Shrubs that have been neglected and left unpruned will develop into a scraggy, dense mass of branches with few flowers, or a tall lanky shrub with bare stems and miserable flowers out of sight at the top. If you’ve let a shrub get into such a state or, more likely, you’ve inherited one, don’t despair. Chances are you can bring it back to its former, happier self. Begin by completely removing any dead branches. Next take out branches that are growing across the shrub and any that are rubbing against each other. You are aiming for an open structure that the air and light can get in to. Finally, cut the entire shrub down by about two-thirds. Yes, it’s drastic, but the plant will benefit. During the year following such severe treatment the plant will be putting all its energy into producing new shoots, so you won’t get many flowers. Pruning shrubs in this way can be done at any time of year. With deciduous shrubs it’s easier to do it in early winter, after the leaves have fallen, so that you can see clearly what you are doing.
Not all shrubs will respond to this sort of treatment. Daphne, Genista and Cytisus (with the exception of C. battandieri) will not re-grow from mature, woody stems. In general, if you can see dormant buds on old stems, you know that the shrub will re-grow. Rhododendrons will respond to this hard pruning even though you can’t see any buds on the stems: they are hidden under the bark.