Hydrangea are a popular hardy garden shrub due to their large 20cm 4083441 diameter flowerheads with paper like petals that retain colour well into the autumn and the fact that they are so easy to maintain they can be planted in sun or shade in garden borders or in large containers hydrangea macrophylla 39blue danube39 has deep blue flowers when planted in acidic soil planting hydrangeas in alkaline will produce pink flowers instead33 height and spread 1m 403934