Hydrangea anomala aka Climbing Hydrangea

Hydrangea anomala, or climbing hydrangea, is a woody climbing plant. It belongs to the hydrangea family, Hydrangeaceae. Its native range runs from the Himalayas into China. It also grows in Myanmar and Taiwan. Wild plants grow in wooded valleys and beside streams. They also occur on mountain slopes. Most plants lose their leaves, though some keep part of them.

In gardens, vines reach about 30–40 feet [9.1–12.2 metres]. One source reports heights above 60 feet [18.3 metres]. Aerial roots help the stems grip their support. Side branches reach out beyond the surface they climb. Without support, plants can form a low, spreading mound. These mounds reach 3–4 feet [0.9–1.2 metres] tall. Mature bark turns brown or reddish brown and peels. The leaves grow in pairs on the stems. Each has a toothed edge and a heart-shaped base. Their upper sides are dark green, with paler surfaces beneath.

White flower clusters appear from May to June. They form broad, flat heads with a light scent. Small fertile flowers fill the centre of each head. Larger sterile flowers frame the outer edge. These outer flowers give the clusters their showy look. Small brown capsules follow the blooms, but draw little notice. Gardeners can cut the flowers or dry them. Peeling bark adds interest when the stems stand bare.

Give this vine rich soil that drains well but stays moist. It grows in partial shade and can tolerate deeper shade. Full sun suits it only when soil stays moist. Shelter it from cold winds that dry the plant. It starts slowly, then grows with much more force. Strong supports must carry the weight of mature vines. Walls, fences, arbors and large trees can support its growth. It can also spread over low walls or bare ground. Missouri Botanical Garden lists USDA zones 5–8. Yet it warns that hot, humid Zone 8 sites often fail. The RHS gives it a UK hardiness rating of H4.

Serious pest problems are not usual, but some attacks occur. Aphids, mites, scale insects and vine weevils may cause damage. Leaf spot, powdery mildew and grey mould can also occur. Honey fungus is a less frequent risk. PFAF records food uses for the leaves and sap. It also records bark as a substitute for paper. These food records should not imply that eating it is safe. The RHS warns that it can cause skin allergy. It also warns that eating it can harm cats and dogs.