Maintaining box (Buxus sempervirens)

Looking after box including problems and diseases

Box is a very versatile shrub, hence it's common use as hedging and for topiary. Being evergreen, with small leaves, tolerating close shearing and even with scented foliage, box has remained a very popular plant.

Box will tolerate hard pruning, however for the purpose of topiary, clip young plants by up to one-third in May and again as often as is required between May and August. For more established topiary forms clip twice during the summer with the first clip around late May and the second before the end of August.

Always clip on a cloudy but dry day, as direct sun can scorch freshly exposed leaves, while wet weather can increase the spread of box blight and other fungal pathogens.

General care of box includes keeping weed free around the base, feeding with a general-purpose organic fertiliser such as fish, blood and bone at a rate of 50g per sq. m, and then applying an organic mulch such as green waste compost to a depth of 5cm. This will help to prevent weeds and improve soil structure as the organic matter breaks down.

Problems and diseases of box

Box can suffer from many problems and diseases, in fact, to such a degree that it may be advised to plant a suitable alternative.

By far the most serious disease is box blight which results in bare patches and die-back and is caused by two types of fungi; Cylindrocladium buxicola and Pseudonectria buxi.

There is no fungicide which can kill these, however research is still on going. Only tebuconazole (Bayer Garden Multirose Concentrate 2) has been found to be an effective protectant. It is important to recognise however, that fungicides are broad spectrum, and can or will destroy fungi populations in the soil which can be critical to soil health and plant health.

Other problems box may encounter are sun-scald and discolouration due to excessive sunlight and bronzing of leaf colour due to environmental stress such as drought.

Box may also be harmed by;

  1. Phytophthora root rot.

  2. Box rust.

  3. Box sucker.

  4. Box tree caterpillar.

  5. Box leaf-mining gall midge.

  6. Mussel scale.

  7. Box red spider mite.

A box which has all the correct nutrients available in a healthy soil is much more likely to resist these diseases.