Having received botanical training, Holttum was given the role of assistant director at the Singapore Botanical Gardens in 1922, with the guidance of Isaac Henry Burkill.[3] In Singapore, he performed some exhaustive studies, and was promoted to director in 1925,[3] following the retirement of Burkill.[6] His areas of expertise were the growth and cultivation of orchids.[3] He continued working at the Singapore Botanical Gardens even during the Japanese occupation of the country.[3]
Holttum and Corner (assistant director at the Singapore Botanical Garden) were once detained at the internment camp in Singapore. Dr. Kwan Koriba and Hidezo Tanaka, who took control of the Gardens, pleaded to keep Holttum and Corner at their posts at the Gardens. The Japanese Emperor Hirohito was an orchid enthusiast, so he granted the plea. This action led to the success of the hybridization of Singapore's national flower.
When the war finished, Holttum and Corner got approved to release Dr. Kwan Koriba from a prisoner camp. Dr. Kwan rejected the offer and chose to stay with his fellow soldiers. Holttum praised his act later.
Returning from Great Britain, where he departed to in 1925, Holttum continued his job as the Garden's director, until he moved to the University of Malaya in Singapore to serve as its first Professor of Botany.[3] Holttum penned many books during his tenure at the educational institution, including Gardening at the lowlands of the Malays (which is credited as the first book on Singaporean gardening[6]) and Plant Life in Malaya.[6] He was also the first head of department for Botany at the Department of Biological Sciences at the National University of Singapore.[7] He founded the Malayan Orchid Society (now Orchid Society of South East Asia) in 1928.[6] He went back to England later in 1954.[3]
Holttum's area of interest was pteridology, such as that of Malayan ferns.[6]
There are at least 23 species of plant named after him, with epithets of holttumiiorholttumianus.
Also in 1924, Holttumia was published, which is a genus of fungi in the family Xylariaceae.[10] Then published in 1964, Rehia which is a genus of plants in the grass family.[11] Then in 1964, Holttumochloa which is a genus of Malaysianbamboos also in the Poaceae family and native to the hill forests of Peninsular Malaysia.[12][13]
^McClintock, David (March 1976). "Professor Richard Eric Holttum, M.A., Sc.D., D.Sc., F.L.S. an appreciation". Biological Journal of the Linnean Society. 8: 1–23. doi:10.1111/j.1095-8312.1976.tb00231.x.
^Holttum, Richard E. (April 1975). "R.E. Holttum, by himself". Flora Malesiana Bulletin. 28: 2477–2500.
