Clematis patens aka Midnight Clematis

Clematis patens is a slender, deciduous vine in the buttercup family, Ranunculaceae. Its native range covers eastern China, Korea, and parts of Japan. Gardeners in Japan have grown this species for many years. In China, it grows in woods, scrub, and on slopes. It occurs at heights of 656–3,281 feet [200–1,000 metres]. Clematis caerulea is another name for this plant.

In gardens, it reaches 8–13 feet [2.5–4 metres] tall. Its spread is about 5–8 feet [1.5–2.5 metres]. The RHS describes plants around 10 feet [3 metres] tall. Plants take two to five years to reach full size. They shed their leaves for winter. Single flowers face upward and reach about 0.43 feet [0.13 metres] across. Their colours range from white to pink and blue. The anthers have reddish-purple tones. Flowers appear from mid-spring into early summer, then again in late summer.

Grow this climber in full sun or partial shade. It accepts chalk, clay, loam, and sandy soils. Acid, neutral, and alkaline soils all suit it. The soil should hold moisture but drain well. Keep the roots and stem base cool and shaded. Nearby plants or a layer of pebbles can provide this shade. Set the crown 0.16–0.26 feet [0.05–0.08 metres] below the soil surface. This helps new shoots form below ground. The RHS gives it hardiness rating H5. Plants For A Future lists USDA zones 5–9.

A trellis or garden obelisk gives the vine support. It suits wall-side beds, courtyards, and cottage gardens. It also fits patio pots and woodland edges. The RHS places it in pruning group two. Take softwood cuttings in spring or semi-ripe cuttings in early summer. Layering offers another way to raise plants. Aphids, slugs, snails, and caterpillars may damage young shoots. Possible diseases include clematis wilt and clematis slime flux. Honey fungus can occur, but the RHS calls this rare.

Handle this plant with care, since it can irritate skin. Wear gloves and other protection when working with it. The RHS also warns that rabbits can suffer harm from eating it. Plants For A Future lists leaves and cooked young shoots as edible. It gives the species a low food-use rating and urges caution. That source reports no direct toxicity records for this species. Its wider warning concerns other members of the genus, so it does not establish safety here. It lists no known medicinal uses.