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Non-Native Plant Species of Alaska
Splitlip hempnettle (Galeopsis bifida Boenn.)
Brittlestem hempnettle (Galeopsis tetrahit L.)
Family: Lamiaceae
Galeopsis bifida Synonyms: Galeopsis tetrahit var.
bifida (Boenn.) Lej. & Court.
Other common name: none
G. tetrahit Synonyms: none
Other common name: none
Description
Splitlip and brittlestem hempnettle are annual plants
with erect, simple or branched stem from ½ to 3 feet
tall. Leaves, 1 to 5 inches long, are short-stalked,
opposite, ovate-lanceolate to lanceolate, and sparsely
pubescent on both sides. The stem is usually swollen
below leaf nodes. The flowers are terminal or borne
in axillary clusters. They range in color from purple
and pink to white, are ½ to ¾ inch long and
bilaterally symmetrical with a split lower lip. Seeds
are egg-shaped, mottled grayish brown (Hultén
1968).
Splitlip hempnettle. Flowering stem.
This taxon is distinguished from other Alaskan
Lamiaceae by having a calyx of five nearly equal
lobes, well developed bracteal leaves in flower axes,
and rounded lobes of the lower corolla lip.
Ecological Impact
Impact on community composition, structure, and
interactions: Hempnettle has been observed
established in disturbed areas, creating a dense midforb layer and reducing the cover of graminoids and
low forbs.
Impact on ecosystem process: Hempnettle consumes
soil moisture and limiting nutrients. It is likely to
delay establishment of native species in disturbed
sites.
Biology and Invasive Potential
Reproductive potential: Each plant is capable of
producing up to 2,800 seeds (Royer and Dickinson
1999). The seeds can remain dormant in soil for
several years. This species does not reproduce
vegetatively.
Role of disturbance in establishment: Both speices of
hempnettle generally occur in disturbed sites.
Potential for long-distance dispersal: The seeds are
large and do not have any apparent adaptations for
long-distance dispersal.
Potential to be spread by human activity:
Hempnettles appear to spread as a contaminant of hay
or other agricultural products.
Germination requirements: Germination occurs at ½
to 1½ inches depth.
Growth requirements: Unknown.
Listing: The species complex Galeopsis bifida and
Galeopsis tetrahit is declared noxious in Alberta,
Manitoba, and Quebec. It is a prohibited noxious
weed seeds in Alaska (Alaska Administrative Code
1987, Rice 2006).
Distribution and abundance
Splitlip and brittlestem hempnettles are plants of
disturbed sites, roadsides, gardens, and agricultural
lands.
Native and current distribution: Native to Europe and
Asia, it is now found throughout Canada and
northeastern quarter of the United States. It is
introduced into New Zealand and Canary Islands
(Hultén 1968, USDA 2002). Galeopsis bifida has
been reported from all three of Alaska’s primary ecogeographical regions (University of Alaska Museum
2003). G. tetrahit is known from South-Coastal and
Interior Boreal ecogeographic regions of Alaska
(Weeds of Alaska Database. 2005).
South Coastal
Interior- Boreal
Arctic-Alpine
South Coastal
Collection Site
Interior- Boreal
Arctic-Alpine
Collection Site
Distribution of brittlestem hempnettle in Alaska.
Management
Both species are difficult to control once it
establishes. Therefore maintaining weed-free areas is
of primary importance. Once established, dense cover
crops planted early may inhibit hemp-nettle.
Herbicides are also effective (Manitoba Agriculture,
Food, and Rural Initiatives 2001).
Distribution of splitlip hempnettle in Alaska.
References:
Alaska Administrative Code. Title 11, Chapter 34.
1987. Alaska Department of Natural
Resources. Division of Agriculture.
Hultén, E. 1968. Flora of Alaska and Neighboring
Territories. Stanford University Press,
Stanford, CA. 1008 p.
Manitoba Agriculture, Food, and Rural Initiatives.
2001. On-Line Document.
http://www.gov.mb.ca/agriculture/crops/wee
ds/fab08s00.html
Rice, P.M. 2006. INVADERS Database System
(http://invader.dbs.umt.edu). Division of
Biological Sciences, University of Montana,
Missoula, MT 59812-4824.
Royer, F. and R. Dickinson. 1999. Weeds of the
Northern U.S. and Canada. The University of
Alberta press. P. 248-249.
University of Alaska Museum. University of Alaska
Fairbanks. 2003.
http://hispida.museum.uaf.edu:8080/home.cf
m
USDA (United States Department of Agriculture),
NRCS (Natural Resource Conservation
Service). 2002. The PLANTS Database,
Version 3.5 (http://plants.usda.gov). National
Plant Data Center, Baton Rouge, LA 708744490 USA.
Weeds of Alaska Database. 2005. Database of exotic
vegetation collected in Alaska. University
of Alaska, Alaska Natural Heritage Program
– US Forest Service – National Park Service
Database. Available:
http://akweeds.uaa.alaska.edu/
Alaska Natural Heritage Program
Environment and Natural Resources Institute
University of Alaska Anchorage
707 A Street, Anchorage, Alaska 99501
Phone (907) 257-2780 Fax (907) 257-2789
Last Updated November 29, 2006