Zantedeschia
Zantedeschia is a genus of eight species of herbaceous, perennial, flowering plants in the aroid family, Araceae, native to southern Africa. The genus has been introduced, in some form, on every continent other than Antarctica.
Common names include arum lily for Z. aethiopica, calla and calla lily for Z. elliottiana and Z. rehmannii. However, members of this genus are not true lilies, and the genera Arum and Calla, although related, are distinct from Zantedeschia, despite visual similarities. The colourful flowers and leaves, of both species and cultivars, are greatly valued and commonly grown as ornamental and garden plants.
Etymology
The name of the genus was given as a tribute to Italian botanist Giovanni Zantedeschi by the German botanist Kurt Sprengel.Description
Zantedeschia species are rhizomatous, herbaceous, perennial plants with some species, e.g., Zantedeschia aethiopica, growing to tall, while Zantedeschia rehmannii does not exceed 60 cm in height, growing in clumps or clusters.Roots: Contractile, emerging from the top of the tubers in Group II.
Stem: The underground portion is variously described as a thick underground stem, i.e., a rhizome or tuber. While the literature is confusing as to the exact terminology, generally the Zantedeschia aethiopica-''Zantedeschia odorata group is considered to have rhizomes and the remaining species tubers. The rhizomes are fleshy and branched.
Leaves: Petioles are long, spongy, sheathed at the bases, and of varying lengths, from 15 cm to 1.5 m. The lamina is simple, elongated, and coriaceous with a variety of shapes, including triangular, oval, with or without a point, heart-shaped, spear-shaped, lance-shaped, oblong, or circular. 15–60 cm in length, 5–25 cm in width. The leaves are dark green in colour, feather-veined, and may be erect or spreading with undulate margins. Some species exhibit transparent flecking, and are therefore described as maculate, while others are immaculate. The leaves contain hydathodes that result in guttation.
| Species | Leaf shape | Leaf size | Maculation |
| Z. aethiopica | Ovate-cordate or hastate | 15–45×10–25 cm | rare |
| Z. odorata | Ovate to cordate | none | |
| Z. albomaculata subsp. albomaculata | Oblong-hastate | 20–50×6–8 cm | rare |
| Z. albomaculata subsp. macrocarpa | Triangular-hastate | 18–20×5–7 cm | sparse |
| Z. valida | Ovate to cordate to ovate-orbicular-cordate | none | |
| Z. elliottiana | Orbicular-ovate | 22×18 cm | present |
| Z. jucunda | Triangular-hastate | dense | |
| Z. pentlandii | Oblong-elliptic to oblong-lanceolate | seldom | |
| Z. rehmannii | Lanceolate | 20–30×3 cm | none |
File:Calla lily.jpg|thumb|upright|Inflorescence of Zantedeschia aethiopica, showing the white spathe surrounding the central, yellow spadix
Inflorescence: Takes the form of a solitary pseudanthium, with a showy white or yellow spathe shaped like a funnel with a yellow, central, finger-like spadix, which carries the true flowers. Both spathe and spadix are carried on or above the leaves on the fleshy flower stem. The shape of the spathe whose overlapping margins form the tubes varies from trumpet shaped to a tight tube with a tapering tip. The spathe is initially green, but as it unfolds becomes coloured. This may be white as in Z. aethiopica, but other species include yellow and pink. Cultivars have a wide variety of other spathe colours including orange and purple. Inside the spathe, the throat may be darkly coloured. The spathe acts to attract pollinators.
