Encephalartos dolomiticus
Introduction
The Wolkberg cycad is an extraordinarily beautiful species characterized by its striking blue colour. Adding to its attraction is the tendency to bear full crowns of leaves, enhancing the plant's overall visual appeal. This species is exceptionally rare and highly sought-after, and it is reportedly now extinct in the wild, as a result of illegal harvesting for private collections. This species is endemic to South Africa, and known from a very restricted area in the Wolkberg, near Penge, in the Drakensberg in southeastern Limpopo Province.
Description
Description
Encephalartos dolomiticus is a small to medium-sized cycad, with a stem up to 2 m long and 250-500 mm in diameter. The stem is aerial and erect, however, long stems tend to become decumbent. The aerial part of the stem is unbranched, but suckers are often produced from the base. Much of the stem crown is covered with buff, greyish, woolly bracts that are 30–60 mm long. Leaves are rigid, blue green on both the upper and lower sides, up to 600–800 mm long. They are straight but often gently curve downwards, with the rachis typically twisted, contributing to the plant's somewhat disorderly appearance. The leathery leaflets are narrow, 120–170 mm in length and 10–14 mm in wide and lack nodules. The upper surface of the leaflet features a subtle transverse concavity (gentle curve when viewed from side to side—perhaps dipping slightly in the middle). In the longitudinal direction, the leaflet may appear either straight or slightly concave along its length. Leaflet apex is sharp, and the margin is either entire or bears one or two teeth on the lower margin only. Terminal leaflets often resemble a banana in shape. Petiole is approximately 120 mm long, is straight, adorned with small spines, and boasts a red-brown collar at the base covered in white silky hair. Male cones are egg-shaped, 300–500 mm long and 50–100 mm in diameter, with a peduncle 80–95 mm long, blue- green, 1–4 cones per stem are produced in early summer (November), with pollen shedding taking place in midsummer (December to January). Female cones are rounded, blue-green, sometimes they become yellowish, 1–4 cones per stem, 300–500 mm long and 180–250 mm diameter, with a peduncle 40–80 mm long that is completely covered by the woolly hair of the stem apex. The cone disintegrates in late autumn to early winter (May to June). Seeds are yellow, 35–45 mm long, 20–30 in diameter.
Conservation Status
Status
Encephalartos dolomiticus is Red Listed as Critically Endangered (Possibly Extinct in the Wild), by the IUCN (International Union for Conservation of Nature). According to the IUCN (International Union for Conservation of Nature), the population of this species has faced a rapid and alarming decrease primarily due to the illegal extraction of plants from their natural habitat. The latest assessment in 2019 documented a mere 4 medium to large plants, with unconfirmed reports suggesting these may have fallen victim to cycad poachers as well. The original population size remains unknown. Initial helicopter surveys conducted in 1993 identified 158 plants, and subsequent surveys in 2004 documented 151 plants, including the discovery of 17 new ones. This indicates a decline from 158 to 134 plants for those recorded in 1993, reflecting a 9% decrease over a decade. A follow-up aerial survey in 2012 tallied 139 plants, but by 2019, the count had plummeted to just 4. Assuming an estimated original population of 175 mature plants in 1993 (comprising the 158 counted in 1993 and the 17 new plants recorded in 2004), the data implies a staggering minimum 98% decline from 1993 to 2019.
This species, known for its slow growth, has historically not been abundant in the wild and the remaining individuals are now too widely dispersed for natural seedling regeneration to occur. The decline in small and restricted cycad populations is a concerning trend, with a significant factor being the increasingly male-biased sex ratio (4:1). This imbalance is attributed to the targeted collecting of female plants, a phenomenon that has escalated in recent years, or the potential differential mortality of female plants, possibly influenced by natural processes such as genetic effects, ecological factors, and climate change (Donaldson 2003). In some instances, entire populations of Critically Endangered species have been reported as Extinct in the Wild, highlighting the urgency of conservation efforts (Donaldson 2003; Da Silva et al. 2012).
