Don't let highlights go to your head: Do not overdo the colour in your garden. When it comes to background, you can choose any shade - as long as it's green, says Stephen Anderton

Last October I spent a weekend in the Lake District looking at trees. The weather was perfect: soft light falling upon soft colours. The top of Borrowdale was idyllic. The steep sides of the valley were clad in a mixture of larches, beech and sitka spruce, producing a rolling tapestry of greens and old gold.

Only one thing ruined it. Next to a generously proportioned white-painted house at the foot of the hill stood a 60ft yellow Lawson cypress, probably the form Chamaecyparis lawsoniana 'Lutea'. In among all these soft and variable colours the cypress was a foul, hard, outrageous acid yellow.

Wordsworth, even in paroxysms of daffodil worship, would have condemned it. It was as artificial and alien in Borrowdale as a 60ft billboard. My companion of the day suggested that the owner should have sought planning permission before planting it.

Well . . . idylls are, by their nature, short-lived. I dare say the tree might have looked less artificial in high summer, against a variety of rich, dark greens. And perhaps, considering it rains more often than not in the Lake District, such a splash of yellow may be regarded locally as cheerful rather than brash.

But there is a big lesson here for gardeners. You do have to be very careful how you use highlights in a garden. They need to remain just that: a glimmer of brightness which clarifies and accentuates the general structure.

There are two common ways of overdoing the thing: either by overcolouring something that is big enough to be part of the background and structure of the garden, or by putting in so many highlights that they cancel each other out.

The Borrowdale tree was a case of overcolouring: something in almost any shade of green would have better blended with the scene.

In a similar way, in topiary gardens, you should keep the structure green. A collection of pieces in dark green yew alone looks eminently classy. By all means add in a piece or two in golden yew, which will lift and lighten the effect. But put in too many and you lose that wonderful, discreet sobriety which is the essence of a topiary garden.

The same holds true for hedges. They are part of the structure of a garden and are almost always more appropriately made of a green foliage, against which the finer details of planting can be contrasted.

A green structure, being plain or 'neutral' coloured, gives you so many more options. You can plant any colour scheme - from pink to yellow to purple - in front of green hedges, without any clashes or near misses; whereas to plant yellow or purple hedges is to take a great risk. They command so much attention that finer adjacent plantings are frequently upstaged.

When the Prince of Wales's garden at Highgrove is featured in print there is always a photograph of the avenue of man-high golden yew domes flanking a broad path up to the house. They are a fine sight, each tightly clipped to a perfect hemisphere, marching along in a parade of old gold. But I have a sneaking suspicion that, from time to time, His Royal Highness may wish that when he took on Highgrove, it had been planted with perfect hemispheres of good, dark- green yew. It would have been so much more flexible.

No gardener would ever be hard enough, surely, to grub out such splendid imperfection, but when you plant a major feature in golden yew, posterity has 500 years to ponder whether or not you got it right. Would anyone buy a shell suit if it had to last 500 years?

Because conifers retain their colour and substance all year round, you should take special care not to plant too many fancy highlight varieties. At a nursery where conifers are raised you are likely to see row upon row of gold varieties, blue varieties, grey varieties, cream- and white-speckled varieties . . . anything, in fact, but green varieties. Every one could be effective as a highlight, but when they are herded together they do themselves no justice at all.

Go into a nursery where buttonhole carnations are reared and you will see colour chaos. But select just one or two varieties and set them against white satin or charcoal worsted, and you have style indeed.

Sticking my neck out (again), I would suggest that a comfortable, relaxed-looking garden of evergreens should contain no more than 10 per cent of yellow or blue foliage; and that if both yellow and blue are to be included, one should be used very lightly. (Think what is said about women who apply the blue eye-shadow with a trowel.)

Shades of green and foliage texture provide all the other variety necessary. Think what value there is in such broad-leaved evergreens as holly, rhododendrons, all the different glossy laurels, Pieris and Osmanthus. There are lighter textures in Azara microphylla, tree heaths and bamboo, and the greener eucalyptus.

We laugh nowadays at the more sombre manifestations of high Victorian gardening, the endless green seas of cherry laurel and Portugal laurel, and free-standing 'specimens' sprouting up from every lawn. It may have been all rather fixed and formal, with little of the complex, mixed planting we enjoy today. But there is no doubt that they knew how to treat fancy, exotic varieties with respect, and to make them undisputed highlights. The Victorians would surely regard the way that we mix blue, green and yellow in equal proportions today as a most indiscriminate mannerism.

(Photograph omitted)