Gardening: Social climbers with a taste for heights - Clematis, for all its singular beauty, performs best when forced to twine through competing greenery, says Anna Pavord

THERE is always room for another clematis in a garden. They are admirably adaptable and unterritorial, since they always look better growing through other plants rather than plastered against a wall on their own. The question is, which other clematis?

You would have thought by now that every combination had been worked out in this large family. Not so. Keith Fair of Valley Clematis in Lincolnshire has introduced 14 new varieties into his catalogue this year.

One of them I could have done without. This is 'Multi-Blue', discovered as a sport in a Dutch nursery, where a plant of the well-known single purple-blue clematis 'The President' suddenly produced an abundance of double flowers. The bloom's centre became like a great prickly thistle, almost totally obscuring the flat outside petals.

This might have worked, if, as in 'Vyvyan Pennell', the doubling centre had the same intensity of colour as the main petals. Unfortunately, because there is so much greenish-white on the backs and tips of the aberrant central petals, 'Multi-Blue' just looks ill. I would have quietly jumped on it at birth and in doing so would have deprived the clematis trade of some useful profit. 'Multi-Blue' has been a great success.

Doubles are more difficult than singles to grow successfully, especially in the wet, windy sort of summer that we have had this year. The blooms are fragile and easily damaged. They need to be sited much more carefully than the easy-going singles.

The double blooms only come from old wood. The flowers that the single clematis 'Mrs Cholmondeley' produces late in the season are exactly the same as those that appeared in the first big May-June flowering, but double-flowered clematis will only

produce singles for their second crop. This is because the late crop is carried on new growth rather than old.

Heavy pruning of a double will also cause it to bear single flowers, as the growth is not sufficiently mature to produce doubles. But at their best, doubles are undeniably showy.

The one I liked most on my recent trip to the Valley Clematis nursery, was 'Royalty'. It is a darker purple- blue than the well-known double 'Vyvyan Pennell' and, I gather, more sensible about the timing of its flowers. 'Vyvyan Pennell' often gets going too early so that its first flower buds are massacred by frost.

'Royal Velvet' was one of the most interesting of the nursery's introductions. Each flower on the same plant seemed to be a different colour. Some were deep purple while others had a magenta stripe on a blue ground. Some were pale violet, the petals suffused around the edges with magenta.

The colour change is not linked to the ageing of the flowers; the greatest variation in colouring comes with the first flush of blooms in May and June. The second crop is invariably pale. It is a compact clematis, which can be an advantage. When you are growing in tubs, for instance, you want to avoid 20ft monsters. Clematis generally do well in containers, provided they are large enough. Half barrels are ideal.

I would not put a clematis in a pot that was less than 18in tall and wide.

A terracotta pot will keep the compost inside cooler than a plastic pot. Use a heavy John Innes compost (No 3) if possible. This holds more nutrients than a soil-less compost. It is also heavier, so that the pot will be less likely to keel over in a wind.

Plant the clematis rather deeper than it has been growing in its nursery pot. This will encourage it to make new shoots and roots. Mulch the surface of the compost thickly with gravel, which will help to conserve moisture and keep the compost cool. In very hot weather, water through a length of pipe sunk vertically into the container, so that the water goes directly to the roots.

'Lady Northcliffe' (one of my favourites) is good in a tub, because it rarely grows more than 8ft high and is generally easy and compact. The flowers are clean and simple, a good, clear, rich purplish blue. The stamens make a contrasting boss of greenish white. 'Lasurstern' behaves equally well.

Stripped of its flowers, clematis are scraggy, insubstantial plants. Because tubs always concentrate the eye, such defects are noticed more in this situation. Even in a tub, you may do better to establish a host shrub first, then add the clematis later.

Senecio would work. It grows easily in a tub and can be snipped and clipped to keep a balanced, manageable shape. When it has reached a reasonable size, introduce the clematis. 'Lady Northcliffe' would show up beautifully against the grey leaves.

So would C. durandii, which has equally rich flowers, although they are borne on longer stems. In winter, you will still have the senecio to look at. If the clematis were growing on its own, there would only be a tangle of dead-looking brushwood.

In a shady position, the variegated dogwood, Cornus alba 'Elegantissima' makes an equally good host. It, too, can be established in a tub, although it will never look as happy as it does growing in open, heavy, damp ground.

Use it as a prop for Mrs Cholmondeley's daughter, 'Alice Fisk', which has pale blueish flowers. This will be a cool combination, but unfortunately the flowers, like the mother's, die noisily. If you want a stronger colour contrast, use 'Niobe', a deep, rich velvety red with pointed petals. This is an excellent clematis, introduced from Poland in the mid-Seventies. 'Rouge Cardinal' has flowers of the same velvety texture but needs sun.

When sending a clematis up a tree, you need something with vigour. C. montana is often recommended. Only on the right tree: it needs to be big and not a spring-blossoming tree. C. montana in an old apple tree is wasted, since apple blossom and clematis flowers come almost at the same time.

On an old fruit tree, you would get better value from a late-flowering clematis, such as one of the viticella types that flower from July to September. 'Polish Spirit', a recent introduction, has purple flowers that are slightly larger than others of this group.

'Gipsy Queen', introduced in 1877, can also confidently tackle a tree. It is vigorous and has flowers of the same velvet purple as the famous C x jackmanii. This variety also has a better middle: a showy boss of dark stamens. 'Madame Baron Veillard' is late, but sometimes too late, getting frosted before it ever comes into flower.

It would be a good plant for a cool

conservatory.

Of course, I did not come away from Valley Clematis empty handed. The choice was difficult: 'Niobe', which I loved for its clear, brilliant colour, or 'Prince Charles', not yet in the catalogue, although Keith Fair hopes to have enough plants to be able to introduce it next year?

'Prince Charles' has small greyish- blue flowers and lots of them. The leaf is small and easy-going. It is just the sort of clematis that I can see working its way happily through a tall winter- flowering viburnum that is very boring for the rest of the year.

In the end 'Prince Charles' won. But I am already finding reasons for another trip to Lincolnshire. Actually, there is always room for several more clematis in the garden . . . .

Keith Fair of Valley Clematis will be at the Hampton Court Flower Show next week. The nursery, at Hainton, near Lincoln is open daily, 10am-6pm, (0507 313398). Mail order plants are sent out from September onwards. Orders must be placed early. Some varieties are always in short supply. Catalogues cost pounds (Photograph omitted)