E. Percy Phillips, botanist, was the son the Cape Town businessman Ralph E. Phillips and his wife Edith M. Crowder. He attended the South African College School, matriculated in 1900, and continued his studies at the South African College, studying botany under Professor H.H.W. Pearson*. He was awarded the Bachelor of Arts (BA) degree, with honours in botany, by the University of the Cape of Good Hope in 1905, and the degree Master of Arts (MA) in botany in 1908. Meanwhile, in 1907, he had succeeded Miss Snowden Treleaven* as assistant in the herbarium of the South African Museum, where Professor Pearson was the honorary curator. He applied himself with vigour to collecting and studying the local flora, mainly in the mountains of the Western Cape. During 1908-1913 he also collected ants in the Western Cape for the South African Museum. His first scientific publication, "Some common Cape fungi" (with Walter T. Saxton*) appeared in the Agricultural Journal of the Cape of Good Hope in 1908. In March 1910 he was given ten months leave of absence to work on the family Proteaceae in the herbarium of the Royal Botanical Gardens at Kew, near London. He described a new genus and six new species of Proteaceae in Kew Bulletin (1910-1911) and, in collaboration with Otto Stapf and John Hutchinson, wrote up this family for the Flora Capensis (1912, Vol.4, pp. 502-718). Several more papers by him on this family appeared in later years.
In 1911 Phillips succeeded Professor Pearson as curator of the South African Museum herbarium. In September that same year he accompanied the Percy Sladen Memorial Expedition to the Kamiesbert, Gifberg, and Olifantsrivierberge (west of Citrusdal). The plants collected were described in four papers in the Annals of the South African Museum (1913). He spent much time on the plants presented to the herbarium from Leribe, Basutoland (now Lesotho), by Madame Anna Dieterlen* and visited the region in 1913 for field studies and to collect some hundreds of specimens. This work formed the basis of his Doctor of Science (DSc) degree, conferred upon him by the University of the Cape of Good Hope in 1915 for a thesis titled A contribution to the flora of the Leribe Plateau and environ, with a discussion on the relationships of the flora of Basutoland, the Kalahari, and the south-eastern regions. The thesis was published in the Annals of the South African Museum (Vol. 16, Part 1, 379p) in 1917.
In May 1918 Phillips was appointed curator of the National Herbarium of the Division of Botany, Department of Agriculture, in Pretoria. During the following years he wrote two of the Memoirs of the Botanical Survey of South Africa, A preliminary list of the known poisonous plants found in South Africa (No. 9, 1926, 30p) and The genera of South African Flowering plants (No. 10, 1926, 702p; rev. ed. No. 25, 1951, 293p). He also wrote most of the text of the first 20 volumes of the illustrated serial The Flowering Plants of South Africa during 1921-1943 and contributed many papers to the first two volumes of the journal Bothalia, established in 1921 to record the work of the National Herbarium. His publications numbered about 200, including two further major works: An introduction to the study of South African grasses, with notes on their structure, distribution, cultivation, etc. (1931, 224p), and The weeds of South Africa (1938, 229p). More than 15 semi-popular articles by him appeared in the Agricultural Journal (Union of South Africa) and various farming magazines from 1922 onwards.
In 1939 he became head of the Division of Botany and Plant Pathology (later the Botanical Research Institute), a post he held until his retirement in 1944. During his five-year term World War II was in progress, with resultant uncertainty, budget cuts, and members of staff joining the armed forces. Nonetheless he continued to publish prolifically. The plant species Leukadendron phillipsii and Agathosma phillipsii were named after him. Shortly before his death he and Estelle van Hoepen were the joint editors of C.A. Smith's Common names of South African plants (Botanical Survey Memoir No. 35, 1966).
Phillips was active in a number of scientific societies. He was a Fellow of the Linnean Society (London), and was elected a Fellow of the Royal Society of South Africa in 1921. As a member of the South African Biological Society he served as secretary from 1919 to 1944, as president in 1950, and was awarded its Senior Captain Scott Memorial Medal in 1925. He became a member of the South African Association for the Advancement of Science in 1915, served on its council for many years, and was elected president of Section C (which included botany) in 1930. His presidential address dealt with "The development of botanical science in South Africa...". He was again elected president of Section C in 1935, was awarded the association's South Africa Medal (gold) that same year, and served as president of the association in 1942. While still in Cape Town he was a keen mountaineer and member of the Cape Mountain Club, serving as its secretary for some time until 1918. In 1931 he was one of the delegates representing South Africa at the centenary meeting of the British Association for the Advancement of Science. In 1934 he visited the United States and Canada with a grant from the Carnegie Corporation of New York and reported on "Herbaria and botanical institutions in the United States of America and Canada in relation to similar institutions in South Africa" in South African Biological Society Pamphlets (No. 8, 1935). He served on the executive committee of the Public Service Staff Association, including terms as chairman and president, from 1920 to 1944, when he became a research officer of the Public Service Commission. From 1946 to 1948 he was the scientific liaison officer of the Council for Scientific and Industrial Research in Washington DC.
In December 1912 Phillips married Edith I. Dawson, with whom he had two daughters. After his wife's death in 1948 he married Susanna Kriel, and in 1950 commemorated her in the plant genus Susanna. He was a hard worker, conscientious and methodical.