|Born||28 May 1851
|Died||2 October 1919
|Known for||identifying the botanical species meant by the term 'shamrock'|
|Influences||Alexander Goodman More
Very little is known about Colgan's early life, but it is believed his parents may have been Nathaniel Watson Colgan and Letitia Phair. After leaving school, Colgan began work as a clerk in the Dublin Metropolitan Police Court and remained there until his retirement in 1916.
He began visiting Europe every summer from 1875, and these trips inspired many of the contributions to a magazine of literary manuscripts, Varieties. He was a regular contributor to the magazine from 1873 and edited it for a number of years. Colgan also contributed to Irish Monthly, Tinsley's Magazine and Hibernia.
Colgan never married and died in Dublin on 2 October 1919.
Botanical and zoological work
Colgan became a keen amateur botanist following his discovery in 1884 of the rare plant saw-wort in Wicklow and was encouraged by Alexander Goodman More to study botany further. Moving to Sandycove in 1900, Colgan developed an interest in marine invertebrates, particularly Mollusca and tunicates. Colgan recorded the marine Mollusca collected during the Clare Island Survey and his large mollusc collections from Co. Dublin and Clare Island were subsequently donated to the Natural History Museum Dublin.
Colgan is noted for his work in identifying the botanical species meant by the term 'shamrock' in the 1890s. He did this by requesting people from around Ireland send him specimens of what they believed to be an Irish shamrock. After tending these specimens until they flowered, Colgan identified five most common plant species. The most common was yellow clover, followed by white clover, red clover, black medic and finally wood sorrel. Dr Charles Nelson repeated the experiment in 1988, marking a hundred years since Colgan's original survey, and found that yellow clover was still the most commonly chosen. Yellow clover is also the species that is cultivated for sale in Ireland on Saint Patrick's Day and has been nominated by Department of Agriculture as the "official" shamrock of Ireland.
Colgan's interest in vernacular and Irish language names for various plants and animals was reflected in his other work into jellyfish, starfish and periwinkles and his contribution to the Clare Island Survey.
- 'The Shamrock: an attempt to fix its species' The Irish Naturalist: a monthly journal of general Irish natural history, Vol. 1, No. 5, 95-97, (August 1892)
- 'The Shamrock: a further attempt to fix its species' The Irish Naturalist: a monthly journal of general Irish natural history, Vol. 2, No. 8, 207-211, (August 1893)
- Flora of the County Dublin. Hodges, Figgis & Co., Dublin (1904)
- 1907 Contributions to a natural history of Lambay: marine Mollusca. Irish Naturalist 16: 33-40 (1907)
- Clare Island Survey: Gaelic plant and animal names, and associated folk-lore. Proceedings of the Royal Irish Academy 31B: 1-30 (1911)
- Clare Island Survey: Marine Mollusca. Proceedings of the Royal Irish Academy 31B: 1-36 (1911)
- The opisthobranch fauna of the shores and shallow waters of County Dublin. Irish Naturalist 23: 161-204 (1914)
- The marine Mollusca of the shores and shallow waters of County Dublin. Proceedings of the Royal Irish Academy 39B: 391-42 (1930)
- Bohan, Rob; Lunney, Linde. "Colgan, Nathaniel". Dictionary of Irish Biography. Cambridge University Press.
- Unknown. "Colgan, Nathaniel (1851-1919)". Global Plants. Jstor. Retrieved 17 February 2015.
- Praeger, R. Lloyd. "Nathaniel Colgan". Some Irish Naturalists: A Biographical Note-book. National Botanic Gardens of Ireland. Retrieved 17 February 2015.
- Nunn, J.D.; Holmes, J.M.C. (2008). "History of the Irish & British Marine Molluscan Collections". A Catalogue of the Irish and British Marine Mollusca in the collections of the National Museum of Ireland - Natural History 1835-2008. National Museums Northern Ireland. Retrieved 17 February 2015.
- Pavord, Anna (2010). The Naming of Names: The Search for Order in the World of Plants. London: A&C Black. ISBN 9781408820766.
- Mulvihill, Mary (2012). "Why is the shamrock a sham?". Ingenious Ireland. Retrieved 17 February 2015.
- Mulvihill, Mary (2003). Ingenious Ireland: A County-by-County Exploration of the Mysteries and Marvels of the Ingenious Irish. Dublin: Simon and Schuster. p. 352. ISBN 9780684020945.
- Lysaght, Sean (1998). "Contrasting Natures: The Issue of Names". In Wilson Foster, John; Chesney, Helena C. G. Nature in Ireland: A Scientific and Cultural History. McGill-Queen's Press. ISBN 9780773518179.
- Colgan, Nathaniel (1911). Part 4. Gaelic Plant and Animal Names, and Associated Folk-Lore. Dublin: Royal Irish Academy. Retrieved 17 February 2015.