[Thistles: The Genus Cirsium East of the Cascade Mts. of Oregon and Washington]
Dinnerplate Thistle, Elk Thistle, Meadow Thistle, Sessile Thistle, Shasta Valley Thistle, Stemless Thistle, Toiyabe Thistle
Cirsium scariosum
Synonyms: Carduus americanus, Carduus coloradensis, Cirsium acaule var. americanum, Cirsium acaulescens, Cirsium americanum, Cirsium butleri, Cirsium coloradense, Cirsium coloradense ssp. acaulescens, Cirsium coloradense ssp. longissimum, Cirsium congdonii, Cirsium drummondii ssp. lanatum, Cirsium drummondii ssp. lanatum, Cirsium drummondii ssp. latisquamum, Cirsium drummondii ssp. vexans, Cirsium drummondii var. acaulescens, Cirsium drummondii var. oregonense, Cirsium erosum, Cirsium hookerianum var. scariosum, Cirsium kelsey, Cirsium lacerum, Cirsium magnificum, Cirsium minganense, Cirsium oreophilum, Cirsium quercetorum, Cirsium scariosum var. americanum, Cirsium scariosum var. robustum, Cirsium scariosum var. scariosum, Cirsium scariosum var. thorneae, Cirsium scariosum var. toiyabense, Cirsium tioganum, Cirsium tioganum var. coloradense, Cirsium tioganum var. tioganum, Cnicus drummondii var. acaulescens, Cnicus tioganus
The photo above shows a close-up of elk thistle (possibly var. scariosum) as seen at Herren Meadow along the Blue Mt. Scenic Highway to the southeast of Heppner, OR.........June 22, 2007. Note the numerous spreading hairs on both leaf surfaces.
Photo at right of elk thistle (?) from
near Picture Rock Pass, Lake County, OR.......July 3, 1996.
Characteristics:
A fairly easy thistle to identify in that it is frequently without stems.
Stems generally very short and thick, with the flower heads sessile. Corollas
white to a pale pink-purple. Leaves spiny, but entire to somewhat scalloped.
Flowers from June into August.
Varieties of Cirsium scariosumEast of the Cascade Mts. of Oregon and Washington:
Dinnerplate Thistle, Sessile Thistle, Stemless Thistle: Var. americanum - Generally stemless plants with numerous flower heads closely subtended by the basal leaf rosette. Lower leaf surface generally gray tomentose. Upper leaf glabrous or joint-hairy. Corollas white to pink-tinged. Located from the Oregon Cascades east across much of central and southeastern Oregon and south into northeastern California south to the Sierra Nevada Mts.
Shasta Valley Thistle: Var. robustum - Plants with stems branched from near the base or throughout, often forming low rounded mounds. Inflorescence of head-like to flat-topped clusters. Lower leaf surface generally thinly to densely tomentose. Upper leaf surfaces joint-hairy to cobwebby-tomentose. Corollas white. Located in the southern Oregon Cascades and North Warner Mountains and south into Siskiyou County of northern California.
Elk Thistle, Meadow Thistle: Var. scariosum (Synonyms: Cirsium americanum, Cirsium foliosum, Cirsium scariosum, Cirsium tioganum, Cirsium tioganum var. tioganum) - Plants with erect, branched or often unbranched stems (a few stemless individuals may be present in the population.). Any branching of the stem is generally from near the base. Heads generally tightly clustered at the tip of stem. Corollas white to pink-tinged. Lower leaf surface generally glabrous. Upper leaf surface glabrous or joint-hairy. Located across much of Oregon and scattered from the Cascade Mts. of Chelan County and Palouse region of Whitman County in Washington and in the eastern Sierra Nevada Mts. of Mono County, California.
Toiyabe Thistle: Var. toiyabense - Plants with generally simple stems, short to moderate in length (0.5 meter). Corollas purple. Lower leaf surfaces generally green and glabrous to white tomentose. Upper leaf surfaces green and glabrous or woolly. Located in southeastern Oregon and into northern Nevada
Habitat:
Meadows and other moist places from the foothills to 3200 m.
Range:
Found from southern British Columbia to Alberta, south along the eastern edges
of the Cascades and Sierra Nevada to southern California, and east to central
Arizona.
- 
Elk thistle (var. americanum) blooming at Willow Creek Campground, Fremont-Winema National Forest......June 29, 2019.
The photo above shows a close-up of the inflorescence of elk thistle (possibly var. scariosum) as seen at Herren Meadow along the Blue Mt. Scenic Highway to the southeast of Heppner, OR........June 22, 2007.
- 
Elk thistle (left) as seen along Forest Service Road #1647 in southeastern Logan Valley, Malheur National Forest.........July 18, 2010. The photo at right shows elk thistle as seen along Forest Service Road #16 in Summit Prairie, Malheur National Forest........August 10, 2015.
- 
Close-up photos of elk thistle (var. americanum?) as seen in the vernally moist meadows of Logan Valley just west of Big Creek Campground, Malheur National Forest........July 2, 2010.
- 
The photo at left shows elk thistle in bloom about 100 meters uphill from the Saddle Camp Trail #3035 trailhead at Olive Lake, Umatilla National Forest........July 28, 2013. The photo at right shows elk thistle in bloom along the North Fork Crooked River about One and one-quarter miles south of FS Road 42, Ochoco National Forest.........June 12, 2015.
- 
An interesting glabrous-leaved elk thistle as seen at left in roadside gravels in Summit Prairie, Malheur National Forest........August 20, 2011. The photo at right shows elk thistle (var. americanum) at Mud Creek Campground, Fremont-Winema National Forest.......July 1, 2019.
- 
Attractive elk thistles with purple foliage as seen along FS Rd 1647 in southern Logan Valley, Malheur National Forest.......June 3, 2011.
- 
An elk thistle with purple-tinged foliage as seen at left in Summit Prairie, Malheur National Forest..........May 28, 2014. White-rayed wyethia (Wyethia helianthoides) surrounds the elk thistle. The photo at right shows elk thistle in bloom along the Hanan Trail #142, Fremont-Winema National Forest........June 17, 2020.
Elk thistle (var. americanum) from Newberry Crater Volcanic National Monument........August 1994.
Paul Slichter