Hydrangeas grow as both a shrub and as climbers. While most of the shrub varieties grow between 3 and 6 feet tall, oakleaf hydrangea grows up to 15 feet high. All shrub varieties and the climbers need pruning, but how and when you do so depends on your particular hydrangea. Your bushes will not bloom if you prune them incorrectly.
The flower buds form on the previous year's growth. After blossoming, cut back the older and dead branches to allow sunlight to penetrate. Additionally, prune any branches that are broken or that rub against each other. Only prune during the summer or early autumn, or the bush will not bloom the following year.
This variety also produces flowers on the previous year's stems. If you do not want the bush to flower, then cut it back to the ground in March or April. Otherwise, trim the bush in late summer after it has finished flowering. Cut the stem back halfway to encourage new growth.
Flower buds of the smooth hydrangea form on new growth. Prune the bush back by one-half in early spring. Cut out all dead, weak or damaged branches. Some people completely cut back the smooth hydrangea to the ground. However, although the bush will flower profusely, the stems will be too weak to support their weight.
Florist hydrangea, or Hydrangea macrophylla, is the most common variety sold as houseplants and grown in containers. The best time to cut back florist hydrangea is when new shoots start growing, after the bush has finished blooming in late summer. Flowers form on the previous year's growth.
Cut back older hydrangeas in January or February. Remove one-third of the older wood to encourage the growth of new stems. This also allows sunlight to reach the centre of the bush.
You only need to cut back climbing hydrangeas when they are mature. Simply prune the unwanted climbers.