Alisma is a genus of flowering plants in the family Alismataceae, members of which are commonly known as water-plantains. The genus consists of aquatic plants with leaves either floating or submerged, found in a variety of still water habitats around the world (nearly worldwide). The flowers are hermaphrodite, and are arranged in panicles, racemes, or umbels. Alisma flowers have six stamens, numerous free carpels in a single whorl, each with 1 ovule, and subventral styles. The fruit is an achene with a short beak.
The nineteenth century British art and social critic John Ruskin believed that the particular curve of the leaf-ribs of Alisma represented a model of ‘divine proportion’ and helped shape his theory of Gothic architecture.
Copóg Phádraig (“leaf of Patrick”) is the Irish name for the water-plantain. It is reputed to ward off fairies.