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Hemp nettle

(Galeopsis tetrahit)

Photo of hemp nettle
Photo credit: Michael Shephard, USDA Forest Service, Bugwood.org

Herbaceous annual that grows to be 1-3’ tall. Stems are square, swollen at leaf nodes, and covered with coarse, downward-pointing hairs intermixed with shorter glandular hairs.

Overview map of hemp nettle classification in WI
Restricted (orange) counties

Other names for this plant include:

  • Common names: brittlestem hempnettle, common hemp nettle, hemp-nettle
  • Scientific names: G. tetrahit var arvensis; G. tetrahit var bifida; G. tetrahit var tetrahit

Classification in Wisconsin: Restricted

Ecological Threat
  • It Invades roadsides, open woods, pastures and fields. In general, hemp nettle prefers disturbed sites creating monospecific stands.
  • Hemp nettle is also considered an agricultural weed and is avoided by most grazers and also is the host for potato fungus and several nematodes.
Identification
CAUTION: Wear long sleeves and gloves when handling. Hemp nettle exposure can irritate the skin in some people.

Leaves: Opposite, coarsely toothed and hairy on both sides. The actual shape can be variable.

Flowers: Purple to pink to white flowers in dense axillary clusters. It has five sharp points that protrude from the flowers—Bloom from June-September.

Fruits & seeds: Each flower produces four nutlets each containing one seed.

Roots: Taproot with lateral roots.

Control

Mechanical: Dig up or hand-pull when in the flower bud stage. Dispose of in landfill since seeds can still mature after removed.

Chemical: Use Dicamba (230 mL/ha) mixed with MCPA (1.1 L/ha) [restricted use].

Resources
Sources for content:
  • Galeopsis tetrahit [exit DNR]. In Klinkenberg, Brian. (Editor) 2012. E-Flora BC: Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver.
Links for more information: