Hēmi Pōtatau was born on 20 May 1904 at Te Mimi o Te Hiki, Nūhaka, the ninth of twelve children of Hata Pōtatau, also known as Tīpene, and his wife, Te Raita (Taraita) Rore, also known as Te Waimātao. His father had links to the ariki Te Kani-ā-Takirau of Ngāti Porou through his mother, and to Te Rarawa of Northland through one of her grandparents; but his main identification was with Ngāti Kahungunu of Wairoa through the hapū Ngāi Te Apatari. Hēmi’s mother had links to Ngāti Whare, a hapū based at Te Whāiti and closely intermarried with Tūhoe, and to Ngāti Manawa, but her hapū at Nūhaka was Ngāti Rangi, and her main iwi was Ngāti Rakaipaaka. Hēmi’s parents were poor; they subsisted by farming and his father also took labouring jobs.
From the age of four Hēmi attended Nūhaka Native School, where the children were whipped with a supplejack cane if they spoke Māori. At 12 he milked cows before and after school for a local couple who cared for him like a son, buying him shoes and clothes. When Hēmi was 14, Sister Edith Walker, a Presbyterian missionary at Nūhaka, asked him if he would cut wood for the mission after school. From 1917 she took responsibility for him as her foster son. Hēmi was baptised an Anglican, but became a Presbyterian to honour her. After he gained a scholarship to St Stephen’s Native Boys’ School in Parnell, Auckland, Sister Edith helped with his expenses. She then arranged for him to attend Scots College, Wellington, starting in 1920. He passed only four subjects in 1923, but completed his matriculation the following year at Wairoa District High School. In 1925 he enrolled at the Theological Hall, Knox College, Dunedin, to study for the Presbyterian ministry. From 1926 he also attended the University of Otago; he played rugby for the university’s second team and occasionally for the top team, but did not finish a degree. He completed his studies at Knox in 1931 and was appointed assistant minister at Taupō.
Pōtatau was at Taupō in 1932–33 and after being ordained at Tāneatua was transferred to Waimana. He assisted at Nūhaka from 1934 to 1936, then moved to Waikaremoana to help Sister Edith. While there he met the prophet and sect leader Tūtekohi Rangi, whom he publicly compared with a crab, moving sideways towards enlightenment; Tūtekohi was addressed as ‘the crab’ by many Tūhoe thereafter. In 1937, after an unhappy relationship, Pōtatau had a year’s leave of absence working on a farm. He returned to Taupō as a minister from 1938 to 1940.
In January 1941 Pōtatau volunteered for military service without the knowledge of his Presbyterian superiors. He entered camp that month and embarked overseas in June, arriving at Cairo in late July. In October he was made a lance corporal, serving with the Composite Signal Depot. After reporting a light at Helwân, which was presumed to be a signal to German aircraft from Arabs hostile to the British, he was seconded to a Middle East security school to be trained in intelligence work. He subsequently monitored the men in his unit: when they were drinking in bars, to check they were not inadvertently divulging information that would be useful to the enemy, and in the NAAFI canteens, to assess morale, especially after major setbacks. He also warned incoming reinforcements against indiscretion, advising Māori soldiers to speak only Māori in public. He monitored the burning of rubbish in case papers were left that might give away strategic information, learnt the local Arabic dialect, and studied French.
After five months with intelligence, Pōtatau was offered promotion provided he learned to type. He refused, and was assigned to work as a company clerk. In November 1942 he joined the Māori Signal Company of the 28th New Zealand (Māori) Battalion. Earlier that year he took his first leave, travelling by train to the Holy Land. Seeing people of different ethnic groups and religions worshipping together at the various shrines made a tremendous impression, and he subsequently visited Palestine whenever the opportunity arose.
Pōtatau eventually got his wish to visit the front, but only when the Germans were retreating from El Alamein; nevertheless, he was nearly killed by a raiding Messerschmitt. He acted briefly as chaplain to the company in 1943, while it was waiting for an Anglican replacement. In 1944 he was sent to learn to type and was promised promotion when a vacancy occurred. He made an unauthorised attempt to get to Italy with the battalion, for which he was court-martialled, but not penalised, as he pointed out he was running towards the battle, not away from it. Sent home in November 1944, he arrived in Nūhaka on 5 January 1945, where he was given an official welcome by Ngāti Rangi and Ngāti Rākaipaaka.
A week later Pōtatau went to Tūrangi to meet Ira Rangiita, with whom he had corresponded during his time in the army. They were married on 28 July 1945 on the Hīrangi marae at Tokaanu. Ira was the daughter of Rangiita Tamaira, also known as Te Rangiita Te Waaka, a leading rangatira of Ngāti Te Rangiita hapū of Ngāti Tūwharetoa, and his wife, Rangimārama Nuku, of Tūrangi. The couple would have no children, but adopted a son and fostered a daughter. Earlier that year, in May, Pōtatau was appointed the first Māori moderator of a Presbyterian Māori missions committee. He held the position until 1947.
In 1945 and 1946 Pōtatau also ministered at Te Whāiti. He was then appointed to Taumarunui, where he remained until 1959. Ira’s ties of kinship in the area gave them positions of influence and leadership. Pōtatau ran both Pākehā and Māori parishes at times, and he was involved in sports administration, especially rugby and hockey. He served as secretary on two tribal committees, and helped set up Mangahouhou 3A Incorporation. About 1948 he chaired a large meeting held to consider the question of the banning of liquor from the King Country, attended by such prominent leaders as Hepi Te Heuheu and Pei Te Hurinui Jones. Pōtatau accompanied Korokī and a delegation of 600 to Wellington in 1949 to demand, unsuccessfully, the continuation of the pact banning liquor.
In 1959 Hēmi and Ira were moved to Ōpōtiki. In 1964 Hēmi became moderator of the Māori synod of the Presbyterian church and they shifted to Whakatāne. His duties included visiting all parishes and having responsibility for positioning staff. Hēmi retired in May 1967 and moved to Auckland with Ira, who was ill with cancer. She died on 2 July that year, and was taken to Waitetoko, Tūrangi, for burial.
In accord with Ira’s last wish that he finish his BA, Pōtatau enrolled at the University of Auckland to study Māori and anthropology. He participated fully in Māori student life, taking part in protests and opposing the All Black tour of South Africa in 1970. After completing his BA at Victoria University of Wellington in 1972 and 1973, Pōtatau assisted in setting up Māori language week.
In 1975 Pōtatau was again elected interim moderator of the Māori synod, serving for a year. In 1977 he was re-appointed minister at Taumarunui and was there in 1978 when the Mongrel Mob held its annual hui at Hiakaitupeka marae. He conducted prayers for them, and although the hui was peaceful he later had to intervene when two of Ira’s relations were involved in violence. In 1979 he moved to Waitetoko, but after a car accident spent long periods in hospital that year and in 1980. After recovering he began writing his autobiography. It was submitted for the first Pegasus Prize for Māori literature in 1984 and was considered an outstanding entry. Published in 1991 as He hokinga mahara , it was the first autobiography to be published in Māori.
In 1988 Hēmi Pōtatau returned to live at Nūhaka. He died on 18 January 1994 in Wairoa, and was buried at Te Mimi o Te Hiki cemetery.