WSU Extension

Hortsense

Weeds : Nightshades : Solanum spp.
(revision date: 4/7/2021)

Family: Solanaceae
Cycle: Annual/Perennial
Plant Type: Broadleaf

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Nightshades are annual or perennial taprooted plants that spread by seeds. They usually have spreading, branched stems to three feet tall. The alternate leaves are broad with pointed tips. They grow one to three inches long and typically have wavy margins. Leaves and stems generally appear smooth and hairless to somewhat hairy. Silverleaf nightshade (Solanum eleagnifolium) has dense, short hairs that give it a silvery appearance. The star-shaped flowers are borne in clusters in the leaf axils and are white to bluish with yellow centers (somewhat resembling tomato flowers in shape). The round to oval berries are green when unripe and, depending on species, yellow, orange, red or purplish-black when ripe. The small green calyx at the base of the fruit is inconspicuous and typically does not enclose or cup the berry. Black nightshade (S. nigrum) is a host for the Colorado potato beetle. SPECIAL INFORMATION: All parts of nightshades including foliage and fruit are toxic. In WASHINGTON and OREGON, silverleaf nightshade is designated as a Class 'A' noxious weed. Eradication or intensive control is REQUIRED by law. In addition, it is on the Washington and Oregon noxious weed quarantine lists, which prohibit sale, purchase, and transport of plants, seeds, and plant parts. Consult your local Noxious Weed Control Board for more information.
Habitat
Nightshades are a weed of waste places and fields on rich soils. They frequently grow in the shade and easily invade disturbed sites. They are not usually a problem in maintained lawn and turfgrass.

Management Options

Non-Chemical Management
  • Maintaining a healthy planting or turf area to provide competition will prevent weed establishment.
  • Cultivation (rototilling or hoeing) will effectively eliminate plants.
  • Reduce weed infestation by handpulling weeds.
  • Mowing to prevent seed production is a very effective means of management. In lawns, mowing regularly at the proper height for the grass species may help minimize weed growth and invasion.
  • Careful digging is useful to manage weed populations. However, digging can carry undesirable weed seed to the surface and foster further germination.
Select non-chemical management options as your first choice!

Chemical Management

Apply according to label directions. Glyphosate products should be applied as spot treatments only! NOTE: Some ingredients listed here are only available in combination. Read the label carefully on combination products to make sure the product is suitable for your specific situation.

Landscape areas
  • glyphosate
  • products containing 2,4-D
Turf areas
  • products containing 2,4-D
  • 2,4-D + MCPP + dicamba
Bare ground areas
  • glyphosate
  • products containing 2,4-D
Images
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Caption: Black nightshade fruit
Photo by: R. Parker
Caption: Black nightshade flower and leaves
Photo by: R. Parker
Caption: Black nightshade line drawing
Photo by: Ciba Geigy
Caption: Cutleaf nightshade
Photo by: R. Parker
Caption: Cutleaf nightshade with fruit
Photo by: D.G. Swan
Caption: Cutleaf nightshade seedling
Photo by: D.G. Swan
Caption: Hairy nightshade flowers
Photo by: D.G. Swan
Caption: Hairy nightshade flowers and fruit
Photo by: T.W. Miller
Caption: Hairy nightshade whole plant
Photo by: T.W. Miller