Background
Collett was born in Thetford, Norfolk and studied at Tonbridge School and at Addiscombe Military Seminary.
Collett was born in Thetford, Norfolk and studied at Tonbridge School and at Addiscombe Military Seminary.
He served as an army officer in the East India Company. He entered the Bengal army in 1855, rising through the ranks to become a lieutenant-colonel in 1879. In the Second Anglo-Afghan War (1878-1880) he acted as quartermaster-general on the staff of Frederick Roberts, 1st Earl Roberts.
He was promoted colonel in 1884, made Knight Commander of the Order of the Bath in 1891, and from 1892 to 1893 he commanded the Peshawar district with the rank of major-general.
He retired from the army in 1893. Collett was keen botanist, collecting plants in Afghanistan, Algeria, Burma, the Canaries, Corsica, India, Java, and Spain.
He was made a fellow of the Linnean Society in 1879. At his death he was working on a book on the flora of Simla, which was published posthumously as Flora Simlensis (1902).
Iris colletti was named after him in 1909.