st photo - a plant with flowers turning to a blue-lavender color. 2nd photo - the calyx tube is about 5mm long with five long-pointed lobes. The small bract that subtends each flower is visible
Below: The stems are 4-angled with some fine appressed hair, the underside of these leaves also show the same hair. 2nd Photo - Examples of the 3-parted leaves. Note the sharp teeth in the upper part of the leaflet. Some plants may not have leaf teeth.
Below: 1st photo - Seed pods beginning to coil - note the fuzzy hair. 2nd photo - mature coiled pods.
Below: Seeds are somewhat kidney shaped, 1 to 1.5mm long. Photo courtesy Steve Hurst, USDA-NRCS Plants Database.
Notes: Alfalfa was introduced to the Wildflower Garden in 1923 by Eloise Butler when she brought in a clump on October 11 from the Belt Line Bridge area (The Belt Line is current Highway 100). Another clump came in August 1925 from Fort Snelling. It was probably not long lasting where she planted it and her successor Martha Crone never replanted it. In Minnesota it is quite widespread as it is a major forage crop for cattle and seeds can escape readily to uncultivated areas. It was a rare small dairy farm in Minnesota years ago that did not grow Alfalfa for farm use. It is also used in seed mixtures for ground cover and erosion control. The same can be said for all of North America as there are only a few areas in the Northern Canadian Provinces where it has not been found. The plant is native to Eurasia. The only other species of Medicago found in Minnesota is Black Medick, M. lupulina
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"