Showy Tick-trefoil is a native erect perennial forb growing from 3 to 6 feet high on leafy stems that branch at the inflorescence. The stem is green, taking on some reddish vertical color lines toward maturity, and has fine white hair.
The leaves are alternate up the stem, 3-parted and on short stalks. Each leaflet oblong to lanceolate in shape, 1/2 to 4 inches long and half as wide, with smooth edges, green to grayish-green color on top and a hairy underside with paler color. The terminal leaflet is larger and is stalked. Leaflets have obtuse bases and rounded tips rather than pointed.
The inflorescence is a branched panicle of numerous spike-like clusters of flowers with small leaf-like bracts at the base of the clusters. The central stalk of the panicle has reddish tones and fine stiff hairs.
Flowers: The flowers can be dense on the spikes, each has a stalk that also has reddish tones and short stiff hairs. Being a member of the Pea family, the flowers are 5-parted with a larger upper banner petal, two laterals and two below forming a keel. The petals have a light pink to purplish-rose colors. The banner petal is spreading with a rounded front edge and a notch and a fold crest down the middle. The reproductive parts are contained within the two keel petals. The filaments of the stamens are united around the pistil until just below the anthers, which are yellow. The single style is pinkish, curves and is longer than the stamens. The calyx is hairy and it is much shorter than the petals and has five long pointed lobes.
Seed: Fertile flowers produce a flat seed pod that has 3 to 5 jointed triangular segments which are sticky and slightly curved, with barbed hairs to catch fur and clothing. These are green initially turning brown at maturity. These pods are called 'loments' in which each seed is dispersed individually enclosed in a pod segment. Seeds do not any special requirement for germination in warm soils other than removing the outer husk.
Habitat: Showy Tick-trefoil grows from a taproot and prefers full to at least partial sun in richer soils with wet to moist to mesic conditions. Seeds can be planted fall or spring and produce vigorous seedlings.
Names: The genus name, Desmodium, is derived from the Greek meaning "a long branch or chain" and thought to refer to the shape of the seed pods. The species name, canadense, means 'of Canada' where the original type was collected (and this gives the alternate common name). The author name for the plant classification is as follows: First to classify was '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended by ‘DC’ which refers to Augustin Pyramus de Candolle (1778-1841), Swiss botanist, who influenced Charles Darwin. He studied plants, began a systematic catalogue and has 2 genera named for him. The common name of 'Showy' is a comparison to the the other Tick-trefoils which make a less fine display compared to this one. 'Tick-trefoil' comes from the 3-parted leaf on a plant that has barbed hairs (ticks) on the seed pods.
Comparisons: The Garden's other Tick-trefoil, the Pointed-leaved, D. glutinosum, has a semi whorl of ovate 3-parted leaves at the base of the inflorescence, not up and down the stem, and very loose flower racemes, not densely populated.
Above: The inflorescence is a branched panicle of numerous spike-like clusters of flowers - quite showy.
Below: 1st photo - The flower stalk, calyx and panicle branch all have hair and reddish tones. In the open flower note the reproductive parts are visible as the keel petals have dropped down. The stamens are untited around the slightly longer style, with only the anthers separating just short of the style tip. 2nd photo - The three-part leaves on the stem. They are oblong, rounded tips, short stalked.
Below: 1st photo - A branch of the inflorescence with a number of flowers open. 2nd photo - The stem has fine white hair and with maturity shows reddish vertical tints. 3rd photo - The underside of the leaf is paler in color with hair on the surface and veins.
Below: The green and the maturing seed pods with the small hooked hairs. Each segment breaks off as a separate seed.
Notes: Showy Tick-trefoil is indigenous to the Garden area. Eloise Butler catalogued it on Sept. 7, 1907. Martha Crone planted it in 1946. It is native to most of Minnesota except counties in the far north and a few counties in west-central. It is more widely distributed then the Pointed-leaved Tick-trefoil Desmodium glutinosum). In North America its range is the eastern 2/3rds of the U. S. (excepting the SE states) and New Brunswick, Nova Scotia, Quebec Manitoba and Ontario in Canada.
There are five species of Desmodium native to Minnesota: D. canadense, Canada Tick-trefoil; D. cuspidatum var. longifolium, Big Tick-trefoil; D. glutinosum, Pointed-leaved Tick-trefoil; D. illinoensis, Illinois Tick-trefoil; and D. nudiflorum, Stemless Tick-trefoil. The latter is on the State Special Concern List.
Eloise Butler wrote of the Tick-trefoils: "You will know them by the scalloped pea-pods, covered with small barbed grapplers. When you pull them off, the scallops separate, each one having a single seed. The tick trefoils have, as the name implies, compound leaves made up of three leaflets. The blossoms are bright purplish pink, clustered in long racemes." Published Aug. 20, 1911, Minneapolis Sunday Tribune.
Thoreau wrote in his journals "I can hardly clamber along one of our cliffs in September in search of grapes without getting my clothes covered with Desmodium ticks. Though you were running for your life, they would have time to catch and cling to you -- often the whole row of pods, like a piece of a very narrow saw blade with four or five great teeth. They will even fasten to your hand. They cling by the same instinct as babes to the mother’s breast, craving a virgin soil -- eager to descry new lands and seek their fortune in foreign parts; they steal a passage somewhere aboard of you, knowing that you will not put back into the same port."
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"