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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

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
Ecological threat:
  • It Invades roadsides, open woods, pastures and fields. In general, hemp nettle prefers disturbed sites creating monospecific stands.
  • Hemp nettle is considered an agricultural weed as well and is avoided by most grazers and also is the host for potato fungus and several nematodes.
Overview map of hemp nettle classification in WI
Restricted (orange) counties

Classification in Wisconsin: Restricted

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for hemp nettle was based upon this literature review [PDF] developed by the department.

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 true shape can be variable.

Flowers: Purple to pink to white flowers in dense axillary clusters. It has 5 sharp points that protrude from the flowers. Bloom from June-September.

Fruits & seeds: Each flower produces 4 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].

Photos

View hemp nettle pictures in our photo gallery!

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: