Box balls can make a really stylish addition to a planting scheme adding evergreen structure and strong shapes against other flowers and foliage.
However, Buxus has been subject to a particular pest in the UK in recent years - the Box tree caterpillar, or Box tree moth which is a relative newcomer from Asia.
Since 2011 Box tree caterpillar has been decimating Box plants in the UK. With their clever camouflage they often are well concealed and can be difficult to spot until it's too late. I have seen them completely ruin large and well established box plants in a matter of weeks. Buxus is not a cheap plant to buy so these tiny caterpillars muching their way through your plant mean that they are also expensive to replace.
If you want to plant something in the style of box topiary but without the worry, maintenance and treatment that Box Moth can result in, here are a few suggestions of other plants that give the same effect without the pests.
Euonymus ball
Some Euonymus varieties work well if they're trained and pruned into rounded shapes. The variegated foliage on this one makes it lighter and adds an element of interest.
Hebe toparia ball
This small evergreen hebe has a dense habit and small green leaves, sometimes slightly grey. This has a mound-forming habit and can be lightly pruned to maintain this shape.
Also has white flowers in summer.
Ilex crenata ball - Japanese Holly
Ilex crenata have a very similar look to Buxus due to their small glossy green leaves and their dense habit.
Pittosporum tenuifolium 'Golf ball'
Pittosporum come in a number of different shapes and sizes - some will grow very large, and the leaf size and shape vary across the genus.
This variety has a compact habit and small leaves making it a good cadidate for replacing box topiary.
Taxus baccata
This small leaved evergreen shrub can also grow into a large tree - common in English churchyards.
However because it is relatively slow growing and because of it's small leaf size it also makes great topiary.
You might also be interested in this article from Gardens Illustrated discussing the merits of an alpine plant called Podocarpus, being used at RHS Garden Wisley as a Box topiary alternative.