Box blight has been bad enough, but now there is a new bug in town, and it is bent on destruction. The box caterpillar has already munched its way through metres of hedging and defoliated treasured topiary on mainland Europe.
The bad news is that the greenish-yellow caterpillar, which lays its pale yellow eggs on the underside of leaves, and weaves cocoons of white webbing, is wiggling its way across London from the south-west of the city, so damage has already been reported in many gardens, especially in Clapham and Wandsworth.
“There are no preventive measures,” says Jenny Bowden of the RHS Advisory Service, which recommends two methods to try to stop the pest in its tracks. “The more organic route is to use a contact insecticide with the active ingredient of pyrethrum. It’s hit and miss, because you have to coat every insect whenever you see them, and by the time you’ve seen them, they may already have done the damage.
“Alternatively, use a systemic spray such as Provado Ultimate Fruit & Vegetable Bug Killer that will poison the caterpillars when they ingest the leaves.”
Bowden says the caterpillar is a worse threat than box blight. “We’re looking at a rough ride for the future of box. At the RHS, we’re advising people not to plant a box hedge.”
What makes sense, then, is to think outside the box and look at suitable choices to replace London’s favourite clipped evergreen. Savvy garden centres such as Clifton Nurseries, though still offering box, suggest alternatives. Matthew Wilson, Clifton Nurseries’ managing director, says the best alternatives to box are shrubby honeysuckle Lonicera nitida and box-leaved holly, Ilex crenata.
“Lonicera has small, glossy leaves and will form a nice tight plant with pruning, although it needs rather a lot of pruning. Ilex crenata is better-behaved and from a distance is indistinguishable from box, apart from being a couple of shades darker. For a ball or cushion shape, try Hebe topiaria, which has a topiary-like shape without the need for pruning. And yew, although having very different foliage, can also be clipped into shapes such as balls and columns and is largely trouble-free.”
Bowden is enthusiastic, too, about Lonicera nitida because it grows well from old wood, and will usefully tolerate shade, as will Ilex crenata. She also suggests Pittosporum tenuifolium for edging and topiary. In her own borders, she has planted the more compact Pittosporum tenuifolium Golf Ball, which forms rounded, apple green punctuation points and responds well to clipping.
“For topiary, you could also use Ligustrum delavayi, the tiny-leaved, dark green privet, which has glossy foliage and little white flowers,” she says. “It’s a darker green than box, and is tolerant of shade and any soil.”
For hedging, she recommends Euonymus japonicus microphylla, which has a neat, upright growth. “In a sunny spot, I might consider Teucrium chamaedrys, which has oval, aromatic dark green leaves, grows to about a foot and makes a lovely edging. And in London, with its sheltered microclimate, you could even grow the small-leafed myrtle, Myrtus communis Tarentina.”
Bowden suggests we see the box problem as a chance to be more creative with evergreens. “Look at different shades of foliage. A lot have gold-leafed as well as variegated varieties.” Call it boxing clever.