COMMON NAME
Canada thistle
FULL SCIENTIFIC NAME
Cirsium arvense (L.) Scop.
FAMILY NAME COMMON
Aster family
FAMILY SCIENTIFIC NAME
Cirsium arvense
IMAGES
 Flowers-white morph |
 Incursion |
 Close-up of flowers |
 Habit |
 Flowers |
 Incursion |
 Leaf close-up |
NOMENCLATURE/SYNONYMS
Synonyms: Carduus arvensis (L.) Scop.
Cirsium incanum (Gmel.) Fisch.
Cirsium setosum(Willd.) Bess. Ex Bieb.
Serratula arvensis L.
DESCRIPTION
Cirsium arvense is a rhizomatous perennial that grows 30 cm-1.5 m (1-5 ft.) tall. The roots of this plant can grow deep into the ground. The leaves are dark green and lanceolate or oblong-lanceolate. They are mostly glabrous above, but their undersides have short, white hairs. They may be pinnatifid and very prickly. The basal leaves can be 12-20 cm (5-8 in.) long. The leaves are usually sessile, but can be slightly clasping. In general, the leaf characteristics are variable across several different varieties and subspecies. The stems of Cirsium arvense do not have conspicuous spines. The plants are polygamo-dioecious, thus there are male and female plants. The female inflorescences are flask-shaped, 1-1.5 cm (0.4-0.6 in.) in diameter, and 1-2 cm (0.4-0.75 in.) tall. The female flowers have a fragrance, while the male flowers do not. The male flowers are more globose in shape than the female flowers and are smaller. The flowers are usually purple in color, but can be pink or white. The plant is in bloom from June to August. The fruits (achenes) are tiny, 2-3 mm (0.1 in.) long and about 1 mm (0.04 in.) in diameter, and have a white to light brown pappus attached. Page Reference Fernald 1542, Gleason & Cronquist 613, Holmgren 583, Magee & Ahles 1016, Newcomb 430, Peterson & McKenny 304. See reference section below for full citations.
SIMILAR SPECIES
Carduus acanthiodes L. (plumeless thistle)
Carduus crispus L. (welted thistle)
The main difference between Carduus acanthiodes, Carduus crispus and Cirsium arvense is that the two Carduus species are both non-rhizomatous biennials while Cirsium arvense is a perennial.
REPRODUCTIVE/DISPERSAL MECHANISMS
Cirsium arvense spreads primarily by rhizomatous vegetative reproduction. Reproduction by seed is secondary. Although the seeds have pappus, most of the time it breaks off leaving the seed to fall close to the plant. The small percentage of seeds that remain attached to the pappus may be dispersed by wind, occasionally over a considerable distance. Water dispersal is also possible.
DISTRIBUTION
Cirsium arvense is native to Europe; it most likely originated from southeast Europe and the eastern Mediterranean, but it has been so widespread for so long that it is difficult to establish its true native range. It presently has a global distribution between 37 and 59 degrees North latitude. It is widespread in all U.S. states and Canadian provinces.
HISTORY OF INTRODUCTION IN NEW ENGLAND
Cirsium arvense was introduced in the northeast sometime early in the 17th century. It was declared a noxious weed in Vermont by 1795. By 1918 it was on noxious weed lists in 25 northern states in the U.S.
HABITATS IN NEW ENGLAND
Abandoned Field,Abandoned Gravel Pit,Agricultural Field,Edge,Open Disturbed Area,Pasture,Railroad Right-of-Way,Roadside,Utility Right-of-Way,Vacant Lot,Yard or GardenCirsium arvense is most commonly found in agricultural and disturbed sites, or sites that are undergoing restoration. It is shade intolerant and therefore is rarely found within wooded sites, except in clearings. It is found in some dry, sandy sites, but more commonly on the edges of wet habitats such as stream banks and lake shores. In the western and northern U.S. it presents a significant problem in prairie and riparian habitats.
THREATS
Cirsium arvense is difficult to remove through mechanical means; the entire rhizomatous system of roots must be removed. Cirsium arvense directly competes with native vegetation; it can reduce species diversity, alter habitat structure, decrease crop yields and reduce forage for pasture.
MANAGEMENT LINKS
Illinois Natural History Survey
General description and management guidelines
DOCUMENTATION NEEDS
Documentation required: A photograph of the habit or inflorescences.
Best time for documentation: Summer, fall.
ADDITIONAL INFORMATION
Integrated Taxonomic Information System
Taxonomic information about the species
The PLANTS Database
General information and map
The Nature Conservancy
Extensive description, biology and control information
Plant Conservation Alliance
Description and control information
Illinois Nature Preserves Commission
Photograph, description and control information
Wisconsin Department of Natural Resources
Description, biology and control information
Ohio Perennial and Biennial Weed Guide
Photographs and description
Virginia Native Plant Society
Factsheet and control information