Her approach favoured the isolation of individual specimens like Datura metel or Lupinus angustifolius. She often worked with watercolour on vellum to achieve a high degree of botanical accuracy. These compositions avoid the dense arrangements seen in typical Dutch flower paintings. Instead, Withoos focused on the specific morphology of a plant, from the texture of the leaves to the curve of the petals. Her use of negative space gives each subject a quiet, formal presence.

Collectors today appreciate the clarity and scientific objectivity of these illustrations. Prints of her work, including Purple Coronilla and Nandina, fit well in modern spaces that prioritise clean lines. The absence of dark, heavy backgrounds makes her botanical studies feel light and accessible. They represent a period when art was used to map the natural world. These prints provide a direct link to the origins of botanical science.