Box is most commonly used in gardens as a clipped, formal plant or hedge, although there are many types available that are ideal for more naturalistic planting - where they are allowed to develop without pruning.
For larger hedges Buxus sempervirens is a popular choice. B. sempervirens ‘Suffruticosa’ is a much slower growing cultivar suitable for parterres and small hedges, whereas B. microphylla is a naturally compact form of box that needs no clipping. For variation in colour grow the yellow spotted B. sempervirens ‘Latifolia Maculata’ or the cream-edged B. sempervirens ‘Elegantissima’.
Planting
Many of the species originate from limestone regions, but box is tolerant of a wide range of soil types, provided they have adequate drainage and do not dry out. A reliably moist soil is especially important if growing in full sun, otherwise the foliage may scorch. Box will tolerate deep shade and is ideal for planting beneath taller trees.
Box should be planted in autumn or spring. On poorer soils spread organic matter, such as well-rotted manure or garden compost, over the prepared area and fork in. Water thoroughly once a week in dry weather and, once established, apply a general-purpose fertiliser in spring and lightly mulch to a depth of 2.5cm (1in). If well cared for, small plants should form a reasonable hedge or parterre within three to five years.
Plant Buxus sempervirens about 30-40cm (12-16in) apart, more compact cultivars, such as ‘Suffruticosa’ and Buxus microphylla, can be planted 10-15cm (4-6in) apart.
If planting in containers use a loam-based John Innes No 3 compost. Top dress established container-grown plants in spring with fresh compost with a little controlled-release fertiliser, Vitax Q4 or blood, fish and bone. During summer liquid feed and ensure plants do not dry out.
Cut back young hedging plants and topiary to encourage bushy growth by up to one-third. Trim mature hedges and topiary twice during the summer with the first cut in about late May and the final cut before the end of August. Old, neglected plants usually respond well to hard pruning in late spring and can be cut back to within 15-30cm (6-12in) of the ground.
Propagation
Box is usually propagated from cuttings. Cuttings of semi-ripe wood will root in the open ground if the soil is moist and there is some shade. More reliable results come from placing cuttings in a cold frame or similar environment; a heated propagator will speed the rooting process. Expect roots to develop after eight weeks as opposed to up to eight months without heat.
Problems
Excessive sunlight can cause discoloration and sun-scald to leaves. General bronzing of the foliage is also due to environmental stress usually following hot, dry spells in summer, although a contributing factor may be root damage due to winter waterlogging.
Over winter leaf tips and margins commonly yellow due to low temperatures. Leaf discoloration will tend to be more common in exposed sites. Young growth in spring can also get caught by frost. Usually an application of fertiliser in spring, to encourage fresh new growth, and clipping rectifies these problems.
General yellowing of foliage may be symptomatic of waterlogging, especially on heavy clay soils. Roots subjected to waterlogging are usually a blue-black colour in cross section and fall apart when teased out. Damaged roots should be removed, top growth trimmed back and the box replanted.
Box is susceptible to box blight and box sucker.
Helen Bostock