Woody vines or erect, ± herbaceous perennials, clumped (or patch-forming from rhizomes in C. socialis). Leaves simple. Leaf-blade 1-pinnate or 2-pinnate, ternate, or finely dissected; ultimate divisions lobed or unlobed, margins entire or few-toothed. Inflorescences terminal and/or axillary, on current-years stems; 3-7-flowered bracteate cymes or flowers solitary or paired, peduncles bracteate [or several-many-flowered panicles]. Flowers bisexual, usually nodding (± erect in some spp., esp. C. morefieldii); sepals ascending, connivent at least proximally and usually much of length, variously colored, lanceolate or oblong to broadly ovate, thick, usually leathery, abaxially glabrous to silky, hirsute, or tomentose; filaments slender, usually pubescent (except C. pitcheri var. dictyota), connectives often ± prolonged (especially in C. pitcheri); staminodes absent. Achenes flattened; beak variable in length, plumose to nearly glabrous.

Distribution

Temperate, mostly North America, a few in Eurasia

Discussion

Species ca. 25 (18 in the flora).

Clematis integrifolia Linnaeus, with relatively wide-spreading, blue sepals, is locally naturalized in Ontario.

Selected References

None.

Key

1 Leaves all simple, blade rarely so deeply lobed that proximal 2 lobes appear as distinct linear leaflets; plants herbaceous or ± woody at base, erect, not viny. > 2
1 At least some distal leaves of main stems distinctly compound or deeply much-dissected; plants erect or viny. > 8
2 Sepals glabrous or sparsely villous, tips acuminate; achene body cobwebby-tomentose distally, or long-pubescent. > 3
2 Sepals (except margins) minutely puberulent, silky, woolly, or nearly glabrous, tips obtuse to acute; achene body pilose or short-pilose. > 4
3 Leaf blade 3.5-11 cm wide, prominently reticulate adaxially; beak not plumose, proximally silky-tomentose, sparsely appressed-pubescent to nearly glabrous distally; Kans., Nebr., Mo. Clematis fremontii
3 Leaf blade 0.2-2(-3.5) cm wide, not prominently reticulate adaxially; beak distinctly plumose; Fla. Clematis baldwinii
4 Leaf blade abaxially moderately to densely soft-pubescent, rarely nearly glabrous; secondary and tertiary veins forming prominent reticulum on adaxial surface. > 5
4 Leaf blade abaxially glabrous or nearly so, sparsely or rarely densely villous on veins; secondary and tertiary veins not forming prominent reticulum on adaxial surface. > 6
5 Stems and abaxial surface of leaf blades moderately silky-pilose with spreading hairs, rarely nearly glabrous; beak yellowish brown to reddish brown; hairs of achene rim appressed-ascending. Clematis ochroleuca
5 Stems and abaxial surface of leaf blades densely silky-tomentose with appressed hairs; beak white to pale yellow; hairs of achene rim spreading. Clematis coactilis
6 Sepals abaxially silky to woolly; beak white to pale yellow. Clematis albicoma
6 Sepals abaxially glabrous to minutely puberulent; beak coppery brown. > 7
7 Leaf blade abaxially glaucous and glabrous; sepals abaxially glabrous. Clematis addisonii
7 Leaf blade abaxially not glaucous, sparsely to densely villous on veins; sepals abaxially nearly glabrous or minutely puberulent. Clematis viticaulis
8 Plants erect or sprawling, not viny; stems to 0.65m. > 9
8 Plants viny, petioles and/or rachises of leaves often functioning as tendrils; stems usually 1-5m. > 13
9 Larger leaf blades (1-)2-3-pinnate or -ternate or deeply dissected. > 10
9 Leaf blade 1-pinnate or simple. > 11
10 Leaflets usually less than 1.5 cm wide, mostly more than 2.5 times as long as wide, mostly unlobed, if lobed then with lateral lobes 1 or 2, usually small, distinctly narrower than central portion; blade abaxially sparsely to densely hirsute; beak plumose. Clematis hirsutissima
10 Leaflets usually more than 1.5 cm wide and/or less than 2.5 times as long as wide, mostly lobed, lateral lobes often nearly as wide as central portion; blade glabrous or nearly so (rachis and petiolules may be ±hirsute); beak glabrous or inconspicuously appressed-pubescent. Clematis bigelovii
11 Terminal leaflets usually tendril-like; blades of simple leaves and lateral leaflets of compound leaves usually more than 2 cm wide; sepals purple or reddish purple, whitish toward tips. Clematis addisonii
11 Terminal leaflets with expanded blade, not tendril-like; blades of simple leaves and lateral leaflets usually less than 2 cm wide; sepals uniformly violet-blue. > 12
12 Plants strongly rhizomatous, forming patches; sepals 2-2.5(-3) cm; beak 1.5-2.5 cm. Clematis socialis
12 Plants not rhizomatous; sepals 2.5-5.5 cm; beak 6-10 cm. Clematis baldwinii
13 Largest leaf blades 1-2-pinnate, leaflets mostly deeply lobed; beak 1-3 cm, inconspicuously appressed-pubescent to nearly glabrous. Clematis pitcheri
13 Largest leaves simple, blades 1-pinnate, or if some 2-pinnate, leaflets of 2-pinnate leaves usually unlobed, rarely 2-5-lobed; beak 2-7 cm, plumose (appressed-puberulent in C.crispa and C.pitcheri). > 14
14 Leaflets abaxially glaucous and glabrous, rarely with a few scattered hairs. > 15
14 Leaflets not glaucous, usually abaxially pubescent, sometimes glabrous. > 18
15 Leaves mostly simple, only distalmost compound. Clematis addisonii
15 Leaves all or mostly compound, simple leaves, if any, only on small branches and near base of main stem. > 16
16 Leaf blade ±thin, secondary and tertiary veins not forming prominent reticulum on adaxial surface. Clematis glaucophylla
16 Leaf blade leathery, secondary and tertiary veins forming prominent reticulum on adaxial surface. > 17
17 Sepals rose-red to scarlet abaxially and at tip adaxially; tips recurved. Clematis texensis
17 Sepals pale lavender or blue-violet to reddish purple abaxially, often paler or greenish adaxially, tips slightly spreading. Clematis versicolor
18 Sepals with thin, crispate margins to 6 mm wide distally. Clematis crispa
18 Sepals without expanded, thin, crispate margins or with margins less than 2.5 mm wide. > 19
19 Leaf blade leathery, secondary and tertiary veins forming prominent reticulum on adaxial surface. > 20
19 Leaf blade thin, secondary and tertiary veins not forming prominent reticulum on adaxial surface. > 21
20 Beak plumose, with spreading hairs; leaf blade finely reticulate (ultimate closed areoles mostly less than 2 mm in longer dimension), even quaternary veins distinctly raised on adaxial surface. Clematis reticulata
20 Beak sparsely pubescent to silky, with ascending to appressed hairs; leaf blade less finely reticulate (ultimate closed areoles mostly more than 2 mm in longer dimension), tertiary and quaternary veins scarcely or not raised on adaxial surface. Clematis pitcheri
21 Stems generally cobwebby as well as villous; bracts near base of peduncle/pedicel; sepals densely silky-pubescent abaxially, pinkish suffused with green, tips spreading to short-reflexed. Clematis morefieldii
21 Stems without cobwebby pubescence; bracts well above base of peduncle/pedicel; sepals sparsely pubescent abaxially, pale lavender to reddish purple, tips recurved. Clematis viorna

