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Non-Native Plant Species of Alaska
Bull thistle
Cirsium vulgare (Savi) Ten.
Synonyms: Carduus lanceolatus L, Carduus vularis Savi, Cirsium lanceolatum (L.) Scop.
Other common names: common thistle, spear thistle
Family: Asteraceae (Compositae)
Description
Bull thistle is a biennial with a short, fleshy taproot.
The stem is 2 to 5 feet tall, conspicuously winged,
bearing many spreading branches. It is green or
brownish, and sparsely hairy. Leaves are pinnately
lobed, hairy and prickly on upper side and cottony
underneath. Leaf blades extend down petiole and
along stem, forming long, prickly wings.
Flowerheads are one to two inches wide with deep
purple flowers. The bristles on the pappus are
feathery (Hultén 1968, Whitson et al. 2000).
This is the only large-headed thistle with a prickly,
winged stem.
Ecological Impact
Impact on community composition, structure, and
interactions: Bull thistle competes with native species
for water, nutrients, and space; displacing native
species, and decreasing forage sites for grazing
animals.
Impact on ecosystem process: Unknown.
Biology and Invasive Potential
Reproductive potential: Bull thistle reproduces only
by seeds. Cross-pollination is required to set fertile
seed; a wide variety of insects pollinate bull thistle.
Average fruit production is nearly 4,000 per plant.
Seeds viability is high and up to 90% may germinate
within a year. No persistent seedbank is known
(Klinkhamer and De Jong 1988).
Role of disturbance in establishment: Disturbance of
soil and vegetation increases greatly seedling
emergence and establishment of bull thistle.
Potential for long-distance dispersal: Most seeds fall
within three feet of the parent plant, but up to 10
percent may travel distances with little wind
(Klinkhamer et al. 1988).
Potential to be spread by human activity: This
species can be spread by the movement of livestock,
vehicles, farm machines, and seed and hay.
Germination requirements: Germination is stimulated
by soil moisture and light. Seed germinate well over a
wide range of temperatures. Seeds have no innate
dormancy; germination is mostly in the spring.
Growth requirements: Bull thistle is most common
on soil with intermediate moisture. It tolerates a wide
range of soil pH.
Listing: Noxious weed in Colorado, Iowa, Kansas,
Maryland, Michigan, Minnesota, New Mexico,
Oregon, Pennsylvania, and Washington; in Manitoba
and Ontario (USDA 2002).
Distribution and Abundance
Bull thistle is most common in recently or repeatedly
disturbed areas such as pastures, rangelands, along
roads and ditches. However, it can also colonize areas
in relatively undisturbed grasslands, meadows, and
forest openings.
continent except Antarctica. It probably was
introduced to North America as a contaminant in seed
or ballast in the late 1800s.
South Coastal
Interior- Boreal
Arctic-Alpine
Collection Site
Distribution of bull thistle in Alaska.
Native and current distribution: Native to Europe,
western Asia, and northern Africa, it is now
naturalized and widespread throughout the United
States and southern Canada and on every other
References:
Hultén, E. 1968. Flora of Alaska and Neighboring
Territories. Stanford University Press,
Stanford, CA. 1008 pp.
Klinkhamer, P. G., T. J. De Jong. 1988. The
importance of small-scale disturbance for
seedling establishment in Cirsium vulgare
and Cynoglossum officinale. J. of Ecology.
76:383-392.
Klinkhamer, P. G., T. J. De Jong, E.van der Meijen.
1988. Production, dispersal and predation of
seeds in the biennial Cirsium vulgare. J. of
Ecology. 76:403-414.
USDA (United States Department of Agriculture),
NRCS (Natural Resource Conservation
Management
This species does not withstand cultivation.
Mechanical cutting of plants at the soil surface is an
effective method of control. Control programs should
be maintained for at least 4 years. Additionally, it is
relatively easily controlled with herbicides. Two
USDA approved insects have been successful in
California. A variety of natural seed predators are
present in The Netherlands (unknown if present in
North America) (Klinkhamer et al. 1988).
Service). 2002. The PLANTS Database,
Version 3.5 (http://plants.usda.gov). National
Plant Data Center, Baton Rouge, LA 708744490 USA.
Whitson, T. D., L. C. Burrill, S. A. Dewey, D. W.
Cudney, B. E. Nelson, R. D. Lee, R. Parker.
2000. Weeds of the West. The Western
Society of Weed Science in cooperation with
the Western United States Land Grant
Universities, Cooperative Extension
Services. University of Wyoming. Laramie,
Wyoming. 630 pp.
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 May 3, 2006