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'. Seasonal grouping Other classifications consider two groups based on their seasonal habits. Zantedeschia aethiopica and Zantedeschia odorata form one group (Group I) typified by retaining their leaves in winter, and flowering from late winter to late spring, while the remaining species (Group II) are in leaf from spring to late autumn shedding their leaves in winter (deciduous) and flower during the summer. Zantedeschia aethiopica may retain its leaves all year round (evergreen), otherwise from autumn to late summer, while Zantedeschia odorata retains its leaves from late winter to late spring. The two groups also vary according to the arrangement of the male and female organs. In the first group they are arranged together in the lower part of the spadix, whereas in the latter they are separate, with the female at the base. The Z. aethiopica group also have a fruit that turns soft and orange, whereas the other retains a firm green fruit. Toxicity 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. However leaves are sometimes cooked and eaten. Uses Extensive commercial production of Zantedeschia for cut flowers and/or planting material occurs in California, Colombia, New Zealand and Kenya. Plant breeders in California and New Zealand continue to produce an extensive range of new hybrid cultivars. The so-called white calla 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. Culture Zantedeschia has often been used in paintings and is featured 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 era, there were strict social codes and flowers were considered the best