Round-headed Bush Clover is an erect to ascending, native perennial forb that grows 2 to 4 feet high on ridged stems that are usually un-branched below the inflorescence; the stem has many fine hairs.
The leaves are alternate and like most clovers, are three parted, oval and point upward from short stalks. Leaves have slender pointed stipules at the base. Like the stem, the leaves are covered with dense appressed hairs, particularly the underside. Each leaflet also has a stalk with the terminal leaflet stalk the longest. The midrib of the leaflet extends beyond the leaf tip forming a sharp point.
The inflorescence consists of a number of dense rounded clusters of flowers in the upper leaf axils.
The flowers of this species and of most species of Lespediza are are two types. Those that form an open flower are called "chasmogamous" (open marriage) [CH flowers] and those that never open are called "cleistogamous" (closed marriage) [CL flowers]. Both types are bisexual (perfect) and set seed but at different times - with CL flowers later if the plant develops them - not all will. Various reasons have been put forth for CL flowers but studies indicate environmental reasons predominate but a lack of pollinators has also been noted.
The CH flowers are bilaterally symmetrical, small, 3/8 inch long, not stalked, 5-parted, and tightly fill the clusters. The corollas are cream color with a pinkish-purple throat. Like most pea flowers the upper petal - the standard or banner petal - is the largest and has the coloration in the throat. Two petals form laterals that project forward and partially enclose the remaining two petals which form a keel. Within the keel are the reproductive parts. The calyx has 5 long linear light green pointed lobes, subtended by small bracts and all the outside of the calyx is covered with fine hair. The CL flowers develop on the lower stem and are quite small, resembling flower buds.
Seed: The flower heads mature to crimson brown, producing an ovate to oblong hairy pod that is only half as long as the calyx lobes and usually contains one seed. These remain on the stem, with a muted brown color, after the leaves have dropped. Seeds only need 10 days of cold stratification for germination but if the hulls remain on the seed, scarification is also needed. An addition of a specific inoculum is also beneficial.
Habitat: Round-headed Bush Clover grows from a taproot with subsurface branching roots. It prefers sunny, drier locations with well drained soils such as sandy loam. Established plants are drought tolerant. As a legume the plant is nitrogen fixing.
Names: The genus Lespedeza was named by Michaux as an honorary for the Spanish governor of Florida, c.1790, Vincente Manuel de Cespedes, but the name was misspelled when Michaux's Flora Boreali-Americana of 1802 was being prepared for printing. The species capitata means 'growing in a dense head' and refers to the flowers of this species. The author name for the plant classification - ‘Michx.’ is for Andre Michaux (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. Two important works of his are the Histoire des chênes de l'Amérique septentrionale (1801 - Oaks of North America), and the Flora Boreali-Americana (2 vols., 1803, published posthumously, containing the description of this species). His son Francois, traveled with him and the father’s notes were later used for the 3-volume North American Sylva.
Comparisons: There are a number of bush-clovers but this one is unique with the dense rounded flower heads. The only other one found in Minnesota in the wild, L. leptostachya, has a spike of separated flowers.
Above: The inflorescence in Summer and Autumn. Leaves are reduced to bracts in the upper portion.
Below: 1st photo - Flowers are in a dense cluster in the upper leaf axils. 2nd photo - The upper standard has purplish nectar guides in the throat.
Below: 1st photo: The stem has dense hair as does the leaf stalks. Each leaf stalk has a pair of awl shaped stipules at its base. 2nd photo - The tripartite leaf has a very short stalk. Each leaflet is also stalked with the terminal leaflet on the longest stalk. Note the pointed projecting tip of the leaf veins.
Below: 1st photo - The calyx of the flower has long pointed green lobes, with fine hair and is subtended by small bracts with reddish lobes. 2nd photo - The underside of the leaf is covered with dense fine hair.
Below: The maturing seed heads (1st photo) are a crimson brown color. After they open to release their single seed they become a more muted brown (2nd photo). The fine hair of the calyx remains on the lobes.
Notes: Eloise Butler recorded Round-headed Bush Clovers presence in the Garden on Sept. 6, 1907. It was also present on Martha Crone's 1951 Garden Census, she had planted it in 1946 in the development of the Upland Garden. The plant is found in the United States from the Great Plains eastward. In Minnesota it is native and found in counties of the southern 2/3 rds of the state with a few scattered exceptions - principally near the Dakota border. While a number of species of Lespedeza have been reported for Minnesota, according to the U of M Herbarium only one other has an actual native population - that is L. leptostachya, the Prairie Bush Clover. It is found in only 13 counties, mostly in the Des Moines river valley, and it is listed on both the Minnesota and Federal Threatened List.
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"