This article gives background information on the taxonomic relationships between plants, for clinicians, patients and students of allergy. A list is provided of plants considered potentially allergenic either by inhalation of pollen or by ingestion of grain products. Distributions in Australia of plant species important in assessing pollen‐related allergy, and the range of foodstuffs that contain cereal‐grain protein, are also indicated. Particular emphasis is placed on the grasses because of their importance as producers of both grain and pollen.