Horticulture/Hydrangea petiolaris

Hydrangea petiolaris is a species of hydrangea native to the woodlands of Japan, Korea and Sakhalin in easternmost Siberia.

It is sometimes treated as a subspecies of the closely related ../Hydrangea anomala/ from China, Myanmar, and the Himalaya; that species differs in being smaller (to 12 m) and having flower corymbs up to 15 cm diameter. The common name Climbing hydrangea is applied to both species.

Description
It is a vigorous woody climbing plant, growing to 20 m height up trees or rock faces, climbing by means of small aerial roots on the stems. The leaves are deciduous, ovate, 4–11 cm long and 3–8 cm broad, with a heart-shaped base, coarsely serrated margin and acute apex. The flowers are, produced in flat corymbs 15–25 cm diameter in mid-summer; each corymb includes a small number of peripheral sterile white flowers 2.5-4.5 cm across, and numerous small, off-white fertile flowers 1–2 mm diameter. The fruit is a dry urn-shaped capsule 3–5 mm diameter containing several small winged seeds.

Growing Conditions
Hydrangea petiolaris is grown as an ornamental plant in Europe and North America, where it is grown either on walls or on trellises or fences. Its clinging rootlets are not as strong as most other wall-climbing vines, and so is often anchored artificially.

Uses
As a climber on walls and fences.

Maintenance
May beed cabling, as the adhesive roots are weak.

Propagation
Stem and root cuttings, seed.

Pests and Diseases
See ../Hydrangea/ for a list of pests and diseases.