Canadian Milk Vetch is a native erect perennial legume growing on ridged stems from 1 to 4 feet high, but can tend to sprawl across other plants. Stems are green, without tendrils, usually branched and with fine hair.
The leaves are pinnately compound with an odd number (15 to 35) of 1 inch oblong leaflets. Leaflets have smooth edges, sometimes with hair on the upper medium green surface and usually with short stiff hair on the underside. When young, the leaflets have a sharp pointed tip that is an extension of the main vein beyond the leaflet tip. Each leaflet has a short stalk. A pair of small long-pointed stipules are placed at the base of the main leaf stalk.
The inflorescence is a tall dense whorled raceme held above the upper leaf axils on a long stalk.
The flowers are 5-parted, about 1/2 to 3/4 inch long, with a greenish-white hairy calyx and a tubular corolla of 5 creamy to greenish-white to purplish-white lobes. In pea-like fashion, one petal (the banner) forms an upward curved upper lip to the corolla. The side margins of this petal are rolled upward. Two petals form forward projecting laterals and two form a keel beneath the laterals, within which are the stamens, pistil and style. Flowers are without scent.
Seed: Pollination is by long-tongued insects. The flower spikes mature to many dark brown seed pods containing two chambers containing several small, smooth, brownish to yellow-green kidney-shaped seeds. Seeds hand planted need scarification and at least 10 days of cold stratification to break dormancy.
Habitat: Canadian Milk Vetch grows from a taproot with rhizomes and tends to colonize an area. The plant requires a sunny, moist but well drained location such as moist prairies, open woodlands, thickets and riparian areas. Plants are short-lived - 3 to 4 years. It self-seeds also.
Names: The genus Astragalus is a Greek word for some of the legumes in this group. The species canadensis, means 'of Canada' where the plant was originally typed. The author name for the plant classification, 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: Of the milk vetches you may encounter in Minnesota, the large dense whorled raceme of Canada Milk Vetch should distinguish this from the others where the racemes are smaller with far fewer flowers. There are other plants that have the word 'vetch' in their name that are in a different genus - such as the Vicia. Those also have smaller racemes.
Above: The inflorescence is a tall dense whorled raceme held above the upper leaf axils on a long stalk. The largest of the 5 petals of the flower are formed into a large banner petal (3rd photo) that has upward rolled edges and an upward curve at the lip.
Below: 1st photo - you see the placement of the two lateral petals projecting forward below the banner, 2nd photo - the two keel petals also project forward and form the bottom of the flower and are partially enclosed by the laterals.
Below: 1st photo - Mid-August seed head. 2nd photo - Late September seed head.
Below: 1st photo - The brownish kidney shaped seeds. 2nd photo - the small pair of stipules at the base of the leaf - best observed early in the season.
Above: The one inch long leaflets number 15 to 35, arranged in pairs plus the odd terminal leaflet.
Below: 1st photo - Upper leaf surface - note the hair on the leaf margin. 2nd photo - Leaf underside with fine short hairs giving a pale color to the underside.
Notes: Eloise Butler introduced Canadian Milk Vetch to the Garden on Sept. 18, 1909. She planted additional ones on June 12, 1912 from Washburn Park, Minneapolis and on Oct. 16 from Groveland Park. The plant is probably indigenous to the Garden as on June 23, 1915 she noted in her log "Discovered Astragalus canadensis south margin of plateau". She planted another in Sept. 1918 from Ft. Snelling. It was not listed on Martha Crones 1951 census of Garden plants although she had planted it in 1949, but is now found in several places in the Upland Garden.
Canadian Milk Vetch is widely distributed in Minnesota with only a few counties in the eastern half not reporting it. It is one of 12 milk-vetches of the genus Astragalus known in Minnesota; varieties are not recognized. In North America it is found in most parts except the far north, the Canadian Maritime Provinces, New England, FL and AZ.
Uses: Canadian Milk Vetch is useful in erosion control, wetland restoration and wildlife food. It is palatable to deer and cattle in the growing season.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"