Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Clematis montana' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous climber of vigorous habit, growing at least 20 ft high; stems glabrous except when quite young. Leaves composed of three leaflets on a common stalk 2 to 4 in. long; the leaflets short-stalked, ovate to lanceolate, pointed, variously and unequally toothed; 1 to 4 in. long, half as wide. Flowers solitary, pure white, 2 to 21⁄2 in. across, each borne on a glabrous stalk 2 to 5 in. long. Sepals four, spreading, oval. Seed-vessel elliptical, glabrous, surmounted by a plumose style 11⁄2 in. long.
Native of the Himalaya; introduced by Lady Amherst in 1831. It is quite hardy, and is undoubtedly one of the loveliest of all climbers. The flowers appear in May, and being produced singly on long stalks, can only be confused with the white variety of C. alpina, and that is not only very different in habit and vigour, but has the petal-like parts of the flower characteristic only of the Atragene section. C. montana is a valuable plant for covering arbours, pergolas, and especially verandas, where its long shoots can be allowed to hang down and form a sort of curtain.
What may prove to be a new species, allied to C. montana, was introduced by Keith Rushforth in 1980 from Mount Omei in western China, under his number 164.
Flowers larger than in the type, up to 3 in. across.