Silvery Scurf-pea is an erect to ascending, bushy, perennial forb, growing 18 to 36 inches high on one or more stems. Stems are often zig-zag and are widely branching in the upper parts. The stem and leaves are what make the plant attractive due to silvery colored hair. Flowers while pretty, are small. In Autumn the above ground portion of the plant breaks apart at the stem joints and provides for self-cleanup.
The leaves are alternate, compound, palmately divided into 3 to 5 short-stalked leaflets that are elliptical to oval to inversely lance-shaped in design, 1/2 to 1-1/2 inches long. Leaves differ depending on whether they are on the main stem or on the branches. Stem leaves tend to have 4 to 5 leaflets, and branch leaves 3 leaflets. All leaves are covered with soft whitish somewhat appressed hairs giving an overall silvery color. Each leaf has a stalk about 1 inch long, but varying from 3/4 to 1-1/2 inches. The central, or midrid, leaflet vein projects beyond the leaflet tip forming a point.
The inflorescence is a 1 to 4 inch tall spike, holding whorls of flowers, which rises from the upper leaf axils. The spike can have 1 to 5 whorls (but usually only 1 to 3), distinctly separated from each other, each whorl containing 2 to 8 flowers. Spike stems have silvery hair also.
Flowers: Each flower is in the pea-flower design with 5 petals - one larger banner (or standard) petal at the top, 2 smaller lateral petals that project forward and two at the base forming what is called the keel. The keel petals are fused at the tip and enclose the reproductive parts - stamens and style. Petals are dark blue in color with a patch of whitish lines on the throat of the banner that act as nectar guides. The banner also has a distinct keel in the center. The calyx of the flower is bell shaped with 5 lobes but divided so as two appear as 2 main lobes - the lower lobe extending far forward around the keel petals - all covered with dense silvery hair. Flower fade to yellowish or brown.
Seed: The fruit is an egg-shaped hairy beaked pod, less than 1/4 inch long, containing a single 1/16 inch triangular smooth reddish-brown seed. Plants must usually be 2 to 3 years old before they bloom and produce seed. There are about 9,000 seeds per ounce. They need 10 days of cold stratification plus scarification in order to germinate.
Toxicity: This species is known to be poisonous to cattle, but they usually avoid it.
Habitat: Silvery Scurf-pea grows from horizontal creeping rhizomes, forming a taproot and a woody caudex. It can form colonies vegetatively from the rhizomes. This is a dry prairie plant requiring full sun, neutral pH and sandy well drained soils. In the wild, it is frequently found with Bluestem grasses.
Names: The genus, Pediomelum is derived from two Greek words - 'pedion' meaning 'a plain' and the 'melum' part means 'apple' - thus an apple of the plains. While this might not sound sensible for this plant, it is a member of the same genus where other species have large starchy edible tubers, all of which species are commonly referred to as 'breadroots'. The species name, argophyllum, means 'whitish leaves'. Synonyms for this species are Psoralea argophylla Pursh and Psoralea collina Rydb.
The author names for the plant classification are as follows: ‘Pursh’ refers to 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. He published on this plant in 1814. His work was amended by ‘J.W.Grimes’ which refers to James Walter Grimes (b.1953) American botanist whose doctoral thesis was on Systematics on New World Psoraleeae. The common name of 'scurf-pea' refers to small glandular dots (or scurf) that can be seen on the leaflets under low magnification. In fact, the older genus name, Psoralea, meant "scabby," and many plants formerly in that genus have been moved into the genus Pediomelum.
Comparisons: Another similar species of Pediomelum is P. esculentum, Prairie Turnip which has edible tubers and Psoralidium tenuiflora, Scurf-pea where the leaves are smaller and not downy.
Above: The plant is bushy and branched in the upper parts. Photo ©Derek Anderson, Wisconsin Flora; 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 - Looking down from above at a whorl of flowers. The large banner petal stands erect with a center keel line and a whitish throat patch with nectar lines. The calyx and stalk are all silvery hairy, as are the leaflets with their appressed hairs. 2nd photo - Stem leaf shown.
Below: The inflorescence consists of whorls of flowers on an erect stalk rising from the leaf axils.
Silvery Scurf-pea is not indigenous to the Garden but it is native to Hennepin County where the Garden is Located. Eloise Butler first introduced the plant in the summer of 1914 with plants obtained at Orchard Lake, MN. She planted more in 1915. '16, '24, '25, '27, and '28. Martha Crone planted it in 1935, '45, and '49.
In Minnesota the plant is found in counties on the west side of the state and across the lower one-third of the state - mostly the original prairie areas of Minnesota. Silvery Scurf-pea is one one two species of Pediomelum found in Minnesota, the other is P. esculentum, Large Indian Breadroot or Prairie Turnip. In North America the plant is found in the interior grassland region of the mid-continent, from Montana east to Wisconsin (where it is listed as Special Concern); south along the eastern side of Rocky Mountains into New Mexico for the western edge of its range and from Wisconsin south to Illinois and Missouri and over to Oklahoma and Texas for the east side of its range. In Canada it is found in Alberta, Saskatchewan and Manitoba.
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"