Pruning methods differ among the various hydrangea varieties. For example, dwarf hydrangea bushes need a different way of pruning compared to what is normally done with an endless summer hydrangea.
Mopheads and lacecaps bloom beautifully even if no pruning is performed. But if you prune them regularly, then you can produce a better show of flowers. This is true for other hydrangea cultivars, including the climbing hydrangea.
Lacecaps and mopheads are the most common garden species of hydrangeas. Mopheads contain full, roundish petals. Lacecaps, on the other hand, have very small flowers on the center with large petals.
When to prune
Prune in late winter or during early spring. For a climbing hydrangea, prune it after it flowers in the summer.
Suitable pruning methods for each type of hydrangea
Remove dead blooms (or dead heads) on mophead hydrangeas in areas with mild weather. Pruning this way can be performed on mopheads, though it is ideal to simply leave the dead blooms on the plant during winter in order to provide protection for the fragile growth buds against frost. Prune the dead flower heads the moment early spring sets in. Cut back until you reach the first healthy and strong pair of buds situated on the lower part of the stem.
Lacecaps are so much hardier than mopheads. They can be pruned by cutting back the faded flower heads until you reach the next pair of leaves below the head. This prevents the seed from growing; the seed drains energy from the entire shrub. In addition, you can also cut one or two of the plant’s oldest stems that are located at the base. Doing this encourages new growth that bears more flowers. You can also prune poor or neglected parts by cutting off all the stems at the base of the plant. This pruning method eliminates all the flowers that are expected to appear for that summer. Take note that the resulting new stems will not bloom until the following year. You will have a flowerless hydrangea all year, but when it flowers, it will be a great show of blooms.
For hydrangea serrata, use the same pruning methods as those on mopheads and lacecaps.
The following hydrangea cultivars -- H. quercifolia, H. aspera, H. sargentiana, and H. villosa –need very little pruning during the spring. Simply remove the over-long and the dead stems.
As for climbing hydrangeas (H. anomala subsp. petiolaris), it is pruned differently. There are certain parts that must not be pruned. Climbing hydrangeas possess overlong shoots which cut back right after the flowering occurs. Most of the flowers appear on the topmost part of the plant. Therefore, always leave as much of this plant region untouched as possible.