Bittersweet Nightshade
Solanum dulcamara
Nightshade family (Solanaceae)

Description: This perennial plant is a semi-woody vine about 2-8' 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 2" 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" (8 mm.) 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 " 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 Nightshade 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 Nightshade 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 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 attract bumblebees and Halictid bees (Macior, 1967). Through the rapid vibration of thoracic muscles, the pollen is extracted from the flowers using "buzz pollination." Nectar is not available as a floral reward. The foliage and roots of Bittersweet Nightshade are attacked by several species of insects, especially leaf beetles (Chrysomelidae). This includes such species as Epitrix cucumeris (American Potato Flea Beetle), Epitrix fuscula (Eggplant Flea Beetle), Epitrix hirtipennis (Tobacco Flea Beetle), Lema daturaphila (Three-lined Potato Beetle), Leptinotarsa decemlineata (Colorado Potato Beetle), Leptinotarsa juncta (False Potato Beetle), Plagiometriona clavata (Clavate Tortoise Beetle), and Psylliodes affinis (European Potato Flea Beetle); see Clark et al. (2004). The foliage of Bittersweet Nighshade is toxic and unpleasant-tasting, therefore it is rarely bothered by mammalian herbivores. The fruits of nightshade species (Solanum spp.), including those of Bittersweet Nightshade, are eaten by such birds as the Wood Duck, Ruffed Grouse, Ring-necked Pheasant, Gray Catbird, Northern Cardinal, and Swamp Sparrow; the Bird Table has a more complete list of these species. Some mammals also eat these fruits, including the Raccoon, Striped Skunk, White-tailed Deer, White-footed Mouse, and Woodland Deer Mouse (Martin et al., 1951/1961; Myers et al., 2004; Hamilton, 1941). Because the seeds are able to pass through the digestive tracts of many animals and remain viable, they are distributed to new locations, enabling this plant to spread. Because these fruits are considered potentially toxic to humans, however, their consumption should be avoided. As a semi-woody vine that climbs fence rows and adjacent vegetation, Bittersweet Nightshade provides good nesting habitat and protective cover for birds and other animals.

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 Nightshade 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) and Celastrus orbiculatus (Oriental Bittersweet), which are long woody vines from another family of plants.