Managing Box Blight

If you are growing, or planning to grow box plants, particularly for topiary or parterres, be vigilant for the fungal disease known as box blight. It can lead to brown leaves, bare patches and die back on your garden plants and can appear at any time of the year, although it is most active in rainy seasons. Caused by the fungus Cylindrocladium buxicola, it mainly affects box plants although other plants in the Buxaceae family are also susceptible.

It is important to watch out for symptoms of box blight, as early diagnosis and management is most effective. The RHS guidance recommends that you look out for:

• leaves that turn brown and fall, leaving bare patches
• black patches and die-back on young stems
• in wet conditions, white spore masses that can be seen on the under-surfaces of infected leaves (place leaves in a plastic bag with moist tissue for a few days to check).

Prevention and Control

To prevent and control box blight in your garden there are a number of measures that you can take:

• hold newly purchased box plants in isolation for three weeks to ensure that they are free of the infection before you plant them outside
• inspect plants regularly for signs of infection, as the disease spreads very rapidly, particularly in wet, warm conditions
• reduce the frequency of clipping (which encourages dense growth) to improve ventilation throughout the branches
• avoid watering your plants from above, and provide a mulch to reduce rain splash, as humidity will increase the likelihood of the fungus appearing and spreading.

If you are unfortunate enough to spot box blight then there are steps you can take to reduce its spread.

• Destroy badly affected plants and cut out the damaged parts of less severely infected plants.
• Remove fallen leaves from the plant and around the base, as well as the top layer of compost, making sure to bag and bin the material. Do not compost it, as this will spread the infection.

Alternatives

To completely avoid box blight there are many alternatives to box that you can use in your hedges and topiary. Try Berberis thunbergii ‘Atropupurea Nana’ AGM, a charming, virtually thornless, dwarf form with colour that increases throughout year, or Ilex crenata ‘Samurai’, a great Buxus substitute with strong growth which is excellent for topiary or growing as a hedge. Osmanthus delavayi AGM is another excellent alternative, with its evergreen, rounded growth and small, glossy, dark green leaves. Luma apiculate ‘Glanleam Gold’ is an evergreen, slow growing shrub which has the additional attractions of aromatic foliage and pretty white flowers in the summer while Lonicera nitida ‘Baggesen’s Gold’ is an evergreen shrub with a dense habit, small, golden-yellow tinted, bronze leaves and a sweet scent.

(Blog post by Jo Chamberlain)