Weed of the Month: Bittersweet Nightshade

For this Weed of the Month, we’re bringing bittersweet nightshade into the light. Here are some tips for identifying and managing infestations to protect your family, pets, and livestock from this toxic invader.

Bittersweet Nightshade Origins:

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Bittersweet nightshade (Solanum dulcamara L.) is native to Eurasia and came to North America prior to the 1800. Despite its toxicity, it likely came here as an ornamental plant or for medical use, and it spread thanks to bird species that can safely consume the seeds.

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Bittersweet Nightshade: Plant Description

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Bittersweet nightshade is an herbaceous perennial vine or semi-woody shrub. The thin stems are smooth and hollow and may reach 6 feet tall or 10 feet long when climbing, and may be dark green to purple toward the tips. Green to purple/green leaves grow alternately a variety of ovate shapes and release an unpleasant odor when crushed. In late spring/early fall, it flowers with a cluster of 5 purple (sometimes white) petals that point backward and yellow anthers that produce egg-shaped berries that begin green and mature to bright red.

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Bittersweet nightshade is toxic to humans and animals thanks to the glycosides solanine (found in green potatoes) and dulcamarine (similar to the toxin in belladonna or deadly nightshade) that permeate the plant. Ripe berries pose an additional risk to kids thanks to their bright coloring.

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Bittersweet Nightshade Habitat

Bittersweet nightshade often grows by roadsides, ditches, streams and wetlands. It can be found near disturbed sites, developments or areas frequented by birds, and it thrives in moist soil and partial shade. It’s commonly found among landscapes and gardens.

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Bittersweet Nightshade Growth

Bittersweet nightshade has an extensive rhizomatous root system that can resprout from fragments. Roots grow horizontally below the soil surface, creating dense infestations that can disrupt native plant life and impede fish movement if it grows into a creek. Berries contain around 30 seeds, which are dispersed by birds.

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Bittersweet Nightshade Management:

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Removing a bittersweet nightshade infestation is important for the safety of pets, livestock, and your family. Managing and removing the threat mostly requires attention and tenacity.

Prevention and cultural control strategies are effective first steps. Monitor areas where bittersweet nightshade grows, and manually remove individual plants or small patches. This works best with wet soil and early growth; manually removing large strands or thick patches leaves root fragments that can resprout. Repeatedly mowing throughout the season works. Inspect the area throughout the season to ensure the job is done.
Solarization works if the area is covered for multiple years, and currently there are no biological control agents for bittersweet nightshade in Teton County.
Larger infestations can be controlled with herbicide. Ideally, treat patches in early to mid summer before they bloom. Fall treatments with systemic herbicides can also kill the root stock.

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Be sure to read the label before using any herbicide, and contact us if you have any questions about how to use an herbicide.

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