He was born in East Hoathly, Sussex and in 1860 started work at the Royal Botanic Gardens, Kew as an Improver, then Assistant for India in the Herbarium, finally Keeper of Herbarium and Library. He wrote a number of botanical works.
- William Botting Hemsley (1873). Handbook of Hardy Trees, Shrubs, and Herbaceous Plants: Based on the French Work of Messrs. Decaisne and Naudin Entitled 'Manuel de L'amateur Des Jardins,' and Including the Original Woodcuts by Riocreux and Leblanc. Estes & Lauriat.
- Biologica Centrali-Americana Botany. Vol. I , 1879–1888
- Biologica Centrali-Americana Botany. Vol. III, 1882–1886
- Botany of the Bermudas and various other Islands of the Atlantic and Southern Oceans, 1885
- Botany of Juan Fernandez, South-eastern Molluccas, and the Admiralty Islands, 1885
- An Enumeration of All the Plants Known from China Proper, Formosa, Hainan, Corea, the Luchu Archipelago, and the Island of Hong Kong. with Francis B. Forbes, 1887
- Hemsley, William (1893). "Early Reminiscences of Kew". The Journal of the Kew Guild. 1 (1): 31–38. Retrieved 10 August 2013.
- "Hemsleya Cogn. ex F.B.Forbes & Hemsl. | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 16 May 2021.
- "Library and Archive Catalogue". Royal Society. Retrieved 18 November 2010.
- IPNI. Hemsl.
- William Botting Hemsley finding aid collection held at Royal Botanic Gardens, Kew archives.