Moreover, studies reveal that small cycad populations in southern Africa often exhibit a low number of fertile seeds and infrequent cone production (Donaldson 2003; Xaba 2014). Raimondo & Donaldson (2003) emphasize the critical impact on the survival of slow-growing, long-lived species when mature, reproductive specimens are removed. The removal hampers recovery, making it a slow process and significantly elevating the risk of extinction. In essence, the intricate interplay of factors, including human-induced pressures and natural processes, underscores the need for concerted conservation measures to safeguard these vulnerable cycad populations.
Distribution and habitat
Distribution description
This particular cycad is limited to a small region in the southeastern part of Polokwane, located in the Limpopo Province of South Africa. Its distribution is confined to the northern extremity of the Drakensberg range. This cycad thrives in rock crevices and amidst substantial dolomitic boulders within open grasslands, situated at elevations reaching 1 200 m above sea level. The area experiences an annual rainfall ranging from 650 to 800 mm, primarily occurring in the summer months. Summers are characterized by high temperatures, while winters are cool to cold, occasionally marked by frost.
Derivation of name and historical aspects
History
The genus Encephalartos was described by the German botanist Johann Georg Christian Lehmann in 1834. The generic epithet is derived from Greek and means ‘bread in head’ and refers to the floury, starchy material in the trunks of some species, which is used as famine food by local people. This species was described in 1988 by John J. Lavranos and Douglas L. Goode. The specific epithet dolomiticus is derived from the soil in which it grows, which is rich in dolomite.
Cycads are considered to be the most threatened taxonomic group of organisms, according to the IUCN (2023), with more than 69% of the species facing imminent extinction in the wild as a direct result of anthropogenic activities. Cycads are the oldest known seed-bearing plants. Cycads are often confused with both palms and tree ferns because of a superficial resemblance, however, they are actually totally unrelated. In fact, the name cycad is even derived from the Greek word cyckos meaning ‘palm-like’. Cycads are grouped into 3 families: Cycadaceae, Stangeriaceae and Zamiaceae. Currently there are about 343 species of cycad recognized worldwide and they are naturally found in the tropical, subtropical and warm temperate regions of Africa, Asia, Australia, and North and Central America.
The African continent is regarded as an important centre for cycad diversity, with representatives of all the cycad families (Cycadaceae, Stangeriaceae and Zamiaceae). South Africa is one of the global cycad hotspots with 38 of the described 343 species, including more than half of the known African species, occurring in the country. In South Africa, the genus Encephalartos is distributed in a continuous range all the way from the Eastern Cape, through KwaZulu-Natal, Mpumalanga and, Gauteng to Limpopo. In these regions, cycads occur in most major river systems, in the gorges near the coast. More than 78% of South Africa's cycads are threatened with extinction compared to the global average of 62%. Furthermore, South Africa also has the highest number of species classified as Extinct in the Wild, and is the only country with recent cycad extinctions (in the last decade) (Donaldson 2012) and also the highest proportion (12 out 37) of Critically Endangered species of which some of them are now presumed Extinct in the Wild.
In South Africa, 7 cycad species are on the brink of extinction, with less than 100 individuals left due to illegal removal. Urgent conservation measures, including awareness campaigns and enforcement, are crucial. While 24 cycad species find refuge in protected areas, the absence of 13 Critically Endangered, 4 Endangered, and 8 Vulnerable species in these areas raises concerns about their conservation status. The challenge lies in balancing efforts to protect these at-risk cycads within and beyond protected areas.
This species is closely related to and often confused with E. dyerianus, E. eugene-maraisii, E. middelburgensis and E. nubimontanus. They share common characteristics such as having blue-green leaves without noticeable basal leaf collars, and their leaflet margins lack prominent teeth. Differences between these species can be identified based on specific characteristics.
E. dolomiticus is characterized by leaves that are not straight, often twisted, with a well-defined petiole. The leaflets typically have smooth edges, occasionally featuring one or two small teeth. The twisting of leaflets occurs gradually along their length and is not limited to the base. Additionally, the cones are blue-green.
