Cirsium discolor (Field Thistle)
|Also known as:||Pasture Thistle|
|Habitat:||sun; fields, along roads, open woods|
|Bloom season:||July - October|
|Plant height:||3 to 7 feet|
|Wetland Indicator Status:||GP: FACU MW: FACU NCNE: UPL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flower head is 1½ to 2 inches across, pink to lavender, or occasionally white. Several to many flower heads branch off the main stem in the upper part of the plant. The bracts are flat, green with a white stripe and resemble fish scales. Each bract has a ¼ inch long needle-like spine at the tip that sticks straight out.
Leaves and stem:
Field Thistle most closely resembles Tall Thistle (Cirsium altissimum), which also has soft needle-like spines on the floral bracts, hairy stems and white on the underside of leaves. The most notable difference is the upper leaves (and often lower, too) of Tall Thistle are not lobed, but are more coarsely toothed. The non-native thistles are distinguished by their sharp spines, especially along the stems. While most references give a height of Field Thistle up to 7 feet, we've seen plants rather taller.
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Photos by K. Chayka taken at Long Lake and Rice Creek Regional Parks, Ramsey County. Other photos courtesy Peter M. Dziuk.
Have you seen this plant in Minnesota, or have any other comments about it?