Clematis occidentalis

Download PDF

Name: Clematis occidentalis (Homem.) DC.

Clematis occidentalisCommon Names: Western Blue Virgin’s Bower, Mountain Clematis, Purple Clematis, Purple Virgin’s Bower (1)

Family: Ranunculaceae (the buttercup family)

Etymology: Clematis comes from the Greek clem, meaning “vine”. Occidentalis comes from the Latin occidens and means “of the west” (6).

Botanical synonyms: Atragene americana Sims, Atragene occidentalis Hornem., Clematis verticillaris DC., Clematis verticillaris DC. var. grandiflora B. Boivin (1, 2, 4)

Quick Notable Features:
¬ Large, showy blue or reddish-purple flowers with large petaloid sepals
¬ Bark green-red or red-purple, then becoming woody
¬ Leaves opposite and trifoliate.
¬ Stamens progressively broader from inside to outside; outermost stamens often sterile and petaloid

Plant Height: The stems grow to a length of 3.5m (7).

Subspecies/varieties recognized: Clematis occidentalis var. albiflora Cockerell (2), Clematis occidentalis var. dissecta (C.L. Hitchc.) J. Pringle, Clematis occidentalis var. grosseserrata (Rydb.) J. Pringle, Clematis occidentalis var. occidentalis (Hornem.) DC. (4) 

Most Likely Confused with: Clematis virginiana, Toxicodendron radicans, Campsis radicans, and saplings of Acer negundo.

Habitat Preference: C. occidentalis is found in calcareous, rocky areas, including cliffs, ledges, woods, clearings, embankments, and talus slopes (7).

Geographic Distribution in Michigan: According to Voss (14), this vine is found in only seven counties in the Upper Peninsula: Delta, Dickinson, Gogebic, Iron, Isle Royale, Keweenaw, and Marquette. Despite this sparse distribution, it is not listed as threatened or endangered in Michigan (15).

Known Elevational Distribution: C. occidentalis has been observed growing up to 1300m (7).

Complete Geographic Distribution: Native to the United States (3), C. occidentalis is found from Colorado north to Saskatchewan (Canada), west to Washington state, and British Columbia (Canada). It is also found in North Carolina and every state on the east coast of the U.S. north of NC as well as Quebec (Canada). Within the Midwest, it is found in Illinois, Iowa, Michigan, Minnesota, Ohio, Pennsylvania, West Virginia, and Wisconsin. In many of these states or provinces, it is rare or endangered (1).

Vegetative Plant Description: A trailing or climbing perennial vine with stems growing as long as 2m (5). The softly villous leaves are opposite along a red-green stem that becomes woody with age. The leaves are trifoliate (though occasionally appearing simple near the apex of the stem) and 2-10cm long. The leaflets margins are usually entire but can be crenate or lobed. The ovate leaflets have rounded to reniform bases with acuminate tips, long petioles, and long petiolules (5, 6, 7, 10, 11, 12).

Climbing Mechanism:  Climbs using twining petioles (11).

clematisocci_pl2Flower Description: The axillary flowers are usually solitary “on peduncles about equaling the subtending petiole” (10). The 5-7.5cm broad flowers are apetalous with four petaloid, ovate sepals that are reddish violet to pale blue, rarely white, and unfused. Stamens numerous, slim in the center whorl,with the outermost stamens petaloid and often sterile. The gynoecium is apocarpous and superior (6, 7, 10, 12, 16).

Flowering Time: In Connecticut, C. occidentalis flowers from April to June (3). It flowers in Illinois from May to June (6).

Pollinator: No specific pollinator was found for C. occidentalis, however, a species of butterfly (Hesperis leonardus) is known to pollinate Clematis species in general (9).

Fruit Type and Description: Many densely villous achenes (1-seeded fruits) form a globular head; the persistent styles are ~5cm long, flexuous and plumose (5, 12). 

clematisocci_frSeed Description: Small (5), with approximately 140 seeds/gram, or 63,500/pound (17). 

Dispersal Syndrome: The persistent, plumose style suggests wind-dispersal.

Distinguished by: Although they both have trifoliate leaves borne on purplish-red petioles, C. occidentalis can be distinguished from Toxicodendron radicans because the virgin’s bower bears opposite leaves (Toxicodendron has alternate leaves). Furthermore, leaves of T. radicans are thicker and generally larger.

Saplings of Acer negundo are superficially similar to C. occidentalis, but Acer saplings are self-supporting and do not creep along the ground or climb other plants. Campsis radicans, like C. occidentalis, has opposite compound leaves. The leaves of C. radicans, however, have ca. 11 leaflets per leaf as opposed to C. occidentalis, which has 1-3. Furthermore, the flowers of C. radicans are red and trumpetlike (not white and downy), and the fruit is a green capsule.

