Prairie Cinquefoil is a native perennial erect forb from 1 to 2+ feet high on stems covered with fine white spreading hairs.
The leaves are pinnately divided with the most basal leaves on long stalks and with 7 to 11 stalkless ovate leaflets, placed in separated pairings with one terminal leaflet. Leaflets have a coarsely serrated margin with some serrations looking like small notched lobes. Leaflets enlarge in size toward the tip and leaflets and leaf stalk have the same covering of hair as the stem. The surfaces are medium green with a pinnate venation although the underside will appear paler due to many whitish hairs with longer hair on the main veins. Upper stem leaves will be smaller with fewer leaflets.
The inflorescence a branched tightly stalked cluster (a cyme) atop the stem. Cluster stalks are hairy.
The flowers are perfect, 5-parted with 5 light green sepals of the calyx with very pointed tips and alternating between them 5 smaller floral bractlets, slightly darker green, which are not quite as long as the sepals but are hidden behind the petals when the flower is open. Both bractlets and sepals are very hairy. The 5 petals of the corolla are white to nearly white. These are broader than the sepals but also have pointed tips and are just as long and alternate in placement with the green sepals. The inner throat of the corolla forms a pentagonal glandular structure from which arise the 20+ stamens which have yellow anthers. The pollen turns a reddish brown at maturity. In the center is the rounded yellow female reproductive structure composed of many pistils. Both the petals and the sepals have a noticeable venation which helps insects find the nectary. The entire flower is only 1/2 inch wide.
Seed: Fertile flowers produce many brown 1/32 inch long dry tear-drop shaped achenes which are enclosed in the partially open calyx until shaken out by the wind. Seeds are small and light - 230,000 to the ounce, and require 60 days of cold stratification for germination - best to plant in the fall and let winter to the work.
Varieties: There are two: var. arguta and var. convallaria, the latter has petals that are yellow to creamy-white and is not found in Minnesota.
Habitat: Prairie Cinquefoil prefers mesic to dry soil conditions, full to partial sun in various soils. The root system is rhizomatous with a stout taproot. It is tolerant of dry conditions.
Names: Some references will list this species as Drymocallis arguta (Pursh) Rydb. The genus name, Potentilla, is from the Latin word potens, meaning 'powerful' and refers to the medicinal power of some species of the genus which have medicinally properties. The species name, arguta, means 'sharply tooted' or 'notched' referring to the teeth on the margins of the leaflets. The author name for the plant classification, ‘Pursh’ is for Frederick Traugott Pursh (1774-1820) German-American botanist who wrote A Systematic Arrangement and Description of the Plants of North America, and was the botanist who catalogued and described the plants brought back by the exploring expedition of Lewis and Clark.
Comparisons: There is only one other white-flowered Cinquefoil found in Minnesota, P. tridentata, Shrubby five-fingers or the Three-toothed Cinquefoil but there the leaves are divided into 3 leaflets and the sepals are much shorter than the petals. All the other Cinquefoils have yellow flowers.
Above left: 1st photo - The 5 petals of the corolla are broader than the sepals but just as long and alternate in placement with the green sepals. The inner throat of the corolla forms a pentagonal glandular structure from which arise the 20+ stamens which surround the rounded yellow female reproductive structure composed of many pistils. 2nd photo - Alternating between the 5 sepals are 5 smaller floral bractlets, slightly darker green, which are not quite as long as the sepals but are hidden behind the petals when the flower is open. Both bractlets, sepals and stalks are very hairy.
Below: The stem leaves have fewer leaflets and the leaflets are more narrow. 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 - The more basal leaves have long stalks and 7 to 11 leaflets. 2nd photo - Only the terminal leaflet has a stalk. Stalks are hairy. 3rd photo - The root is rhizomatous and develops a stout taproot.
Below: 1st photo - The leaf underside is very hairy with longer hair on the main veins. 2nd & 3rd photos - The inflorescence is atop a tall stem well above the uppermost leaf as seen in the 3rd photo. Note the darker color of the pollen at maturity.
Below: 1st photo - The drying seed capsule retain the dense hair of the calyx. 2nd photo - Each capsule contains many brown 1/32 inch long dry achenes which are enclosed in the partially open calyx until shaken out by the wind.
Notes: Prairie Cinquefoil should be considered indigenous to the Garden area. While Eloise Butler had not reported it in the first years after the Garden was established she discovered it growing at the south end of the Garden on July 27, 1915. She brought in two plants in Oct. 1919 from Columbia Heigths. Martha Crone planted it in 1946 when she was developing the new Upland Garden. Prairie Cinquefoil (var. arguta) is native to most of Minnesota with only a few widely scattered county exceptions. In North America it is known throughout the U.S. from the Rockies eastward but north of the states along the Gulf Coast and north of the Atlantic coast states up through North Carolina. In Canada it is found from Alberta eastward except the Maritime Provinces. The other variety, var. convallaria, is found from the Rockies westward except for California.
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"