Zantedeschia the southern African arums

A great find for landowners in Limpopo and Mpumalanga would be to discover populations of the two rare yellow arums, so far only known to occur in Sekhukhuneland in the rainshadow of the Drakensberg, writes Cameron McMaster.
Issue date: 06 February 2009

- Advertisement -

A great find for landowners in Limpopo and Mpumalanga would be to discover populations of the two rare yellow arums, so far only known to occur in Sekhukhuneland in the rainshadow of the Drakensberg, writes Cameron McMaster.

Maybe the white arum is so commonplace we hardly notice it.  So prolific in vleis and wetlands, it has a host of common names, some quite derogatory, like pig lily (Varkoor), an allusion to the shape of the flower resembling a pig’s ear, or perhaps to the fact that although poisonous to humans the corm is relished by porcupines. However, when commercially cultivated on a large scale for the cut flower industry, they’re called calla lilies. Check the décor in some American soapies and you’ll often see South African arums used in flower arrangements.

Arum flowers are minute and crowded onto a central, usually yellow spike surrounded by a large, white-to-pink or yellow funnel-shaped spathe which most people regard as the petal. After pollination by flying beetles, the tiny flowers develop into firm green berries tightly clumped in a composite fruit head. When ripe the berries change colour and become softer, eventually disintegrating and releasing seed.

- Advertisement -

The common white arum bears the Latin name Zantedeschia aethiopica, inferring its African origins. It’s one of eight different species in the small southern African genus Zantedeschia, which is included in the large and predominantly tropical family Araceae. The genus was named after Francesco Zantedeschi, an Italian physician, botanist and writer.

Defining the species
Zantedeschia aethiopica is a common plant in ditches and damp spots in the Western Cape, but it’s found in massed displays in damp habitats throughout the country. It was introduced into Europe as early as 1644 and because of its elegance and longevity was prized as a cut flower. The plant remains evergreen if kept damp, even tolerating waterlogged soil and shade, making it a suitable easy-care garden subject. A pale pink form has been selected and its name registered as marshmallow. Green goddess, a very large form with green-streaked flowers, is a popular garden subject.

Zantedeschia odorata is very similar to the common white arum, except it’s deciduous and strongly scented. It’s rare and found only on the Bokkeveld plateau near Nieuwoudtville where it flowers from July to August in seasonally moist dolerite outcrops. It’s listed in the Red Data List of threatened plants. Most other arums aren’t often seen in the wild. They’re all summer-growing and deciduous, going dormant in winter. Probably the most common in the summer rainfall areas is Zantedeschia albomaculata, the spotted-leafed arum. This species is found in damp spots and on rocky outcrops. Populations extend into central Africa at high altitudes such as in Lesotho. The flowers vary from white to cream with a dark purple centre at the base of the spathe. Occasional pinkish and orange forms occur which are known as the popular Helen O’Connor variety.

Another KZN sub-species of Zantedeschia albomaculata, with unspotted, heart-shaped leaves, has been elevated to a full species as Zantedeschia valida.
Zantedeschia rehmannii is a small pink species with sword-shaped leaves occurring in KZN, the eastern Free State, Mpumalanga and Swaziland. It’s become popular as a horticultural and pot plant subject and is widely cultivated in Europe and the US. It would be an exciting find on your property.

The two spectacular bright yellow arums, Zantedeschia pentlandii and Zantedeschia jucunda, have a limited distribution in Sekhukhuneland near the border of Limpopo and Mpumalanga. They are both rare and because of their limited distribution are listed as vulnerable in the Red Data Book. While they look similar, the populations are separate and there are clear taxonomic differences between them. While Zantedeschia jucunda has more pointed triangular leaves that are invariably heavily spotted, Zantedeschia pentlandii has oblong leaves, generally without spotting.

Defining differences and relationships
Charles Craib made an intensive study of the relationship between these two plants and human activity, published in the journal of the International Bulb Society, Herbertia Volume 57, 2003, and published an account of their current status in the September 2003 issue of Veld and Flora, the organ of the Botanical Society.

He observed that Zantedeschia jucunda is endemic to the summit of the Leolo Mountains in Sekhukhuneland at altitudes of between 1 600m to 1 900m, where it occurs in crevasses on cliffs and among piles of boulders constructed by the Pedi people. There is exploitation with bulbs sold to the horticultural trade, but the plant appears to exist compatibly with human activity. Zantedeschia pentlandii occurs at altitudes of between 1 800m and 1 900m in the region north east of Roossenekal and in the Tonteldoos area. While previously fairly widespread in the region, plants are now confined to rocky areas protected from livestock grazing and porcupine predation.
A strange anomaly is the Zantedeschia elliottiana, a yellow species known only from cultivated material and freely available in the horticultural trade. While its origin is unknown, it’s assumed to be a hybrid of the two Sekhukhuneland species. Perhaps the greatest challenge for landowners in Limpopo and Mpumalanga is to discover further populations of the two rare yellow species which so far only occur at Sekhukhuneland. Contact Cameron McMaster at [email protected].     |fw