Heinrich (also Hendrik or Henrik) Bernhard Oldenland (or Oldeland) studied medicine and botany under Professor Paul Hermann* at the University of Leiden, the Netherlands, from May 1686. Towards the end of 1688 he came to the Cape in the service of the Dutch East India Company and from 4 January to 10 April 1689 accompanied an expedition into the interior led by Ensign Isaq Schrijver. They travelled via present Caledon, Swellendam and Riversdale, over the Attaquasberg to the Little Karoo near present Oudshoorn, eastwards and then through the Suurbergspoort to present Willowmore, and northwards to some 30 km north-west of where Aberdeen was later established. Oldenland was the first trained botanist to collect plants so far into the Karoo and found many new species, some of which (e.g., Aloe humilis) he grew in the Company's garden. He was also in charge of the expedition's medicines.
In a letter dated 17 December 1690 the directors of the Dutch East India Company suggested to Governor Simon van der Stel* that he should appoint Oldenland, with his three years training in medicine and botany, to collect and grow indigenous medicinal plants which could be supplied to the company's settlements in Ceylon and Batavia. However, Oldenland left the company as a free burgher in June 1691, with the intention of becoming a farmer, at the time that Jan Hartog* was employed in the Company Garden. Around the beginning of 1693 Oldenland again entered the company's service and was appointed as master gardener, while also serving as land surveyor and supervisor of public works. As a surveyor the first diagram drawn by him is on a grant dated 11 December 1691, though he was officially appointed only in January 1693. In July that year he married the widow Margaretha H. van Otteren, with whom he had one son.
With the encouragement of Van der Stel, Oldenland and Hartog extended, developed, and changed the nature of the Company Garden. Whereas it had been used mainly to produce vegetables, they added sections in which many indigenous plants were grown, as well as nurseries of foreign trees and shrubs. In later years visitors declared that no garden in Europe or India contained so great a variety of trees, shrubs, vegetables and flowers. Meanwhile Oldenland, who was a painstaking collector and cultivator of plants, had assembled a herbarium of indigenous plants, with a catalogue of Latin descriptions, comprising fourteen volumes. The work was terminated by his death early in 1697. Peter Kolbe*, who was at the Cape from 1705 to 1714, saw the herbarium and included a list of plants collected by Oldenland and Hartog in the German edition of his book on the Cape (1719). The list included 28 aloes. F. Valentyn*, who had met Oldenland at the Cape in 1695, also admired the herbarium during another visit in 1714 and published a list of plants similar to Oldenland's catalogue in his Beschrijvinge van de Kaap der Goede Hoope... (1726). Some years later the herbarium was taken to the Netherlands by H. Donker, who had married Oldenland's widow, and came in the possession of the botanist J. Burman of Amsterdam, who included essentially the same list of plants in his Thesaurus Zeylanicus (1737). Burman's son later took the herbarium to Uppsala as part of a larger collection of Cape plants, where it was studied by the Swedish botanist C. Linnaeus. The latter recognised Oldenland as only the second trained botanist (after Paul Hermann) to collect at the Cape. The herbarium was later incorporated in the Conservatoire et Jardin botaniques in Geneve, Switzerland. Other plants collected by Oldenland were taken to England after his death by the Ship's surgeon Sylvanus Landon for the apothecary and natural history collector James Petiver, and ended up in the Sloane Herbarium of the British Museum (Natural History). Some more plants collected by him are in the University of Oxford Herbarium. He also sent seeds of Cape plants to Hermann at Leiden.
Oldenland was a competent draughtsman and may have produced a number of early drawings of Cape plants now in the National Botanical Institute in Pretoria, the British Museum (Natural History), and the Rijksherbarium, Leiden. Furthermore, 24 original drawings of South African Proteaceae that H. Boerhaave received from Hartog and reproduced in his Index alter plantarum (1720), may also have been made by Oldenland.
The genus Oldenlandia (Family Rubiaceae) was named after him by Plumier in 1703 and the name later confirmed by Linnaeus, in recognition of his contribution to knowledge of the flora of the Cape of Good Hope.