The group of Pieris shrubs fall into the very easy to prune category, because basically they do not need to be pruned – unless we gardeners have done something wrong, or there has been some form of damage. The Pieris are closely related to the Rhododendrons – sharing the same likes and dislikes as most others in the Ericaceous family.
Pruning Pieris can generally be confined to dead heading the flowers before they set seed and generally start to look a little untidy. Pieris tend to flower in March, through until early April, but in some seasons a little earlier.
The drooping clusters of tight bell flowers resemble the flowers of the Lily of the Valley – hence one of its common names.
Pieris are normally hardy in the right situation, but because of the timing of their flowering period, can be affected by hard frosts. The same is true of the flaming red young foliage for which the shrubs are better known.
Unless you are wishing to save seed, then Pieris should have the old flower sprays nipped off at the base. This will both tidy up the shrub in readiness for the spectacular new foliage, and also strengthen the plant by stopping it from setting seed.
Simply cut off all the stems of faded blooms with secateurs, but do not cut back into the main branch unless intending to restrict the size or shape. If Pieris are pruned in summer or autumn, they will forfeit the flowers for the following year, but otherwise suffer no damage.
However, pruning should not take place after the end of august, for this can initiate new shoots which will invariably be damaged in the following winter.
In frost prone areas that suffer from late frosts, the new shoots of the Pieris foliage can be blackened to the extent of spoiling the foliage display. If this is the case, prune off the frost-damaged shoots, back into the supporting branch. It will then send out another flush of shoots which can be as colourful as the dead frost-damaged shoots.
If the shrub has outgrown its position, Pieris can be cut back to shape, or even hard pruned to rejuvenate the whole shrub. This is best carried out in early to late spring, but I have been successful to regenerate Pieris by cutting back hard in late winter.
This will invariably mean a loss of flowers for a year or two, but will have the advantage of successive flushes of colourful new shoots, as the shrub will quite rapidly try to attain the size it was before the pruning operation. Pieris respond vigorously to hard pruning, and will soon recover with a good shape and dense habit of growth.