C. occidentalis may be distinguished from C. virginiana by the leaflets and flowers. C. virginiana has white, relaxed sepals that expose the floral parts, and C. occidentalis has reddish purple to blue sepals that usually enclose the floral parts (although they are sometimes relaxed). In addition, the leaflet margins of C. occidentalis are generally entire, as opposed to serrate or dentate in C. virginiana.

Other members of the family in Michigan: Clematis (2), Aconitum (1), Actaea (3), Anemone (5), Aquilegia (2), Caltha (1), Consolida (2), Coptis (1), Delphinium (1), Enemion (1), Helleborus (1), Hepatica (1), Hydrastis (1), Nigella (1), Pulsatilla (1), Ranunculus (18), Thalictrum (5) (source: [1])

RANUClematisoccidentalisMAPEthnobotanical Uses: The Blackfoot Indians used Clematis for several purposes: an infusion was made for a horse diuretic, the flowers were worn by children at night to keep ghosts and evil spirits away, and the leaves were used “remove ‘ghost bullets,’ supernatural objects shot into people by ghosts” (8).

Phylogenetic Information: According to Missouri Botanical Garden’s Tropicos Phylogeny (13), “Ranunculaceae are a classic example of a ‘famille par enchaînement’, nothing in particular holding them together, but recent work suggests that it is largely monophyletic.” It is also suggested that Ranunculaceae are among the basal eudicots, as they have several ‘primitive’ characters (usually apocarpous and superior gynoecia among others). Within Ranunculaceae, Clematis falls into the Ranuncuoloideae tribe (13).

Literature and websites used:

  1. USDA, NRCS. 2008. The PLANTS Database, Version 3.1, National Plant Data Center, Baton Rouge, LA 70874-4490 USA.  Accessed 29 September 2008.
  2. International Plant Names Index. Accessed 29 September 2008.
  3. Connecticut Botanical Society, 2000-2008. Accessed 29 September 2008.
  4. ITIS: Integrated Taxonomic Information System Accessed 29 September 2008.
  5. Gleason, H.A. & A. Cronquist 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. Bronx, New York, USA: New York Botanical Garden Press.
  6.  Iverson, L.R., D. Ketzner, & J. Karnes 1999. Illinois Plant Information Network. Illinois Natural History Survey and USDA Forest Service.
  7. Whittermore, A.T. & B.D. Parfitt 1997. Ranunculaceae Family. Flora of North America’s Vol. 3. Oxford University Press: Oxford, United Kingdom, Great Britain.
  8. Moerman, D. Native American Ethnobotany Database. Accessed 29 September 2008.
  9. Scott, J.A. & R.E. Stanford 1981. Geographic variation and ecology of Hesperia leonardus (Hesperiidae). Journal of Research on the Lepidoptera 20(1): 18-35.
  10. Gleason, H.A. 1963. Illustrated Flora of the Northeastern United States and Adjacent Canada, Volume 2. New York: Hafner Publishing Company, Inc.
  11. Wood, A. 1854. Class-Book of Botany. Claremont, New Hampshire.
  12. Fernald, M.L. 1950. Gray’s Manual of Botany. American Book Company: United States.
  13. Stevens, P.F. 2001 onwards. Angiosperm Phylogeny Website. Accessed 29 September 2008.
  14. Voss, E.G. 1985. Michigan FloraPart II. University of Michigan Press: Ann Arbor, Michigan, United States.
  15. Michigan Department of Natural Resources. Accessed 8 October 2008.
  16. Hitchcock, C.L. & A. Cronquist 1981. Flora of the Pacific Northwest and Canada. University of Washington Press: Seattle, Washington, United States.
  17. Young, J.A. & C.G. Young 1992. Seeds of Woody Plants in North America. Dioscorides Press: Portland, Oregon, United States.
  18. Pringle, J.S. Flora of North America, Vol. 3.


Image Credits (all with permission):
1. The first picture of the plant is courtesy of Emmet J. Judziewicz (Photographer) and the University of Wisconsin-Stevens Point.

2-3. The second picture of the plant and the picture of the fruits is courtesy of Janet Novak, Connecticut Botanical Society.

4. Species distribution map, derived from the Michigan Flora Online.

PRIMARY AUTHOR: ReBecca Sonday with editing by John Bradtke, Robyn J. Burnham, and Cristine V. Santanna

For additional information on these web pages please contact Robyn J. Burnham via email: rburnham“at”

© Robyn J. Burnham, University of Michigan