ARUM LILY (Zantedeschia aethiopica)
The familiar Arum Lily, with its opulent and sophisticated pure white spathes which brighten up watercourses and wetlands throughout the region in spring and summer, belongs to an indigenous genus which is restricted to the African continent.
Seven species of arum are recognised: Zantedeschia aethiopica, Z. albomaculata, Z. elliottiana, Z. jucunda, Z. odoratum, Z. pentlandii (Golden Arum) and Z. rehmannii (Pink Arum). The common arum is found from the Western Cape through the Eastern Cape, KwaZulu-Natal, Mpumalanga and into Limpopo Province. It is evergreen or deciduous depending on the habitat and rainfall regime. In the Western Cape it is dormant in summer and in the summer rainfall areas it is dormant in winter. It will remain evergreen in both areas if growing in marshy conditions which remain wet all year around.
Although called the arum lily, it is neither an arum ( the genus Arum) nor a lily ( genus Lilium). But it is associated with the lily as a symbol of purity and these elegant flowers have graced many bridal bouquets
The flowers are faintly scented and this attracts various crawling insects and bees which are responsible for pollinating the flowers. Cross pollination occurs as the anthers of each flower ripen before the ovaries. A white crab spider of the family Thomisidae visits the flower to eat the insects. This spider does not spin webs and uses its whiteness as camouflage against the spathe. In the western Cape, a tiny frog, Hyperolius hopstocki is also attracted to the arum lily flowers. The spathe turns green after flowering and covers the ripening berries. It rots away when these are ripe and the succulent yellow berries attract birds, which are responsible for seed dispersal.
In the Western Cape it is dormant in summer and in the summer rainfall areas it is dormant in winter. It will remain evergreen in both areas if growing in marshy conditions which remain wet all year around.
Zantedeschia aethiopica grows from 60cm to 1m but may get taller in the shade. It has lush looking dark green leaves with an arrow head shape. The size varies according to the amount of shade. The white arum forms large colonies in marshy areas ranging from the coast to an altitude of 2,250m. Thus one will find them contending with humid, salt laden air at the coast and freezing, misty mountain grasslands at high altitudes. They are very versatile in the garden as a result.
The rhizome is large and eaten by wild pigs and porcupines and the ripe fruit enjoyed by birds. Traditionally the plant is boiled and eaten. Raw plant material causes swelling of the throat because of microscopic, sharp calcium oxalate crystals. The leaves are also traditionally used as a poultice and a treatment for headaches. A heated poultice made from the leaves is traditionally used to treat boils, wounds and sores. A boiled rhizome and honey mixture is gargled for a sore throat or swallowed for heartburn and bronchitis.
The white arum is very easily cultivated by seed or division. Seed should be sown in spring. The fruit is ripe when it has turned yellowish and is soft. The pulp should be removed and the seed dried off. The grey seeds can be sown in clean seedling mix and covered lightly. Take care not to sow them too thickly as they will need space to form the fleshy roots. The fleshy rootstock can be divided when the plant is dormant, it should be re-planted about 5 cm deep. It may also be propagated by division where the plant is not dormant, use a sharp spade to cut out a section for replanting.
The white arum may be used as a marginal plant along streams, or on the edge of a pond. Plant it near a tap or in partial shade if there is no permanent water. It can be planted as a foliage plant in deep shade under trees but will not flower well in this position. It is fast growing and likes very rich, well-drained conditions. Always add plenty of well-rotted compost. Mulch and replenish whenever necessary.
Arums are excellent and long-lasting as cut flowers.