Pieter Heinrich (also Hendrik) Polemann (sometimes Poleman, Pohlmann), an apothecary at the Cape, was the son of Ernst H. Polemann, a director of the Royal Danish Bank, and his wife Anna R. Pralenn. His birthplace, Altona (now part of Hamburg), was then in Denmark. Hence Polemann was sent to Copenhagen where he studied pharmacy, botany and chemistry and qualified as an apothecary. On 14 April 1802 he arrived at the Cape, having been recruited as an assistant by the surgeon and apothecary Dietrich Pallas of Cape Town, who had no formal qualifications. When the Supreme Medical Committee was established in 1807 to regulate medical practice at the Cape, Polemann was registered as an apothecary, chemist and druggist. However, in August that same year the Committee reprimanded him for "profitting by the ignorance or credulity of the inhabitants by selling [a herb] void of any medical virtue" (Craven, 1987/8, p. 154). On the basis of his experience Pallas was permitted to continue practising as an apothecary, provided he had a qualified partner or assistant. Hence the firm Pallas & Polemann, with Polemann as a partner from 1810, traded in Strand Street until Polemann's death in 1839. He was the leading Cape Town pharmacist of his time. Among the assistants employed by the firm were the naturalists C.H. Bergius*, C.F. Ecklon*, G.L.E. Krebs* (who became a friend), and C.F. Dr?ge*. Polemann became a citizen of the colony in 1807 and on 25 November 1811 married Aletta J.S. Schweinhagen (also Schwynhage), eldest daughter of Pallas's wife from her first marriage. They had no children.
Polemann applied his scientific knowledge in various activities. Shortly after his arrival he began experimenting with the poor quality local wines and in 1806 had devised a method to improve local brandy by double distillation with powdered charcoal in the wine being distilled. Many years later, in 1826, he was co-opted on the newly established Cape Wine Trade Committee and presented a paper to them on the improvement of Cape brandy. The paper was well-received and issued as a pamphlet later that year, entitled Hints on the making of brandy, and the improvement of common Cape brandy..., with a Dutch edition published at the same time. At some time before 1816 he appears to have surveyed the Cango Caves, but the results of the survey have not been found. Over the years he accumulated a geological collection which was considered valuable enough to be bought by the government after his death. In August 1827 he attended a meeting to discuss the introduction of silkworm culture into the colony, but nothing came of this scheme.
Polemann's most important scientific activity, however, was plant collecting. As early as 1803 he applied unsuccessfully to the governor for permission to produce oil from the Buchu plant. During 1803-1806 he went out collecting on Sundays with Dr M.H.K. Lichtenstein*. Later he befriended W.J. Burchell*, and in April 1812 they travelled together to Caledon, Genadendal, Tulbagh, Paarl and Stellenbosch. In 1815 he befriended Reverend C.I. Latrobe*, who spent much time with him. Four years later he visited Germany and renewed his acquaintance with Lichtenstein. The genus Polemannia was named in his honour by Ecklon and C.L.P. Zeyher*, and the species Mystropetalon polemanii by W.H. Harvey*. Plant specimens collected by him are in the herbarium of the Botanischer Garten und Botanischer Museum, Berlin-Dalheim, Germany.
In 1824 Poleman was one of a group of persons who tried to establish the South African Literary Society, but permission was refused by Governor Charles Somerset. During 1837-1838 he was a member of the council of the South African Literary and Scientific Institution. When the South African College was founded in 1829 he supported the venture by buying a share of ?10. In July 1833 he became a subscriber to the Cape of Good Hope Assiciation for Exploring Central Africa, which sent Dr Andrew Smith* on an expedition into the interior. After the expedition's return in 1836 he was elected a member of the association's management committee. From 1834 to his death he served on the newly reorganised Colonial Medical Committee. By this time he was suffering from gout.
Polemann left an estate of some ?25 000 to his widow. After his death the two branches of Pallas & Poleman were sold separately. In February 1840 his widow announced that the remaining stocks of drugs, medicines, utensils, chemical apparatus, retorts, crucibles, stoppered bottles, chemical and scientific works, etc., would be sold without reserve on the 25th of that month.