Pieter le Fras Nortier, medical practitioner and agricultural researcher, was the son of Esaias Andreas Johannes Lourens Nortje and his wife Maria Susanna, born Ferreira. Pieter changed the spelling of his surname back to the original French, but was still listed as Nortje in the Medical, Dental and Pharmacy Directory of South Africa for 1926/7. He attended the Boys' High School in Stellenbosch and passed the matriculation examination of the University of the Cape of Good Hope in 1903. Continuing his studies at Victoria College, Stellenbosch, he passed the intermediate examination for the BA degree (equivalent to the first year of study) in 1904. His excellent academic performance earned him a Rhodes scholarship, which enabled him to study medicine at the University of Oxford (1905-1908) and at the University of Liverpool (1908-1911), qualifying as Bachelor of Medicine (MB) and Bachelor of Surgery (ChB) in 1911. Thereafter he worked at the Royal Infirmary, Liverpool, for a few years and was awarded the degree Doctor of Medicine (MD) for his research on venereal diseases by the University of Liverpool in 1916.
Upon his return to South Africa Nortier was registered to practice medicine on 1 May 1912. He served in the military campaign in German South West Africa (now Namibia) during the early stages of World War I (1914-1918). He began to practice medicine in Clanwilliam (where he was also a railway doctor and district surgeon) in 1916 and remained there for the rest of his life, becoming the doyen of the medical profession in the districts north of Cape Town for nearly 40 years. His popularity with his patients is shown by the fact that on two occasions they collected enough money to make him a gift of a motorcar. In 1949 he served as vice-president of the Medical Congress held in Cape Town.
In his spare time Nortier conducted agricultural experiments on his farm on the banks of the Olifants River. His work on the indigenous rooibos-tea resulted in methods of treating the seed to improve germination and procedures for growing, harvesting and treating the crop, and as a result he has been called the father of the rooibos-tea industry in South Africa. He also cultivated the Clanor seedless orange and experimented with various sub-tropical fruit trees, fertilisers, and compost making. He was largely responsible for the establishment of a school of agriculture in the town, acted as an agricultural adviser, could speak with authority on any topic relating to the Cedarberg area, and was elected to numerous positions in Clanwilliam and the surrounding districts.
Nortier shared a strong interest in nature and its conservation with his friend, Dr C F L Leipoldt*. They collected plants together in Namaqualand and Nortier cultivated these in his garden. The Leipoldt-Nortier Memorial Library at Clanwilliam was established in their honour in 1958. As a result of Nortier's efforts the farm Otterdam (on the west coast just north of Lambert's Bay) was declared a nature reserve in 1935 and named the Nortier Reserve, but in 1957 it was taken over by the Department of Agriculture and developed into the Nortier Experimental Farm. He also collected plants with Mrs H M L Bolus* and some succulents were named after him. The University of Stellenbosch conferred upon him an honorary DSc (Agric) degree in 1948 in recognition of his contributions to agriculture. He was also posthumously awarded an honorary DSc (Med) degree by the University of Cape Town in 1955. He retired from the medical profession in 1952.
In 1917 Nortier married Agatha Krige, with whom he had four daughters. A collection of his manuscripts and correspondence is held in the Gericke Library of the University of Stellenbosch.