Bittersweet nightshade is an herbaceous perennial vine or semi-woody shrub in the Solanaceae (nightshade) family. It produces thin stems that may reach 6 feet tall or 10 feet long when climbing. These stems are smooth and hollow. Stems are woody at the base and may be dark green to purple toward the tips. Leaves occur alternately on the stem and are green to greenish-purple. Leave may occur in three shapes: ovate, ovate with a single lobe at base (mitten-shaped), or ovate with a lobe on each side at the base. Bittersweet nightshade flowers from late spring to early fall. Flowers occur in loose clusters. Flowers have 5 purple (sometimes white) petals that point backward and distinct yellow anthers. Each flower produces an egg-shaped berry that begins green and matures to a bright red. Bittersweet nightshade has an extensive rhizomatous root system.
Bittersweet nightshade contains the glycosides solanine and dulcamarine which are toxic to humans, livestock, and wildlife. Solanine, the toxin found in green potatoes, is ubiquitous in the Solanaceae family. Dulcamarine is similar in structure to atropine, the toxin found in belladonna or deadly nightshade. These glycosides are found in all parts of the plants and in high concentrations in unripe fruit; however, the colorful, ripe fruit may be attractive to children increasing the risk of poisoning.
Bittersweet nightshade is native to Eurasia. It was introduced to North America prior to the 1800s as a medicinal and ornamental plant. It creates dense infestations by spreading rhizomes and seeds and is frequently dispersed to new locations by seed. Spread is facilitated by several bird species that can safely consume the berries. Bittersweet nightshade is frequently found in disturbed sites, near development, and in and around areas frequented by birds (willows, fence lines, etc.). It may also be found in riparian areas, forests, gardens, and landscaping.
Prevention strategies and cultural control strategies should be utilized as much as possible. Solarization may be utilized, but covering must remain in place for multiple years. Currently there are no biological control agents available for control of bittersweet nightshade in Teton County.
Hand pulling and digging out of large stands is not usually recommended because rhizome fragments are capable of resprouting. However, pulling may be effective for individual plants or small patches, especially when soil is damp, but areas must be inspected multiple times each growing season as bittersweet nightshade can resprout from root fragments. Mowing is not recommended unless repeated multiple times each growing season.
Larger infestations can be controlled with herbicides. Early to mid summer treatments prior to bloom can be effective; fall treatments with systemic herbicides can also effectively kill the root stock. Read the label before using any herbicide. Contact TCWP if you have any questions about application rates or how to use an herbicide.
