Peter (or Pieter, at the Cape) E. Wahlstrand, a Swedish apothecary, married Catherine J. M?ller in about 1796. He emigrated to the Cape Colony and in 1800 took over the apothecary business of J.F.W. Schmidt in Long Street. In August 1807 he applied for burghership and became one of the first nine apothecaries to be licensed to practice in the colony by the Supreme Medical Committee. In July 1818 his insolvent chemist and druggist business, situated at 63 Long Street, was sold to John H. Tredgold*. During the next few years he was listed in the directory of the African court calendar as a chemist residing in Plein Street (1819) and then in Kasteel Street (1821, 1822).
In 1818 Wahlstrand initiated systematic quantitative meteorological observations in Cape Town, the first of their kind in southern Africa. He appears to have inspired others to follow his lead, for similar observation were made in the Swartland, Stellenbosch, Tulbagh, Worcester, Swellendam, George, Uitenhage, Bathurst, and Albany. From September 1818 to June 1825 Wahlstrand published meteorological reports in the Goverment Gazette, including daily observations of air pressure, air temperature, direction of wind, and humidity for nine stations. Cuttings of the reports for 1821-1823, bound in three volumes, are held by the National Library of South Africa in Cape Town.