Photographs by Connall Oosterbroek.
SPECTACULAR BULBS, CAUDICIFORMS, SUCCULENTS AND XEROPHYTES FROM THE SEKHUKHUNELAND CENTRE OF FLORISTIC ENDEMISM.
The Sekhukhuneland centre of floristic endemism lies mostly in South Africa’s Limpopo Province with the southern section located in north western Mpumalanga. Most of Sekhukhuneland lies in the rain shadow of the Transvaal Drakensberg and is rather arid and hot. The Leolo Mountains run north-south through Sekhukhuneland. This mountain range and its foothills are home to several endemics.
One of the most spectacular bulbous plants in South Africa is Zantedeschia jucunda. This handsome arum lily has hastate leaves densely spotted with white or cream spots. The flowers vary from a rich golden yellow at the southern end of the Leolo Mountians to bright lemon yellow and creamy yellow in the central and northern part of the range. Z. jucunda is often found growing in crevices in boulder outcrops and cliffs on the summit of the mountain. The handsome foliage and flowers of the plants are particularly striking amongst the ochre lichen blotched rocks in which they grow.
Some populations of Z. jucunda have heavily tubercled leaves and others have the external sides of the yellow spathes richly coloured with a mauvish brown bloom.
The variations in Z. jucunda would make it a very useful candidate for arum cultivar production programmes. The plants are, however, hardly known in cultivation. Few people have seen them in the wild owing to the remoteness and inaccessibility of the Leolo Mountains where they grow.
1. The Leolo Mountains in Sekhukhuneland are rich in unusual plants and endemics. The rocky summit of the Leolo Mountains is home to the beautiful endemic yellow arum Zantedeschia jucunda.
This photograph was taken in mid-December the peak of the Z. jucunda flowering season. A storm is approaching from the Steelpoort area visible in the far distance of the photograph.
2. Zantedeschia jucunda has rich golden yellow flowers and copiously white spotted hastate leaves. It often grows in cracks or fissures on lichen blotched norite boulder cliffs high up on the summit of the Leolo Mountains.
The well known yellow arum of the Sekhukhuneland Centre of Floristic endemism is Zantedeschia pentlandii. This species used to be more widespread but is now mostly confined to the hilly and mountainous country around Roossenekal and Tonteldoos.
The flowering season is late November and December. This is also the peak flowering period of Z. jucunda on the Leolo Mountains. The flowers of Z. pentlandii are less variable in colour than those of Z. jucunda. The spathes are usually a deep yellow, more rarely creamy yellow. The leaves are usually plain but some plants are occasionally found with white spotted leaves. There are a few populations where plants have deep yellow flowers and well spotted leaves.
Z. pentlandii seems to have disappeared from much of its grassland distribution range to the west of the Steenkampsberg. The reason seems mainly to be related to porcupines which excavate the tubers which are easily removed in loamy soil. The abundance of porcupines is related to an increased food supply in the area owing to agriculture.
3. A new genus, probably monotypic, is found in seepage areas on the summit of the Leolo Mountains. The genus which will soon be formally described is considered to be related to Tulbaghia and Allium.
A new genus with apparently only one species has been found recently in seepage areas on the summit of the Leolo Mountains. These bulbous plants are considered to be related to Allium and Tulbaghia. They have white upright cup shaped flowers with a pinkish bloom and these are borne on short stems. The leaves are thin and wiry and usually twisted.
The seepage areas in which the plants grow are often at the bases of huge sheets of exposed norite on the mountain summit. Norite gives rise to heavy clayey soils and runoff from the sheets of rock keeps the habitat saturated for weeks during rainy periods in summer.
This new genus may have strong medicinal and insecticidal properties. It does not appear to have many or possibly any natural predators. It is consequently capable of occurring in quite high concentrations in the limited seepage areas on the mountain summit.
The new Genus is expected to be described during the course of this year.
An unusual robust form of Cyphostemma humile occurs on very rocky sun drenched parts of the southern summit region of the Leolo Mountains. It is not usually encountered on the lower drier slopes of the mountain and is also absent from the lower areas which are hot and arid and lie in the rain shadow of the Transvaal Drakensberg.
4. The seepage areas in which the new Genus occurs are usually in depressions surrounded by vast sheets of exposed norite rock. These undescribed plants are perfectly adapted to conditions of sticky wet clayey norite derived soil. The habitat is permanently moist in summer and dry in winter.
5. An unusual form of Cyphostemma humile is found on the summit plateaux of the Leolo Mountains. It flowers in the second half of December when the main summer rains begin.
The northern foothills of the Leolo Mountains are characterised by norite hills covered in large black boulders. These areas are very hot and have much less rainfall than the summit of the mountain. They are home to an extremely beautiful Sekhukhuneland endemic, Hibiscus barnardii. This shrub usually has numerous small branches covered in rounded densely pubescent leaves. During the later summer months the plants are covered with very ornamental pinkish red flowers with contrasting rich golden pollen on the anthers.
The hibiscus was once classified as red data species but it is one of the plants that have benefited from heavy grazing in the Sekhukhuneland lowlands.
An extremely attractive geophytic Cyphostemma also grows in the same arid habitat as the hibiscus. It has masses of compound foliage that resembles the fronds of maidenhair ferns. The placement of this Cyphostemma and others in Sekhukhuneland awaits the results of a revision of this genus currently under way at the National Botanical Institute in Pretoria.
Another unusual recent discovery in the black norite hills of Sekhukhuneland is a new stylochiton species which awaits formal description. It has large greyish green leathery leaves and cream flowers. The species is usually found around boulders and at the edges of sheets of exposed rock, situations which usually remain wettest for the longest period after rainfall.
Much of Sekhukhuneland’s rich flora has not yet been introduced to horticulture. Z. pentlandii is one of the exceptions and has been in cultivation for some time. A common complaint with the yellow arum species is that they do not flower well in cultivation. They require large deep containers in a sunny position with well aerated soil and the addition of good quantities of leaf mould. These conditions usually promote flowering. If the two yellow arum species are grown in the garden care must be taken to ensure that the situation is kept moist in the growing season and that the ground does not become hard and compacted.
6. Zantedeschia pentlandii differs in several respects from Z. jucunda the Leolo Mountain endemic. Its leaves are usually plain and it is invariably found growing on boulder outcrops where the tubers escape predation from porcupines.
Z. pentlandii is largely confined in modern times to rocky hillsides near Roossenekal and Tonteldoos.
Readers interested in the autecology of these two arums should consult “Zantedeschia jucunda and Zantedeschia pentlandii, the beautiful yellow arums from the Sekhukhuneland Centre of Floristic Endemism”. This paper written by Charles Craib is expected to appear in the June or September Veld and Flora, the Journal of the Botanical Society of South Africa.
The new genus and further aspects of the autecology of the two Zantedeschias are covered in two papers submitted for publication in the 2002 Herbertia, Volume 57, the journal of the International Bulb Society. These papers are also written by Charles Craib.
Readers interested in further details about these papers should contact Caroline Voget, the editor of Veld and Flora. Caroline’s e-mail address is
voget@kingsley.co.za and the editorial address is:
The Editor
Botanical Society
Private Bag X10
Claremont
7735
Western Cape
South Africa
Dr. Alan Meerow the editor of Herbertia may be contacted at e-mail
miaam@ars-grin.gov or at the editorial address:
Alan W. Meerow,
Editor
Herbertia
USDA-ARS-SHRS
13601 Old Cutler Road
Miami
FL 33158
United States of America