Clematis viorna aka Leather Flower

Clematis viorna is a perennial vine in the buttercup family. Its common names include northern leatherflower and vase-vine. It comes from the north-central and eastern United States. This fast-growing climber sheds its leaves each year. It reaches 8–13 feet [2.5–4 metres] tall in gardens. Its spread reaches 3–5 feet [1–1.5 metres]. It can climb a trellis or spread across the ground.

The green leaves feel leathery and have hairy undersides. Leaves may be simple or pinnate, with several leaflets. Some leaflets have lobes, while others have smooth edges. Their shapes range from narrow to egg-shaped. Stems may be nearly hairless or bear soft hairs near nodes. Winter growth dies back to a woody base. The plant needs hard pruning before new spring growth starts.

The nodding flowers resemble small bells or urns. Thick, fleshy sepals give each bloom its shape. Their tips curl back, sometimes showing cream against purple. Flowers measure about 0.08 feet [0.025 metres] across. RHS gives the season as late spring through late summer. NC State reports blooms from May into fall. Brown achenes follow in showy heads during autumn. Each fruit carries a hairy tail that aids wind dispersal.

Grow this vine in moist soil that drains well. It accepts clay, loam, sand and chalk. RHS lists acid, neutral and alkaline soils as suitable. NC State favours dappled light or part shade. RHS also allows full sun, with roots kept cool. Shade the base with nearby plants or pebbles. Plant the root ball about 0.26 feet [0.08 metres] below soil level. Its hardiness ratings are USDA zones 4–9 and RHS H6. Grow it on trellises, banks or borders, or as ground cover. It also suits native gardens and small privacy screens.

The flowers draw bees, butterflies and hummingbirds. Birds eat the seed heads, while insect larvae feed on stems and leaves. NC State reports no major pest or disease problems. RHS lists aphids, clematis wilt and slime flux as possible troubles. Honey fungus occurs rarely; cutworms and voles may damage young stems. The plant resists deer but is unsafe to eat. Its leaves contain the toxin protoanemonin. Eating it can cause mouth sores, vomiting and other serious symptoms. It harms people, dogs, cats and horses. Contact can also cause burning, red skin; wear gloves when handling.