Cirsium pumilum var. hillii (Hill's Thistle)

Plant Info
Also known as: Hollow-root Thistle
Genus:Cirsium
Family:Asteraceae (Aster)
Life cycle:perennial
Origin:native
Status:
  • State Special Concern
Habitat:sun; open fields, prairies, sandy soil
Bloom season:June - August
Plant height:1 to 2 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct

[photo of flowers] Flower heads are reddish to deep purple, 1½ to 3 inches broad. There is a single flower head at the top of the stem, and a single flower at the end of the occasional branch in the upper plant.

[photo of bracts] Bracts are generally long and narrow, tipped with a slender erect to spreading spine and fine cobwebby hairs around the edges, often becoming smooth with age. Like most native thistles it has a white stripe up the center of the bract.

Leaves and stem: Leaf attachment: alternate Leaf type: lobed Leaf type: simple

[photo of leaves] Leaves are lobed with wavy edges, oblong to elliptic, mature leaves 6 to 8 inches in length. Both stems and undersides of leaves are densely woolly with a whitish appearance but not sharp. Leaf edges have short, dense spines. Stems are stout, often single or lightly branched. It is also noted to have thickened, hollow roots.

Notes:

Minnesota's least common, and certainly spiniest, native thistle, its continental range is also smaller than most related native thistles. Like many prairie species, populations across its range have declined due to habitat loss primarily from agriculture and commercial development. According to the DNR, it was listed it as a Minnesota Special Concern species in 1984. Its often short stature makes it difficult to detect at a distance and so one often stumbles upon it right under foot. The blooms are typically around 2 inches across but can reach a diameter of 3 inches. It is truly a spectacular sight to come across such a bloom. Hill's Thistle often goes by Latin name Cirsium hillii but it is now treated as a variety of Cirsium pumilum (Pasture Thistle), var. hillii, with var. pumilum a more eastern species.

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More photos

Photos by K. Chayka taken at Lost Valley SNA in Washington County, Ordway Prairie in Pope County, and along Hwy 64 in Cass County. Photos courtesy Peter M. Dziuk taken at Gray Cloud Island SNA, Dakota County.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Gordie - Pope County, MN Glenwood area
on: 2010-07-19 21:01:57

I have quite a few of these along with other wild flower species.it's a good year for wild flowers with the moisture we've had.

Posted by: Keith - Blanket Flower SNA
on: 2014-08-17 22:09:07

My wife and I hiked the Blanket Flower SNA on 8/17/2014. My target was Gaillardia aristata, but we did not locate it on the SNA. We hiked the Northern sector quite thoroughly without finding Blanket Flower. However, I did find and photograph a Hillís Thistle plant and you are correct that when you come upon them, they are a spectacular sight! During the hike, since we were not locating G. aristata I sent her in a southerly direction and I went to the north edge to cover more ground. When we met, she told me that she had found a very different looking thistle that she had photographed and when I looked at her photograph, I determined that she had found and photographed a second Hillís thistle and her photograph was better than mine! The SNA is a beautiful place with rolling hills of glacial moraine and someday I will go back to hike the Southern sectionís more thoroughly. We were not disappointed. This place has an ancient feel to it and a magical one.

Posted by: Arne - Clear Lake SNA, Sherburne County
on: 2016-07-14 11:40:17

There are numerous plants in the open meadow area in the SE portion of the SNA.

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