Weeds: Nightshades – Solanum spp.

categories: I-Po Weeds

revision date: 2024-06-22 08:14

  • Family: Solanaceae
  • Cycle: Annual/Perennial
  • Plant type: Broadleaf
Cutleaf nightshade with fruit.
Cutleaf nightshade with fruit
Photo by: D.G. Swan

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

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • 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.
  • 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • 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

  • 2,4-D + MCPP + dicamba
  • products containing 2,4-D

Bare ground areas

  • glyphosate
  • products containing 2,4-D

Additional Images