The origins of this remarkable garden go back to 1868 when Edward Walpole, a Dublin businessman, purchased the lease of a small tuck-mill in a wooded valley on the edge of Rossanagh demesne. It was intended as a weekend retreat, but before long his three sons, Thomas, George and Edward, began enthusiastic ally transforming its one acre of ground into a garden. Edward was so taken with his sons' efforts that he transferred the property to their names in 1875. They continued to develop and enlarge the garden until their deaths - filling it with a huge number of rare and tender plants collected from nurseries throughout the world. From an early stage the Walpoles adopted the naturalistic style of planting advocated by William Robinson, who personally visited and approved of the garden in the early 1880s. This form of planting was continued by a grandson, E. Horace Walpole (1880 1964), and later in turn by his son Robert who sold Mount Usher to Madelaine Jay in 1980. It is this adaptation of a consistent gardening style over most of its long history that has contributed enormously to Mount Usher's distinctive charm.

The entrance into the garden lies at the far end of a courtyard housing a number of antique and craft shops. Passing through a gate the visitor enters a quadrangular area known as the Orchard, bordered by a fine beech hedge planted in 1927. This compartment contains a display of dwarf conifers, a long herbaceous border laid down in the mid 1980s and a number of flowering trees and shrubs, including a small collection of lilac trees. From a hole in the hedge a winding path uphill passes a small pavilion dedicated to the Walpole family and leads on to the Maple Walk - a grassy ride aligned on the river. The colours along here are brilliant in autumn, a palette of scarlet and gold from the maples mingling with the striking blues of the waterside hydrangeas. Summer colour is provided by manuka or New Zealand tea trees, including the rosy red-flowering Leptospermum scoparium 'Chapmanii', while several conifers in the area give contrast, notably a small but elegant Juniperus recurva coxii with gracefully drooping branches and a beautiful false larch, Pseudolarix amabilis, whose pale green leaves turn a golden yellow in autumn.

The Maple Walk draws the visitor down towards the river - the focal point of the garden - where bold and highly effective plantings frame the water's margins. Huge gunnera, royal ferns and umbrella saxifrages have all naturalised here; so too have yellow and white-flowering Iysichitons, mimulus, hostas and numerous candelabra, polyanthus and other primulae. Clumps of New Zealand flax, cordylines, bamboos and pampas give an exotic touch to the waterside, while delicate seasonal colour is provided by a happily balanced planting of conifers and deciduous trees. The views along the river are particularly striking in autumn, the water reflecting the rich yellows, oranges and crimsons of liquidambars, fothergillas, cercidiphyl lums, amelanchiers, acers, willows, dogwoods, swamp cypresses (Taxodium distichum) and a number of very beautiful tupelo trees (Nyssa sylvatica) which look particularly impressive beside clumps of white pampas grass.

South of the suspension bridge lies the main wood land garden at Mount Usher. Dissected by a network of paths meandering their way around an old pond, a wishing well and back down across the old drive, it shelters a wealth of shrubs - viburnums, hydrangeas, pieris, embothriums and rhododendrons - while amongst some of the outstanding plants is a lovely scented Magnolia obovata from Japan, a large Chilean Lomatia ferruginea and a very tender Agathis australis - the Kauri pine. Visitors will also come across a beautiful New Zealand rimu (Dacrydium cupressinum) and a good specimen of the unusual kawaka (Libocedrus plumosa).

The croquet lawn close to the river boasts some especially memorable trees: two rare and striking Chinese firs (Cunninghamia lanceolata), a tall and very lovely specimen of Cupressus cashmeriana with drooping branches planted in 1875 and a magnificent fifteen-foot-high American Eastern hemlock (Tsuga canadensis 'Pendula'). From here visitors taking the Azalea Walk will notice an imposing fifty-foot-high Pinus montezumae from Mexico planted in 1906 by Lord Powerscourt, perhaps the most august tree at Mount Usher. The Azalea Walk, a long grassy ride through the garden, is lined with rhododendrons, a variety of fine davidias and azaras, the fragrant white flowering Magnolia salicifolia and a quantity of Eucryphia glutinosa whose large white, golden centred flowers are a splendid sight in the fading months of summer.

At the far end of the Azalea Walk a grove of spectacular eucalyptus trees includes E. viminalis, E. stuartiana, E. delegatensis and E. urnigera, some over 130-feet tall. Over seventy varieties of eucalyptus have been planted in the garden since 1905 when seed was first imported from Australia, and today Mount Usher can claim the finest collection in Ireland.

Crossing the southernmost bridge, built in 1924, the visitor next arrives at the imposing Palm Walk - a broad grassy vista that extends outwards from the house and lined with Chusan palms (Trachycarpus fortunei). In the area to the south stretches the main eucryphia collection which features clumps of the special hybrids E. x nymansensis 'Mount Usher', the result of a cross made in 1916 between E. glutinosa and E. cordifolia. The Lime Walk to the north has an excellent collection of ornamental southern beeches seeded in 1928. Among the eight species represented are Nothofagus solandri and N. menziesii from New Zealand, both over fifty-feet high. Certain to astonish is a fragrant silver wattle from Australia (Acacia deal bata) that was planted in 1950 and now stands an amazing sixty feet in height.

Running beyond the house, a tributary path leads past one of the original plantings at Mount Usher - a redwood Sequoia sempervirens planted around 1870. From here the visitor enters the area known as the Island which is crossed by a maze of little meandering paths. Plants to note include an Acer laevigatum reticulatum with net-veined leaves, the evergreen Chinese spindle tree (Euonymus wilsonii) and a large Magnolia x veitchii that is a glorious sight in spring with thousands of purple-pink flowers blooming on naked stems. A lily pond on the edge of the area is surrounded by ornamental rushes - such as the reed mace Typha augustifolia - and with water irises.

The Riviera is the most recently planted area of the garden - a long narrow strip bordering the river. This section can be quite noisy, particularly during market time on Mondays, but a walk along here is nevertheless rewarding. Tree enthusiasts will be pleased by a fine grouping near Penelope's bridge: a massive spreading eucalyptus, a lovely golden-yellow Thuja plicata 'Semperaurescens', a number of slender taxodiums, a fine erect Lawson cypress 'Silver Queen' and a splendid Pinus montezumae tree whose branches trail the river's edge. Before leaving the garden, visitors should walk along the Kitchen Garden wall where a fine specimen of the Japanese banana tree (Musa basjoo) graces the scene - always a popular plant at Mount Usher and a suitable climax to a journey around this verdant Wicklow paradise.

Located in Ashford on the main Dublin to Wexford Road. NGR: T 258977. Tea room. Gift shops. Toilet facilities. Partly suitable for wheelchairs. No picnics. No dogs. Admission charge. Tel: (0404) 40116.

From the Appletree Press title: Irish Country Houses.