Look after them properly and privet, holly, box and yew will give your garden colour and structure all winter, says Monty Don How to keep your greens evergreen

EVERGREENS carry winter magic. When the whole of the plant kingdom seems to be dying and shrivelling up they remain clear and strong, and a potent symbol of life. That’s why we have Christmas trees, holly and mistletoe in our homes at Christmas – to celebrate the evident life in them at the darkest point of the year. The garden needs that lifeforce during these increasingly bleak winter months.

But of course, evergreen plants do much more than just cheer us up. They provide the structure or ‘bones’ to a garden. This can be formal with clipped hedges of box, yew, holly, privet, Japanese holly (Ilex crenata) or half a dozen other evergreen shrubs that make good formal hedges. They can be repeated shapes of topiary cones, balls or even, as I have in my own garden, great blocks of tightly clipped box plants that create a surface like a billiard table. Or you can use this structure informally with trees and shrubs such as mahonia, sarcococca, holly, pines, hebe, choisya, Portuguese laurels, Irish yews, viburnum, camellias, phillyrea, pittosporum, skimmia, pyracantha, euonymus, trachycarpus, and the magnificent holm oak – to name but a few.

I confess I love the clipped structure of green hedges in winter. However, this has become an increasing problem with the spread of box blight. This is a fungus that manifests itself by reducing the otherwise green leaves of box plants to brown shreds and tatters.

The plant will regrow fresh green foliage but this in turn will be even more vulnerable to the spores of the fungus when warm, wet weather returns next summer. Gradually the plant becomes less and less vigorous and more and more of it dies back, so topiary and hedges look terrible all year round. But all is not lost. There are a few varieties that seem to be much more blightresistant than others. I use Buxus sempervirens ‘Handsworthiensis’ for all my larger box topiary and hedges, and varieties such as ‘National’ and ‘Rococo’ are more resistant than many others. Buxus microphylla and especially B. microphylla ‘Faulkner’ seem to be more blight-resistant, and much work is underway breeding more varieties that are resistant to blight.

The main problem is that box fungus gets to the plant via wounds. These can be caused by accidental damage or insects but are almost entirely made by trimming. There is no incidence of box blight in wild or untrimmed box plants. However, topiary or low hedges that are left uncut lose their point. But cutting when the weather is dry (warm, moist air stimulates the spores), disinfecting the blades and giving hedges convex, rather than flat, surfaces so water can run off more easily will all help limit the spread of the fungus.

I am also starting to use yew (Taxus baccata) to replace box and this summer at Sofiero Castle in Sweden I saw a superb parterre made from the yew Taxus baccata ‘Nana’ with hedges clipped to a mere 30cm high. Ilex crenata makes a convincing box lookalike – though it needs some shade and fairly moist growing conditions to thrive.

So we gardeners who want our winter garden to be as green as possible must box clever. Think of all the possible evergreen alternatives, research the best box varieties, practise good plant hygiene and maximise ventilation. But whatever you do and whatever you use – green your winter garden as much as you can.

HOW TO SPOT BOX BLIGHT

There are two types of box blight to look out for.

Cylindrocladium buxicola: The infestation shows first as black spots on the leaves. After a few days these leaves will fall from the bushes and the bare twigs show black streaks.

Volutella buxi: The first symptoms are leaves turning brown. They then dry out but stay attached to the plant for a while. On the underside of each leaf will be the pale pink residue of the spores. Both are serious, although plants show better recovery from V. buxi. n ÷Monty’s new book, Down To Earth: Gardening Wisdom, is published by DK, priced €25.20 from www.easons.com