Zantedeschia rehmannii aka Red Calla Lily

Z. rehmannii is the most compact species in the genus, typically reaching about 40 cm (15 in) tall and 30 cm (12 in) wide. Genus-level extension data give a slightly larger range of 1-3 ft tall by 1-2 ft wide because cultivars and hybrids vary. Growth is moderate and the plant is considered low-maintenance.

Zantedeschia rehmannii is only slightly frost hardy. Genus-level guidance places it in USDA zones 7a-10b, but in cooler climates the rhizomes should be lifted and stored dry, or the plant grown in containers and protected from frost.

This is a deciduous summer-growing geophyte from a summer-rainfall climate. Expect active leaf and flower growth in spring through summer, followed by natural dormancy as the foliage dies back in autumn. Reduce watering during dormancy and resume regular watering as new shoots emerge.

The summer-borne inflorescence is a pink to mauve or rose-purple spathe with paler margins, slender in form, wrapped around a yellow spadix. Leaves are unmarked green, semi-erect and elliptic-lanceolate rather than the arrow shape seen in Z. aethiopica.

Z. rehmannii is one of the parent species of the modern coloured calla hybrid range; selected forms and the species itself have received the RHS Award of Garden Merit.

Grow outdoors in moist, humus-rich, well-composted soil in part shade with shelter from strong winds. Hardy at genus level in USDA zones 7a-10b; in colder areas grow in containers or lift the rhizomes for dry winter storage.

Propagate by division of the dormant rhizomes, separating offsets when growth is starting in spring. Genus extension guidance also notes propagation by seed sown in fall.

The Araceae inflorescence consists of small flowers tightly packed on a spadix surrounded by a coloured spathe; insect pollination by beetles or flies is typical of the family. No Z. rehmannii-specific pollinator data was found in the consulted sources.

All parts of Zantedeschia contain calcium oxalate raphides that cause severe oral burning if chewed raw. While the leaves of some Zantedeschia species are sometimes cooked and eaten in their native range with careful preparation, the plant should otherwise be regarded as inedible and unsafe to consume.

Zantedeschia species, including Z. rehmannii, are widely grown as ornamental garden plants and as cut flowers. Z. rehmannii in particular has been important in the breeding of modern coloured calla hybrids.