As assistant botanist Fyles labelled the trees, shrubs and herbaceous perennials in the Arboretum and was responsible for identifying the large number of plants sent to, or collected by, the division. She also offered to draw botanical specimens in her spare time. On July 11, 1914, Fyles left Ottawa to tour western Canada collecting weeds. Upwards of 800 specimens of weeds representing 44 different species were collected, pressed, dried and shipped to Ottawa. Her first sole authored publication was in 1914 where she was accredited with the ‘Systematic Botany’ chapter in the Report of the Dominion Botanist for 1913. In 1914, Fyles travelled through Western Canada to prepare a bulletin, "Principal Poisonous Plants of Canada", which was illustrated with her own paintings and sketches. Additional publications (Wild Rice Bulletin, 1920; and the expansion of the herbarium came from her work in the Department. During World War I, Fyles (Fyles, 1915) conducted research on a fungal disease of wild rice called ergot and realized that the wild rice fungus was a new species. She formally described it scientifically in her wild rice bulletin in 1920 following the war (Fyles, 1920a). That year she also published her bulletin (Fyles, 1920b) on poisonous plants that also mentions the wild rice ergot now known as "Claviceps zizaniae" (Fyles) Pantidou ex Redhead, M. E. Corlett & M. N. L. Lefebvre (Redhead et al 2008). Additionally in 1920, Fyles became the first artist employed by the Horticulture division, where she worked under William Tyrrell Macoun. Her paintings were intended to provide illustration of true colour and technical data of individual specimens. This was especially important in terms of experimenting with and documenting different varieties of fruit, vegetation and seeds. Her watercolours illustrate publications such as Cultivation of the Apple in Canada and The Raspberry and its Cultivation in Canada. In 1931, poor health forced her retirement, but she continued painting in oils, pastels and watercolours. For two decades she had entered her work in Royal Canadian Academy of Arts exhibitions that expressed an appreciation of nature’s beauty, especially that of plants and flowers. She also held her own exhibitions, such as one in Ottawa in 1924 where 17 of her 36 pictures on display were sold, including one to Lady Byng, wife of the Governor General of Canada who later had Fyles paint scenes from her garden.