Box alternatives trial at RHS Garden Wisley

Box blight (and the box tree caterpillar) are now widespread throughout the UK but there are other plants you can choose as alternatives to box. RHS Wisley has been putting them through their paces and Curator Matt Pottage shares the successes and failures to date
 

Box blight started to damage the box hedges at Wisley around 2006. Careful pruning and some spraying were implemented to control it, but it didn’t always work well. The arrival of the box tree moth in 2014, and the speed at which it destroyed the hedges, made it clear that more sensible (and sustainable) alternatives were needed. We found ourselves at a crossroads.

The RHS was inundated with gardeners asking for advice on how to save their box hedges, and it was clear we needed to find a more sensible solution than spraying or picking off the caterpillars. The blight and the caterpillar were established in the South East, and quickly spreading to other areas of the UK.

More sensible, and sustainable, alternatives were needed. We found ourselves at a crossroads

We tried Ilex crenata, which many thought would be a solution, but it didn’t work well in the Wisley climate, which is hot and dry in the summer and has sandy soil. So we decided to look for other shrubs and conifers that had good ‘clipability’; small-leaved shrubs and conifers that could be clipped closely.

The Wisley team came up with a brilliant design for an informal trial in the Walled Garden East, where different genera and cultivars were used to create small hedges, pyramids, and taller hedges. Some of the early plant inclusions were edited out, as some shrubs couldn’t cope with the level of clipping forced upon them. The final plants were chosen for their vigour and their ability to cope with close clipping.

The Wisley team designed a garden that would showcase alternatives to box

The display at Wisley offers a range of alternatives, with different colours, textures, and forms. Gardeners can choose from options they may have never considered before and the display raises the question of whether a plant can be a box alternative if it doesn’t look the same as box.

The Wisley team hopes that people will be more open to using plants with coloured and variegated leaves, as they can be a positive replacement for ravaged box hedges. For example, spheres of the white-speckled Pittosporum tenuifolium ‘Irene Patterson’ can be used to great effect in a small garden.

If you’re looking for a shrub that most closely resembles box, try Podocarpus nivalis. It is simply superb, and can be seen in the display at Wisley. It doesn’t grow too fast, propagates easily, and can even regenerate from old wood. To top all of that, it can also cope with full sun to part shade.

As a fan of coloured foliage, I also enjoy some of the podocarp cultivars such as ‘Chocolate Box’, which flushes a magnificent bronze when the weather turns cooler in the autumn.

Despite the traumas our box plants have gone through, we do have one survivor, and that is Buxus sempervirens ‘Bowles’s Blue’, whose tough, slightly puckered, larger glaucous leaves appear to be the last option for both the blight and the caterpillar. Because of these characteristics, it doesn’t clip to a particularly tight hedge but it is the only box hedge we now showcase in our battle against the blight.

Our box survivor - Buxus sempervirens ‘Bowles’s Blue’