Buttercup family (Ranunculaceae)
Description: This herbaceous perennial plant is about 1-2' tall. The basal leaves occur in whorls from long stalks that emerge out of the ground. They are divided into 3-5 lobes and have dentate margins. From each whorl of the basal leaves often emerges a second whorl of leaves. These secondary leaves are smaller than the basal leaves, but otherwise similar in form. From each whorl of the secondary leaves emerges a long stalk bearing a single white flower. In less mature plants, sometimes the basal leaves produce flowering stalks, rather than whorls of secondary leaves. Sometimes there are small alternate leaves sparsely distributed along the flowering stalks, but they are more narrow and less lobed than the whorled lower leaves. There are scattered white hairs on both the leaves and their stalks. Each flower is about ¾" across, and has 5 petal-like sepals that often fail to open fully. In the center, is a small green cone that is surrounded by numerous stamens with yellow anthers. As the flower withers, the green cone develops into an elongated fruit that resembles a cylindrical green thimble up to 1½" long, hence the name of the plant. This thimble is at least twice as long as it is wide.
The blooming period occurs from early to mid-summer and lasts about a month. There is no floral scent. The thimble-like fruits develop during the summer, and then become transformed into cottony tufts during the fall. These cottony tufts contain scattered dark seeds and persist during the winter. The seeds are distributed by the wind. The root system consists of a taproot and tough slender rhizomes, which can form vegetative offsets. This plant produces an allelopathic substance, protoanemonin, which inhibits seed germination and seedling growth of many species of plants.
Cultivation: The preference is full to partial sun, and mesic to dry conditions in a rather sandy or gritty soil. In rich fertile soil, this plant has trouble competing with taller, more aggressive plants. Thimbleweed is often temperamental about being transplanted and difficult to start from seed; transplantation should occur during the spring after danger of hard frost has passed. Established plants, however, are reliable and easy to deal with. Foliar disease is rarely a problem.
Range & Habitat: The native Thimbleweed occurs occasionally in northern Illinois, it is scattered and uncommon in central Illinois, and rare or absent in southern Illinois (see Distribution Map). Habitats include dry upland areas of black soil prairies, loess hill prairies, scrubby barrens, limestone glades, sandy Black Oak savannas, open sandy woodlands, abandoned fields, and open areas along roadsides. This plant is usually found in less disturbed habitats.
Faunal Associations: The abundant pollen of the flowers attract small bees and Syrphid flies. The bee visitors include Plasterer bees and Halictid bees. Mammalian herbivores usually avoid consumption of this plant because the foliage is toxic, causing a burning sensation in the mouth and irritation of the gastrointestinal tract.
Photographic Location: The photographs were taken at the webmaster's wildflower garden in Urbana, Illinois.
Comments: This unusual plant has attractive thimble-shaped seedheads that later look like white tufts of cotton; otherwise, its appearance isn't particularly showy. Among the native anemones, Thimbleweed has the greatest fidelity to prairies and the best tolerance of drought (not including the Pasque Flower). It can be distinguished from other anemones by the cylindrical seedheads, which are at least twice as long as they are across. Unlike Anemone canadensis (Canada Anemone), Thimbleweed's leaves have petioles, whereas the leaves of the former are sessile. Thimbleweed's leaves differ from Anemone virginiana (Tall Anemone) by having less dentation along the margins, and some of its leaves are palmate.