Buttercup family (Ranunculaceae)
Description: This native perennial plant is a woody vine up to 20' long. Its stems can twine about fences and adjacent vegetation and they branch occasionally. These stems are initially green or dull red, but they eventually turn brown and woody; young stems are sparsely pubescent, round or angular, and become somewhat enlarged at the base of the petioles. The opposite leaves are primarily trifoliate, although some of them are simple. The petioles of these leaves are up to 2" long; they are green or dull red and sparsely pubescent, like the stems. The leaflets and simple leaves are up to 4" long and 2" across; they are ovate, dentate or shallowly cleft along the margins, and nearly hairless. The underside of each leaf may be slightly pubescent, especially along the major veins. Each leaflet has its own petiole (petiolule); the petiole of the terminal leaflet is longer than those of the lateral leaflets.
Occasionally, flat-headed panicles of white flowers are produced from the axils of the leaves. Each panicle can span several inches across. A single vine can produce all staminate flowers (male), all pistillate flowers (female), or all perfect flowers (both male & female). Regardless of its gender, each flower is about ¾" across and has 4 petal-like sepals that are white or cream. Each staminate flower has abundant long stamens in its center that have white filaments and pale yellow anthers. Each pistillate flower has several green carpels in its center, each with a short curly style. Each perfect flower has green carpels in its center, which are surrounded by one or two rows of stamens. The blooming period occurs from mid- to late summer and lasts about a month. The staminate flowers quickly wither away, but each of the pistillate and perfect flowers develop a cluster of pubescent achenes with elongated styles (up to 2" long) that are more or less hairy. These achenes and their persistent styles are initially green and silky in appearance, but they eventually turn brown. Each achene contains a single large seed. This plant spreads by reseeding itself.
Cultivation: The preference is partial sun, moist to mesic conditions, and a fertile soil that is loamy or silty. Full sun is also tolerated, although the leaves may turn yellowish green.
Range & Habitat: Virgin's Bower occurs occasionally throughout Illinois (see Distribution Map). It is a little more common in northern and western Illinois than other areas of the state. Habitats include edges of woodlands, moist thickets, moist meadows in floodplain areas, banks of rivers and large drainage ditches, and fence rows. Virgin's Bower can be found in both disturbed and natural areas. It is sometimes cultivated as an ornamental garden plant.
Faunal Associations: The nectar of the staminate flowers attracts Halictid bees (including Sphecodes clematidis), wasps, and various kinds of flies. No information is available for pistillate flowers. The caterpillars of two moths, Thysis maculata (Spotted Thysis) and Thysis sepulchralis (Mournful Thysis), feed on Virgin's Bower and other Clematis spp. Birds and mammalian herbivores apparently don't utilize these species as a food source to any significant degree.
Photographic Location: A moist thicket near a drainage ditch in Champaign, Illinois. The flowers in the upper photograph are staminate.
Comments: The flowers of Virgin's Bower are attractive and often abundantly produced; the staminate flowers are slightly more showy than the pistillate flowers. The achenes with their silky-hairy styles are also interesting because of their unusual appearance. The only other species that resembles Virgin's Bower in Illinois is Clematis terniflora (Autumn Clematis), which has been introduced from East Asia as an ornamental plant. Autumn Clematis is also a woody vine that produces masses of white or cream flowers. The flowers of this latter species, in my experience, are slightly larger (about 1" across) and more fragrant than those of Virgin's Bower. These two species can be easily distinguished by their foliage: The leaflet margins of Virgin's Bower are dentate or shallowly cleft, while the leaflet margins of Autumn Clematis are smooth.