E. dyerianus is characterized by leaves that prominently curve outward near the base and then gently curve inward towards the rest of the leaf. This species boasts a dense leaf crown and cones are yellowish-green.
E. eugene-maraisii is characterized by slightly curved leaves with noticeable petioles. The leaflets, mostly with smooth edges, may occasionally display a small tooth. Towards the leaf's outer half, the leaflets take on an S-shaped pattern with a 90-degree angle, twisting at the base. The cones are reddish-brown.
E. middelburgensis is characterized by straight leaves with a distinct petiole. Mature plant leaflets have smooth margins, though juvenile ones may have slight teeth. Terminal leaflets often twist into an S-shape. The cones are green to reddish-brown.
E. nubimontanus is characterized by slightly twisted leaves that form a rounded and arching crown atop the stem. The leaflets have either smooth margins or a few small teeth, and the straight petioles lack prickles. The cones are green.
Ecology
Ecology
For a long time it was thought that all cycads were wind pollinated, as most coniferous plants are, and the fact that cycads generally produce high volumes of pollen, supported this argument. However, objections were raised based on the following points: species such as Encephalartos cycadifolius, E. ghellinckii, E. heenanii, E. friderici-guilielmi and E. lanatus have very woolly cones, which make it difficult for wind pollination to happen. Other cycad species such as E. villosus, E. ferox and Stangeria eriopus occur in forest where there is no wind. Current research shows that insects are the pollinators of all 10 cycad genera. Most cycads are thermogenic (able to produce heat) and emit volatile odours. In nature when the male cone reaches maturity, the central axis elongates and the scales move apart to make room for the release of the pollen, which is distributed by insects. The release of pollen varies between species but usually lasts for two weeks, on average. At the same time, the female cone also reaches maturity, the cone heats up, causing it to elongate, and it produces a smell, which attracts the insects, the pollen vectors, to the female cone. The scales move apart to allow the insects to enter and to pollinate the cone. The fleshy outer coat of the seed is eaten and the seeds dispersed by animals, mainly birds, rodents, small mammals and fruit-eating bats.
Uses
Use
In isiZulu language, most of the cycads are referred to as isqgiki–somkhovu. This name refers to witchcraft practices, where a person is converted into becoming a zombie and is used for witchcraft. The cycad is planted in front of the gate of the homestead to protect it from the evil spirit. If someone practices any witchcraft using umkhovu, this zombie will sit on top of the cycad, which is referred as isqgiki, which means ‘chair’, and that is where the common name is derived from.
The upward and dense arrangement of its leaf crown makes this species a captivating choice for garden decoration, serving as an attractive focal point or complementing succulent groupings. This species has become common in private collections, but the occurrence of the wild species has declined so much, that this species is reported to be extinct in the wild. The decline of this species is partly because plants cone infrequently and it was never abundant. Therefore obtaining seeds and seedlings is difficult and expensive. It is also imperative that material is legally obtained, with the required permits, from registered suppliers.
Growing Encephalartos dolomiticus
Grow
Encephalartos dolomiticus thrives in full sunlight but can also withstand light shade and frost. Like many other blue-hued cycads, this species has a slower growth rate. Successful cultivation is achievable when planted in well-drained soil, and it's essential to avoid excessive moisture. Ideally suited for subtropical and warm temperate areas, propagation is done through seeds and suckers.
In the cultivation process, artificial pollination is essential for a successful seed harvest. It's crucial to regularly visit the male plants and record the date when cones appear. This helps estimate the optimal harvest time. Collect pollen as soon as it starts shedding and store it at -15°C. Monitoring the opening of female cone scales is imperative, as the duration varies among individual plants, ranging from three days to two weeks. After gathering female cones, clean the seeds by removing the outer coat using a table knife or soaking them in water for 2 to 3 days, then rubbing off the flesh. Conduct a seed viability test, employing the floatation method. Healthy and fertilized seeds will sink, while infertile ones will float. However, note that this is a guide, and not all seeds that sink will necessarily germinate. Subsequently, store the seeds at room temperature to mature for a year before sowing at the beginning of summer.
