[1] In April 1920, Hubbard left the Sandringham Estate to join the Royal Botanic Gardens, Kew, initially working in the temperate house and arboretum.
[1] At the request of the Government of Queensland, Hubbard travelled to Australia in 1930, in exchange for the Australian botanist W. D. Francis, who spent a year at Kew.
[3] He visited the herbaria in Sydney, Melbourne, Adelaide and Perth,[1] as well as examining every grass specimen in the Queensland Herbarium in Brisbane.
[1] On 1 October 1957, Hubbard was promoted to Keeper of the Herbarium and Library at Kew, and rose to deputy director in April 1959.
[4] Hubbard is perhaps better remembered for his popular science book Grasses: a Guide to their Structure, Identification, Uses and Distribution in the British Isles, published in 1954, with a second edition following in 1968.