The summit of the southern end of the Leolo Mountains photographed in mid-December when the main summer rains begin and the bulk of the Z. jucunda are in flower.
Z. jucunda coming into flower in early December on a boulder outcrop, a typical habitat of the species on the Leolo Mountains.
Z. jucunda is one of South Africa’s most spectacular flowering plants and has been the subject of two recent papers by Charles Craib. One of them was published in Veld September 2003, the journal of the Botanical Society of South Africa. It is entitled “Zantedeschia jucunda and Zantedeschia pentlandii, the beautiful yellow arums from the Sekhukhuneland Centre of Floristic Endemism”. The other paper to be published in Herbertia 57, the journal of the International Bulb Society, is entitled “The Autecology of Zantedeschia jucunda and Zantedeschia pentlandii from South Africa’s Limpopo and Mpumalanga Provinces”. Both these papers discuss in some detail the two yellow arum species in their natural habitats. The purpose of this newsletter is to cover in more depth some aspects of the research which has been finalised more recently.
ZANTEDESCHIA JUCUNDA, THE JEWEL OF THE SEKHUKHUNELAND CENTRE OF FLORISTIC ENDEMISM.
PHOTOGRAPHS BY CONNALL OOSTERBROEK.
The Leolo Mountains run north south through the centre of Sekhukhuneland. The steep eastern and western slopes lead up to an extensive summit plateau covered with further rock outcrops and tumbled boulder mountains. The highest mountain peak at the southern end of the mountain range is the Thama Kgoshi at 1932.5 metres. The peaks at the northern end of the range tend to be lower, with the highest northern most peak at 1519 metres.
Z. jucunda grows mainly at an altitude of 1500 – 1900 metres and is absent from the drier eastern and western slopes. The northern sections of the mountain tend to be drier but the plants are found right along the range.
The summit of the mountain contains good tracts of fertile and arable land, and is settled by the Pedi. Fields are ploughed in the summer for traditional pastoralism and cattle, sheep and goats are herded in the grassland and on the rocky outcrops.
The summit plateaux of the central Leolo Mountains photographed in February at the peak of the rainy season.
The autecology of Z. jucunda is closely linked to settlement and land use patterns on the mountain top. Most of the plants grow in rocky niches on boulder outcrops, and also in densely packed groups on cliff faces. A significant artificial habitat consists of stone walls built by the local people. The arums may be common on some parts of the mountain where stone walls are extensive. The bulbs also grow in stone walls around homesteads and in rock piles beside ploughed lands. These rock piles consist of stones that have been removed during the clearing of the veld for ploughed land.
Grazing throughout the year, coupled to winter grass fires from May to September, has had the effect of keeping the grass short and letting in lots of light. These circumstances have created ideal conditions for the arums to grow and flourish. The present population dynamics of the species is to some extent commensal with traditional pastoralism and land use patterns. There is a tendency towards increased settlement on the mountain and this may change the status quo of the arum populations in the future.
The typical colour of the spathes of Z. jucunda on the summit of the southern end of the Leolo Mountains is a beautiful rich chrome yellow. The leaves are copiously marked with numerous fine white spots.
Close up details of a handsomely marked leaf of Z. jucunda.
Z. jucunda has very variable colouring to its spathes on some parts of the Leolo Mountains. This very rare clone has cream spathes with a rich burgundy wash. The colouration of the unopened spathes is particularly dark.
The plants on the summit are very variable both with regards to the colours of the spathes and the amount of spotting on the leaves. The integrity of this variation is preserved by the fact that there is a constant exchange of genetic material across the arum populations. The monkey beetle pollinators are common on the mountain and large numbers of flowers get successfully pollinated. This is in contrast to populations of the closely related Zante-deschia pentlandii which occurs in the mountains in the south eastern corner of the Sekhukhuneland Centre of Floristic Endemism. Much of the habitat in this area has been altered or destroyed and many of the populations are found in areas that are now isolated from one another. In addition porcupines, which have become abundant owing to extensive crop farming and a ready food supply, consume large numbers of arum tubers when food is scarce.
Stone walls built on the summit of the mountain by the local people have become an important artificial habitat for Zantedeschia jucunda on the Leolo Mountains.
The fissures in stone walls resemble the natural rock niches in boulder outcrops on the Leolo Mountains. Z. jucunda is slowly increasing on sections of the mountains where stone walls are extensive.
Z. jucunda is sometimes found growing beside walls around the mountain top homesteads of the local people of the summit plateaux of the Leolo Mountains. This cream flowered clone has particularly well spotted leaves.
Z. jucunda is protected by public sentiment on several parts of the Leolo Mountains. In some areas, mainly in the southern part of the range, bulbs are dug up by the local people and sold. This activity is limited to the months of December and January when flowering is at its peak. Bulbs were not removed before or after the flowering period. This activity has, however, had a limited effect on arum populations. Bulbs are often not completely removed from their rocky niche habitat and resprout from parts of the tubers that are left behind.
Zantedeschia pentlandii is endemic to the Roossenekal and Tonteldoos areas to the south east of the Leolo Mountains. This species has creamy yellow to golden yellow spathes and usually plain leaves. In some areas a few plants in the populations have spotted leaves. The autecology of the two species is however, somewhat different and the leaves of Z. jucunda are distinctively hastate when compared to the oblong lanceolate leaves of Z. jucunda.
Z. jucunda has a very interesting pollination biology along the Leolo Mountains. Pollinators are attracted in large numbers to big groups of flowering arums. In some years only a few arums in a large population flower. These are usually plants growing in dense grass cover that has not been grazed or burnt in winter grass fires. The large populations with many flowering plants tend to attract the pollinators. The situation changes continually on the mountain, and a poorly pollinated group of plants in one season may be well pollinated the next. The pollination process ensures that no one arum population can be said to have an annual average seed production. The erratic distribution of seedling and young plants across the mountain is accounted for by the irregular pollination and hence a very variable seed production process.
The horticulture of Z. jucunda and a detailed profusely illustrated account of the species on the Leolo Mountains will be published in a book currently under research by Charles Craib with photography by Connall Oosterbrook. This book concerns plants in natural landscapes in the summer rainfall region of South Africa.
FURTHER READING.
Additional details about the taxonomy and autecology of both the yellow arums of Sekhukhuneland, and the Sekhukhuneland Centre of Floristic Endemism may be found by consulting the following references:
Craib C. (in ed.) The Autecology of Zantedeschia jucunda and Zantedeschia pentlandii from South Africa’s Limpopo and Mpumalanga Provinces. Herbertia 57. (Herbertia is the journal of the International Bulb Society and the editor is Dr. Alan Meerow. E-mail: miaam@ars-grin.gov )
Craib C. Zantedeschia jucunda and Zantedeschia pentlandii – The Beautiful yellow arums from the Sekhukhuneland Centre of Floristic Endemism. Veld and Flora September 2003: 106-109. (Veld and Flora is the journal of the Botanical Society of South Africa. E-mail info@botanicalsociety.org.za)
Letty C. The Genus Zantedeschia. Bothalia ll (1 and 2) 1973: 13-17.
Singh Y. et al. Know your Arums. Veld and Flora 81(2) 1995: 54-55.
van Wyk A.E. and Smith C.F.
Regions of Floristic Endemism in Southern Africa, Umdaus Press, Hatfield Pretoria 2001, Chapter 8, The Sekhukhuneland Centre. Pgs. 126-133.
The Umdaus Press web site address is www.succulents.net. Their e-mail address is umdaus@succulents.net
PHOTOGRAPHS BY CONNALL OOSTERBROEK.