Zantedeschia is a genus of eight species of rhizomatous, herbaceous, perennial flowering plants in the aroid family Araceae, placed in the order Alismatales. The genus is native to central and southern Africa, ranging from South Africa northeast to Malawi, Nigeria, and Tanzania, and has been introduced — in some cases invasively — to every continent except Antarctica.
Plants are typically clump-forming, growing from thick rhizomes (in Z. aethiopica and relatives) or tubers (in the remaining species). Stems and petioles are fleshy and spongy; leaves are long-stalked with a simple, variably shaped blade — triangular, cordate, hastate, or lanceolate — dark green, feather-veined, and often bearing transparent silvery spots (maculation). Heights range from about 60 cm in Z. rehmannii to 1.2 m in Z. aethiopica.
The distinctive inflorescence is a solitary pseudanthium: a broad, funnel-shaped spathe — white in Z. aethiopica, yellow or pink in other species, and a wide spectrum of orange, red, and purple in cultivated hybrids — that wraps around a central finger-like spadix bearing small, petalless unisexual flowers. Fruit are beaked orange or red berries.
Zantedeschia is the sole genus in the tribe Zantedeschieae (Araceae). Common names include arum lily (Z. aethiopica) and calla lily or calla (Z. elliottiana, Z. rehmannii), though the plants are neither true lilies (family Liliaceae) nor true members of the genera Arum or Calla.
All parts of the plant are toxic, containing calcium oxalate raphides that cause oral irritation and occasional vomiting if ingested. Despite this, Zantedeschia species are widely grown as ornamentals and are important cut-flower crops, with commercial production centred in California, New Zealand, Colombia, and Kenya.
Etymology
The genus name honours Italian botanist Giovanni Zantedeschi (1773–1846) and was bestowed by the German botanist Kurt Sprengel (1766–1833).
Distribution
All eight species are endemic to central and southern Africa, spanning from South Africa northward through Eswatini, Mozambique, Zimbabwe, Tanzania, Kenya, and Nigeria. Z. aethiopica is the most widespread, tolerating marshy and disturbed habitats, and has naturalised extensively across temperate and subtropical regions worldwide — including New Zealand, Australia, and parts of Europe and North America — where it is often considered an invasive weed.
Ecology
Z. aethiopica favours seasonally wet and marshy ground, persisting when water is available and entering dormancy during drought; it can tolerate light frost. The spathe functions to attract pollinators to the tiny unisexual flowers on the spadix. Leaf hydathodes cause guttation (water droplet exudation at leaf margins). All species produce toxic calcium oxalate raphides that deter herbivory, though cooked leaves are occasionally eaten.
Cultivation
Zantedeschia falls into two broad horticultural groups: a frost-hardier group with large white spathes (Z. aethiopica and Z. odorata) grown outdoors in temperate gardens, and a less hardy group with maculate (silver-spotted) leaves and colourful spathes in yellow, orange, pink, and purple derived chiefly from Z. albomaculata, Z. pentlandii, Z. elliottiana, and Z. rehmannii. Extensive commercial cut-flower production occurs in California, New Zealand, Colombia, and Kenya. Plant breeders in California and New Zealand continue to develop new hybrid cultivars.
Taxonomy Notes
Zantedeschia is the sole genus in the tribe Zantedeschieae within Araceae (per a 1997 classification). The genus is placed in the order Alismatales, family Araceae (per GBIF). Eight species are currently recognised. Z. elliottiana is known primarily from horticultural sources and is probably of hybrid origin. Common names — arum lily, calla, calla lily — are shared with distinct but related genera (Arum, Calla), causing frequent confusion.
