spiny plumeless thistle

Carduus acanthoides L.

Description from Invasive.org

Appearance

Carduus acanthoides is an annual or biennial herbaceous plant that grows to 5 ft. (1.5 m) tall.

Foliage

This thistle may exceed two meters in height and can form weedy monotypic stands. The stem and foliage are spiny and sometimes woolly.

Flowers

Flowering occurs from May to August. The flower heads are reddish-purple in color and up to 1 in. (2.5 cm) in diameter. Flower stems are branched with spiny wings extending to the flower heads.

Fruit

Seeds are oblong, striate, and slightly curved.

Ecological Threat

Carduus acanthoides infests open, disturbed areas such as pastures, roadsides, and railroad right-of-ways. It can form thick stands that reduce the forage potential of pastures and suppress the growth of desirable vegetation.

Resources

• Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
• Carduus acanthoides - Burke Museum of Natural History and Culture
• Weed Field Guide - USDA Forest Service

Selected Images from Invasive.org

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Flower(s)
Gary L. Piper, Washington State University, Bugwood.org
Additional Resolutions & Image Usage

Plant(s)
Gary L. Piper, Washington State University, Bugwood.org
Additional Resolutions & Image Usage

Foliage
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage

Flower(s)
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage

Plant(s) in flower
Todd Pfeiffer, Klamath County Weed Control, Bugwood.org
Additional Resolutions & Image Usage

Flower(s)
Todd Pfeiffer, Klamath County Weed Control, Bugwood.org
Additional Resolutions & Image Usage

Foliage
Todd Pfeiffer, Klamath County Weed Control, Bugwood.org
Additional Resolutions & Image Usage

Plant(s)
Todd Pfeiffer, Klamath County Weed Control, Bugwood.org
Additional Resolutions & Image Usage

Plant(s)
Todd Pfeiffer, Klamath County Weed Control, Bugwood.org
Additional Resolutions & Image Usage