Ontario Weeds: Plumeless Thistle

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
5. Leaves
6. Flowers and Fruit
7. Habitat
8. Similar Species
9. Related Links

Name: Plumeless thistle, Carduus acanthoides L.

Other Names: CRUAC, chardon épineux, Welted thistle

Family: Composite or Aster Family (Compositae) 

General Description: Very similar to Nodding thistle with its deeply lobed, spiny leaves

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Photos and Pictures

Plumeleses thistle. A. Stand of plants

Plumeleses thistle. B. flower head.

Plumeless thistle. A. Rosette and lower stem leaves.

B. Flowering branch with flower heads on spiny-winged stalks.

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Leaves: Distinguished from Nodding thistle by usually having the lobes or clusters of lobes separated from each other by distinct spaces along the midrib of the leaf. The inner margins of these spaces usually with smaller and fewer spines than on the lobes.

Flowers & Fruit: Flower heads smaller (usually less than 2.5cm, 1 in. wide) and clustered or sometimes solitary but on shorter stalks which are spiny-winged right to the base of the head. The incolucral bracts surrounding its flower heads are narrower and more numerous than in Nodding thistle and mostly point upward rater than outward or backward.

Habitat: Plumeless thistle occurs throughout southern Ontario in siliar habitats to Nodding thistle and, where the two occasionally grow in the same locality, hybride are often produced having characteristics intermediate between the two species.

Similar Species: Very similar to Nodding thistle.

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Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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