The common name “bittersweet” applies to two distinctly different plants: a native woody vine prized for decoration and an introduced member of the nightshade family. Understanding which plant you have encountered requires careful observation of the vine structure, flowers, and fruit composition. The differences between the two species are substantial, particularly regarding their toxicity and overall impact on the local environment. Clarifying these distinctions is necessary for safe gardening and effective landscape management.
Defining the Two Bittersweet Species
The name “bittersweet” refers to two unrelated plants. The first is American Bittersweet, scientifically known as Celastrus scandens, a species native to central and eastern North America. This sturdy, twining, woody vine is valued for its vibrant autumn foliage and persistent, colorful berries.
The second is Bittersweet Nightshade, or Solanum dulcamara, which is considered an invasive species in North America, having been introduced from Europe and Asia. This plant is a sprawling, semi-woody perennial shrub or herbaceous vine, not a true woody vine. It belongs to the Solanaceae family, which also includes potatoes, tomatoes, and deadly nightshade.
Identifying the Vines and Berries
The easiest way to tell the two species apart is by examining the structure of their vines and how their fruit develops. American Bittersweet produces thick, robust, woody stems that twist tightly around host trees and structures. Its berries form in dense, conspicuous clusters only at the very ends of the branches, known as terminal panicles. As the fruit ripens in autumn, a round, orange-yellow capsule splits open to reveal three scarlet-red seeds inside. These woody capsules and bright red seeds are persistent, remaining on the vine throughout the winter, which is why they are so popular for decorations.
In contrast, Bittersweet Nightshade has a thinner, more herbaceous stem that may only become slightly woody near the base. Its flowers are small, star-shaped, and typically purple or blue-violet, featuring a prominent cone of bright yellow anthers. The fruit appears in small clusters along the stem at the leaf axils, not just at the tips of the branches. Its berries are fleshy, ovoid, and resemble elongated tomatoes, transitioning from green to yellow, and finally to a translucent, bright red when ripe. These berries are less persistent than the American variety and generally drop off the vine before deep winter sets in.
Toxicity: Distinguishing Safe from Dangerous
Understanding the toxicity profile is the most important distinction between the two plants. Bittersweet Nightshade (Solanum dulcamara) is toxic, especially the unripe berries and the foliage. This plant contains steroidal glycoalkaloids, primarily solanine and dulcamarine, which are poisonous to humans, pets, and livestock. Ingestion can lead to gastrointestinal distress, including nausea, vomiting, and diarrhea, and in larger doses, it may cause nervous system effects.
The unripe, green berries contain the highest concentration of these toxic compounds. While the ripe red berries have a lower level of toxins, consuming any part of the nightshade plant is strongly discouraged. American Bittersweet (Celastrus scandens) berries are considered mildly poisonous if consumed in quantity. However, the toxicity level of the American species is significantly lower and less likely to cause severe poisoning in humans than the nightshade species.
Common Uses and Control Methods
The primary human use for American Bittersweet is ornamental, with its highly valued branches used extensively in wreaths and dried floral arrangements. Gardeners who cultivate the native vine should manage its growth carefully, as its strong, twining stems can girdle and potentially damage small trees and shrubs. Pruning is necessary to maintain its shape and prevent it from becoming overly aggressive.
Bittersweet Nightshade is often viewed as a noxious weed due to its invasive nature and toxicity. Its dense, sprawling growth can outcompete native vegetation, particularly in moist areas like stream banks. Control methods focus on removing the entire plant, including the extensive root system, to prevent regrowth from fragments. Small infestations can be managed by hand-pulling while wearing gloves, but larger areas may require chemical control using herbicides like glyphosate or triclopyr.