Pointed-leaved Tick Trefoil is a native erect perennial forb, with a tall green, mostly smooth stem 1 to 4 feet high, unbranched below the inflorescence.
The leaves appear in a cluster (not quite a whorl) at the top part of the stem just below the inflorescence. Each leaf is 3-parted on a long stalk which has hair and has a pair of narrow hairy stipules at the base. Each of the three leaflets are broadly oval with the center leaflet more so and it is also larger than the laterals. Leaflets have smooth to slightly hairy edges, oblique to rounded bases and taper to a sharp pointed tip. Each leaflet is also stalked with the terminal leaflet stalk much longer than that of the lateral leaflets. The leaf surfaces usually have fine hair but sometimes sparsely.
The inflorescence is an open panicle that rises above a whorl of leaves. The central stalk of the panicle has reddish tones and fine stiff hairs.
Flowers: The flowers are not dense on the panicle, 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 an upper and larger banner petal, two laterals and two below forming a keel. The petals have 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, but not hidden by them. The filaments of the stamens are united around the pistil until just below the anthers, which are yellow, turning darker at pollen maturity. The single style is white, curves and is longer than the stamens. The calyx can have a small amount of fine hair. It is much shorter than the petals and has five short triangular lobes.
Seed: Fertile flowers produce green flat seed pods that have 2 or 3 jointed triangular segments and are sticky and slightly curved, with barbed hairs to catch fur and clothing. The pods turn brown at maturity. These pods are called 'loments' in which each seed dispersed is individually enclosed in a pod segment.
Habitat: Pointed-leaved Tick Trefoil grows from a taproot in richer soils of woods and savannas where there is partial shade and mesic to dry moisture conditions.
Names: The genus name, Desmodium, is derived from the Greek word desmos, meaning "a branch or chain" and thought to refer to the shape of the seed pods. The species name, glutinosum, means 'very sticky'. The authorship of the plant classification is a bit complex. The first to publish - ‘Muhl’ - refers to Gotthilf Heinrich Ernst Muhlenberg (1753-1815) American Botanist who produced several catalogues of plants after retiring as a Lutheran pastor. His work was incomplete and was amended by ‘Willd.’ which refers to Carl Ludwig Willdenow (1765-1812), German botanist, a founder of the study of the geographic distribution of plants. He was director and curator of the Botanic Garden of Berlin. The last person to add to the chain was ‘Alph. Wood’ which refers to Alphonso Wood (1810-1881) American botanist and Professor of Botany at the Female Seminary of Cleveland Ohio. He wrote several books on botany that made scientific research available for distribution as textbooks. He is sometimes listed as A.W.Wood. '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 Canada, or Showy Tick-trefoil (Desmodium canadense) has less oval shaped alternate leaves up the stem and a much tighter panicle branching. D. glutinosum is the only Tick-trefoil with leaves in a semi whorl below the inflorescence.
Above: 1st photo - Flowers are on a widely branched panicle above an unbranched stem. 2nd photo - Individual flowers are stalked, stalks hairy as is the main stem. 3rd photo - The center leaflet of the 3-part leaf. Note the fine surface hair.
Below: Detail of flowers. Pea type flowers have an upper banner (or standard) petal, two side petals and two lower petals that form a keel enclosing the reproductive parts. Here, the banner has a notch at the tip with a crest on the outer surface. The shape of the two laterals and the keel is clearly seen in the 2nd photo.
Below: Unlike some pea flowers, the reproductive parts are not completely enclosed by the keel. The pistil (1st photo) protrudes. The stamens are united around the pistil except at the tip. The anthers turn a darker color at pollen maturity.
Below: 1st photo - The leaves form a whorl-like cluster at the main stem. Note the linear stipules at the base of each leaf stalk and the surface hair on all the parts. 2nd photo - A typical leaf of three leaflets - the center leaflet being larger.
Below: Green seed pods (called loments). Each section with its seed will break away from the group at maturity.
Notes: Pointed-leaved Tick Trefoil is indigenous to the Garden area. Eloise Butler catalogued it on Sept. 6, 1907. It is native in Minnesota in a wide band running from the SE corner to the NW, absent in the SW, the far North and the Arrowhead. It is less distributed then the Showy Tick-trefoil (Desmodium canadense). In North America its range is the eastern 2/3rds of the U. S. and New Brunswick, Nova Scotia, Quebec and Ontario in Canada.
There are five species of Desmodium native to Minnesota: D. canadense, Canada (or Showy) 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"