Flowers: Zantedeschia is monoecious, in which separate male and female flowers are carried on the spadix. The flowers are small and non-blooming without a perianth. The male flowers contain two to three stamens fused to form a synandrium, and the female flowers have a single, compound pistil with three fused carpels and three locules.
| Species | Spathe colour | Flowering period | Throat darkened |
| Z. aethiopica | white-pink | late winter – late spring | No |
| Z. odorata | white | late winter - late spring | No |
| Z. albomaculata subsp. albomaculata | white-pale yellow-coral pink | late winter | Yes |
| Z. albomaculata subsp. macrocarpa | yellow | summer | Yes |
| Z. valida | cream | summer | Yes |
| Z. elliottiana | gold-yellow | summer | Yes |
| Z. jucunda | gold-yellow | summer | Yes |
| Z. pentlandii | lemon-chrome yellow | summer | Yes |
| Z. rehmannii'' | white-pink-maroon | summer | No |
Fruit: Beaked orange or red berries.
Taxonomy
Zantedeschia is the sole genus in the tribe Zantedeschieae in a 1997 classification of the Araceae.Species
Eight species are currently recognized:- Zantedeschia aethiopica Spreng. – giant white arum lily or common arum lily – South Africa, Eswatini, Lesotho
- Zantedeschia albomaculata Baill. – spotted arum lily – widespread from South Africa north to Nigeria and Tanzania
- Zantedeschia elliottiana Engl. – yellow or golden arum lily – Mpumalanga Province of South Africa
- Zantedeschia jucunda Letty – Leolo Mountains of northern South Africa
- Zantedeschia odorata P.L.Perry – Western Cape Province
- Zantedeschia pentlandii Wittm. – Mpumalanga Province of South Africa
- Zantedeschia rehmannii Engl. – pink arum lily – South Africa, Eswatini, Mozambique
- Zantedeschia valida Y.Singh – KwaZulu-Natal Province of South Africa
Distribution and habitat
Introduction
Zantedeschia was introduced to Europe in the seventeenth century as Z. aethiopica, and is now widely naturalised in Europe, North America, Central America, South America, Oceania, and Australasia. In many places it is considered a dangerous invasive species that displaces native vegetation. In the South-West of Western Australia, Z. aethiopica was introduced for horticulture, but has become a widespread and conspicuous weed of watercourses, heath, and wet pastures to the extent that it has been declared a pest in Western Australia and landowners must control it and attempts to sell plants must be reported. Zantedeschia in North America is primarily grown as ornamental cultivars in home gardens.Habitat
Z. aethiopica grows naturally in marshy areas and is only deciduous when water becomes scarce. It grows continuously when watered and fed regularly and can survive periods of minor frosts. Z. aethiopica is a very strong and sturdy plant, being able to grow in many soils and habitats, multiplying by rhizome-offsets.Cultivation
All Zantedeschia produce large, showy flowers spathes and are often grown both as ornamental plants and for cut flowers. Zantedeschia are relatively hardy plants, but some are more winter-hardy than others. In this regard there may be considered two groups, a hardy outdoor group with large white flowers and less hardy group with white-spotted leaves and flowers in many colours, such as yellow, orange, pink and purple.Hardy forms (arum lilies)
These include Zantedeschia aethiopica and Zantedeschia pentlandii and their cultivars. Zantedeschia aethiopica and some of its relatives can survive at minimum winter temperatures below -23 °C and many others can be grown in even warmer areas where all the ground does not freeze. Z. pentlandii hybrids include 'Millennium Gold'.Tender forms (calla lilies)
The more tender specimens are mainly cultivars of Zantedeschia elliotiana and Zantedeschia rehmannii, but also Zantedeschia albomaculata and Zantedeschia jucunda. These less hardy forms can only survive winter temperatures to −12 °C. This plant must be grown as tender bulbs or houseplants in cooler areas. Species and hybrids between Z. elliotiana, Z. jucunda, Z. pentlandii and Z. rehmannii appear to have an optimum temperature for growth near 25 °C, with growth being suppressed once daily average temperatures persist at 28 °C.Z. rehmannii hybrids include 'Amethyst', 'Crystal Blush' and 'Neon Amour', while an example of a Z. elliotiana × Z. rehmannii hybrid would be 'Blaze'. Z. elliotiana × Z. maculata hybrids include 'Lemon Drop'. Z. elliotiana hybrids include 'Solar Flare'.