Galeopsis tetrahit (Brittlestem Hemp-nettle)

Plant Info
Also known as: Common Hemp-nettle
Genus:Galeopsis
Family:Lamiaceae (Mint)
Life cycle:annual
Origin:Europe, Asia
Status:
  • Weedy
Habitat:part shade, shade; woods, roadsides, waste areas
Bloom season:June - September
Plant height:1 to 3 feet
Wetland Indicator Status:GP: FACU MW: FACU NCNE: FACU
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: irregular Flower shape: tubular Cluster type: whorled

[photo of flowers] Flowers are in whorls of 2 to 6 at the top of the plant and at leaf axils in the upper part of the plant. Individual flowers average about ¾ inch long, are irregularly tubular with a broad upper lip and a 3-parted lower lip with the middle lobe the largest. The outside of the upper lip is covered in long white hairs. The inside of the lower lip is striped with purple and usually has 2 bumps and 2 white or pale to bright yellow spots near the throat. There are 4 stamens that arc along the inside of the upper lip. Flower color ranges from pink to purple and is sometimes white. Plants are often branched with flowers on each branch.

Leaves and stem: Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are up to 2½ inches long and 1½ inch wide, hairy, roughly egg-shaped, pointed at the tip, rounded or wedge-shaped at the base, with serrated edges and hairy stalks. Attachment is opposite, with each pair at right angles to the pair below it.

[photo of stems] Stems are square, bristly hairy, swollen below the leaf nodes, and typically many-branched.

Fruit: Fruit type: seed without plume

The flower heads dry to dark brown as fruit matures. A flower produces 4 nutlets, each containing a single seed.

Notes:

This is becoming a serious pest along the North Shore of Lake Superior, as well as in other parts of Minnesota, and is likely much more widespread than the distribution map indicates. A single plant generates hundreds of seeds, which stay viable for several years. The seeds drop near the mother plant and masses of seedlings can pop up the following spring. I had a bad infestation in my own yard for some years but after diligent hand pulling and increasing native plant diversity it has dwindled down to almost nothing. There are 2 varieties recognized in Minnesota, though the trend is to treat them as separate species: var. bifida, the more common in the state and also known as Galeopsis bifida, and var. tetrahit. The descriptions in different references conflict, but according to Flora of North America (actually Flora of China), G. bifida has mostly white flowers, rarely pink. Other references say G. bifida has mostly pink flowers with a notch in the lower lip. The vast majority of plants in Minnesota have pink flowers, but the notching they refer to is unclear and not obvious in our own images. We'll wait for the Bell Herbarium and DNR to decide what we really have here.

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More photos

Photos by K. Chayka taken in Lake and Ramsey counties. Other photos courtesy Peter M. Dziuk.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: John - Soudan
on: 2010-02-18 10:11:14

All over my driveway. send Peter up in the late summer he can stomp it out with his bare feet. its on the outhouse path to so you do need slippers. eradication by blow torch works well so no herbicide.

Posted by: K. Chayka
on: 2010-02-18 11:33:41

Torching it sounds like a good method of control to me. :-)

Posted by: Jill - Itasca County, near Effie, MN close to Deer Lake
on: 2011-08-09 07:59:28

The patch I've photographed fits the description to a T except that the flowers are slightly smaller..... 1/8 - 1/4 inch. Is the flower size related to soil, light, ??

Posted by: Randy - Duluth, MN
on: 2012-11-25 18:16:26

I have these in our fields on the Sustainable Agriculture Project's Farm at the UMD Farm... ca. 4 miles north of Duluth... prickly and poisonous, right?

Posted by: Theo - Duluth, MN
on: 2014-08-16 21:05:53

These have sprung up in every new garden bed we made earlier this year. Various site conditions, on top of sheet mulched beds and Hugelkultur beds. We were wondering what they were, now we just need to find a use for them.

Posted by: Chad - Aurora WMA in Steele County near Bixby
on: 2015-08-06 13:05:08

Found in a wetland with dogwood and willows at the road's edge (SE 54th Ave).

Posted by: Gary W - Carlton, St. Louis, Lake, and Cook
on: 2017-06-26 14:10:37

Shows up on paths and logging roads, disturbed soils in clear-cuts. I have seen an insect, the white-margined burrower bug, eat the seeds of this plant.

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