Part of the fascination of Altamont is its complex history. The central portion of the house was built by the St George family in the 1770s, incorporating an earlier building which may include portions of a medieval nunnery. The early house faced north, but after the building of a new road to the east it was reversed and new avenues laid down with handsome gates and surrounding beech plantations. These remain unchanged, but the area to the north was dramatically altered during the 1840s by the Dawson Borrer family who had by then acquired the property. Using the abundant labour available during the Famine, a large lake was dug, terraced lawns created and a central broad walk extended down to the lake with flanking yews and beds. In the early part of the present century the property was acquired by Feilding Lecky Watson, a plantsman with a keen interest in rhododendrons which he grew from seeds acquired through sponsorship of Himalayan expeditions, such as those of Kingdon Ward's, and through exchanges with other gardens. After his death in 1943 the garden slid into genteel ossification, but since the 1970s his daughter and present owner, Mrs Corona North, has embarked on a major programme to revitalise and transform the gardens. The lake has been dredged, the walks cleared, new areas created, such as the Bog Garden, and a wide ranging collection of plants have been added.

Upon arriving visitors pass the bowed front of the house, whose mellow-coloured façade is covered with a venerable wisteria and Parthenocissus henryana. On the east wing stands a beautiful thirty-foot-high Rhododendron augustinii, one of the finest of all rhododendrons and named after Augustine Henry, the Irish customs official and plant collector. To the left of the hall door, amidst a variety of lush planting, is a fine specimen of the fragrant Clerodendrum trichotomum fargesii - a present to Altamont from Lord Rosse around 1960 and noted for its bright blue berries in autumn.

From the car park the visitor approaches the gardens through an antique iron gate, passing the tea room and a little courtyard opposite filled with plants, including a thriving Myrtus apiculata 'Glanleam Gold'. A small gate beyond leads onto the beech-lined Nun's Walk whose origins may go back as early as the seventeenth century. In the shade of the trees to the right, flanked by aromatic skimmas, lies the entrance to the garden centre and nursery in the Walled Garden. Further down the walk a path to the left, leading to the formally laid out beds in front of the house, passes beneath a spreading Parrotia persica whose leaves turn a lovely crimson gold in autumn.

Flanked on either side by substantial beds, a rectangular goldfish pond shimmers directly below the perron in dramatic alignment with the central walk to the lake. The bed on the right, bordered with box hedging, contains a collection of dwarf conifers and shrubs underplanted with heathers and bulbs. Plants here include Picea koraiensis, grown from seed brought from Peking, a specimen of Abies koreana and the Irish dwarf pine Pinus sylvestris 'Hibernica'. The opposite bed contains a wealth of plants: golden bays (Laurus nobilis 'Aurea'), a silver-variegated dogwood (Cornus alterifolia 'Argentea') and the tree peony P. lutea ludlowee - a splendid variety brought back from Tibet by Kingdon Ward. There are also choice buddleias and willows, aromatic French lavender and a variety of perennials, notably the variegated brunnera, the deep purple-leaved heuchera and foxtail lilies, whose stately spires always make a great show in summer. Here too are clumps of the Irish-bred Primula 'Garryarde Guinevere' first shown in Dublin in 1935 and distinguished by its yellow-eyed purple-pink flowers and its fine bronze foliage.

The central broadwalk down to the lake is flanked by clipped Irish yews and box-hedged beds framing roses that are underplanted with daffodils and tulips for spring colour. Modern floribunda and hybrid tea roses occupy the top beds, while further down old fashioned varieties predominate, such as the richly fragrant Damask rose 'Mme Hardy' and the gorgeous light pink Alba rose 'Celeste'. Across the lawn to the left is a little octagonal pool shadowed by a large Magnolia stellata and beyond, a fine fern-leaf beech probably planted around the 1 840s. An equally old holm oak dignifies the area, while other fine trees along this side of the garden include a yew at least three centuries old, a sweetly scented balsam poplar and adjacent to the lake, a venerahle Prunus 'Ukon' with unusual creamy-green flowers.

The lake-side planting beyond the sundial proffers quite a variety of moisture-loving plants, including a good selection of hostas, candelabra primulas, astilbes, gunnera, hydrangeas, saxifrages and some blue poppies, such as the Kingdon Ward variety Meconopsis betonicifolia. In this area striking specimens of the swamp cypress Taxodium distichum and the rarer T. ascendens, as well as a Kilmacurragh cypress and a dawn redwood, flourish.

To the right of the sundial a lovely pocket handker chief tree and a tulip tree, both planted thirty years ago, reward the eye. Close by is a splendid Rhododendron cinnabarinum with scented tubular flowers of terra cotta orange, planted in 1917. The path here to the Azalea Walk passes a border of peonies underplanted with orange tiger lilies, cyclamens and colchicums for seasonal colour. At the bridge another old rhododen dron branches forward - an unnamed arboreum cultivar with pink-red flowers and black freckles.