The gardens cover twenty acres, including a four-acre walled garden, and lie to the west and north of Malahide Castle. They form part of a 250-acre demesne park acquired by Dublin County Council in 1976 following the death of Lord Talbot de Malahide. The history of the Talbots at Malahide stretches back to the end of the twelfth century, but the gardens are the creation of Milo, the seventh Lord Talbot de Malahide-a noted plantsman who assembled a collection of over 5,000 species and cultivars between 1948 and 1973. Close connections with Australia resulted in Australasian genera being particularly well represented, but Lord Talbot also had a fondness for South American plants and was a recognised authority on the genus Olearia-interests that are still reflected in the planting today.

Visitors approach the main garden ñ a varied mixture of trees and shrubs known as the West Lawn ñ from the front of the castle. Passing just beyond a blue conifer, Cupressus glabra 'Pyramidalis', the main focus of the garden layout comes into view on the left ñ a spacious lawn dominated by a large cedar with spreading cyclamen below. The main shrubberies, divided by a network of grass rides and interlinking paths, are to the right, while the avenue area, which also contains some rare and outstanding plants, lies on the opposite side of the lawn.

The shrubberies are entered by a long tarmacadam path flanked by borders containing a variety of shrubs and herbaceous perennials, many noted for their fragrance as well as for their flowers. Among these are the Californian poppy (Romneya couteri), the large white-flowering Philadelphus 'Beauclerk', the honey-scented yellow Pittosporum eugenioides 'Variegatum', and the flowering quince Chaenomeles speciosa 'Vermillion'. Here also lies a large-leaved Meliosma dillineifolia, while off the grass rides to the north east stand several interesting trees, including an unusual variety of the strawberry tree (Arbutus unedo 'Rubra'), a very wide-spreading Pterocarya fraxinifolia and the rarely seen Aralia spinosa, known as the devil's walking stick because of its viciously spiny stems.

The path around the lawn in front of the castle brings the visitor past some fine shrubs and specimen trees, most notably the aromatic Ozothamnus ledifolius from Tasmania, the Mexican orange blossom (Choisya ternata) and the Mount Etna broom (Genista aetnensis) which in summer yields a profusion of fragrant pea-like golden yellow flowers. From here the visitor passes through the old main avenue area where a number of different species of olearias and hydrangeas flower, in addition to podocarpus shrubs, crinodendrons, magnolias and even a tender hakea in the shade of the trees. The return path, past a hedge of Cotoneaster conspicuus and some fine sorbus trees, leads the visitor to the south-west wall of the castle with its magnificent Magnolia grandiflora whose large creamy-white fragrant flowers continue to bloom throughout the summer. More plants are found behind the castle, including some old roses and the spectacular vine Vitis coignetiae.

The finest part of the Malahide plant collection lies in the four-acre Walled Garden, but problems with vandals in recent years have meant that this part of the garden is only open on Wednesday afternoons. The area is subdivided into several sections, each with an identity of its own. The first of these, the old Rose Garden, is used for testing the hardiness of new tender species as they become available, while the section beyond, known as the Haggard, has a selection of cottage-type plants as well as a number of wall plants and climbers. One of the two glasshouses here shelters a small collection of tender species, including Luculia gratissima 'Rosea' and the bromeliad Puya alpestris. A small enclosed yard beyond the Haggard reveals raised beds of alpine plants as well as shrubs-notably Banksia dentata, Acradenia frankliniae and Eucryphia milliganii. As this yard is so small, the area formerly known as the Tresco Wall has been altered to accommodate a large collection of alpines.From the new alpine beds and the reconstructed sunken greenhouse, the garden opens out onto a wide lawn of shrubberies. Among the plants here are a number of garryas raised from seed by Lord Talbot. It was from this selection that he chose the hybrid which won him an Award of Merit from the Royal Horticultural Society, later named Garrya x issaquahensis 'Pat Ballard'. There are two greenhouses here, one of which contains the rare Paeonia cambessedesii, while to the south a large pond succours Gunnera manicata along its banks. An old peach house containing a selection of tender climbing plants and correa species lies along the south wall in addition to a shrubbery full of exotic plants: Clematis 'Etoile Rose', Azara dentata, the silk tree Albizia julibrissin 'Rosea' and the vigorous yellow-flowering Fremontodendron 'California Glory'.