The systematics and cultural history of economically significant plants.
The history of science and of botanical illustration.
The Robert Brown Handbook (due September 2021), with David Moore (deceased) and Jacek Wajer (Natural History Museum London)
A revision of the huanglongbing (citrus greening) host genera Bergera and Murraya (Rutaceae), with Prof. Andrew Beattie and team (Western Sydney University)
The nomenclature of Assam tea (Camellia, Theaceae)
A revision of the genus Citrus (Rutaceae)
The 'London' Australian natural history drawings of Ferdinand Bauer
A revision of Dysoxylum sensu lato (Meliaceae), with Prof. dr. Alexandra Muellner and team (University of Leipzig, Germany)
The genetics of Linnaeus’s apple (Rosaceae), with Dr David Chagne and colleagues (Plant and Food, Auckland, New Zealand)
The nomenclature of flannel flowers (Actinotus, Umbelliferae), with Dr Murray Henwood (University of Sydney) and Prof. dr. H. Walter Lack (Botanischer Garten, Berlin)
The origins of Hibiscus rosa-sinensis and other cultivated Pacific Hibiscus, with Dr Lex Thomson and colleagues (University of the Sunshine Coast)
The botanical contributions of Hippolyte Arnaud, with Dr Valery Malecot (University of Angers, France)
Mabberley’s Plant-book ed. 5
Editor, Cultural History of Plants (due March 2022), a multivolume work (Bloomsbury, London), with Prof. A. Gieseke (University of Delaware)
Origins and dispersal of f'ei bananas, with Dr Lex Thomson and colleagues (University of the Sunshine Coast)