Clematis triloba Thunb.

Clematis orientalis has been reported from Idaho; it probably can be expected elsewhere.

This species has been divided by C. Grey-Wilson (1989) into five varieties, partly correlated with their distribution in Asia. Naturalized plants in North America seem best referred to C . orientalis var. robusta Grey-Wilson, native to Afghanistan.

Although Clematis orientalis has been naturalized in the Rocky Mountains since the late nineteenth century, it has spread especially rapidly since ca. 1975, becoming weedy and, in some localities, constituting a threat to young trees and native shrubby and herbaceous species.

Stems climbing, 2-8 m. Leaf blade pinnately 5-7-foliolate, proximal leaflets sometimes 3-foliolate; leaflets lanceolate to elliptic or ovate, usually 2-3-lobed proximally, 1-5.5 × 0.5-3.5 cm, margins entire or coarsely few-toothed; surfaces at least abaxially pubescent, glaucous. Inflorescences axillary, sometimes terminal, 3-many-flowered cymes or flowers solitary. Flowers bisexual; pedicel (0.5-)1-11 cm; sepals wide-spreading and recurved, greenish yellow, ovate-lanceolate to elliptic, 0.8-2 cm, length ca. 2.5 times width, margins densely pubescent, abaxially and adaxially pubescent or abaxially glabrous; stamens 20-40; filaments pilose proximally; staminodes absent; pistils 75-150. Achenes turgid, not conspicuously rimmed, pilose; beak 2-5 cm.

Vines suffruticose. Branches flat or shallowly 6--10-grooved, glabrous or sparsely puberulous. Leaves 1- or 2-pinnate; petiole 2.5--5.5 cm; leaflet blades ovate-lanceolate, narrowly ovate, or linear-lanceolate, 1.2--4.5 × 0.5--1.6 cm, papery, undivided or 3-lobed near base, both surfaces glaucous, glabrous or rarely abaxially appressed puberulous, base rounded to broadly cuneate, margin usually entire or sometimes to 2-denticulate, apex acute; basal veins abaxially nearly flat and inconspicuous; terminal lobes larger, lanceolate to linear-lanceolate. Cymes axillary, 3--15-flowered; peduncle 1.5--4.5 cm; bracts petiolate, lanceolate, 0.8--2 cm. Flowers 1.8--3 cm in diam. Pedicel 1.4--5.5(--7.6) cm, glabrous or rarely puberulous. Sepals 4, yellowish, ascending, lanceolate to elliptic, 1.2--2 × 0.3--0.6 cm, abaxially glabrous or puberulous, adaxially puberulous, margin abaxially velutinous, apex acute. Stamens 6--10 mm; filaments sparsely puberulous; anthers narrowly oblong to linear, 2.2--3.5 mm, glabrous, apex obtuse. Ovaries puberulous. Style 8--10 mm, densely villous. Achenes narrowly ovate, oblong, or narrowly obovate, 3--3.5 × 1.2--2 mm, puberulous; persistent style 2.5--4 cm, plumose. Fl. Jun--Aug, fr. Aug--Sep.

introduced; Ont.; Colo., Nev., N.Mex., Utah; native to Eurasia.

NW Gansu, Xinjiang [Afghanistan, NW India, Kazakhstan, Kyrgyzstan, N Pakistan, Russia, Tajikistan; W and SW Asia].

Flowering summer-fall.

Roadsides, other secondary habitats, open woods; 0-2600m.

Slopes, along streams; 400--3800 m.

Viticella orientalis (Linnaeus) W.A. Weber