Calla is a monotypic genus of flowering plants in the family Araceae (order Alismatales), containing a single species: Calla palustris, commonly known as bog arum, marsh calla, wild calla, or water-arum. It is the only genus in the tribe Calleae of the subfamily Aroideae, though its systematic position has long been considered puzzling — it has at various times been placed in its own family (Callaceae) or its own subfamily (Calloideae) based on its unusual pollen morphology and anatomy. Molecular phylogenetic studies now place it within Aroideae.
Calla palustris is a rhizomatous herbaceous perennial that grows in bogs, marshes, and at pond margins across cool temperate regions of the Northern Hemisphere. The leaves are rounded to heart-shaped, 6–12 cm long on 10–20 cm petioles. Like other aroids, it bears a spadix inflorescence — a greenish-yellow spike 4–6 cm long — enclosed in a bright white spathe. The fruit is a cluster of striking red berries, each containing several seeds.
The plant is toxic when fresh due to a high oxalic acid content. However, the rhizome can be rendered edible through drying, grinding, leaching, and boiling — a preparation shared with related genera such as Caladium, Colocasia, and Arum.
Although the genus formerly included species from tropical Africa, these have since been reclassified into the separate genus Zantedeschia. Those plants are still widely sold as "calla lilies," but they are not true Calla and should not be confused with C. palustris. The genus was first described by Carl Linnaeus in 1753.
Etymology
The name Calla was applied by Carl Linnaeus in his 1753 description of the genus and its sole species, Calla palustris. The genus formerly encompassed tropical African species now classified under Zantedeschia, which retain the popular name "calla lily" despite belonging to a separate genus.
Distribution
Calla palustris is native to cool temperate regions of the Northern Hemisphere. Its range spans central, eastern, and northern Europe (from France and Norway eastward, but excluding Britain), across northern Asia, and into northern North America — including Alaska, Canada, and the northeastern contiguous United States.
Taxonomy Notes
The systematic position of Calla within Araceae has been described as "puzzling." Its pollen grains are unusually small and ornamental within the family, with a distinctively constructed exine. Morphological and anatomical studies historically separated Calla from other aroids, leading to placements in its own family (Callaceae) or subfamily (Calloideae). Modern molecular phylogenetic studies place it within the subfamily Aroideae in its own tribe Calleae. The genus was described by Linnaeus in 1753 and is the sole member of its tribe.
