Climbing hydrangea, known botanically as Hydrangea anomala petiolaris, is a deciduous, woody flowering shrub with a vining and twining growth habit. It is prized for its dense green foliage, large white blooms in summer and the ability to perform when growing to heights of up to 80 feet. It is hardy in USDA Zones 4 through 8 and is not consistently troubled by pests or disease. It can experience a few problems endemic to the hydrangea species and to those plants that do best in acidic soils.
Pale Yellowing Leaves
Hydrangea petiolaris can suffer from fading and yellowing of the leaves caused when the alkalinity of the soil is too high. Hydrangeas prefer a nutrient-rich, acidic-to-neutral soil pH. Fertilizing with an organic or synthetic fertilizer designed for acid-loving plants, according to label directions, should remedy the problem and restore the foliage to a deep green.
Botrytis blight, also known as gray mold, can occur on all species of hydrangea and commonly affects plants that have been cultivated or grown in a nursery or greenhouse setting. It occurs during wet, humid, still and cloudy weather and affects the buds and blossoms and occasionally the leaves. It is identifiable by what look like water stains on the petals that turn reddish and then brown. It is a fungal disease and can be treated with spray fungicides containing the active ingredients iprodione, mancozeb, dithane or thiophanate-methyl. Apply the spray according to label directions when weather is overcast and rain not expected. The spores breed in the dead plant material under your hydrangeas, so work to keep the soil surface scrupulously clear of any petals, leaves, stem cuttings, weeds or any other botanical material.
Powdery mildew can affect the foliage of climbing hydrangeas, causing pale whitish-gray splotches or coating over the leaf surface. It is not deadly to the plant but can discolor and deform severely infected foliage. As with powdery mildew on most garden plants, spray liquid fungicides should be employed for heavily infected foliage to prevent the spread of spores. When treating your climbing hydrangea look for fungicide products containing the active ingredient azoxystrobin, fenarimol, parafinnic oil or triophanate-methyl. Be vigilant about cleaning up all plant litter on the soil surface to prevent a breeding ground for more spores.