Prairie Cinquefoil
Potentilla arguta
Rose family (Rosaceae)

Description: This native perennial plant is unbranched, except slightly near the inflorescence, and up to 3' tall. The central stem is stout and covered with spreading white hairs. The pinnate compound leaves are also covered with white hairs, and consist of 3-11 leaflets. They are located primarily at the base of the plant, although a few small compound leaves alternate along the central stem above. Each leaflet is up to 3" long and 2" across, with the leaflets becoming larger toward the tip of the compound leaf (away from the stem). A leaflet is coarsely serrated along the margins, pinnately veined, and has an ovate or oblong shape (with blunt tips). The entire plant appears light or whitish green.

The inflorescence occurs as a tight cluster of the flowers at the apex of the plant, sometimes with smaller side clusters. A flower has 5 white petals, 5 light green sepals, 20 or more golden stamens, and a small golden reproductive structure in the center. It is about ¾" across and resembles the flower of a strawberry plant. There is no floral scent. The blooming period occurs during mid-summer and lasts about a month – only a few flowers are open at the same time. The small seeds are distributed to some extent by the wind. The root system consists of a central taproot, and there are rhizomes that help to spread the plant, although it is not particularly aggressive.

Cultivation: The preference is full sun and mesic to dry conditions. This plant is not particular about soil type, as long as the site is well-drained. In native habitats, it's often found in soil that contains some clay, rocky material, or sand. Drought tolerance is excellent, and foliar disease is rarely observed. This plant is easy to grow if the above requirements are met.

Range & Habitat: Prairie Cinquefoil occurs occasionally in the northern half of Illinois (see Distribution Map). Habitats include mesic to dry black soil prairies, clay prairies, sand prairies, gravel prairies, hill prairies, Black Oak savannas, and abandoned pastures. Unlike some of its weedy relatives, this plant is normally found in high quality habitats, rather than disturbed areas.

Faunal Associations: The flowers are visited primarily by small bees and flies. This includes Little Carpenter bees, Halictine bees, Syrphid flies, Tachinid flies, Blow flies, and others. Wasps and small butterflies are less common visitors. The larvae of a Gall Wasp (Gonaspis sp.) forms galls on the stems. The leaves and stems are occasionally eaten by some mammalian herbivores, such as rabbits and livestock, but it is a minor food source.

Photographic Location: The upper photograph was taken at Meadowbrook Park in Urbana, Illinois, while the lower photograph was taken at a prairie of Parkland College in Champaign, Illinois.

Comments: This rather ordinary-looking plant resembles Potentilla recta (Sulfur Cinquefoil), an introduced plant, in its erect habit and overall appearance. However, Prairie Cinquefoil has white or cream flowers and hairy pinnate leaves, while Sulfur Cinquefoil has light yellow flowers and less hairy palmate leaves. When ultra-blue light is made visible through a special filter, patterns are revealed in the flowers of many cinquefoils that are not apparent to the human eye, but perceptible by most pollinating insects. These ultra-violet reflecting patterns help the flowers stand out from the background, and may function as nectar guides. Thus, the flowers are colored a combination of white and bee-blue.

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