Dr Hardham is distinguished for her studies of the cytoskeletal basis of plant morphogenesis and host-pathogen interactions, focusing on properties of cell surface components. She was first to determine the nature of cortical microtubule arrays of plant cells and to quantify their augmentation by interpolation; she also characterised microtubule reassembly and roles in cell-shaping. Her innovative cytological, immunological and molecular researches on the zoosporic agents of infection of the dieback fungus, Phytophthora cinnamomi, have yielded significant new knowledge of infection processes used by this destructive plant pathogen, and of fundamental aspects of cell polarity, cytokinesis, Golgi function, secretion, chemotaxis and phylogeny, as well as practical applications in the form of diagnostic assays.