When to repot and prune a hydrangea

QI have a hydrangea that has been planted in a halfbarrel container for many years. The barrel is now rotten and disintegrating around the plant. When is the best time to repot it and should I prune it before doing so?

Caroline McGuigan, via email

AYou can carefully remove your hydrangea from the rotting barrel and repot it now, but do not prune it until spring.

Hydrangeas thrive in humus-rich, slightly acid, moist but well-drained soil or compost.

Correct pruning is required to keep hydrangeas flowering well and this will vary according to which species of hydrangea you have.

For the popular mopheads and lacecaps, the flowering shoots grow from wood produced during the previous season, and it is important that this is not removed.

In mid-spring remove the dead flower heads, cutting back to the nearest pair of large, healthy buds.