There are two roads leading from Chepstow to Monmouth, the A466 through the Wye Valley via Tintern and the other, the B4293 on the western side of the hills, overlooking small fields and hedgerows in this part of rural South Wales. Along this road is the village of Devauden and nearby is Veddw House (pronounced Vedd oo) where Anne Wareham and Charles Hawes have spent the last 13 years making a garden full of allegory and symbolism as well as plants, with more than a dash of fun and fantasy.

They have 0.8ha (2 acres) of garden and about the same area of woodland. Anne designs and plants the ornamental areas, including the woodland, while Charles concentrates on the immaculate geometry of the vegetable plots and on growing his other passion, clematis. The whole is a highly personalised place for people who love to garden, with broad effects and, on closer inspection, intricate details. It is also somewhere for Anne to display many of her artistic creations.When considering the layout and the design of the garden which is still in progress Anne is concerned first with space and form.

The terrain of Veddw House is difficult, with slopes in many directions, and she tries to create pleasing lines. She will remove plants to reveal the curve of the land, while in other places she will use one plant en masse, such as a triangle of 1.5 m (5ft) tall, spiky, blue green Leymus arenarius (Lyme grass), to emphasise a particular area or shape.

In front of the house there are four rectangular flower beds punctuated by spheres of clipped box, Osmanthus and honeysuckle. Bravely, Aegopodium podagraria 'Variegatum' (variegated ground elder) is used as ground cover to unify the planting, despite its invasive tendencies. Behind the garage, rapidly disappearing beneath Rosa filipes 'Kiftsgate' and a Clematis montana, a semicircle of lavender overlooks a grey border with eucalyptus, R. Felicia and buddleia.

There is a north south axis not quite straight through the garden that follows that of the house. It continues between two sentinel juniperus scopulorum 'Skyrocket' and an embryo hornbeam tunnel into a flower meadow and orchard. An avenue of Corylus colurna (Turkish hazel) is called Elizabeth's Walk after Elizabeth Evans, who lived in the house in the 19th century. It leads to an enamel dolphin made by Anne, given pride of place for its graceful shape.

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A cotoneaster walk along the northern boundary contains several hollies and is underplanted with geraniums. A pedestal, with a raised design of grapes and ivy picked out in gold, is a tribute to writer and critic Sir Roy Strong, who believes there is a place for gold in every garden.

Elsewhere, a concrete model of a pig has also received a coat of gold paint and it cocks a snook at good taste from under a cotoneaster hedge.Arches festooned by clematis, including Clematis macropetala 'Wesselton', lead you into the vegetable garden. S mall beds surrounded by wooden edging are divided by brick paths, with box balls in the corners. In the centre are splendid holly lollipops of Ilex aquifolium'. C. van der Tol. The compost bins have been cleverly disguised as beehives.

Apart from tending to vegetables, Charles collects clematis and there are 35 in the vegetable garden alone, including many of the large flowered types deemed too flamboyant for other parts of the garden. On one side of the vegetables is a border of Tulipa 'White Triumphator', Allium hollandicum 'Purple Sensation', delphiniums and Lilium 'Enchantment'.Behind the house, facing south, are the terrace, raised pool and conservatory with pots of tender Clivia, ginger plants and abutilons.

The pool is chest height which makes it perfect for peering into. Behind is the Crescent border, particularly eye catching when many Campanula lactiflora in varying shades of blue are in flower. To the side of this is a holly enclosure which contains three of Anne's enamelled fish, swimming in a sea of Helleborus argutifolius. Anne likes to go wholeheartedly with a plant, using large groups or masses. 'With a strong enough line or planting to start with, you can then add detail to make a bed interesting throughout the year,' she says.

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These south gardens have been laid out in the small V shaped valley which slopes steeply down to the back of the house from the woods above. It is a challenging site. To the east, diagonally behind the 'Fish Garden, broad, new gravelled steps lead up to an imposing black pot. Box plants mask either side of each step, as Anne decided the staircase was too broad but could not be remade: a case of design as problem solving.A magnolia walk, with cultivars of Magnolia stellata and M. soulangeana, has been planted in the shade of the surrounding woodland.

