Family: Asteraceae
Canada thistle, creeping thistle, field thistle
[Carduus arvensis (L.) Robson, more...]
Paul Drobot
Robert Bierman
University of Wisconsin - Madison (WIS-VP)
Etymology: arvense = of planted fields
Plants: erect, perennial, 1'-4' tall, spiny forb with deep, colony-forming, creeping roots
Leaves: usually pinnately-divided, more or less whitish below
Flowers: head 1/2" wide with pink disk flowers; inflorescence of many heads in usually flat-topped clusters; blooms June-Oct.
Fruits: dry seed on fluffy, feathery-divided pappus
Habitat: disturbed sites, fields
Invasiveness: Restricted Invasive - Eradicate!
Conservation Status: Introduced - naturalized; ecologically invasive and noxious weed
Plants: erect, perennial, 1'-4' tall, spiny forb with deep, colony-forming, creeping roots
Leaves: usually pinnately-divided, more or less whitish below
Flowers: head 1/2" wide with pink disk flowers; inflorescence of many heads in usually flat-topped clusters; blooms June-Oct.
Fruits: dry seed on fluffy, feathery-divided pappus
Habitat: disturbed sites, fields
Invasiveness: Restricted Invasive - Eradicate!
Conservation Status: Introduced - naturalized; ecologically invasive and noxious weed
Spiny perennials from spreading, extensively creeping underground roots. Stem slender, 5-10 dm tall, sub-pilose to glabrous. Leaves lanceolate to oblong, generally pinnatifid, the lobes acuminate and spiny margined, tipped by a firm straw-colored spine, or entire with few, short slender spines, generally glabrous to woolly-pubescent beneath. Heads most often with pale purple corollas, rarely white, usually crowded in 2's, 3's or 4's on cobwebby, often leafy peduncles, imperfectly dioecious, the female heads with short corollas and long pappus, the male with long corollas and shorter pappus. Involucre 1- 2 (-3) cm high, the bracts numerous, appressed, generally spineless or the outermost with short spines. Achenes 2-3 mm long.
Johnson, M.E. and H.H. Iltis. 1963. Preliminary reports on the flora of Wisconsin: No. 48. Compositae Family. Wisconsin Academy of Sciences, Arts & Letters. 52:255-342.
A native of Asia and Europe, not of Canada, in Wisconsin a terrible and ubiquitous weed especially in good, deep agricultural soil. Flowering from late June to early August (to early October); fruiting from early July through late October.
Johnson, M.E. and H.H. Iltis. 1963. Preliminary reports on the flora of Wisconsin: No. 48. Compositae Family. Wisconsin Academy of Sciences, Arts & Letters. 52:255-342.
Other Treatments:
Additional Resources:
Additional Resources:
Robert Bierman
Paul Drobot
Christopher Noll
Stephen L. Solheim
Stephen L. Solheim
Merel R. Black
Paul Drobot
Matthew L. Wagner
Kurt Stüber
Botanical Illustration
Botanical Illustration
Botanical Illustration