"connivent" is not a number."thick" is not a number.

... more about "Clematis subg. Viorna"
flattened +
James S. Pringle +
A. Gray in A. Gray et al. +
cuneate +, truncate +  and cordate +
Undefined subg. Viorna +
curved +  and straight +
plumose +
1.2 cm12 mm <br />0.012 m <br /> (11 cm110 mm <br />0.11 m <br />) +
scale-like;leaflike +
globose;cylindric +
bracteate +  and 3-7-flowered +
paired +  and solitary +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
Temperate +, mostly North America +  and a few in Eurasia +
filiform +  and flattened +
bracteate +  and 3-7-flowered +
paired +  and solitary +
showy +  and inconspicuous +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
sessile +  and aggregate +
flattened-ellipsoid;terete;flattened-ellipsoid;terete;lenticular +
axillary +  and terminal +
2-pinnate +  and 1-pinnate +
cordate +  and orbiculate oblong lanceolate or oblanceolate lobed or unlobed +
cordate +  and orbiculate oblong lanceolate or oblanceolate lobed or unlobed +
palmate +  and pinnate +
few-toothed;entire +
1-many-flowered +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
distinct +
conspicuous +
spurred +, funnel--shaped +, cup-shaped +  and plane +
reduced +
5 +  and 150 +
Syn. Fl. N. Amer. +
not arillate +  and stalked +
not persistent +
distinct +
abaxially glabrous +  and silky hirsute or tomentose +
3 +  and 6 +
oblong +  and broadly ovate +
0.6 cm6 mm <br />0.006 m <br /> (6 cm60 mm <br />0.06 m <br />) +
persistent +
Clematis subg. Viorna +
Clematis +
subgenus +
annual +  and perennial +