Gardening: Ponds' beauty treatments - A pool in the garden can be set off to enchanting effect by the right foliage, says Anna Pavord

Reginald Farrer, the celebrated Edwardian gardener, had this advice for anyone about to build a water garden: 'Don't' He went on to paint a gloomy picture of slime and duckweed, rotting leaves, diminishing bank accounts and ruined dreams.

The dream, though, is a potent one: you imagine dragonflies and flag iris, you hear in your mind that cool, soothing, rippling sound that water makes as it comes out of a wall fountain or tips itself over a small waterfall. Italy in Fulham.

It can be done. Go to Anthony Noel's London garden to see how. Being a garden designer, he has an unfair lead over the rest of us when it comes to interpreting the dream. His garden could scarcely be smaller but he thinks big, and his fountain is only the latest in a series of grand gestures, all of which are made in a patch only 17ft wide.

To visualise the fountain, think fireplace. It is built against one of the side boundaries, a brick wall about 6ft high. The plumbing is hidden inside a matching brick facade (the fireplace) that juts out about a foot from the wall. This is topped off with a mantelshelf of stone. On the front is a big mask, with water gushing from the mouth. The size of the mask is important. It is three times bigger than most you see, and three times more effective. The water falls into a raised rectangular pool, also built of brick, which butts on to the boundary wall. The walls of this pool are topped with the same stone as the mantelshelf.

Most people would have stopped there. Mr Noel took the conceit one stage further and added jets which spray from the two outer corners of the pool back towards the mask. Then he stood two large, stumpy watering cans on the corners of the pool so it looks as if the jets are coming from them. At this stage, for me, it becomes too clever by half, but the rest I covet unreservedly.

On the mantelshelf he has set a series of topiary box balls, planted in terracotta pots. They echo the stone balls balanced along the top of the boundary walls. More pots, smallish ones, mass-planted, sit on the pool's retaining walls with the watering cans. This is not the kind of pool that needs much planting. It is formal, classical, architectural.

This kind of water feature, more upright than horizontal, is ideal in a garden where ground space is at a premium, but is not as common in English gardens as the informal pool, usually made with a butyl liner and planted quite thickly round the edges with bog-loving plants. Paradoxically, I think this style is more difficult to achieve than a formal water feature.

Many informal pools are too small. This is scarcely surprising when you consider the cost and labour of excavating them, but if they are mingy the rest of the garden looks uncomfortable, too. The pool must look like a pool, not like an oversized puddle that happens not to have drained away. Then there is the shape. The ideal shape for an informal pool echoes the lines that water would take if it had happened to flow into that spot. Curves need to be gentle, outlines simple.

Foliage and water are as natural a double-act as Laurel and Hardy, but for the best effect you must be sure that the scale of the one is in keeping with the size of the other. Avoid weeping willows, which at maturity can be as much as 80ft wide and high. That is more than most gardens can take. If you plant an upright willow, perhaps one with brightly coloured winter bark, you can pollard it in the old-fashioned way and keep it within bounds. Pollards grow into trees of great character. You still see old ones along the waterways of the Somerset levels.

You can get the right effect of lush leafiness without using a tree, but before you start planting bog plants, you need to be sure that the ground you are putting them in will retain the right level of bogginess.

Your best friends will be rodgersias, astilbes, hostas, primulas, all of which will contrast with the stiff upright sword leaves of a water iris, perhaps the variegated I pseudacorus 'Variegata'. If you are planting a larger stretch of water, you need plants built on a grander scale, perhaps gunnera, which has leaves big enough to picnic under in a rainstorm.

Rodgersia aesculifolia has a leaf made up from a series of leaflets arranged like the spokes of a wheel, radiating out from a central stalk. Most leaves grow in the same plane as their stalks. The rodgersia's are at right angles to it.

When the leaves emerge in spring, they are richly bronze. Later, usually some time in June, the leaves are accompanied by thick sprays of buff-pink flowers, the texture of plush. This is a plant that never has an off-season, but unfortunately it is not evergreen.

The bronze foliage of rodgersia and many astilbes provides an excellent backdrop for grassy clumps of the golden sedge Carex elata 'Aurea'. Sedges are not grasses, but they look and behave like ornamental grasses and have the added advantage of doing best in damp soils. They are evergreenish. The -ish implies that there is a particular period in winter when they look so tatty that you wish they would go the whole hog and die down until the spring.

Now, though, they are at their best, shining with new spears of green-gold grassy leaves. The flowers are brown, furry caterpillars climbing up the stems towards differently furry spears at the top. They are bizarre in the extreme.

The iris can be planted in the water, if need be, or at the water's edge in the boggiest part of the ground. If you are planting in the water, you will need to sink the roots in a wire basket, weighted down with stones. Like many variegated plants, the leaves are at their most striking now, early in the season. The flowers which come in early summer seem to suck their yellow colour from the leaves, for after blooming, the iris's foliage loses much of its variegation. I pseudacorus 'Variegata' has leaves striped with a pale greeny yellow, not such a dramatic livery as the variegation of the other popular water iris, I laevigata 'Variegata'. But the other is taller. That can be an advantage.

Do not plant too closely. Plants with fine form, such as the rodgersia, are less effective when jostled too close by other distracting vegetation. If you combine the rodgersia, the iris and the sedge with late- flowering hostas and lobelias, a poolside planting can have a long season of interest.

Use a hosta such as H plantaginea, which has huge paddle-shaped leaves and late, beautifully scented spikes of flower. Royal ferns (Osmunda regalis) and various primulas would be equally at home in this type of planting.

Anthony Noel's garden at 17 Fulham Park Gardens, London SW6, is open tomorrow (2.30- 6pm), also 19 June, 10 July and 18 September; admission pounds 2.

(Photograph omitted)