[2] Through her studies Isherwood learned an appreciation of linear perspective and accurate draughtsmanship which she later applied with great skill to her rural landscapes.
An exacting teacher, she stalked her perspective drawing students with a kneadable putty eraser in hand, challenging their skills with arrangements of battered metal rubbish bins, piles of broken chairs and, on rainy days, a dripping sixteen-rib umbrella.
From that time onwards, she became primarily a landscape painter, and, through her attachment to the countryside, a major exhibitor in the art competitions held in conjunction with the shows run by the local Agricultural Societies and culminating each year in the Sydney Royal Easter Show with its exhibition attracting hundreds of entrants.
Isherwood, as a child, and like most other Australian children for many years, learnt by heart Dorothea Mackellar's iconic poem, "My Country", in which an Australian explains to an English listener how she is not moved by the gentle landscape of England with soft, dim skies and green lanes, but by the harsh beauty of Australia.
In 1982 Isherwood heard on the radio that a statue was to be erected as a memorial to Dorothea Mackellar at Gunnedah, on Australia Day, 26 January 1983.
Prompted by the imminent celebration, Isherwood created a series of thirty four watercolour paintings for exhibition in Gunnedah in conjunction with the unveiling of the statue.
The images represent the diversity of the Australian landscape and include "the filmy veil of greenness' seen from Isherwood's own window, a flood on the Darling River, a bushfire in the Blue Mountains and a forest of ringbarked trees near Armidale.
As is usual in a watercolour, those parts of the painting which are white are left unpainted, in this case a forest of dead tree trunks.
[citation needed] From 1946, Isherwood had nineteen exhibitions, of which three were with her daughter, Jaqueline Dabron, in the state capitals of Sydney, Brisbane and Melbourne.
In 2012, thirty-two of Isherwood's watercolors were featured in Sister Cities, the inaugural exhibition of Gallery Lane Cove on Sydney's north shore.