After working in a variety of technical jobs, including with the Forests Commission of Victoria and the Botany Department of The University of Melbourne, Ian Clarke was for many years employed in the plant identification service of the National Herbarium of Victoria. He transferred to a position as honorary associate there in 2003.

He is the author and illustrator of a companion text, Name those Grasses: Identifying Grasses, Sedges and Rushes, published by the Royal Botanic Gardens Victoria in 2015. Between 1975 and 1990 he was associated with the Council of Adult Education in Melbourne as a tutor in flowering plant identification.