Ontario Weeds: Scotch thistle
Excerpt from Publication 505, Ontario Weeds, Order this publication
Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Scotch thistle. A. Rosette of basal leaves. B. Branch with flower head.
Stems & Roots: Stems erect, tall, 1-2.4m (3-8ft) high, often much-branched, densely white woolly with broad, spiny, leaf-like wings; leaves of first-year rosette large (to 60cm, 24in. long and 30cm, 12in. wide), lobed or coarsely toothed, densely white woolly (like a felt insole), margins wavy and spiny; stem leaves similar but smaller, alternate (1 per node), the margins of the leaf blades usually continuing down the stem as wings.
Flowers & Fruit: Flower heads (at ends of branches and from leaf axils, large, 2.5-5cm (1-2in.) across, nearly spherical, surrounded by numerous, over-lapping, narrow, spine-tipped involucral bracts; ray florets absent; disk florets numerous, purple, showy; seeds about 5mm (1/5in.) long, light brownish-gray to dark gray and wrinkled crosswise. Flowers from late June to September.
Habitat: Scotch thistle occurs in scattered localities throughout southern Ontario in waste places, fence lines, and around old buildings, usually in gravelly soils where it has escaped from cultivation.
... on general Weed
... on OMAFRA Noxious Weeds Profiles
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control
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