Zantedeschia

Zantedeschia species are rhizomatous, herbaceous, perennial plants with some species, e. g., Zantedeschia aethiopica, growing to 1.2m tall, while Zantedeschia rehmannii does not exceed 60 cm in height, growing in clumps or clusters.[5][6]
Roots: Contractile, emerging from the top of the tubers in Group II.[5]
Stem: The underground portion is variously described as a thick underground stem, i. e., a rhizome or tuber.[7][8][9] While the literature is confusing as to the exact terminology, generally the Zantedeschia aethiopica-Zantedeschia odorata group (Group I) is considered to have rhizomes and the remaining species tubers.[5] The rhizomes are fleshy and branched.[10]

Hastate leaf shape with maculation

Lanceolate leaf shape with undulate form

Leaves: Petioles are long, spongy, sheathed at the bases, and of varying lengths, from 15 cm (Zantedeschia rehmannii) to 1.5 m (Zantedeschia aethiopica). The lamina is simple, elongated, and coriaceous with a variety of shapes, including triangular, oval (ovate), with or without a point (elliptic), heart-shaped (cordate), spear-shaped (hastate), lance-shaped (lanceolate), oblong, or circular (orbicular). 15–60 cm in length, 5–25 cm in width. The leaves are dark green in colour, feather-veined (pinnate), and may be erect or spreading with undulate margins. Some species exhibit transparent flecking (maculation), and are therefore described as maculate, while others are immaculate. (see Table I, also New Zealand Calla Council Leaf Shape Images[11])[5][6][7] The leaves contain hydathodes that result in guttation.[6][10]

Inflorescence of Zantedeschia aethiopica, showing the white spathe surrounding the central, yellow spadix

Inflorescence: Takes the form of a solitary pseudanthium (false flower), with a showy white or yellow spathe (a specialised petal like bract) 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 (Z. pentlandii) to a tight tube with a tapering tip (Z. rehmannii). 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.[5][12] The spathe acts to attract pollinators.
Flowers: Zantedeschia is monoecious, in which separate male (staminate) and female (pistillate) flowers ("imperfect" or "unisexual" 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.[5][7][10]

Fruit: Beaked orange or red berries.[10]

All species are endemic to central and southern Africa, from Nigeria to Tanzania and South Africa. 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; it is naturalised and regarded as a weed throughout much of the world. Z. odorata is a rare species, resembling Z. aethiopica, but deciduous and smelling like freesia, endemic to a few localities in South Africa. Z. albomaculata is a widespread and variable species, growing from South Africa north to Kenya, varying in shades of white to cream and pink to orange-shades. Z. jucunda and Z. pentlandii are rare species with large yellow showy flowers. Z. rehmannii is a pink-flowered species with sword shaped leaves. Z. elliotiana is known from horticultural sources only and is probably of hybrid origin.

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 (arum lilies) and less hardy group with white-spotted leaves and flowers in many colours (calla lilies), such as yellow, orange, pink and purple.[19]

Tender forms (calla lilies)

The more tender specimens are mainly cultivars (hybrids) of Zantedeschia elliotiana and Zantedeschia rehmannii (referred to as elliotiana or rehmannii cultivars or hybrids, or as e.g. Z. x rehmanii), but also Zantedeschia albomaculata and Zantedeschia jucunda.. These less hardy forms can only survive winter temperatures to -12 °C (Zones 8). 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.[19][21]

Zantedeschia x rehmanii 'Neon Amour'

Zantedeschia elliotiana x maculata 'Lemon Drop'

Z. rehmannii hybrids include 'Amethyst'.,[22] 'Crystal Blush'.[23] and 'Neon Amour',[24] while an example of a Z. elliotiana x Z. rehmannii hybrid would be 'Blaze'.[25] Z. elliotiana x Z. maculata hybrids include 'Lemon Drop'.[26] Z. elliotiana hybrids include 'Solar Flare'.[27]

Zantedeschia shares the general properties of the family Araceae in causing contact irritation. Zantedeschia species are also poisonous due to the presence of calcium oxalate crystals in the form of raphides. All parts of the plant are poisonous, typically producing local irritation or a burning sensation in the mouth and occasionally vomiting and diarrhea.[28][29] However leaves are sometimes cooked and eaten.[10][30]

Zantedeschia bridal bouquet with mix flowers

Extensive commercial production of Zantedeschia for cut flowers and/or planting material occurs in California, Colombia, New Zealand and Kenya.[21] Plant breeders in California and New Zealand continue to produce an extensive range of new hybrid cultivars. The so-called white calla is derived from Z. aethiopica. All varieties with flowers with shades of yellow, orange, red, purple are mainly derived from Z. albomaculata, Z. pentlandii, Z. elliottiana and Z. rehmanni.

Zantedeschia has often been used in paintings, and is visible in many of Diego Rivera's works of art (see The Flower Vendor, amongst others). It was a favourite subject of the painter Georgia O'Keeffe.

During the flower language boom in the Victorian period of the 19th century, there were strict social codes and if one had to express ones feelings, flowers were the best medium. Flowers delivered the feelings subtly and every part of gifting a flower, carried secret flower meanings. The person who made the offer to the way the flowers were arranged, all had a specific meaning. Thus passionate messages were delivered to the recipient, without the use of words through flowers. During this time, calla lily was used to express many such hidden symbols. Due to its physical resemblance to female genitalia, calla lily was called an overtly sexual one. This sexual calla lily meaning was brought forward to admirers by Freud and other artists like Georgia O'Keeffe.[31]

Wikimedia Commons has media related to Zantedeschia.

Wikispecies has information related to Zantedeschia

• Pacific Callas
• Germplasm Resources Information Network (GRIN): Zantedeschia
• University of Connecticut: Zantedeschia aethiopica
• University of Connecticut: Zantedeschia elliottiana
• Snijder, R.C. 2004. Genetics of Erwinia resistance in Zantedeschia: impact of plastome-genome incompatibility. PhD thesis Wageningen University. ISBN 90-5808-975-4 - p. 112.