Val Bourne on worries over fungal disease box blight

Autumn seems to have come early this year and the beech leaves are already cascading down on my car a good month earlier than usual.

Box blight, a fungal disease that attacks box hedging (Buxus sempervirens), comes in two forms. Cylindrocladium buxi, officially identified in early 1990s, is considered the most serious. Affected leaves develop brown spots and the stems get black lesions. Volutella buxi, which has been around far longer, produces lots of pinkish fungal spores but is less harmful. This year’s a bad year and Dr John David, the RHS’s chief scientist, has had more enquiries about box blight this year than in the same period last year. It’s probably due to the damp, mild winter of last year.

These fungal diseases are no respecters of wealth and fame. Prince Charles had to remove all his box from the Walled Garden at Highgrove in 2010. He replaced it with Teucrium x lucidrys, a cross between Wall germander (Teucrium chamaedrys) and Sage-leaved germander (Teucrium lucidum). This is more upright than Wall Germander, with greener foliage, and it’s trimmed after flowering so that it stays compact throughout winter. It looks well within the vegetable garden, but doesn’t have the same crisp profile needed for a smart parterre.

More recently Monty Don removed some of his box hedging on camera, citing milder winter weather as one of the major factors in the disease’s spread.

Roy Strong, who also gardens in rain-soaked Herefordshire as Don does, has lost his box framework too.

The National Trust has had to remove hedges from Buckland Abbey in Devon, another mild damp county in the western half of Britain. However, central England is not immune either. Abbotswood Garden, near Stow on the Wold, also lost a box parterre and they and Buckland have chosen to replace it with a slow-growing hardy Japanese holly (Ilex crenata).

Some have tried this and ripped it out: it’s incredibly slow. Other contenders have been Lonicera nitida (Box leafed honeysuckle) which is not at all suitable. It sends out long wands every few weeks, looking scruffy. Smaller-leaved hebes are also being championed but these can be seen off by hard winters and, in any case, they are not long-lived.

There is no easy answer. However, on a recent day visiting Cotswold gardens I saw some interesting approaches to the problem, possibly the light at the end of the tunnel. Stephanie Richards of Eastleach House, near Lechlade, (www.eastleachhouse.com) owns a fabulous garden that opens for groups by appointment. She was forced to cut down and burn a whole section in her Walled Garden two or three years ago.

With one full time gardener and two part-time helpers assisting her in this huge garden, the stumps were left for removal in the winter. To the team’s astonishment the hedge grew from nothing and looked completely healthy, so it was left alone. It’s almost a hedge once again. No fungicides were applied, although a thorough clean and tidy took place after they had burnt the diseased box.

Visiting another private garden on the same day, their box had also suffered. All the affected areas were snipped out and burnt as soon as they were spotted. Then seaweed plant food, which not only feeds but toughens up the foliage, was watered on to all the box in the growing season. Their box balls looks gappy as yet, but healthy.

Waterperry Gardens have had similar struggles, but they have replanted using a box with a golden edge because Garden Manager Rob Jacobs has noticed that this slightly variegated form escaped box blight. I can also say that the variegated form ‘Elegantissima’ does the same. I have never seen it look anything other than healthy.

In Holland the gardeners have started to cut their box in winter, when temperatures are cooler, in order to prevent the fungus from spreading.

At Broughton Grange, near Banbury (pictured above), they adopt a more organic approach and allow their parterre the freedom to form contours. Those rounded hummocks throw off the rain far more efficiently than flat-topped hedges and look more modern.

We need to change the way we treat box. Cutting it back year after year in high summer scorches the new growth and stresses the plant.