Peter MacOwan, botanist and teacher, was the son of Reverend Peter MacOwan (or McOwan) and his wife Jane Townsend. After completing his schooling in 1846 he tutored at Bath and later at Colchester. In 1853 he became housemaster of the Wesleyan school at Woodhouse Grove, near Leeds. In 1857 he was appointed to teach chemistry at Huddersfield College, Yorkshire, and that same year was awarded the Bachelor of Arts (BA) degree in chemistry by the University of London. Two years later he became professor of chemistry at Huddersfield. However, he became interested also in botany and started a collection of flowering plants and mosses. In 1858 he married Amelia Day and they eventually had a son and two daughters. Health problems caused him to resign in 1861 and emigrate to the Cape Colony.
Settling in Grahamstown MacOwan assumed duty as principal of the newly established Shaw College (a high school) in 1862 and began to collect the plants of the Eastern Cape, building up an extensive private herbarium. He also took charge of the herbarium of Albany Museum soon after his arrival, and in 1867 lodged his large collections of Australian and United States plants in the museum as an adjunct to the Cape Government Herbarium. At that time he served on the first council of the Albany Natural History Society, and on 9 October 1867 read the first paper before it, "Notes on the botany of Grahamstown". He also served on the committee of the Grahamstown Botanic Garden. He befriended local amateur scientists such as Dr W.G. Atherstone*, Mrs M.E. Barber* and Henry Hutton*, and exchanged specimens with botanists such as W.H. Harvey* in Dublin, J.D. Hooker* at Kew Gardens, and Professor Asa Gray in the United States. Harvey thanked him for "several hundred species of the plants of his district, most carefully and beautifully dried" in the preface to Volume 3 of the Flora Capensis (1865). However, his field labels, like those of some of his contemporaries, tended to be uninformative about the plants. The strong overseas demand for Cape plants led MacOwan to establish the South African Botanical Exchange Society in 1866, with himself as secretary and Dr Atherstone as treasurer. Its purpose was to encourage botanical collecting and obtain more plant specimens from local collectors for exchange. To this end he published a Catalogue of South African plants for the use of the South African Botanical Exchange Society (Grahamstown, 1866), a list of 4682 species based on the first three volumes of the Flora Capensis. By the end of 1868, when the society ceased its activities, nearly 9000 duplicates had been distributed and in return he received plants from North America, Australia and Europe. Meanwhile he had befriended Harry Bolus*, then living in Graaff-Reinet, who became joint secretary of the society.
In 1869 MacOwan became professor of chemistry at Gill College, Somerset East, which opened that year as a high school and university training centre for boys. His botanical interests were wide and during his years at Somerset East he spent much time studying and collecting lichens and parasitic fungi, particularly in the Bosberg. He was often accompanied by Mr W. Tuck*, and found many new species. Some of these he described himself (1880, 1883), but most of his fungi were named by the mycologists F. von Thuemen (in six papers between 1875 and 1878) and C. Kalchbrenner and Cooke (1880-1882). The lichens were described by J. Stirton (1877), leading to a rapid extension of knowledge about these groups in the Cape Colony. In 1872 he donated plants and grasses to Albany Museum, followed by mosses in 1877. From 1873 he was in charge of the Gill College Museum, which included an herbarium. His personal herbarium was presented to Gill College, where it remained until 1904, when it was handed over to Albany Museum. During the twelve years he spent in Somerset East he published some descriptions of new plants in the Journal of the Linnean Society (1869), Herbarium notes for the use of students of Cape botany (Grahamstown, 1877), and articles in the Cape Monthly Magazine on "Colonial stock food plants" (1877) and other topics.
Having decided to become a full-time botanist MacOwan resigned his post in February 1881 and moved to Cape Town where he succeeded James McGibbon* as director of the Government Botanic Garden and curator of the Government Herbarium, and in October that year was appointed also as professor of botany at the South African College. The herbarium was in a neglected state, housed in an unsuitable building constructed largely of wood, and required much work to combat insect pests and remount specimens. MacOwan sent large numbers of duplicate specimens to the Albaby Museum to create a partial replica of the herbarium for fear that it would be destroyed by fire. He added a large number of specimens from the Eastern Cape and methodically built up the collection so that by the time he retired in 1905 it contained some 44 000 sheets, of which about 25 500 represented Cape plants. This was achieved in part by regularly issuing sets of Cape plants to overseas herbaria for exchange, under the joint title Herbarium Normale Austro-Africanum. H. Bolus participated in the venture until 1892 and the last set, Number 20, was issued in 1898. MacOwan also distributed teaching collections to local schools and colleges. Lichens that he collected around Cape Town were sent to Europe and many new species described by Stitzenberger in 1890. He was alone in the herbarium until 1895, when Miss S. Treleaven* was appointed as his assistant. This enabled him to undertake botanical excursions to Tulbagh, Houwhoek, Caledon and the Hottentots Holland Mountains (1896), the Eastern Cape (February 1897), and, with Bolus, to Clanwilliam and Wuppertal (1897).
Because of a shortage of lecturing halls at the South African College MacOwan presented his classes in the lodge of the Botanic Garden. As this site was outside the college it enabled him to arrange a class for female students, something which was then not allowed in the college itself. His lectures, like his writings, sparkled alternately with satire and humour, and he often underscored a point with an anecdote, reminiscence, or quotation from the classics - the latter to such an extent that it somewhat obscured his scientific writing. He was a most enthusiastic lecturer, and an outstanding conversationalist with an extensive general knowledge.
