Dr Nicolle, from Adelaide in South Australia, has been interested in Australian native plants since childhood. By the age of 16 he was devoted to seeing in the wild, and attempting to grow, every known species of eucalypt.

Dr Nicolle is qualified with a Certificate in Horticulture at Urrbrae High School, a Bachelor of Applied Science and a Bachelor of Science (Honours in Botany) at Adelaide University, and a Ph.D. in eucalypt systematics at Flinders University of South Australia. He has named over 70 new species and subspecies of eucalypts and has authored over 75 peer-reviewed scientific publications, all relating to eucalypts, as well various reference books including Native Eucalypts of Victoria and Tasmania, South-eastern Australia (2022), Smaller Eucalypts for Planting in Australia (2016), Taller Eucalypts for Planting in Australia (2016), Native Eucalypts of South Australia (2013) and Atlas of Leaf Venation and Oil Gland Patterns in the Eucalypts (2013).

Dr Nicolle is self-employed as a consulting arborist, botanist and ecologist, specialising in the eucalypts. He established and maintains Currency Creek Arboretum in South Australia, a specialist research arboretum growing over 800 species of eucalypts. His research associated with CCA has involved extensive field research throughout Australia and abroad.

In 2003 Dr Nicolle received a Centenary Medal awarded by the Governor-General for service to the community through the establishment of a eucalypt research arboretum, and in 2015 he received the inaugural Bjarne K Dahl Medal for providing an outstanding contribution to eucalypt conservation and education. In 2018 he was awarded a Medal of the Order of Australia (OAM) for services to the conservation of Australian eucalypts.