Encephalartos dolomiticus can be propagated through both seeds and suckers. To start from seeds, plant them in river sand and keep them on a heated bench at 24–28°C. Ensure the seeds are level with the sand surface, and germination typically begins 6–8 weeks after sowing, although some may take longer without heat. Once the seedlings are sufficiently grown, transfer them to 3-litre plastic bags filled with a mix of 50% compost and 50% river sand. Water the young seedlings sparingly until they are well-established.
When a sucker reaches a size of about 80 mm diameter, dig the soil away from around the main cycad to expose the sucker and clean any dirt from the sucker and the main cycad. Use a sharp, clean, cutting tool, such as a saw, chisel or knife, to cut off the sucker. Make a clean cut at the point of attachment of the sucker to the main plant. As a precaution, especially with valuable species, apply fungicide, sulphur or a tree seal to the cut area, on both the sucker and the mother plant, to prevent disease and attacks by pests.
If the sucker is large enough (minimum of 250 mm) and it has enough roots, it is best to immediately plant it straight into the ground. Smaller suckers and suckers with no roots of their own must be taken to the nursery, where they should be left in a cool, dry area to dry for a few weeks, to allow the wounds to form a callus, before potting.
Highveld blue-leaved cycads often face challenges from various pests, including scale insects, beetles, chewing insects, and woolly aphids. Effective control measures involve the application of either contact or systemic insecticides.
References
- Bösenberg, J.D. 2022. Encephalartos dolomiticus. The IUCN Red List of Threatened Species 2022: e.T41885A50905617. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T41885A50905617.en.
- Da Silva, J.M., Donaldson, J.S., Reeves, G. & Hedderson, T.A. 2012. Population genetics and conservation of critically small cycad populations: a case study of the Albany cycad, Encephalartos latifrons (Lehmann). Biol J Linn Soc. 105: 293–308.
- DEA. 2015. National strategy and action plan for the management of cycads. Publication of Department of Environmental Affairs, Department: Environmental Affairs, Republic of South Africa.
- Donaldson, J.S. (ed.) 2003. Cycads, status survey and conservation action plan. IUCN/SSC Cycad specialist group. IUCN, Gland, Switzerland and Cambridge, UK.
- Donaldson, J.S. 2009. Encephalartos dolomiticus Lavranos & D.L.Goode. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2023/11/10.
- Goode, D. 2001. Cycads of Africa. Cycads of Africa Publishers, Gallomanor.
- Grobbelaar, N. 2002. Cycads with special reference to the southern African species. Published by the author, Pretoria.
- Raimondo, D.C. & Donaldson, J.S. 2003. Responses of cycads with different life histories to the impact of plant collecting. Biological Conservation 111(3): 345-358.
- Ulwazi, Sharing indigenous knowledge. Isihlahla sesigqiki somkhovu. https://www.ulwaziprogramme.org/2016/10/isihlahla-sesigqiki-somkhovu/ Accessed on 2019/01/23.
- Xaba, P.M.A. 2014. Pollination and germination as limiting factors in the propagation of threatened cycads, Encephalartos (Zamiaceae). MSc Thesis, University of Western Cape, South Africa.
Credits
Lungisani Zondi and Bongekile Ndlovu
Walter Sisulu National Botanical Garden and Pretoria National Botanical Garden
December 2023
Acknowledgements: the authors thank Winfred Ngwenya for supplying images of the plants in the Lowveld National Botanical Garden.
Plant Attributes:
Plant Type: Shrub, Tree
SA Distribution: Limpopo
Soil type: Loam
Flowering season:
PH:
Flower colour:
Aspect: Full Sun, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Average
Special Features:
Drought resistant
Feature plant
Good potplant
Horticultural zones
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