Nightshade family (Solanaceae)
Description: This adventive perennial plant is a semi-woody vine about 2-6' long. It can become semi-erect by climbing over adjacent vegetation or fence rows, otherwise it sprawls along the ground. The stems are initially purple and slightly pubescent, or they have scattered appressed hairs. Later, they become brown and woody. These woody stems are semi-hardy in Illinois and may survive some winters to produce foliage. The alternate leaves are up to 4" long and 2½" across. The larger leaves have a triangular outline and 3 deep lobes. These lobes are broadly ovate or cordate, with the terminal lobe being much larger than the side lobes. The margin of each leaf is smooth, while the upper surface is either glabrous or has scattered appressed hairs. The terminal lobe tapers gradually into an elongated tip. The smaller leaves often lack lobes and have an ovate shape, otherwise they are quite similar to the larger leaves. The foliage exudes a rank bitter odor, particularly when the leaves or stems are damaged. Occasionally, angular clusters of 6-12 violet flowers are produced from the stems or the axils of the leaves. The flower buds and their branching stalks are also violet.
Each flower is about 1/3" across, consisting of a purple corolla with 5 triangular lobes, several yellow anthers that are united together to form a slender cone, and an inconspicuous style that extends beyond the anthers. As the lobes of the corolla unfold, they spread outward and then curve sharply backward to expose the anthers. The small calyx is green, purple, or brown, and has 5 shallow lobes that are well-rounded. It is persistent and slightly pubescent. The blooming period usually occurs during the summer and lasts 2-3 months. There is no noticeable floral scent. Each flower is replaced by a shiny little fruit that is oval in shape and about ¼" long. Each fruit is initially green, but later turns yellow or orange, and finally becomes bright red. The fruit is juicy and contains yellow seeds that are circular in shape and flat-sided. The root system produces abundant rhizomes that become somewhat woody with age. This plant often forms sprawling vegetative colonies.
Cultivation: Bittersweet prefers full or partial sun, and moist to mesic soil that is loamy and fertile. However, because of its robust nature, this plant can adapt to drier conditions and other kinds of soil. It can spread aggressively and be difficult to get rid of because small pieces of rhizome in the soil can regenerate new plants. It is wise to wear gloves while attempting to remove this plant by hand as the foliage is toxic.
Range & Habitat: Bittersweet occurs primarily in the northern half of Illinois, where it is fairly common in most areas (especially in the NE). In southern Illinois, however, it is less common or absent (see Distribution Map). This species is adventive was from Europe, and it also occurs in Asia. Habitats include openings in woodlands, thickets, marshes and bogs, brushy areas and rock piles, fence rows, gardens and edges of yards, and miscellaneous waste areas. This plant prefers disturbed areas, although it sometimes occurs in natural habitats.
Faunal Associations: The flowers are subjected to "buzz pollination" by bumblebees. This involves the rapid vibration of the thoracic muscles to release the pollen, which is the only reward of the flowers. The foliage of this plant is toxic and unpleasant tasting, therefore it is rarely bothered by mammalian herbivores. The bright red fruit, however, is eaten by small mammals to a limited extent, including the Raccoon, Striped Skunk, and Pocket Gopher. Some upland gamebirds, songbirds, waterfowl, and shorebirds also eat the fruit (see Bird Table). The seeds remain undamaged and are distributed far and wide by these animals. Because the fruit can be toxic to humans and colorful in appearance, children should be warned not to eat it.
Photographic Location: The rocky slope of a drainage canal at the Windsor Road Prairie in Champaign, Illinois.
Comments: As a semi-woody vine with deeply lobed leaves, Bittersweet differs from all other members of the Nightshade family that occur in the wild in Illinois. It is somewhat variable in regard to the hairiness of its stems and leaves, and there is an uncommon form with white flowers. Because of the similarity in common names, this introduced vine should not be confused with Celastrus scandens (American Bittersweet), which is a native woody vine from another family of plants. Sometimes Solanum dulcamara is referred to as Bittersweet Nightshade.