Thefamily is one of the big and important families from the garden standpoint and one which contains climbing as well as bushy plants. All are deciduous and all thrive best in fairly fertile soil that does not dry out severely in summer. All will grow in sun or shade.
Hydrangea macrophylla is the species that has produced the greatest number of garden varieties and these have variously colouredin summer and early autumn. In some all the flowers are sterile and have large sepals so that the flower head is ball shaped. These are often known as Hortensias. In other varieties the flowers are arranged in a flat, more or less circular cluster with small fertile flowers in the centre and sterile flowers with showy sepals forming a ring outside. These are often known as Lacecaps. In both types, if the sepals are coloured, the colour will be changed by the character of the soil, tending towards pink and crimson in alkaline soil and to blue or violet purple in acid soil. White sepals remain the same whatever the soil.
All forms of macrophylla are a little tender, some more so than others. They do best in warm, sheltered gardens, particularly in towns, near the sea and in thin woodland which provides some protec tion from frost. Old flower heads should be removed in winter or early spring and at the same time weakcan be removed. As a rule this is all the required, but if bushes get too large stems can be cut back in early spring but with loss of flower.
Hydrangea paniculata and H. arborescens grandiflora can be hard pruned each March without loss of flower since they bloom on strong young stems. Both are fully hardy. H. paniculata has white flowers fading reddish, in large conical heads in August—September. Variety praecox starts to flower in July, and variety grandiflora has larger flower trusses. H. arborescens grandiflora has white flowers in ball-shaped clusters from July to September.
Hydrangea petiolaris climbs by aerialand can reach the tops of tall trees. Its white flowers are produced in June in flat, lacecap trusses. It can be pruned in spring, but only with some loss of flower that summer.