What’s in a name? The South African plants commonly called callas or calla lilies are several species of Zantedeschia (the botanical name of the genus, from the family name of an Italian doctor/botanist of the late 18th-early 19th century). The Zantedeschia we call calla lilies are not true lilies (genus Lilium), but members of the Araceae (Arum) family. There is also a genus Calla in the Arum family containing just one species, Calla palustris, known by the common names arum lily, water arum, bog arum or wild calla.
The six species of Zantedeschia bulbs and their various cultivars fall into two groups. The large white-flowered Zantedeschia aethiopica bulbs accept almost any growing conditions, are evergreen in mild climates, and bloom from winter to spring. The shorter Zantedeschias, which bloom in many colors, like sun and dry conditions, are deciduous, and tend to bloom in summer. In Holland, the two different groups of Zantedeschias are treated as unrelated plants. American gardeners call both of them calla lilies, even though the name calla has supposedly been considered incorrect by horticulturists since 1818!
The bulbs of the two varieties look totally different. The large Zantedeschia aethiopica bulbs are oblong with a pointed end and look like a raindrop. Orient the larger end, where you’ll see an “eye” or dried leaves, upward when you plant them. Although aethiopica comes from a Greek term which implies that the plant originated in sun-scorched conditions in the land of the Moors, large callas will grow and bloom in shady conditions. When they are planted in the sun they perform better if the soil is moist. They can be grown as marginal aquatic plants, in 10- to 12-inch diameter pots filled with heavy loam soil, in water up to twelve inches deep.
The bulbs of the smaller Zantedeschia species are flat and round and have bull’s eyes or dark circles on them, which should be on the upper side when they are planted.
When in doubt, plant a bulb sideways; it will work its way up.
These bulbs need hot sun and should not be allowed to sit in water. They need to dry out between waterings. You can leave the bulbs in the ground over the winter in most areas of the Pacific Northwest if you provide them good drainage. In fact, you can plant them any time of the year in the garden. However, the smaller Zantedeschia bulbs grown in outdoor containers need to be kept dry in the winter, as they rot easily. Place them under the eaves of the house or in the garage for the winter, and put them back in the rain in April/May.
Contemporary artists follow the lead of famous artists of the past such as Henri Matisse, Diego Rivera and Georgia O’Keefe, when they choose calla lilies as their subjects. There is no need to rely solely on artistic renditions of Zantedeschia to grace your home, however. They last well in arrangements. Plant lots of them in your yard and in containers so that you will be able to pick them and enjoy them indoors as well as outside, whenever they are in bloom.