Victorian glasshouse, Glenarm Castle Walled Garden

Glenarm's present walled garden belongs to the remodelling of the castle by Anne Catherine, Countess of Antrim, in the 1820s with the architect William Vitruvius Morrison, according to the estate manager; Parks & Gardens places the new walled kitchen garden in the works of 1823-24 and 1831-32, and mentions an earlier kitchen garden north of the house in the 1750s with a glasshouse at its centre. The official Northern Ireland survey (HB06/02/001 C) notes that a building is shown on this spot on the 1832 map and that the 1833 valuation describes a glasshouse of about the same length in three lower sections; the 1858 map shows a structure similar to today's, and the present greenhouse appears to post-date 1858. The listing dates it to 1860-1879, and Wikidata retains 1879.

The garden then fell into neglect: Randal McDonnell, who took over the estate in 1992, describes it as completely derelict apart from the yew circle, the beech circle and a few shrubs. The survey of May 2001 records a major rebuilding of the greenhouse in the 1990s, judged sympathetic to the building. The estate ties the garden's restoration to a project begun in 2001 by Lord and Lady Antrim and opened to the public in 2005; the garden designer Catherine FitzGerald, who laid out the new spaces, counts the glasshouse among the heaviest structural tasks. In 2023 Glenarm became the first Northern Ireland garden shortlisted for the Historic Houses Garden of the Year award, and the Historic Houses listing states that it won the award that year.

The Northern Ireland survey describes a long single-storey lean-to greenhouse built back to back with a row of rubble-built stores, against the north wall of the walled garden, north-west of the castle. The whole is about 50 m long, the greenhouse being slightly longer than the stores; the estate and local press give 56 m and one magazine says 100 m, so the figures differ. The frame is timber on a low brick base; the gables, sloping roof and vertical south wall are glazed. Opening lights along the glazing work by a geared mechanism, and internal gables divide the space into bays. The stores, of limestone rubble under a slate roof, form small cells with plank doors and an 8/8 sash window in a rhomboid opening; some open directly into the greenhouse. Because the ground slopes, both structures follow it, which gives the stores a sloping ridge.

According to the Causeway Coast visitor guide, the glasshouse still grows peaches, apricots and grapes; local press mentions a range of fruits and plants. The estate manager says the garden's east-west layout was meant to maximise sun for vegetables and fruit, exotic kinds such as pineapples among them. The garden itself was redesigned by Catherine FitzGerald as six "rooms": five echo the productive role of a kitchen garden in an ornamental way (apple orchard, cherry garden, herb garden, pear garden, medlar garden), the sixth being the Mount, from which the others can be seen. There are also herbaceous borders, including a Hot Border, a potager-style vegetable garden and a tulip festival each May. The Woodland Walk, entered from the top of the garden, brings camellias, rhododendrons and wild garlic in spring, and its collection of maples colours the autumn.

The glasshouse runs along the north wall and is met on a walk through the walled garden, which is open every day in season (the Historic Houses listing gives 17 March to 1 November, with a caveat). The Mount gives a view across the North Channel to Scotland, and the Woodland Walk extends the visit from the top of the garden. The tulip festival in May is one of the high points of the year; in 2026 children under 12 enter free. On site are the Antrim McDonnell Heritage Centre, a tea room and several shops. The castle is open only on certain dates.