Johannes Jacobus Kotze attended the Boys' Public School in Malmesbury, Western Cape, and passed the matriculation examination of the University of the Cape of Good Hope in 1907. Continuing his studies at the South African College, Cape Town, he was awarded the Bachelor of Arts (BA) degree, with honours in History, by the University of the Cape of Good Hope in 1910. In January the next year he joined the civil service and in August 1912 was appointed as second class clerical assistant in the administrative branch of the Department of Forestry. The next year he proceeded to the University of Edinburgh, where he obtained a BSc degree in Forestry in 1916.
Upon his return he was appointed as assistant to C.C. Robertson* at head office in Pretoria and became administratively involved in various functions, including the organisation and control of the departmental seed store, the botany of indigenous species, identification of eucalypts and other exotic trees, and the building up of an herbarium of forest trees. Later he became involved in the coordination of the work of regional research officers at Pretoria, Tokai, Deepwalls, Knysna, and Pietermaritzburg.
In 1930 Kotze was appointed Chief Research Officer and in 1935 became Conservator of Forests in Cape Town, a post which he held until 1944 when he was appointed Deputy Director of Forestry. After his retirement in March 1952 he became forestry consultant to the Union Corporation until March 1963.
Kotze produced at least 15 or so silvicultural publications during 1919-1961, including the following: "A note on the genus Faurea Harv." (with E.P. Phillips; South African Journal of Science, 1919); "Pinus patula Schlectd. & Cham: Its introduction into and growth in South Africa" (Ibid, 1926); "Some remarks on the establishment and tending of timber plantations, with special reference to the Cape Province" (South African Journal of Natural History, 1921); "The growth of Eucalypts on the High-veld and south-eastern mountain veld of the Transvaal" (with C.S. Hubbard; South Africa, Department of Forestry, Bulletin No. 21, 1928); Forest fungi: The position in South Africa (Pretoria, 1935); "Reclamation of the Cape Flats" (Journal of the South African Forestry Association, 1940); "Nomenclature of the South African yellowwoods" (with C.A. Smith, Ibid, 1943); and "The growing of Eucalyptus saligna on short rotations" (Ibid, 1955).