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Hemp nettle

Hemp nettle (Galeopsis tetrahit)

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

Regulated areas of hemp nettle
Hemp nettle is 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

Ecological threat:

  • 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.

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 developed by the department.

Identification

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

Flowers: Purple to pink to white flowers in dense axillary clusters. 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.

CAUTION: Wear long sleeves and gloves when handling. Hemp nettle exposure can irritate skin in some people.

Distribution

Known county distribution of hemp nettle
Counties in WI where hemp nettle has been reported (as of July 2011). Both vouchered and unvouchered reports included.

Do you have hemp nettle in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical: Dig up or hand pull when in 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

Last revised: Friday May 31 2019