Flora of North America species comparison

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Clematis occidentalis

Clematis subg. Atragene

blue clematis, clématite occidentale, Columbia bower, Columbia clematis, Columbia virgin's bower, purple clematis, purple virgin's-bower, rock clematis, western blue clematis, western blue virginsbower, western clematis
Stems

viny, climbing or trailing (plants scarcely viny perennials in var. dissecta).

Leaf

blade 1-ternate (or terminal leaflet sometimes ternate in var. dissecta), ± firm but not succulent;

leaflets lance-ovate to triangular or suborbiculate, lobed or unlobed, margins entire or toothed.

blade 1-3-ternate, lobed or unlobed, margins entire or coarsely serrate.
Inflorescences

terminal on short shoots or rarely terminal on long shoots, 1[-2]-flowered with bractless peduncles subtended by 1 or 2 pairs of leaves.
Flowers

sepals violet-blue, reddish violet, or white, lanceolate to ovate or elliptic-oblong.

bisexual, ± nodding;

perianth widely bell-shaped to rotate;

sepals ascending or tardily spreading, not connivent, usually violet-blue, sometimes reddish violet, or white, ovate to oblong, thin, margins densely pubescent, abaxially sparsely pubescent;

staminodes present between stamens and sepals, flattened, petaloid, bearing reduced, sterile anthers;

filaments flattened, pubescent at least on margins.
Achenes

flattened;

beak over 2 cm, plumose.
Woody

vines or rhizomatous herbs with short, tufted stems.

Clematis occidentalis

Clematis subg. Atragene
Distribution
from FNA
CO; CT; DE; IA; ID; IL; MA; MD; ME; MI; MN; MT; NC; NH; NJ; NY; OR; PA; RI; UT; VA; VT; WA; WI; WV; WY; AB; BC; NB; ON; QC; SK; YT
[WildflowerSearch map]
[BONAP county map]
Temperate to subarctic and subalpine North America and Eurasia
Discussion

Varieties 3 (3 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species ca. 5 (2 in the flora).

F. B. Essig (1992) suggested that Clematis subg. Atragene might be included in Clematis subg. Clematis. Because of its distinctive inflorescence and floral morphology, however, and because it has not been successfully crossed with species in any other subgenus, its subgeneric status is retained here.

The two North American species have been known to hybridize in Montana.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaflets lobed or unlobed, margins entire or crenate-serrate (or terminal leaflet sometimes ternate); stems tufted or, if viny, up to 0.5(–1.5) m.
var. dissecta
1. Leaflets unlobed or some 1–3-lobed, margins entire or shallowly serrate; stems ± viny, climbing or trailing, 0.25–3.5 m.
→ 2
2. Sepals reddish violet, rounded-mucronate to nearly acuminate.
var. occidentalis
2. Sepals violet-blue to pale blue, rarely white, usually distinctly acuminate.
var. grosseserrata
1. Leaf blade consistently 2–3-ternate.
C. columbiana
1. Leaf blade 1-ternate (or terminal leaflet sometimes ternate in var. dissecta).
C. occidentalis
Source FNA vol. 3. FNA vol. 3.
Parent taxa Ranunculaceae > Clematis > subg. Atragene Ranunculaceae > Clematis
Sibling taxa
C. addisonii, C. albicoma, C. baldwinii, C. bigelovii, C. catesbyana, C. coactilis, C. columbiana, C. crispa, C. drummondii, C. fremontii, C. glaucophylla, C. hirsutissima, C. lasiantha, C. ligusticifolia, C. morefieldii, C. ochroleuca, C. orientalis, C. pauciflora, C. pitcheri, C. recta, C. reticulata, C. socialis, C. tangutica, C. terniflora, C. texensis, C. versicolor, C. viorna, C. virginiana, C. vitalba, C. viticaulis, C. viticella
Subordinate taxa
C. occidentalis var. dissecta, C. occidentalis var. grosseserrata, C. occidentalis var. occidentalis
C. columbiana, C. occidentalis
Synonyms Atragene occidentalis subg. Atragene
Name authority (Hornemann) de Candolle: Prodr. 1: 10. (1824) (Linnaeus) Torrey & A. Gray: Fl. N. Amer. 1: 10. (1838)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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