Edgeworth, Michael Pakenham (1812–81), botanist and administrator in India, was born at Edgeworthstown, Co. Longford, on 24 May 1812, the youngest son of Richard Lovell Edgeworth (qv) of Edgeworthstown, Co. Longford, author and scientist, and his fourth wife, Frances Anne, née Beaufort, who was a daughter of the Rev. Daniel Augustus Beaufort (qv). Michael's half-sister Maria Edgeworth (qv) recalled that in his teens he was a keen gardener with his own botanical collection. He was educated at Charterhouse from 1823 to 1827 and at Edinburgh University, where he studied Oriental languages and botany. He joined the Indian civil service in 1831, and was appointed to Ambala and then to Saharunpore. A list of plants he sent from India in June 1841 included names of some of the earliest introductions from the sub-continent into cultivation in Europe. He was on leave from 1842 to 1846, and on 17 February 1846, at Old Machar, Aberdeen, he married Christina Macpherson (1819–82), daughter of Dr Hugh Macpherson, professor of Greek at King's College, Aberdeen. The steamer in which they travelled to India stopped briefly to refuel at Aden, and Edgeworth went ashore to collect plants; in two hours he discovered eleven species new to science. He was stationed at Banda from 1846 to 1850, and afterwards was chosen as one of the five commissioners for the settlement of Punjab (in 1850–59), first at Mooltan and then Jullundur. As a result of overexposure to the sun he became seriously ill, and was obliged to return to Europe in 1859.
Edgeworth's principal publications took the form of articles in the journals of the Linnean Society, London (1851–66); the Caryophyllaceae section of the Flora of British India; A grammar of Kashmiri; and a widely respected work on palynology, Pollen (1877–8). Edgeworth's manuscript diaries, which run to more than 8,000 pages, contain sketches and observations on all aspects of colonial and native life in India, as well as on botany and other interests, and form a rich source for historians. The papers are on deposit in the Bodleian Library, Oxford, and have been microfilmed. Edgeworth was a pioneering photographer, one of the earliest to have a connection with Ireland; he made a calotype likeness of Maria Edgeworth before his return to India in 1846. He also experimented with botanical photography. Botanical specimens from his Indian and Ceylon collections are held at the botanic gardens of Glasnevin, Dublin; Trinity College, Oxford; and Kew; his portrait is at the Hunt Library in Pittsburgh. A number of species, including Rhododendron edgeworthii and Edgeworthia chrysantha, were named in his honour. He died suddenly at Eigg, in the Hebrides, on 30 July 1881, survived by his wife and one of his two daughters. His other daughter had died as an infant in India in 1848. A grandson, Harold Edgeworth Butler, was professor of Latin at University College, London. Francis Ysidro Edgeworth (qv) was a nephew.