A wild garden contains salmon coloured Oriental poppies, their large, blousy, highly bred flowers quite contradicting the notion of 'wild'. Tough perennials grow in the grass below a thyme scat along with wood anemones and dog violets, which were already resident when Anne and Charles took over, and are a part of the garden's history. There are four cheerful wooden parrots, brightly painted cut-out shapes, that also live here, peeping through the meadow grasses.On the western slope of the tiny valley is a border divided into box compartments, shaped to resemble in miniature the fields on the 1842 tithe map of the area. The 'fields' are planted up with different grasses, and contain two standing stones. These small beds, filled with different greens, evoke the Welsh border country in miniature. Grasses look incongruous with many garden plants, Anne believes.' However, they are an ideal filler for a parterre.' Here, the compartments or 'fields' are filled with tussock forming species such as Pennisetum, Stipa, Fanicum virgatum, Briza media, Festuca amethystina, Deschampsia caespitose and Lazula nivea (snow rush), the latter not strictly a grass.

View over grasses parterre. © Charles Hawes

The low growing grasses do not obstruct the view over the narrow Veddw valley and broader Wye valley. A blue bench is inscribed with a quotation from William Wordsworth's Lines Composed a Few Miles Above Tintern Abbey, which is most apposite to the ancient, mixed hedges of the area:' hardly hedgerows but a line of sportive wood run wild'.A tumble of stones covered in ivy and periwinkle was once a cottage. The surrounding area is more sparsely populated today than in the past and every house here seems to be accompanied by the ruins of an earlier habitation. Near these ruins tough garden plants are often found. At Veddw House there are snowdrops and two different vincas (periwinkles).

The path to the cottage is bordered by beech trees that were once part of a laid hedge. Now their thick, mossed trunks are L shaped: horizontal to the ground for several metres before making a dramatic right an e and growing straight up towards the sky.At the top of the valley, sunlight plays through the branches of the trees over large, moss covered stones, probably dug out of slopes first ploughed after the Napoleonic Wars and piled up here. In summer ferns splay out, adding patterns of light and shade, and a flat trompe d'oeil of an urn on a pedestal stands in the path.

Scattered everywhere are reminders of the site's history, not only of the immediate past inhabitants but also of a much older Wales, symbolised by the standing stones with their rippled and lichened surfaces. Placed to look like the remains of one of the area's many stone circles, they add resonance and a sense of timelessness to the design of the garden.The bottom of the valley has been divided into four compartments with yew hedges. One compartment will be a garden of more shaped yew hedges. The cornfield garden is divided into rectangular plots edged with clipped box and rails decorated in gold with the names of wild flowers. Cornfield annuals are grown in the beds. The two other spaces are gardens yet to be. One will have a reflecting rectangular pool, but the other awaits a decision on its future use.

Reflecting pool. © Charles Hawes

The wood represents the wilder side of the garden. Its gate was made by Anne and contains a silhouette of a waltzing fox and hare, an indication of the slightly surreal atmosphere that lies ahead. An enamelled lizard is captured in time climbing a tree trunk. Other trees are distinguished with plaques and poems on enamelled tablets, again made by Anne. Lines from TS Eliot and Philip Larkin create a thoughtful mood. It is reminiscent of lain Hamilton Finlay's garden at Little Sparta in Scotland, a place to be reflective in, but on a more homely scale. A 'Green Man' stares from the trunk of a tree, seemingly growing from the bark, with its fine texture and subtle shades of turquoise and lime green lichen. As in the garden, there are broad effects together with a wealth of detail.

Beyond the boundary of the wood but still visible from it is an old car, gradually disappearing beneath the bracken and undergrowth. Within the wood ' snatching the attention back from the automotive alien are an equally arresting pair of blue chairs and a television, seemingly arranged so that ghostly wood dwellers can relax there in the evening.Planting in the wood, by contrast to some of the ornamentation, is understated. Much of it was larch plantation 15 years ago, but this was felled to allow Anne and Charles to replace the larches with other tree species, shrubs and some perennials.

In a natural, near circular stand of beech embracing a lone oak, the circle has now been emphasised by interplanting holly with the beeches. Elsewhere in the wood they have gradually added different species and cultivars of holly, beech and oak, an avenue of birch and some maples for autumn colour.It sometimes seems today as if garden designing only takes place on perfectly flat,'greenfield' sites with no previous history. Anne Wareham says she does not know what she would do if given a completely flat, clean slate. By weaving in some of the site's early history and the surrounding landscape, what she and Charles have managed to do is to respect the genius loci of Veddw House, its past and its setting, while also making a garden that is very much of its time.

Barbara Abbs is a freelance garden writer and author of Gardens of the Netherlands and Belgium.