Harvey was born at Summerville near Limerick, Ireland, in 1811, the youngest of 11 children.
His father Joseph Massey Harvey, was a Quaker and prominent merchant.
William started his education at Ballitore School in County Kildare and by the age of 15 had already established algae as his over-riding interest.
After leaving school he joined the family business.

Harvey was an authority on algae and bryophytes (mosses), and author of A Manual of the British Algae (1841), Phycologia Britannica (4 vols.,
1846–51), Nereis Boreali-Americana. (
3 parts 1852–85) and Phycologia Australica (5 vol.,
1858–63).
He spent several years in South Africa, and was the author, with German botanist Otto Wilhelm Sonder, of the Flora Capensis (7 vol.
in 11, 1859 – 1933).
Harvey's main algal herbarium is located at Trinity College, Dublin.

Harvey's discovery in 1831 of the moss Hookeria laetevirens at Killarney, new to Ireland, led to a lifelong friendship with Sir William Jackson Hooker, who was then Regius Professor of Botany at Glasgow University.
Hooker recognised the talent of the young man and lent him books and specimens.
Soon afterwards Hooker invited him to contribute the section on algae to his British Flora (1833) as well as the section on algae for The Botany of Captain Beechy's Voyage.

In 1835 Harvey went to South Africa aboard the vessel "Carnatic", with his brother Joseph who had been mistakenly nominated as Colonial Treasurer by Thomas Spring Rice instead of William.
When Joseph's health failed in the following year, William took over his duties.
They left for Britain together on 14 April 1836 and Joseph died on the voyage.

Back in Cape Town, and now officially Treasurer-General, William took up residence at Bishop's Court, rising before dawn every day, collecting in the mountains or sea-shore, and working on the plants at night.
In March 1837 he wrote: 'I have taken so many excursions lately that I almost fear I shall earn the sobriquet of Her Majesty's pleasurer general'.
In the same year he enlisted the services of botanical collector Karl Zeyher, who was in Uitenhage, to collect specimens.
He developed a close friendship with Baron von Ludwig who had started his famous gardens in Cape Town, and dedicated his Genera of South African Plants to him.
Under the patronage of Sir George Grey and with the assistance of a team of collectors and of Otto Wilhelm Sonder, he set about writing a Flora Capensis in English – he lived long enough to see the first three volumes completed and published in Dublin, the third in 1865.
He came home in 1842, having resigned his position due to illness.

In 1844 Harvey became curator of the Trinity College Herbarium (TCD) and in 1848 Professor of Botany of the Royal Dublin Society.

In 1853 he made a three-year voyage, visiting South Africa, Ceylon, Australia, New Zealand, Tonga, Fiji, and Chile.
On his return he published further important books dealing with the botany of North America and South Africa and in 1858 was appointed Professor of Botany at Trinity College, Dublin.

He died from tuberculosis on 15 May 1866 at Torquay and was buried there.
Harvey was born at Summerville near Limerick, Ireland, in 1811, the youngest of 11 children. His father Joseph Massey Harvey, was a Quaker and prominent merchant. William started his education at Ballitore School in County Kildare and by the age of 15 had already established algae as his over-riding interest. After leaving school he joined the family business.
Harvey was an authority on algae and bryophytes (mosses), and author of A Manual of the British Algae (1841), Phycologia Britannica (4 vols., 1846–51), Nereis Boreali-Americana. (3 parts 1852–85) and Phycologia Australica (5 vol., 1858–63). He spent several years in South Africa, and was the author, with German botanist Otto Wilhelm Sonder, of the Flora Capensis (7 vol. in 11, 1859 – 1933). Harvey's main algal herbarium is located at Trinity College, Dublin.
Harvey's discovery in 1831 of the moss Hookeria laetevirens at Killarney, new to Ireland, led to a lifelong friendship with Sir William Jackson Hooker, who was then Regius Professor of Botany at Glasgow University. Hooker recognised the talent of the young man and lent him books and specimens. Soon afterwards Hooker invited him to contribute the section on algae to his British Flora (1833) as well as the section on algae for The Botany of Captain Beechy's Voyage.
In 1835 Harvey went to South Africa aboard the vessel "Carnatic", with his brother Joseph who had been mistakenly nominated as Colonial Treasurer by Thomas Spring Rice instead of William. When Joseph's health failed in the following year, William took over his duties. They left for Britain together on 14 April 1836 and Joseph died on the voyage.
Back in Cape Town, and now officially Treasurer-General, William took up residence at Bishop's Court, rising before dawn every day, collecting in the mountains or sea-shore, and working on the plants at night. In March 1837 he wrote: 'I have taken so many excursions lately that I almost fear I shall earn the sobriquet of Her Majesty's pleasurer general'. In the same year he enlisted the services of botanical collector Karl Zeyher, who was in Uitenhage, to collect specimens. He developed a close friendship with Baron von Ludwig who had started his famous gardens in Cape Town, and dedicated his Genera of South African Plants to him. Under the patronage of Sir George Grey and with the assistance of a team of collectors and of Otto Wilhelm Sonder, he set about writing a Flora Capensis in English – he lived long enough to see the first three volumes completed and published in Dublin, the third in 1865. He came home in 1842, having resigned his position due to illness.
In 1844 Harvey became curator of the Trinity College Herbarium (TCD) and in 1848 Professor of Botany of the Royal Dublin Society.
In 1853 he made a three-year voyage, visiting South Africa, Ceylon, Australia, New Zealand, Tonga, Fiji, and Chile. On his return he published further important books dealing with the botany of North America and South Africa and in 1858 was appointed Professor of Botany at Trinity College, Dublin.
He died from tuberculosis on 15 May 1866 at Torquay and was buried there.
William Henry Harvey