Thinking outside the box

One of the things I like best about RHS Wisley is how useful it is – beautiful to walk around, pleasant to visit, but also how just being there can answer a multitude of gardening questions: ‘Will this plant survive outside?’ ‘Just how big can an Indian Bean Tree get?’ or ‘How best can I display alpine plants in my small garden?’

But one of the most useful parts of RHS Wisley helps to answer a question that has become louder and more frequent with every passing year, especially here in the South East:

‘What can I use to replace my ravaged box hedges?’

‘Thinking Outside the Box‘, one of the walled gardens just beyond the Jellicoe Canal, was first planted around 2016 with a wide range of possible box (Buxus sempervirens) alternatives, ie: plants that could be clipped and shaped into tight, small hedges and weren’t prey to the ubiquitous problems of box blight and box hedge caterpillar. Some were obvious contenders, such as Lonicera nitida, others less so, such as Leptospermum or Podocarpus.

Visiting in 2022, it would seem that there are definite winners and losers, but also a good range of plants to satisfy differing preferences for colour, form and habit. There’s a notice specifically explaining that Ilex crenata didn’t perform well and was removed, running contrary to the fact that it’s the alternative that is most often recommended across the land. I’m sure that various Euonymus (both E. japonica and E. fortunei) cultivars have been tried over the years, but I didn’t see any on my recent visit. I contacted the RHS to ask why and they said that they had not been removed because they failed, but to make room for other plants. This doesn’t explain why there’s such a preponderance of Pittosporum ‘Collaig Silver’ – surely some of them could have made room for new plants instead of removing all the Euonymus?

Several other Pittosporum also seem to have done very well and certainly it’s a genus that earns its place as a box alternative. There’s also more than one Corokia (which look surprisingly good), several Lonicera and a low growing yew (Taxus baccata ‘Repandens’) which edges all the beds quite beautifully.

Here are my picks for the top box alternatives at Wisley – very much my own opinion! I visited just when they were due for a trim, so some look a bit shaggy. However, it was obvious that they would topiarise very nicely.

5. Pittosporum tenuifolium ‘Golf Ball’

4. Ligustrum sinense ‘Sunshine’

3. Corokia x virgata ‘Sunsplash’

2. Corokia x virgata ‘Silver Ghost’

1. Pittosporum tenuifolium ‘Tandara Gold’

Which would you choose, and do you have other recommendations?

Ali

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Useful links about box problems and alternatives:

• RHS: Box blight (includes links to alternatives)
• RHS guide to box tree caterpillar (includes links to alternatives)
• Gardeners’ World: Alternatives to box (lists lots of options not featured in the RHS lists)
• Gardeners’ World Episode 14 (18 June) 2021 has Nick Bailey visiting RHS Wisley and looking at several of the plants listed above (feature starts at 22 minutes).