Box, Buxus sempervirens, is a British native tree, most commonly used for hedging and topiary thanks to its small, evergreen leaves and dense growth. In April and May, it produces insignificant yellow flowers, that are nonetheless rich in nectar and popular with bees. Left untrimmed, box plants can reach 5m tall, but most never reach this as they are clipped regularly.
Box is synonymous with formal gardens, particularly parterres and knot gardens, and can be clipped into all manner of shapes. It’s beautiful, versatile and useful, but in recent years, it has suffered the double whammy of box blight and box tree caterpillar, both of which weaken and can kill the plants. This means box is no longer the hedging or topiary plant of choice in many areas of the UK, and it’s best to grow alternatives to avoid these problems.
How to grow box
Grow box in moist but well-drained soil in full sun or shade. Prune from mid- to late summer to keep in shape and keep an eye out for box blight and box tree caterpillar, both of which can harm the look and health of your box plants.
More on growing box:
Growing box: jump links
- Planting box
- Caring for box
- Pruning box
- Propagating box
- Growing box: problem-solving
- Best box to grow
Where to grow box
Plant box in any moist but well-drained soil in sun or shade. You can also grow box in containers – it looks especially good shaped as topiary.
How to plant box
Box plants are usually bought in pots and can therefore be planted at any time of year, as long as the ground isn’t frozen. The best time to plant, however, is spring or autumn. Dig a generous hole, adding plenty of well-rotted compost and mycorrhizal fungi to give the plants a good start. Alternatively, buy bare-root box plants from autumn to spring. Soak them overnight before planting them at the same level they were planted in the field.
It’s advisable to quarantine your plants for a month away from any other box plants before you plant them, to check that they are free of box blight. Commercial growers use fungicides that can suppress blight but does not get rid of it.
Follow Monty Don’s guide to planting box as a hedge, in this clip from Gardeners’ World:
If you’re planting box in containers, choose as large a container as you can (at least 45cm wide) and plant into loam-based compost such as John Innes No.3.
If you’re planting a hedge, you can plant plants up to 30-40cm apart (less if you are impatient) and they should have knitted together within three to five years.
Caring for Buxus sempervirens
Box plants in the ground shouldn’t need watering once they’re established, except in periods of drought.
Feed with a general-purpose fertiliser in spring, then mulch around the base of the plants with well-rotted manure or garden compost.
Give plants in pots a monthly liquid feed in summer, and keep the compost moist.
Keep an eye on your plants to check for box blight and box tree caterpillar.
How to prune box
Trim box hedges from mid to late summer. However, if you are creating topiary, prune your shape initially in spring and then later in the summer. To avoid box blight, only prune in dry conditions and clear the prunings away promptly. Disinfect your shears between each plant to reduce accidental spread of the disease. Pruning just once a year results in a slightly looser plant that is hopefully less prone to box blight as it has better air circulation.
If box has become overgrown, it can be cut back hard in late spring.
Follow Monty’s guide to pruning box hedges, including how to keep them looking neat all winter:
Mulch box plants every year with well-rotted manure or compost.
Growing box: problem-solving
Box blight (Cylindrocladium buxicola) is a fungal disease that causes leaf loss and ultimately weakens box plants. It spreads rapidly in warm, wet or humid conditions. Signs include brown leaves that fall off the plant, leaving bare patches, black streaks and dieback on young stems, and white patches on the undersides of leaves.
If you notice box blight, it pays to take prompt action in order to save your plants as it is difficult to treat once it has taken hold. Cut out any badly affected areas on a dry day, removing more than you think you need to, as the disease has probably spread further down the plant but is not yet visible. Remove any debris from around the plant and clean your tools between each plant. Remove very badly affected plants immediately, and do not replant box in the same area.
Find out how to identify box blight and prevent its spread, in this clip from Gardeners’ World:
Here, Monty Don takes action to rescue his diseased box hedging. Armed with a hedge trimmer, he demonstrates how to cut out the blight-affected growth, explaining how and where to cut, and why this should help to save diseased box plants. Afterwards, he shows you how to clean your tools and what to do with your clippings to avoid spreading the blight spores to other unaffected box plants:
Box tree caterpillar
Box tree caterpillar is a serious problem that is now affecting box across much of the UK. It is the larvae of the box moth, which feeds on box leaves, rapidly defoliating the plant and reducing it to a bare skeleton. Native to East Asia, it has no known predators in Britain and therefore causes huge damage to the host plant. Signs to look out for include distinctive cobwebbing around the foliage and small eggs laid on the underside of leaves. Box moth caterpillar must be managed promptly. Caterpillars can be picked off by hand if you can spot them, and the webbing around leaves removed. They can also be managed by careful and repeated use of pheromone traps, biological controls and insecticides. Be sure to examine the whole plant carefully and treat it thoroughly.
There is also another type of blight that affects box, but this does less damage to plants. Symptoms are similar to box blight, but there is no black streaking and you may notice pink spores on the undersides of the leaves. Cut out the affected areas in dry weather, binning the prunings and disinfecting your tools afterwards.
Yellow, orange or red leaves
This is a sign of some kind of stress to the plant – usually not enough water in summer, or waterlogging in winter. If the plant is growing in a pot, it may be rootbound, or is not getting enough nutrients from the compost in the pot.
Yellow leaf tips
Yellow leaf tips and edges are usually due to cold weather in winter.
Stunted, cupped growth
Box sucker can cause the tips of leaves to look stunted or cupped in spring. It is not a serious problem – cut away any affected areas.
How to propagate box
Box is easy to propagate by taking cuttings. You can also grow box from seed, but it takes several years to produce plants suitable for planting out.
Follow Monty’s guide to taking box cuttings, below:
Buxus sempervirens varieties to try
- Buxus sempervirens – the common box is native to the British Isles and has small, evergreen leaves and a dense habit. It’s a popular choice for hedging and can be clipped into all manner of shapes for topiary.
- Buxus microphylla ‘Golden Triumph’ – one of the hardier cultivars of this Asian species, with slow growing, smaller leaves. Young foliage starts yellow, turning a yellowish green two-tone. It can be grown in full or partial sun and thrives in moist, yet well drained soil.
- Buxus sempervirens ‘Suffruticosa’ – this dwarf form is a slow growing, denser shrub than common box. It’s a good choice for low hedging and is commonly used for parterres and knot gardens.
- Buxus sempervirens ‘Blauer Heinz’ – a slow-growing box variety with blueish-green foliage. This plant is used for hedging and topiary, especially balls.
- Buxus sempervirens ‘Rocket’ – a fast-growing variety, with a narrow, upright habit that makes it a good choice for taller hedging.
- Buxus sempervirens ‘Elegans’ – a variegated type of box with a medium growth habit. Leaves have a creamy-silvery border.