Hydrangea macrophylla ‘Blaue Donau’ (Blue Danube) is compact, bushy, deciduous shrub with broad, ovate, dark-green foliage and large, rounded clusters of blue or dark pink flowers in summer. The colour of the blooms are decided by the acidity level of soil. Darkest of blues in blooms are produced in acidic soil and deep pink in neutral. Flowers July-September. Height 100-150cm. Supplied in a 3 litre pot.