Rose family (Rosaceae)
Description: This adventive plant is an annual, biennial, or short-lived perennial. It initially consists of a rosette of basal leaves about 6" across, later developing flowering stalks about 1-2' long. The basal leaves are trifoliate with long hairy petioles. Each leaflet is obovate or oval, coarsely serrated, and slightly hairy across the upper surface; it is typically about 2" long and 1" across. The flowering stalks have long spreading hairs and alternate trifoliate leaves. They are often reddish green in appearance and semi-erect or spreading. The lower to middle alternate leaves are similar in appearance to the basal leaves, except that they are slightly smaller and have shorter petioles. The upper leaves are often simple and sessile, resembling narrow leaflets of the lower leaves. Individual flowers may develop from the axils of these upper leaves on short pedicels, although most of the flowers occur in a terminal inflorescence consisting of a panicle of cymes. This inflorescence has leafy bracts and its hairy stems have a tendency to zigzag between the cymes of flowers. Each flower is about ½" across, consisting of 5 yellow petals that are obcordate, 5 green sepals that are triangular and spreading, 10-20 stamens with yellow anthers, and a dome-shaped receptacle that is also yellow. The sepals are slightly longer than the petals and clearly visible from above. Under each flower, there are 5 green bracts that are spreading and ovate-triangular. They are initially shorter than the sepals, but become about the same length when the flower blooms. The blooming period occurs during the summer and lasts about 1-2 months; the flowers bloom sporadically during this period. The seeds are somewhat flattened, asymmetrically reniform, and dark brown. The root system consists of a shallow branching taproot. This plant spreads by reseeding itself.
Cultivation: This is an adaptable plant that can be found in full or partial sun, slightly moist to dry conditions, and fertile to sterile soil, including loam, clay-loam, and stony soil. The foliage is initially attractive, but becomes worn-out looking by the time the flowers begin to bloom.
Range & Habitat: Rough Cinquefoil is a common plant in northern and central Illinois, but less common or absent in many areas of southern Illinois (see Distribution Map). Mohlenbrock (2002) considers this species to be adventive from Eurasia, but other authorities think native strains exist that are difficult or impossible to distinguish from those of the Old World. I am inclined toward the former view because this species is typically found in areas that are weedy and disturbed. Habitats include disturbed areas of mesic prairies and savannas (particularly where fire has occurred), fields and pastures, gardens and edges of yards, edges of parking lots, vacant lots, and miscellaneous waste areas.
Faunal Associations: The nectar and pollen of the flowers attract small bees and flies primarily. Rabbits, groundhogs, and livestock occasionally eat the foliage of Potentilla spp. (Cinquefoils). The seeds of Cinquefoils may be able to pass through their gullets and remain viable, thus these mammalian herbivores may play an important role in their dispersion to new areas.
Photographic Location: Near the edge of an abandoned parking lot at Judge Webber Park in Urbana, Illinois. This plant was growing in stony ground.
Comments: This is a rather coarse and weedy plant. During an early stage of its development, Rough Cinquefoil resembles Fragaria virginica (Wild Strawberry), but it later develops leafy flowering stalks with yellow flowers that fail to produce any fleshy fruits. Rough Cinquefoil differs from Potentilla simplex (Common Cinquefoil) by its trifoliate leaves and terminal inflorescence; the latter has palmate leaves with 5-7 leaflets and only axillary flowers. It also resembles Potentilla millegrana (Diffuse Cinquefoil) as both species have a similar growth habit and trifoliate leaves. However, Diffuse Cinquefoil has stems that are softly pubescent and smaller flowers (about ¼" across), while the stems of Rough Cinquefoil have coarse spreading hairs. Diffuse Cinquefoil is uncommon in Illinois and unlikely to be encountered; it more common further to the west.