O'Neill, (Katharine) Jean (1915–2008), Lady O'Neill of the Maine , plantswoman and horticulturalist, was born 16 January 1915 at 41 Brook Street, Mayfair, London, one of five children of William Ingham Whitaker, landowner and horticulturalist of Pylewell Park, near Lymington, Hampshire, and his wife Hilda (née Dundas), a daughter of the 6th Lord Melville, a Scottish peer. The Whitaker family's fortune had been made in the eighteenth century by importing Marsala wine from Sicily; relatives still lived in Palermo and Rome in the early twentieth century in almost princely style. Jean grew up on the family estate at Pylewell Park, where her father and grandfather had developed extensive gardens on the shores of the Solent in which tender and even exotic species grew well. As a young girl, Jean accompanied her father and the head gardener as they selected new specimens, and her interest in botany and in gardening became a lifelong passion. Educated at home with her older sisters, she had no opportunity to study botany at university but, although she lacked formal training, her almost intuitive knowledge of plants was remarked by the academics with whom she worked in later life.
As a young woman she preferred gardening and outdoor activities to the social life of the London season; in 1937 she visited Hungary with her friend and fellow debutante Anne Hamilton-Grace. The next year, wanting to visit the Balkans, the two bought an old Ford V8 car in England and drove it all the way across Europe. They shared the driving and adventures; they were pursued by police in Romania for taking photographs, were almost pushed off the road by an Italian chauffeur, and were shot at by bandits outside Dubrovnik. Jean Whitaker visited her friend Unity Mitford in Munich, but was appalled by Mitford's Nazi sympathies. When war broke out in 1939, Whitaker joined the Voluntary Aid Detachment to help nurse wounded servicemen in Grimsby and later in the Royal Naval Hospital at Gosport, Hampshire, close to her home.
She had known Terence O'Neill (qv) for several years; he was serving in the Irish Guards, and their wedding took place in the Guards' Chapel in Wellington Barracks, London, on 4 February 1944. In September 1944, Terence O'Neill was wounded and evacuated from the Netherlands back to his wife's home in Hampshire, remaining until the war ended. The couple moved in 1946 to the Glebe House, a former rectory outside Ahoghill, Co. Antrim. Jean O'Neill loyally supported her husband's career in Northern Ireland politics, from his first election as a Stormont MP for Bannside in 1946, through troubled times as prime minister (1963–9). She travelled with him on visits to Great Britain, Europe and the United States; in 1966, on the occasion of the first official visit of a Northern Ireland prime minister to France, she had to stand in for her husband and make a speech at an official banquet hosted in the British embassy, when he was called back to an emergency in Belfast. She was well known and liked in Ulster, and campaigned locally in all weathers for O'Neill during elections, but was never at home in the grimly sectarian and divisive world of Northern Ireland politics.
Instead, she focused on her family (a son, Patrick, was born in January 1945, and a daughter, Penelope, in 1947), while also creating an impressive garden and working for local horticulture and voluntary societies. She was chairman of the Ballymena Horticultural Society, and first president of the Rose Society of Northern Ireland (1968–75). As chairman of the National Trust gardens committee she made very significant contributions to the restoration of the trust's garden at Rowallane, Co. Down, as well as to the ongoing development of other trust gardens in the province. She was a judge of the important International Rose Trials in Belfast from 1964. Her wide knowledge of historical gardens and of garden plants was shared in articles in journals such as Country Life and the Journal of Garden History. She contributed a twenty-seven-page article on plants to a classic book edited by Graham Thomas, Recreating the period garden (1984), and also wrote for the Oxford companion to gardens (1986). Her greatest contribution to the history of garden plants was a book on an eighteenth-century quaker merchant, Peter Collinson, who supplied American plants to British gardeners. Peter Collinson and the eighteenth-century natural history exchange (2008), based on thirty years' research in American and British records and libraries, was published by a collaborator after Lady O'Neill's death.
As the Northern Ireland troubles began in the late 1960s, Terence O'Neill's reforming initiatives were attacked by hardline unionists such as Ian Paisley (qv) and by William Craig (1924–2011), and the family felt threatened by the hostility expressed on all sides. O'Neill was pushed out of office in April 1969, and in 1970 took a seat in the house of lords as Baron O'Neill of the Maine; thereafter, the couple lived at Lisle Court, Lymington, close to Jean's childhood home.
There Lady O'Neill made another notable garden, internationally known for its southern hemisphere trees and shrubs. In 1986, as vice-president of the Hampshire Gardens Trust, she was involved with the creation of a historically accurate garden with seventeenth-century planting, Compton Garden, at St Cross Hospital, Winchester. In the 1980s she made several visits to the US to lecture on garden and plant history to societies in Pittsburgh, Boston, Cleveland and Missouri, and, aged almost 90, accompanied the taxonomist and Kew Gardens director, Professor Sir Ghillean Prance, on a trip to collect plants along the river Amazon. She was particularly interested in the classification and cultivation of tender plants from the Americas and from Australia (where her son lived), and into her 80s regularly went on long and arduous walks through the Australian bush collecting specimens and seeds. She was a fellow of the Linnean Society, and in 2000 was awarded the Royal Horticultural Society's Veitch medal for her contribution to the science and practice of horticulture. She was also vice-president of the Garden History Society.
Lady O'Neill was widowed in 1990; living alone in England, she was burgled several times. On one occasion, a burglar, apparently impressed by her bravery, repented sufficiently to apologise to her and alerted the police to her plight, left tied up after being harassed and threatened by masked men. It was typical of her that her death in Hampshire on 15 July 2008, caused by a stroke, took place shortly after she had re-potted an extremely rare Australian Wollemi pine.