Occupying a beautiful forty-eight acre site on the banks of the Tolka River it contains over 20,000 different plant species and cultivars including many exceptional specimens. There are some lovely trees, many outstanding displays of shrubs and perennials and, of course, the famous glasshouses, including Turner's magnificent curvilinear range.

The botanic gardens were established in 1795 under the auspices of the Dublin Society, later the Royal Dublin Society, at the behest of the Irish Parliament to 'promote a scientific knowledge in the various branches of agriculture'. The twenty-seven-acre site chosen for the garden lay outside the hamlet of Glasnevin on the former demesne of Thomas Tickell, a minor poet and ardent admirer of Joseph Addison, the statesman and writer. A survival from this period is a double line of yew trees known as Addison's Walk which Tickell probably planted in memory of his much-esteemed patron.

The original botanic gardens were laid out by their first director, Dr Walter Wade, Professor of Botany to the Dublin Society, with the help of the first superintendent, John Underwood. After Wade's death in 1825 the gardens went into a period of decline but were resurrected and redesigned by the new director Ninian Nivan between 1834 and 1838, with further modifications carried out by his successors Dr David Moore (1838-79), Sir Frederick Moore (1879-1922), J. W. Besant (1922 44) and Dr T. J. Walsh (1944-68).

Over the past two centuries the gardens have played a central role in botanical and horticultural advance ment in Ireland. Plants and seeds have been imported and new cultivars and species distributed to gardeners and nurserymen. The fastigate gorse Ulex europaeus 'Strictus', found at Mount Stewart in 1804, was the first cultivar to be introduced from Glasnevin and this has been followed by numerous others, such as the pampas grass Cortaderia selloana, the pink-flushed lily Crinum moorei from Nepal, the beautiful Chatham Island daisy-bush (Olearia semidentata), the exquisitely scented Abelia triflora, and the giant lily Cardiocrinum giganteum. In the 1840s orchids were cultivated from seed to flowering stage for the first time at Glasnevin and it was here in 1869 that hybridisation of the insectivorous pitcher-plants sarracenia was first carried out successfully.

The soil of the Glasnevin Botanic Gardens is heavy alkaline boulder clay, which confines the growing of calcifuge plants such as rhododendrons and ericas to specially prepared peat beds. There are, however, a wide range of habitats within the garden and these are incorporated within a botanical rather than geographical layout. They include special areas devoted to roses, ground cover plants, economic and poisonous plants, native plants and herbs and vegetables. Glasnevin also houses a large rockery, a bog garden, a wild garden and a double, curving herbaceous border which is a marvellous sight in summer.

Many more plants are grown in the Victorian glasshouses. These buildings have long been a great attraction of Glasnevin, especially the curvilinear range which was commissioned by David Moore in the 1840s and is now in the process of being restored. The central pavilion and one wing of this range was built by Richard Turner, the Dublin-born ironmaster, and completed in 1848. Twenty years later Turner ingeniously doubled the building in size by removing the walls and extending it back.

The Great Palm House containing the tropical tree collection and notable now for its cycads was built in 1884, while its side wings, housing orchids and flowering pot plants, belong to an earlier building. On the east side of the garden lies the Victoria or Aquatic House which was built in 1854 to protect the gigantic Amazon water lily - at that time only recently introduced and one of the wonders of the age. The lily can still be seen growing here during the summer months. On one side of this building lies the Cactus and Succulent House built in 1890, while on the other stands the Fern House - a rather dull aluminium glasshouse constructed in 1966 to replace an attractive Victorian octagonal conservatory. This Fern House is divided into separate compartments for tree ferns and tropical species. Here amidst dense foliage the visitor will find the native but rare Killarney fern Trichomanes speciosum and the Australian tree fern Todea barbara, which had been transferred here in 1969 from the old Trinity College Botanic Gardens and is reputed to be 400 years old.

Although the gardens at Clasnevin will celebrate their bicentenary in 199S, very few of the trees and shrubs were planted more than a century ago. One of the older plants is the Chusan palm (Trachycarpus fortunei), planted outside the curvilinear range in 1870. Other majestic, patriarchal trees are a Cedrus atlantantica 'Pendula' planted some time before 1877 and a large Zelkova carpinifolia that looks especially good in winter.