This plant is most often found growing on old walls. It has reddish-green flowers in late summer, and soft hairy non-stinging leaves. It has separate male and female petal-less flowers, with the female flowers generally at the tip of the inflorescence, and the male flowers below. The stamens are bent in under the tips of the sepals; a slight shock liberates them and they spring out violently scattering their pollen, which is caught and dispersed in air currents.