Box is an incredibly useful and versatile plant in the garden. With its naturally dense, evergreen growth, it has been used for centuries to create year-round structure in the garden. It can be used to create topiary, including box balls, to provide useful accents in the garden. Grown into a low hedge, it can be used to edge a border or a parterre.
But box is under threat. There are two problems that threaten the health and vitality of box plants: box blight and box moth caterpillar.
Box blight has become a real problem in recent years. Telltale signs include leaves that turn brown and fall, leading to bare patches. You may also spot black streaks, dieback on young stems and spores of the fungus on infected leaves (these may be white or pink). Blight is caused by two types of fungus, Cylindrocladium buxicola and, to a lesser extent, Volutella blight. It can spread quickly in warm, humid conditions.
There’s currently no cure for box blight, although certain care techniques can help. If plants are badly affected, dig up and burn them in order to save others. On less severely affected plants, cut back or cut out the affected areas (disinfect pruning tools to avoid spreading the disease further). Remove fallen leaves and burn infected plant material (don’t compost). It’s also a good idea to remove the top layer of soil where fungal spores may remain, and feed plants with a general-purpose fertiliser to aid recovery. Mulch plants annually (for example with mushroom compost).
Other ays to prevent the spread of blight include not pruning in wet weather and not watering from above, to keep the leaves dry. Improve the air flow around the plant by not letting other plants grow too closely around it, and remove overhanging perennials nearby.
In addition, you could apply a fungicide, especially before and after pruning. Always read the label before applying and bear in mind that fungicides can damage the overall health of your garden, as well as put insects such as bees at risk.
- Longmeadow, Monty Don’s garden, is affected by box blight. Watch his two-part video guide to dealing with box blight.
Box tree caterpillar, Cydalima perspectalis, has been decimating box plants in London and the surrounding counties in recent years. The caterpillars eat the leaves, leaving the plant looking bare, and create webbing around their feeding area. You may spot the pupae, concealed in a white cocoon, green/yellow caterpillars with black and white stripes (up to 4cm long), or yellow eggs on the undersides of the leaves. If you shake the plant, white and brown moths, around 4cm wide, may fly off. You can try picking off caterpillars, cutting away infested areas, applying a nematode or spraying with insecticide frequently (again, bear in mind that insecticides will kill more than the box tree caterpillar).
If you already have box blight or box tree caterpillar in your garden, or want to avoid these potential problems altogether, it pays to look at alternatives – just as many well-known head gardeners and garden designers are already doing.
Here are some plants that look similar to box and can be treated in the same way.
Yew, Taxus baccata, is the replacement plant of choice for many head gardeners and garden designers. A British native, it withstands hard clipping and can be grown as topiary or a low hedge. Grow in moist but well-drained soil in sun or shade.
Suitable for: balls, cones, topiary shapes, low hedging, cloud pruning.
Japanese holly, Ilex crenata, has small, slightly glossy green leaves. It bears small, white flowers in summer and may produce black fruits in autumn. Tolerant of shade and urban pollution, it can be clipped into shapes or grown as a low hedge. It looks especially good when cloud pruned.
Suitable for: balls, cones, low hedging, topiary, cloud pruning.
Mock privet, Phillyrea angustifolia, is a member of the olive family. It makes excellent topiary and looks especially good when cloud pruned. It is slightly tender so do not grow in very cold areas.
Suitable for: balls, cones, other topiary shapes, cloud pruning
Hedge germander, Teucrium x lucidrys, was traditionally used to edge knot gardens and makes a good low hedge to line a border or parterre. It’s a drought-resistant, with dark green crinkly edged leaves. In early summer, short spires of small pink flowers appear. Teucrium fruticans has silvery leaves and a more airy look.
Suitable for: low hedging
Osmanthus delavayi and Osmanthus x burkwoodii are compact evergreen shrubs with glossy, dark green serrated leaves. In spring, they produce masses of scented, white, jasmine-like flowers, much-loved by bees.
Suitable for: balls and hedging
Euonymus japonicus is a compact, glossy evergreen that makes good low hedging – use to line a knot garden or parterre. It’s salt and wind tolerant, making it a good choice for exposed or coastal gardens. Try Euonymus japonicus ‘Green Spire’, Euonymus japonicus ‘Microphyllus’ or ‘Jean Hugues’.
Suitable for: low hedging
Hebes have a naturally rounded shape, so lend themselves well to forming rounded mounds that don’t need much clipping. They also make a good low hedge. Try Hebe topiaria, Hebe pinguifolia ‘Sutherlandii’, Hebe subalpina or Hebe ‘Green Globe’.
Suitable for: mounds, low hedging
Lavender makes a beautiful low hedge that is at its peak in summer, when it flowers. It has the addition of scented flowers and foliage. Use it to line a path or even a herb garden or parterre. It likes well-drained soil in a sunny spot and is drought tolerant. Try ‘Munstead’ or ‘Hidcote’.
Suitable for: hedging, balls
Boxwood honeysuckle, Lonicera nitida has smaller leaves than box and grows more quickly. This tough plant responds very well to clipping so is useful for fine topiary, such as spirals. It can also be used for hedging. ‘Baggesen’s Gold’ has golden leaves for an unusual look.
Suitable for: topiary, hedging
Portuguese laurel, Prunus lusitanica, has large, glossy green leaves and attractive red stems. Despite being a native of Portugal and Spain, it is very hardy. ‘Angustifolia’ is the most widely used variety.
Suitable for: topiary, balls, hedging
Berberis has dense, small leaves that are good for topiary. Try the evergreen Berberis x stenophylla or the deciduous Berberis thunbergii varieties for an unusual look – they have good autumn leaf colour.
Suitable for: topiary, low hedging
Wire bush, Corokia, is a small genus of shrubs and small trees native to New Zealand or Australia. Corokia x virgata is a popular hedging plant, bearing small leaves and yellow flowers, followed by red berries. Cultivars include ‘Frosted Chocolate’, which has dark brown autumn foliage, and ‘Sunsplash’, which has variegated foliage.
Suitable for: topiary, hedging, low hedging
Avoiding box blight
If you don’t have box blight in your garden and want to keep it that way, there are several things you can do. Ensure there’s some space around your box plants to improve air flow around them – don’t underplant them and cut back neighbouring shrubs or perennials. Water from below to avoid getting the leaves wet and only prune during dry weather; don’t prune to closely. Don’t trim any later than August, when the spores are more prevalent. Mulch annually and check plants regularly for signs of disease.