In some genera the spathe is very conspicuous and brilliantly coloured (e.g., many Anthurium species) while in others the spathe is small and leaf-like (e.g., many Pothos species). In the North American genus Orontium the spathe is so reduced that it appears to be absent altogether and in Gymnostachys, a peculiar genus restricted to eastern Australia, debate continues as to whether a spathe is in fact present or, indeed, if Gymnostachys might be better removed altogether from the aroids. The behaviour of the spathe varies from genus to genus. In some (e.g., Cryptocoryne) the spathe completely encloses the spadix, while in others the spathe reflexes to leave the spathe clearly visible (e.g., most Anthurium, Spathiphyllum). In some genera the spathe is shed as soon as the inflorescence reaches anthesis, either falling completely (e.g., Rhaphidophora) or partially (e.g., Schismatoglottis). The spathe ranges in size and shape from 5mm long and simple in Homalomena humilis to the fluted and pleated vase 1m wide and 1.5m tall found in Amorphophallus titanum.

The sex of the individual flowers and their arrangement on the spadix are among the characters used to define taxonomic groups. Depending on the genus the spadix may bear either unisexual or bisexual flowers. If bearing bisexual flowers there are uniformly arranged over the spadix. Almost without exception bisexual flowers are subtended by reduced tepals termed a perigon. If unisexual, the flowers are usually arranged with the females at the base of the spadix occasionally terminated by a sterile appendix. In the genus Arisaema individual inflorescences are usually either male or female. The sex of the inflorescence in Arisaema is governed by the age of the plant, its health, and the type of conditions in which it is growing.