Much of his time was taken up attending to the Botanic Garden, the cost of which was supposed to be recovered at least in part through the sale of plants. He was also increasingly consulted with regard to agricultural and horticultural matters, particularly from 1887, when the Cape Government employed him as official consultant in economic botany. Among others he served as a member of the Phylloxera Commission from 1886 to 1893. None the less he managed to compile various publications, among them "Novitates Capensis: Descriptions of new plants from the Cape" (with H. Bolus, Journal of the Linnean Society, 1880), Botanical diagrams for the use of schools of the Cape Colony (Cape Town, 1884), Plants that furnish stock food at the Cape (Wynberg, 1887), and Exploitation of the olive and its products (Cape Town, 1888). In 1882 he and Bolus published an historically important paper, "Catalogue of printed books and papers relating to South Africa. Part I. Botany", in the Transactions of the South African Philosophical Society (Vol. 2, pp. 115-187). It listed 551 items, some with brief annotations.
MacOwan resigned his teaching post in October 1888 but consented to continue his duties to the end of the academic year in June 1889. In 1892 the Botanic Garden was taken over by the municipality of Cape Town and MacOwan was appointed government botanist in the Department of Lands, Mines and Agriculture, a post that included the curatorship of the Government Herbarium. In his new post he dealt with many agricultural and horticultural matters, often by means of scholarly but charming articles in the Agricultural Journal of the Cape of Good Hope. These dealt with topics such as fodder plants, tobacco culture, wattle growing, and many more. He also did much to promote commercial fruit-growing and, with C.E. Pillans*, published A manual of practical orchard work at the Cape (Cape Town, 1896) which remained a standard work for many years. During his 16 years as government botanist he wrote well over a thousand reports, many of which appeared in the Agricultural Journal. His later publications included "New Cape plants" (Journal of the Linnean Society, 1890), Monsonia - the Cape remedy for dysentery (Pamphlet No. 7, Cape Department of Agriculture, 1897), "The Verbenaceae of South Africa" (Flora Capensis, Vol. 5, 1901), "Some observations on Welwitschia mirabilis" (Philosophical Transactions of the Royal Society of London, 1906, 1909), "The travels of a botanist in South West Africa" (Geographical Journal, 1910), and "Thymeleaceae" (Flora of tropical Africa, Vol. 6, 1913). W. Thiselton-Dyer*, editor of later volumes of the Flora Capensis, praised him in the preface to Volume 6 for his indefatigable services to botany and for keeping Kew Gardens informed of developments in the study of the Cape flora. His valuable contributions to agriculture included the introduction of the Australian salt-bush and other fodder plants that eventually turned large areas of brak land into useful pastures.
Outside botany MacOwan participated in many other scientific and cultural activities. He served on the council of the University of the Cape of Good Hope as a convocation member from 1876 (representing Gill College) to 1891. From 1881 to 1891 he was one of the university's examiners in science, setting papers at the BA, BA(Hons) and MA level in inorganic, organic and agricultural chemistry, and in geology, mineralogy and crystallography. The university awarded him an honorary Doctor of Science (DSc) degree in 1902 and recorded that "since his arrival in South Africa [he] has carried on the study of South African botany with enthusiastic zeal and great success, and his scientific work in systematic and applied botany is held in the highest esteem in South Africa as well as in Europe" (Juritz, 1909, p. 74). When the South African Philosophical Society was founded in 1877 he became first a corresponding member at Somerset East and then an ordinary member, served on its council for many years and as president in 1885. His presidential address, "Personalia of botanical collectors at the Cape", published in the society's Transactions (1887, Vol. 4), was an important contribution to the history of Cape botany. He was elected a Fellow of the Academy of Natural Sciences of Philadelphia (1874), the Linnean Society (1885), and the Royal Horticultural Society (1885), and was a member of the Deutsche Botanische Gesellschaft (1888), and the Massachusetts Horticultural Society (1889).
In June 1905 he retired (aged 74) and returned to Grahamstown. The Government Herbarium to which he had contributed so much was incorporated in the South African Museum and is now housed at Kirstenbosch. The post of colonial botanist ceased to exist. One of his daughters, Flora, was married to Dr Selmar Schonland* and MacOwan stayed with them for some time while working on the Albany Museum Herbarium, which by this time included his own collection. He spent part of the last years of his life with his other daughter in Uitenhage, where he died. He was a methodical and untiring worker and for many years an acknowledged expert on South African botany and on all matters pertaining to plant culture. His personal library was acquired by the Division of Botany and Plant Pathology, Pretoria. His valuable collection of almost 1000 carefully executed casts of seals, ecclesiastical, municipal, scholastic and personal, as well as a number of full size rubbings from the monumental brasses of English churches of the 14th to 16th centuries, were presented to the Albany Museum, the latter at some time before 1883. The same institution purchased his collection of South African mosses in 1913. The genus Macowania (Fam. Compositae), the cryptogamic genera Macowanites and Macowaniella, and many species were named after him. Specimens presented by him can be found in many herbaria, including those at Albany Museum, National Botanical Institute (Pretoria), Kew Gardens, the British Museum (Natural History), the Compton Herbarium (Cape Town) and other institutions in Geneve, Paris, Vienna, and Zurich. His collection of fungi was later transferred from the Albany Museum to the Plant Protection Research Institute in Pretoria.