E-Flora BC: Electronic Atlas of the Flora of British Columbia

Cirsium scariosum Nutt.
elk thistle
Asteraceae (Aster family)

Introduction to Vascular Plants

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Distribution of Cirsium scariosum
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SUBTAXA PRESENT IN BC

Cirsium scariosum var. scariosum

Species Information

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Illustration Source: The Illustrated Flora of British Columbia

General:
Biennial or perennial herb from a taproot; stems erect, thick, fleshy, ribbed, sparsely hairy, simple or with a few short upper branches, 0.2-1.0 m tall.

Leaves:
Basal leaves egg-shaped to elliptic, entire to nearly entire, stalked; lower stem leaves narrowly egg-shaped, tapering to the base, stalked, shallowly to pinnately lobed, marginally spiny with numerous, slender, yellow spines up to 10 mm long, lobed 1/2 or less the width of the blade, segments lanceolate to deltoid, green and nearly glabrous above, woolly-hairy below; the uppermost leaves narrower, ascending, extending beyond the compact group of heads.

Flowers:
Heads discoid, 5-15, in a terminal cluster or rarely at the ends of the few branches or in the leaf axils; involucres bell-shaped, 2-3 cm tall; involucral bracts without glands, essentially glabrous except for the sparse marginal hairs, outer ones egg-shaped to lanceolate, with a slender 2-4 mm long spine, inner ones unarmed, the tips membranous, often dilated, papery and irregularly-margined; disk flowers white to pink, 18-30 mm long, the tubes 9-13 mm long, the lobes 4-6 mm long.

Fruits:
Achenes 5.5-6.5 mm long, light or dark brown with a narrow, yellow apical band; pappus light yellow, 2-3 cm long, shorter than the corollas by 4-5 mm.

Source: The Illustrated Flora of British Columbia

Key to the Species and Taxonomic Notes

TAXONOMIC KEY TO CIRSIUM

1. Heads small; involucres 1-2 (rarely 2.5) cm tall; plants introduced.

2. Stems distinctly spiny-winged; plants with perfect flowers C. palustre
2. Stems not conspicuously spiny-winged; plants partly of male and female flowers........ C. arvense

1. Heads large; involucres more than 2 cm tall; plants native (except C. vulgare).

3. Leaves bristly-spiny above, stems distinctly spiny-winged............ C. vulgare
3. Leaves cobwebby to loosely woolly-hairy, woolly or nearly glabrous above, stems not spiny-winged.

4. Pappus of mature seeds exceeding the corollas by 1-10 mm.............. C. foliosum
4. Pappus of mature seeds shorter than the corollas.

5. Heads large; involucres 3-5 cm tall........... C. drummondii
5. Heads small; involucres less than 3 cm tall.

6. Outer involucral bracts more than 2 mm wide at base, slightly if at all hairy and if so, then mainly marginal.

7. Outer involucral bracts strongly glandular; lowermost leaves deeply pinnately lobed more than 1/2 the width of the blade.............. C. undulatum
7. Outer involucral bracts without glands; lowermost leaves shallowly pinnately lobed to 1/2 or less the width of the blade............... C. scariosum

6. Outer involucral bracts less than 2 mm wide at base, densely cobwebby.

8. Corollas white or creamy-white, rarely pinkish; involucral bracts greenish............. C. hookerianum
8. Corollas purplish-red to purplish-pink; outer involucral bracts purplish.

9. Styles exceeding the corollas by at least 3 mm; achenes 5-6.5 mm long; leaves usually lobed more than 1/2 the width of the blade.............. C. edule
9. Styles nearly equal to or exceeding the corollas by only 1.5 mm; achenes 4-4.5 mm long; leaves usually lobed less than 1/2 the width of the blade................. C. brevistylum

Source: Illustrated Flora of British Columbia

Habitat / Range

Dry open forests in the montane zone; rare in SE BC, known recently only from Crowsnest Pass and Akamina Creek; E to AB and S to ID, MT, CO and AZ.

Source: The Illustrated Flora of British Columbia

Status Information

Origin Status	Provincial Status	BC List (Red Blue List)	COSEWIC
Native	S3	Blue	Not Listed

BC Ministry of Environment: BC Species and Ecosystems Explorer, the authoritative source for conservation information in British Columbia.

Taxonomic and Nomenclatural Links

Flora North America treatment for Asteraceae
Flora North America treatment for Cirsium scariosum
Genetic information (NCBI Taxonomy Database)
International Plant Names Index
Taxonomic Information from the World Flora Online
Integrated Taxonomic Information System

Additional Range and Status Information Links

Burke Museum of Natural History (Washington State records)
CalFlora
Consortium of Pacific Northwest Herbaria records
Jepson Interchange
NatureServe Explorer
USDA

Additional Photo Sources

Images From CalPhoto
UT Austin's Native Plant Database
Google Image Search
Flickr Image Search

General References

Google Scholar Search
Family References
General Botanical References for BC

Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2020. E-Flora BC: Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-06-14 10:01:42 AM ]

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