Bittersweet nightshade identification and control

Why it's a problem

Bittersweet nightshade grows as a vine or woody shrub and can take over natural areas such as small streams, causing channel disruption. It can overtake and outcompete native vegetation by adding weight and blocking sun. Bittersweet nightshade is toxic to people, pets, and livestock.

Plant description

Bittersweet nightshade is native to Europe and Asia. It is a perennial vine or semi-woody shrub, depending on conditions. Branches grow and die back 3 to 6 feet each year. They are known to climb 30 feet or higher up trees. Plants grow singly or in dense patches.

Its leaves are distinctive. They are dark green to purple-tinged with often 1 or 2 small ear-like lobes near the base.

Bittersweet nightshade flowers mid-May to September. Flowers are purple and star-shaped with fused cone-shaped yellow stamens (male fertilizing part of a flower).

Berries grow similarly to tomatoes, they are small, round, or egg shaped, and vary in color depending on ripeness. Green berries are unripe. Orange ones are somewhat ripe. Red berries are ripe. Berries are poisonous, especially when unripe.

Crushed leaves and bark have an unpleasant smell.

Bittersweet nightshade spreads via seeds (birds can eat these berries) and by stem and root fragments.

Be aware of look-alike plants

Bittersweet nightshade is often confused with:

Silverleaf nightshade

Black nightshade

Perennial pepperweed

When in doubt, take photos and report them on iNaturalist.

What to do if you find it

Because bittersweet nightshade is very widespread, we are not tracking locations. Property owners are not required to control it, but it is strongly encouraged. If you are concerned about where the plant is growing on public lands or trails, we can direct you to the agency responsible for that area.

Control methods

We recommend using a combination of methods to control weeds. In areas with few weeds, it is important to act quickly before they become harder to control. Make a long-term plan as it often takes several years to get rid of most weeds. Start in the least infested areas first and then move into more heavily infested areas. 

For more in-depth control information, read Best Management Practices (BMP) for bittersweet nightshade (235KB)

Manual control

Small infestations (less than 200 square feet) can be hand pulled or dug up in most cases. Remove as much root as possible. Try to minimize soil disturbance and refill holes made in the removal process.

To prevent or mitigate erosion, remove in sections or put a stabilizing agent (such as mulch or fabric) in place.

Larger infestations can be cut back and then covered with a thick layer of mulch, or some sort of geotextile/tarp fabric.

Chemical control

Stay safe when using herbicide:

• Always read the label before use.
• Wear a long-sleeved shirt, long pants, shoes, and eye protection.
• Follow state and local regulations.

Foliar herbicide applications are effective. If the site is not wet or near water, you can apply broadleaf herbicide. If near native grasses, pastures or lawns, be sure to use broadleaf selective herbicides.

Avoid spraying where there is a chance that herbicide will enter a waterway or wetland unless you are using a state-approved aquatic herbicide and have the required permits and licenses to do so. Use of pesticides in water is regulated in Washington state.

See Washington Department of Ecology Aquatic Pesticide Permits for details.  

For more information or a site-specific control recommendation in King County, contact the noxious weed program. For information in other counties in Washington state, contact your local weed board or your local cooperative extension office.

Disposal

Dispose of plant root balls and stems with berries in garbage. You can compost stems and other plant parts with yard waste or on site if left high and dry where they cannot reach damp soil. Bittersweet nightshade will re-root if left on moist soil.  

Noxious Weed Disposal - Washington State Noxious Weed Control Board

Are your weeds piling up? - Noxious Weeds Blog