Underwood, John (d. 1834), horticulturist, believed to be Scottish by birth, was elected an associate of the Linnean Society of London on 19 January 1796, when he was living at an address in Brompton, Middlesex. In September 1798 he was appointed as the first head gardener at the Botanic Gardens, Glasnevin, which had been established three years earlier by the Dublin Society; he took up his appointment under the committee of botany on 25 October 1798. Underwood's duties involved supervising and expanding the plant collections, listing duplicate stock, keeping sales accounts, and conducting visitors around the gardens. In January 1802 he was given full responsibility for overseeing the gardens and staff, and was then referred to as ‘head gardener and superintendent’; in 1812 he was also made responsible for training apprentices. Underwood published lists of material pertaining to the gardens, most notably the second catalogue of the collections, listing some 6,000 species and varieties, which appeared in 1804 as ‘A catalogue of plants indigenous and exotic cultivated in the Botanic Garden belonging to the Dublin Society at Glasnevin’ in the Transactions of the Dublin Society (iv, 1–134). He also made daily meteorological observations at Glasnevin, thus laying the foundation for the Glasnevin weather station; the records for 1801–8 were published each year in the Transactions as ‘A diary of the weather at the Botanic Garden’.
After his early achievements, Underwood was threatened with dismissal and severely censured in 1819–20 when a rare Norfolk Island pine, Araucaria excelsa, died through a combination of circumstances not of his making. From then onwards there were mounting criticisms of the neglected state of the gardens, partly attributed to Underwood's declining capacities. The decision to replace him was taken in December 1833 and a successor, Ninian Niven (qv), was appointed with the new title of ‘curator’ on 6 March 1834. Underwood was awarded a ‘superannuated allowance’.
John Underwood married Mary Newcommen in 1799; their seven recorded children (five daughters and two sons) were born between 1805 and 1818. On his appointment to Glasnevin in 1798 Underwood lived in a house there provided by the Dublin Society; after the new entrance gates and two lodges were built in 1815 he and his family occupied one of the lodges. On his retirement he and his wife moved to a model cottage within the gardens, where Mary Underwood continued to reside on a pension after his death, in August 1834; she died in 1862.