James Niven, Scottish gardener and plant collector, was the son of James Niven, a weaver, and his wife Anne Wilson. He completed an apprenticeship at the Edinburgh Botanic Garden from March 1795 to February 1796, when he became gardener to the Duke of Northumberland in Middlesex, near London. In 1798 or early 1789, as a young man of 22, he was employed by George Hibbert, a well known nurseryman in London, and sent to the Cape of Good Hope as Hibbert's resident collector. Niven stayed at the Cape to 1803. Two years later, in 1805, he returned to the Cape, this time to collect plants for Empress Josephine of France and Messrs James Lee & Kennedy, nurserymen at Hammersmith, near London. This time he remained at the Cape until 1812.
Niven collected over a large part of the Cape Colony, eastwards to the Albany division and northwards to Clanwilliam and the Kamiesberg, but mainly in the Western Cape. His large collections included live plants, seeds, bulbs and herbarium specimens, and contained many new species. The heaths (family Ericaceae) were particularly well represented in his collection and were described by him in an unpublished manuscript that was presented to the herbarium at Kew Gardens. Niven was the first person known to to have found rust on an indigenous plant, namely the gall-forming fungus Aecidium resinicolum, which he found on a species of Rafnia (family Leguminosae). Based on his specimens, the fungus was described as a new species by Rudolfi in 1829. The live proteas that he collected were cultivated by Hibbert and were studied by R.A. Salisbury, Hibbert's gardener. In 1809 Salisbury made the first serious attempt to define and limit the genera of what he called the Order Proteeae, based mainly on Niven's extensive collection and incorporating details of localities and information on the habits of various species, based on Niven's notes.
The genus Nivenia (family Proteaceae) was named after Niven by Robert Brown*, who studied his herbarium specimens belonging to this family. He was also commemorated in, among others, the species names Erica nivenia, Serruria nivenii and Gladiolus nivenii. His specimens ended up in the herbaria of, among others, the British Museum (Natural History), the Conservatoire et Jardin botaniques in Genève, the Royal Botanical Gardens at Kew, the Irish National Herbarium in Dublin, and the Swedish Museum of Natural History in Stockholm.
After his return to England in 1812 Niven returned to his birthplace, Penicuik, just south of Edinburgh, where he went into business. In 1817 he married Alison Abernethy, with whom he had five children.