The depredations of the boxtree caterpillar, Cydalima perspectalis, have reached such a pitch in Kensington that Rassells Nursery has stopped sellling box plants for hedges. Instead they are offering a miniature holly, Ilex cornuta ‘Luxus Globe’,
Its leaves are smaller and darker than box. Its paler new growth at this time of year is quite pretty, but no one can pretend it will ever be a substitute for the mainstay of garden design for, literally, thousands of years. The Romans relied on it. Pliny the Younger cut it into extravagant figures at his villa by the sea. Populations of box trees are often evidence that Romans colonized a district. Where we lived in the Auvergne the outlines of a Roman town were still just visible, but the valley below was thick with ancient box trees. You didn’t find them anywhere else near there.
We all know its qualities as the trim and malleable friend of gardeners in the European tradition. Not everyone likes the evocative small of a box parterre on a dewy morning in summer, but the thought of a unique tradition chewed to oblivion to feed a nondescript little moth is hard to stomach.
We are defending our little hedges with whatever treatments are allowed. The caterpillars last year arrived in August ; in this strange spring they became obvious in chewed leaves and tiny webs in late March. The tiny caterpillars are hard to find but munch alarmingly fast. Even with daily inspection some survive – and turning your back to go away for a week is seriously ill-advised.
Ash trees, even elms, can be replaced with other trees, however we may miss their familiar silhouettes. Box, alas, has no real substitute. At Wisley there is a bed planted with possible replacements, trmmed as low hedges ; none, I fear, really cuts the mustard. Perhaps the best is Teucrium x lucidrys, or by its medieval-sounding name of hedge germander. The Prince of Wales evidently thinks so ; he has replaced box with it at Highgrove. Its chief drawback is its spikes of pink flowers, but I’m told hard trimming avoids them. Meanwhile, pray for a predator keen on cydalimas.