Plants I love

Hedging out of the box

A caterpillar is threatening the box hedges of Europe. The Asian import is bingeing on miles and miles of delicious buxus hedging that it doesn’t have to share. Until the arrival of Cydalima perspectalis, the box tree moth, box was thought to be imperviousness to nibblers of all kinds, a factor which, coupled with its longevity and eminent clipability, made box the go-to plant for hedges and topiary for thousands of years of European garden-making.

It’s awful to watch this hungry caterpillar chomping through so much garden history, but even in this dark cloud, there may be a sliver of silver lining. A risk to box could be the cure for box boredom, a condition imposed by seeing too many newly planted box-edged urban gardens. Traditional gardens are bound by tradition, but for most of us, it is possible to hedge outside the box.

Some of the best alternatives are home-grown and The Australian Botanic Garden Mount Annan is a good place to see some of these in action. Chris Cole is the gardener of the Big Ideas garden at Mount Annan and in his patch has experimented with a range of different natives as hedges. My favourite here is Sannantha ‘Howie’s Sweet Midget’. (For a few hundred years this plant was called Backea virgata. It was put into a new genus in 2007 and because that’s not very long ago you will probably also find it as Babingtonia virgata.) The original form is a lovely arching shrub a couple of metres tall, but this mini cultivar gets to just half a metre if you are nice to it, less in difficult conditions. It has tiny leaves on arching stems that form a dense little mound that demands to be patted. In summer the bright green foliage is covered with starry white flowers. A hedge of it is more like a lineup of clouds than a straight line, but for those who don’t want to bother with clipping, it’s perfect.

Sannantha, syn. backea virgata

Here’s the Sannantha, which I still think of as backea, behind a soft line of fine-leafed lomandra at The Big Ideas Garden at The Australian Garden, Mount Annan

For a square-edged low hedge, the local best offer is a lillypilly, Syzygium australe ‘Tiny Trev’. Trev is rarely affected by the psyllids that cause unsightly pimples on the leaves of larger, older lillypillies, and grows well in sun or part shade. It makes a dense dwarf hedge. Chris Cole recommends overplanting a hedge so that if an individual plant fails, its neighbours can fill the gap. Trim the hedge so that the top is slightly narrower than the bottom, allowing the base to get enough sunlight to stay leafy and dense. For the neatest, densest hedge with the clearest, sharpest outline, prune early and prune often, says Cole.

Where box is dark green, ‘Grey Box’ is, yes, grey. This new cultivar of westringia, the most common common name for which is coastal rosemary, is this year’s Nursery and Gardens Industry Australia’s Plant of the Year.

Grey box westringia hedge

This is ‘Grey Box’ in the gardens at Ozbreed. The westringia behind it is ‘Aussie box’.

If left alone it will form a sphere about 45cm high and wide. Get the clippers out and it can be given a short back and sides to keep it at a minimum of 30cm by 30cm. ‘Grey Box’ has white flowers in flushes from spring through to late autumn and prefers a sunny spot. It is not bothered about soil, can be planted in a greenwall, and shrugs off salt-laden winds, frosts, drought and scorching heat. Caterpillars aren’t interested.

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