White Prairie Clover is a native, erect, perennial forb growing on slender stems one to less than 3 feet high. Stems are usually unbranched and hairless; they are pale green with vertical ridge lines.
The leaves are pinnately compound with an odd number of narrow leaflets (usually 5 to 9), hairless, with each leaflet being about 1 inch long, one forth as wide, having smooth margins and translucent gland dots on the underside.
The inflorescence is a dense cone-shaped spike, 1 to 3 inches long on a leafless stalk held above the leaves. If the plant is branched, side stems will also have a spike. There are a few widely separated bract-like scaly leaves on the inflorescence stalk.
The flowers are small 1/4 inch 5-parted, with a green calyx and white corolla. The stamens number 5, have white filaments and usually pale yellow anthers. The white style is longer than the stamens. The petals of the corolla have an upright banner like most Pea family flowers, but the other 4 petals are much reduced allowing the stamens and style to be visible and to be exserted from the corolla. Flowers open from the bottom of the spike to the top.
Seed: Bumblebees and other bees will pollinate the flowers which when fertile, produce a small dry thin seed pod, usually containing a single irregularly shaped seed, which is dispersed by the wind when mature, falling close to the plant. Seed will usually germinate in warm soil without the need for cold stratification, but if stored, storage should be dry and cold.
Varieties: There are two accepted varieties - details below the photo section.
Habitat: White Prairie Clover has a taproot making it somewhat drought tolerant and as a member of the pea family, it fixes nitrogen in the soil. It grows best in full sun, sandy to loamy soils with dry to mesic conditions. It does not spread aggressively. In the home landscape use a rabbit preventative as they like the foliage.
Names: Some books list the genus as the older Petalostemon, however, USDA and the University of MN Herbarium have adopted the newer classification to the genus Dalea, an honorary for Samuel Dale, (1659-1739), an English botanist and botanical collector and author of several botanical books. The species name candida is for "shining" or "pure white".
The author names for the plant classification are as follows: 'Michx.' refers to 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 and 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. Additional later more defined authorship is given to 'Willd.' who was 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.
Comparisons: D. candida is similar in appearance to the slightly shorter Purple Prairie Clover, D. purpurea.
Above: The inflorescence is a dense cone-shaped spike. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - Flowers open first from the bottom of the spike. 2nd photo - The thin dry seed capsules usually contain a single irregularly shaped seed.
Below: 1st photo - The leaves usually have from 5 to 9 leaflets, grayish-green on the upper surface and paler on the underside (2nd photo) which is dotted with translucent oil glands.
Below: 1st photo - Upper surface of the pinnately compound leaves. 2nd photo - The taproot of White Prairie Clover. As a member of the pea family, it fixes nitrogen in the soil.
Notes: White Prairie Clover was first introduced to the Garden by Eloise Butler on July 12, 1910 with plants she obtained from the grounds of the Agricultural College in St. Paul. She listed it with the older genus name of Petalostemum (spelled that way back then); she added more in 1922. With the same name Martha Crone catalogued it on her 1951 census of plants in the Garden. Martha also planted seeds in 1944 and '53, and plants in 1945 and '52.
White Prairie Clover is native to Minnesota to all but a handful of counties in the SE and also absent in most counties of the NE Quadrant of the state. It has wide native distribution in the United States ranging from the states of the great plains area of the west and reaching into some areas of the Appalachians in the east. It is most abundant in the uplands of the true prairie.
Varieties: Two are accepted - var. candida and var. oligophylla. The former is described above and has a larger range - extending into the eastern states. Var. ologophylla is more restricted to the states of the Great Plains. It has larger flowers, not so densely clustered on the spike. Both varieties exist in Minnesota with some overlap but var. oligophylla is only found in six counties in the western side of the state.
Special Concern: In the wild var. ologophylla is listed on the Minnesota DNR's "Special Concern" Plant List. Var. candida is considered "endangered" in Tennessee.
D. candida is one of four species of Dalea in Minnesota. The others are the Purple Prairie Clover, D. purpurea; Foxtail Prairie Clover, D. leporina; and Silky Prairie Clover, D. villosa.
The plant is attractive to butterflies and bees, a tea can be made from the taproot that is said to reduce fever. On grazeland is a palatable and nutritious forb.
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"