Weeds: Horseweed (Marestail) – Conyza canadensis

categories: F-H Weeds

revision date: 2024-06-22 08:11

  • Family: Asteraceae (Compositae
  • Cycle: Annual
  • Plant type: Broadleaf
Horseweed flowerheads.
Horseweed flowerheads
Photo by: T.W. Miller

Biology

Horseweed plants range from one to five feet tall. The erect stems may be branched, especially near the top. The alternate, rather narrow leaves are one to three inches long and closely crowded on the stems. The leaf surface is hairy. Lower leaves typically have short petioles and may be slightly toothed; upper leaves usually lack petioles and are smooth-margined. The small, inconspicuous greenish-white flowers are borne at the tips of stems in mid- to late summer. SPECIAL INFORMATION: The leaves and flowers of horseweed contain a compound which is particularly irritating to horses.

Habitat

Horseweed grows in pastures, waste areas, along roadsides, and in cultivated fields. It is native to grasslands.

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.
  • 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.
  • Apply organic mulches, such as bark, compost, grass clippings, straw, and other materials, in a layer from two to several inches thick for effective weed management.

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.
  • 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

Turf areas

  • 2,4-D + MCPP + dicamba

Bare ground areas

  • glyphosate

Additional Images