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Yellow star thistle

(Centaurea solstitialis)

Photo of yellow star thistle
Photo credit: Mark Schwarzlander, University of Idaho, Bugwood.org

Winter annual (germinates in the fall and flowers the following May through September). 1.5-3' tall.

 Overview map of prohibited classification in WI
Prohibited (red) counties

Other names for this plant include:

  • Common names: golden star thistle, yellow cockspur, yellow centaury, St. Barnaby's thistle
  • Scientific names: Leucantha solstitialis

Classification in Wisconsin: Prohibited

Ecological Threat
  • Reported in disturbed sides such as roadsides and pastures.
Identification

First-year plant leaves: Simple, deeply lobed, and 2-3" long.

Second-year plant leaves: Alternating leaves on the stem become shorter and narrower with pointed tips as they move up the branch; the base of leaves creates a winged appearance, dull green color, covered with woolly hairs.

Flowers: Yellow flower heads are 1" wide and have spines at the base; one flower at the end of each stem.

Fruits & seeds: One plant can produce 100,000 seeds. They generally do not move far unless seeds cling to animal fur, feathers or humans.

Roots: Taproot.

Control

Mechanical: Plants can be pulled, mowed, or tilled before bloom. Controlled burns in the early flowering stage and repeated for three consecutive years.

Chemical: Foliar spray of glyphosate, triclopyr, clopyralid or picloram.

Resources
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