Frans Petter Oldenburg may have been a pupil of the Swedish scientist C. Linnaeus and may have come to the Cape as a ship's surgeon with the intention of collecting natural history specimens for Linnaeus (Brinck, 1955). Whatever the case may be, he had arrived at the Cape and was a soldier in the employ of the Dutch East India Company by March 1771, when he met Sir Joseph Banks* and Daniel Solander* on their visit to the Cape with the expedition of Captain James Cook. The Swedish botanist C.P. Thunberg* stated in his Flora Capensis that he trained and encouraged Oldenburg in botany and that the latter often collected with him on the Cape Peninsula during 1772. On 10 December that year Oldenburg left Cape Town with Francis Masson* to act as Dutch interpreter during Masson's first journey into the interior. They visited Paarl, the French Hoek Valley and Stellenbosch, crossed the Palmiet and Bot rivers to the warm baths at present Caledon, and after spending two days at Swellendam returned to Cape Town by the same route, arriving on 18 January 1873. Oldenburg collected many plants on this journey. While at the Cape he corresponded with Solander in London and with C.H. Bergius* in Stockholm.
About a thousand Cape plants collected by Oldenburg in 1772, as well as some plant drawings by him, were bought by Sir Joseph Banks and were later taken up in the herbarium of the British Museum (Natural History). Oldenburg was a competent draughtsman and it has been suggested that he painted the stapelias in Masson's Stapelia novae (e.g., Phillips, 1930). However, this idea is now regarded as unfounded. The South African plant genus Oldenburgia (Family Compositae) was named after him by the German botanist C.F. Lessing.
In 1774 Thunberg was invited by governor van Plettenberg to join an expedition to Madagascar as ship's surgeon, to barter for slaves and study the natural history of the island. Thunberg declined but recommended Oldenburg, who sailed on the Hoeker as surgeon's mate. According to Thunberg he collected some plants on the island, but died there of a fever.