The arum lily or calla lily is a beautiful South African plant, hardy in mild moist places out of doors, and even in colder areas may sometimes be grown as an aquatic plant if covered with water in an outdoor pool during winter. Pot up the rhizome-like roots in large pots, big enough to accommodate them comfortably, in spring or autumn. Use any of the usual potting composts with some charcoal granules added, water thoroughly and keep nicely moist at all times.
After flowering, from March to June, the plants can be placed outside, although the large glossy arrow-shaped foliage is quite handsome. A slightly shaded place is preferable. In winter, only frost protection is necessary.
The plants will lend themselves to gentle forcing in warmth for early flowering. This is sometimes done by nurseries to produce early flowers for cutting. When the plants are producing leaves freely they can be watered generously and ’cd with liquid feeds. In this case, it is quite in order to stand the pots in shallow containers of water which can be kept topped up.
There are a number of cultivars with slight variations of spathe colouring. ‘Green Goddess’ has green striping. ‘Crowborough’ is particularly good for pots, as it is rather more compact and is reputed to be exceptionally hardy. Zantedeschia aethiopica is sometimes called Richardia africana and may sometimes be listed under that name. Anoth-er common name is lily of the nile. The flowers are among the most important for growing commercially for cutting.
Repotting
Repotting of this species is best done in late autumn to early winter, although the roots are often listed in spring bulb catalogues. Look out for a dwarf form called ‘Little Gem’, which is particularly good as a houseplant. It grows to only about 45cm (1 ½ ft). which is about half the normal. Unfortunately this form has recently become difficult to find. A few other species may be encountered occasionally, including the yellow-llowered Z. eUiottiana. Z. aethiopica is rarely troubled by pests and diseases, although aphids are a possibility. In unsatisfactory potting composts, made with unsterilized garden soil, for example, root rot may occur. This usually kills the plant.
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