Minnesota Wildflowers


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Carduus acanthoides (Plumeless Thistle)

Plant Info
Also known as: Spiny Plumeless Thistle
Genus:Carduus
Family:Asteraceae (Aster)
Life cycle:biennial
Origin:Eurasia
Status:
  • Invasive - ERADICATE!
  • Noxious Weed
  • Prohibited or Restricted species
Habitat:sun; fields, pastures, roadsides, waste areas, disturbed soil
Bloom season:July - October
Plant height:3 to 6 feet
USDA PLANTS database:Minnesota county distribution map

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Detailed Information

Flower: indistinct round

[photo of flowers] Purple with an occasional white, smaller than most comparitive thistle species, generally 1 inch wide with solitary heads or clusters of 2 to 5. The bracts are narrow and spreading with very short spiny tips.

Leaves and stem: alternate lobed

[photo of leaves] Leaves are deeply lobed with lobes segmented and densely spiny. Lower leaves are up to 8 inches long, shorter at upper tips. Leaf undersides can be either smooth or have dense, bristly hairs, especially along major veins.

[photo of stem] The main stems are densely covered with leafy spine-tipped “wings” that typically angle downward. Stems may also be bristly hairy.

Notes:

Plumeless Thistle resembles Bull Thistle (Cirsium vulgare), whose flowers are larger and leaves hairier, but is more closely related to Nodding Thistle (Carduus nutans), whose flowers are also larger and have broad showy bracts. The spiniest of all thistles, Plumeless Thistle is on the noxious weed list for Minnesota and a relative new comer here, dispersing rapidy from the Dakota's over the last thirty years to the rest of the state. A common pasture/roadside pest, this species can invade high grade native habitats. According to one source, a mature plant can produce 10,000 seeds. They may disperse within 10 days of flowering and over 90% will germinate.

Where to buy native seed and plants

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  • Out Back Nursery and Landscaping - Where Ecology and Horticulture Unite
  • Shooting Star Native Seeds - Native Prairie Grass and Wildflower Seeds
  • Prairie Restorations - Bringing people together with the land
  • Shop for native seeds and plants at PrairieMoon.com!

Map of native plant purveyors in the upper midwest

More photos

Photos courtesy Peter M. Dziuk, collected from west central, Metro and south eastern MN sites

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