Caring for a ‘snowball tree’

My Viburnum opulus ‘Roseum’ is 60cm (2ft) high and must stay in a pot until the autumn when I expect to plant it out. What is the best way to care for it and how should I prune it for optimum blooms?

The so-called ‘snow ball’ tree is a sterile form of a beautiful British native shrub known as the guelder rose. The leaves are lobed – almost like maples – and in the wild, fertile form, the lace-cap flowers are followed by scarlet berries. The variety ‘Roseum’ has large creamy white, globe-shaped blooms and doesn’t produce berries.
This is a large, easy shrub, happy in almost any alkaline or neutral soil, in sun or semi-shade. Growth is rapid and dimensions likely to exceed 4m (13ft 6in) in height and width, so give it space!
Pruning is not necessary, but you can trim the bush immediately after flowering. Every five years, the shrub benefits from being pruned very hard back in late winter.