Rose family (Rosaceae)
Description: This perennial plant is 1¼–2½' tall, branching frequently in the upper third of the plant. It is erect in habit, rather than sprawling or stoloniferous. The stems are terete and covered with long white hairs. The alternate leaves are palmately compound. The lower leaves have long hairy petioles and 5-7 leaflets, while the upper leaves are nearly sessile, smaller in size, and often have 3 leaflets. Each leaflet is up to 3½" long and ¾" across; the middle leaflets are larger in size than the side leaflets. Each leaflet is oblanceolate to elliptic and coarsely toothed. The upper stems terminate in flat-topped clusters of flowers. Each flower is about ½-¾" across, consisting of 5 pale yellow petals, 5 hairy green sepals, about 30 stamens with yellowish anthers, and a bright yellow receptacle in the middle with numerous pistils. The spreading petals are obcordate, while the triangular sepals are a little shorter than the petals. The blooming period usually occurs from early to mid-summer and lasts about a month. Each flower produces numerous dark brown seeds, which are somewhat flattened and finely ridged. The root system of a mature plant consists of a shallow crown with coarse fibrous roots; sometimes multiple stems develop from the crown. Reproduction is by seeds.
Cultivation: The preference is full sun, mesic to dry conditions, and a somewhat heavy soil containing clay or gravel. This plant is quite tolerant of alkaline soil.
Range & Habitat: The non-native Sulfur Cinquefoil is a common plant that occurs in most counties of Illinois (see Distribution Map). It was accidentally introduced into North America from Eurasia. Habitats include limestone glades, pastures and abandoned fields, vacant lots, gravelly areas along railroads, compacted soil along grassy paths or dirt roads, and weedy meadows. This plant prefers disturbed open areas with alkaline soil.
Faunal Associations: The nectar and pollen of the flowers attract Halictid bees, masked bees (Hylaeus spp.), Andrenid bees, Syrphid flies, and small butterflies. Two aphids, Chaitosiphon fragaefolii and Macrosiphum pseudorosae, suck sap from Potentilla spp. (Cinquefoil species), while the larvae of a moth, Tinagma obscurofasciella, are leaf-miners. Some grasshoppers, such as Melanoplus borealis (Northern Grasshopper), feed on the foliage. Among vertebrate animals, rabbits occasionally browse the lower leaves of this plant, but it is not a preferred food source. Cattle and other livestock also browse on the foliage. There is some evidence that the seeds of this and other Cinquefoil species can pass through the digestive tract of livestock and remain viable. Thus, these animals may facilitate their distribution into new areas.
Photographic Location: A railroad overpass containing shallow gravelly soil along the tracks in Urbana, Illinois.
Comments: Sulfur Cinquefoil has reasonably attractive flowers and foliage. The latter has some resemblance to the foliage of Cannabis sativa (Marijuana). However, Marijuana is usually a taller plant with very different flowers. Its leaflets are more elliptic and slender than those of Sulfur Cinquefoil. There are many kinds of Potentilla spp. (Cinquefoil species), both native and introduced, that are often difficult to distinguish. Sulfur Cinquefoil can be identified by its erect habit, palmate leaves with 5-7 leaflets, pale yellow petals that are longer than the sepals, and terminal clusters of flowers that are flat-headed. In contrast, other Cinquefoil species differ on one or more of the following characteristics: 1) their stems are sprawling or stoloniferous, 2) their leaves are either palmate with only 3 leaflets or they are pinnate, 3) their flowers have bright yellow petals, 4) their sepals are as long as the petals or longer, and 5) their flowers develop individually from the leaf axils.