Buttercup family (Ranunculaceae)
Description: This perennial vine is semi-woody and up to 30' long. Young stems are green, glabrous, and terete, while older stems are brownish green to brown. Opposite pairs of compound leaves occur at intervals along the stems. These compound leaves are odd-pinnate and they usually have 5 leaflets. The long petioles of these compound leaves can lean or bend around neighboring objects for support; tendrils are not present. This vine can climb small trees, fences, and similar objects; in more open areas, it sprawls across the ground. The leaflets are up to 3" long and 1½" across; they are ovate or ovate-cordate, glabrous, and smooth along their margins. The upper surface of each leaflet is medium green, while the lower surface is dull light green; its major veins are parallel. Each leaflet has a petiolule (or small stalk) at its base of varying length.
From the axils of the upper leaves, there develops flat-headed panicles of flowers. The flowers are usually bisexual, although monoecious vines (with separate male and female flowers) may occur. Each bisexual flower has 4 petal-like white sepals (less often 5), many long stamens, and 5-6 pistils with elongated styles toward the center. Both the stamens and styles of the pistils are white or cream-colored. True petals are absent. The branches and branchlets of the panicle are green and slender. The blooming period occurs from late summer into fall, typically lasting about 1½ months. The flowers have a strong sweet fragrance. After the blooming period, each flower is replaced by a cluster of achenes with long spreading styles. These persistent styles are covered with long white hairs, which provides them with a feathery appearance. The large achenes are ovoid and flattened in shape; they are thinly covered with appressed silky hairs. Because of their feathery styles, the achenes are distributed to some extent by the wind. This perennial vine reproduces by reseeding itself.
Cultivation: Autumn Clematis thrives in full sun to light shade, moist to slightly dry conditions, and a loam or clay-loam soil. It also tolerates gravelly soil and probably sandy soil as well. This vine can smother small shrubs and is rather aggressive; sometimes it even climbs up the trunk of trees to occupy the lower branches.
Range & Habitat: Autumn Clematis has naturalized in widely scattered locations across Illinois (see Distribution Map). This vine is undoubtedly more common than official records indicate, and its abundance within the natural areas of the state is still growing. Habitats include edges of woodlands, thickets, fence rows, areas along railroads and roads, and waste land. Autumn Clematis is native to East Asia and it is often cultivated as an ornamental plant. This species can be considered somewhat invasive.
Faunal Associations: The caterpillars of the moths Horisme intestinata (Brown Bark Carpet), Thyris maculata (Spotted Thyris), and Thyris sepulchralis (Mournful Thyris) feed on the foliage of Clematis spp. The caterpillars of the latter two species are leaf-rollers. There is a lack of information about floral insect visitors for Autumn Clematis, but they are probably similar to the visitors of the native Clematis virginiana (Virgin's Bower). The insect visitors of this latter species include Halictid bees, various kinds of wasps, and an abundance of flies. Most of these insects are seeking nectar from the flowers, although some of them may feed on the pollen or collect it. Because the foliage of Autumn Clematis is toxic, it is not eaten by mammalian herbivores.
Photographic Location: Meadowbrook Park in Urbana, Illinois.
Comments: Like the native Clematis virginiana (Virgin's Bower), Autumn Clematis has showy white flowers. The latter is often found in drier habitats than the former and it blooms later in the year. These two species of Clematis are easy to distinguish: Virgin's Bower has leaflets that are shallowly cleft and dentate, while the leaflet margins of Autumn Clematis are smooth (or nearly so). During the late summer or fall, when the achenes develop, it is also possible to distinguish these species according to their styles: Autumn Clematis has feathery styles, while the styles of Virgin's Bower are more smooth. Other Clematis spp. that occur in natural areas of Illinois have nodding purplish flowers with a very different appearance; they are called 'Leather Flower' vines. Because the leaflets of some Leather Flower vines have smooth margins, it is possible to confuse these species with Autumn Clematis when the flowers are not in bloom. Another scientific name of Autumn Clematis is Clematis dioscoreifolia.