These deciduous shrubs of the Hydrangeaceae family are native to E Asia where they grow up to 1.5 m (5 ft) high. Theare borne in rounded, flat or conical heads depending on the variety. They all prefer partial shade without direct sun. Water exclusively with lime-free water. Hydrangeas need acid such as azalea or rhododendron compost to release the metal elements necessary to develop their famous blue colour. Besides applications of fertilizer every 14 days, the blue varieties also need a monthly application of aluminium sulphate or they may revert to pink. Because the buds are very sensitive to frost, hydrangeas should be moved to a bright or dark place where the temperature is between 0-5° C (32-41°F).
In winter the plants should be watered only sparingly. From February onward, the plants need more light again. Dead blooms should be cut back to next new shoot and older specimens can be pruned hard after flowering. They is propagated from semi-ripe cuttings in summer. The leaves can cause skin allergies.