Look at a distribution map of the genus Encephalartos and you will see a dense concentration of species in southern and eastern Africa — South Africa alone hosts over 40 species — thinning northward through central Africa, and then, unexpectedly, a scattering of dots in West Africa: Nigeria, Ghana, Benin, Togo. These dots represent Encephalartos barteri, the only widespread gymnosperm in West Africa and one of the most biogeographically isolated members of the entire genus. Separated from its nearest congeners by thousands of kilometres of forest, savanna, and the vast Congo Basin, Encephalartos barteri occupies a position in the genus comparable to a linguistic isolate — a species that speaks a language none of its neighbours understand, surviving in a region where cycads, by all conventional biogeographic logic, should not exist.
The species was among the first tropical African Encephalartos to reach European science — described in 1868, a full century before most of the central and East African species were even discovered. Yet it remains poorly studied, its populations scattered and declining, its ecology barely documented, and its future uncertain as the savanna woodlands of the Guinea-Sudanian zone are progressively converted to farmland.
Taxonomy and nomenclature
Encephalartos barteri Carruth. ex Miq. was first published in 1868 in Archives Néerlandaises des Sciences Exactes et Naturelles (volume 3: 243). The species is named in honour of Charles Barter (1821–1859), a British botanical collector who gathered the type specimen (Barter 1692) at Jeba in northern Nigeria in 1858. Barter died at the age of 38 during the Niger Expedition, just one year after collecting the cycad that would bear his name. The type was confirmed by Melville in his 1957 revision (Kew Bulletin 12: 243) and is deposited at Kew.
The species comprises two recognised subspecies:
Encephalartos barteri subsp. barteri — the typical form, distributed across Benin (Atakora, Borgou, Collines, Donga, Zou Departments), Ghana, Nigeria (Kwara, Plateau States), and Togo. This is the more widespread subspecies, occurring on rocky hillsides and in seasonally dry woodland across the Guinea-Sudanian savanna zone between approximately 7° and 11°N latitude.
Encephalartos barteri subsp. allochrous L.E. Newton — a distinct form whose description was published by Leonard E. Newton. The epithet allochrous (Greek: “of a different colour”) presumably refers to differences in cone or leaf colouration. This subspecies has a more restricted range. The IUCN assessed it separately (Bösenberg 2022).
The species has no other taxonomic synonyms. Within the genus, Encephalartos barteri is taxonomically isolated: it has no close morphological relative among the other Encephalartos species, and its position in the genus has never been resolved by molecular phylogenetics. The vast geographic gap between its West African range and the nearest congeners in central Africa (Encephalartos septentrionalis in South Sudan/CAR, Encephalartos laurentianus in DRC/Angola) — a distance of over 1500 km across the Congo Basin — suggests a deep evolutionary separation.
Common names: Barter’s cycad (English); kaldo (Angas, Nigeria); mamponmerε (Akan, Ghana).
Morphological description
Habit and caudex: Encephalartos barteri is a medium-sized, vigorously suckering cycad. The trunk is erect, slow-growing, reaching up to 2.6 m in height. The species suckers freely from the base, forming multi-stemmed clumps over time — a growth habit shared with many fire-adapted Encephalartos species and an important reproductive strategy in the fire-prone savanna habitat.
Leaves: The fronds are bright green (not blue or glaucous — a notable difference from the southern African blue-leaved complex), 1–2 m long (some sources report up to 1.7–2 m). The median leaflets are 19–28 cm long and 10–25 mm wide (considerable variation exists among populations), reducing in size toward the base of the rachis and ending in a series of spine-like thorns. The overall appearance is of a full-crowned, bright green, moderately armed cycad — more reminiscent of the East African green-leaved species (hildebrandtii, kisambo) than of the blue-leaved South African species.
A population genetics study by Ekué et al. (2008) documented significant leaflet morphological variation among five populations in Benin sampled along a north–south latitudinal gradient (7°34′ to 10°20’N), suggesting phenotypic plasticity and/or local adaptation across the species’ range. The morphological differences between populations were not correlated with geographic distance — an indication that environmental factors (rainfall, soil, fire regime) rather than simple isolation are driving the variation.
Reproductive structures: The species is strictly dioecious. Male cones are spindle-shaped (fusiform), yellow, 8–23 cm long and 3–5 cm wide, with broad, rhombic-shaped microsporophylls. Female cones are ovoid, green, substantially larger than the male cones, 15–35 cm long and 8–15 cm in diameter, with warty (verrucose) macrosporophylls. Seeds are oblong, 20–30 mm long and 18–23 mm wide, enclosed in a red sarcotesta.
The yellow male cones and green female cones create a chromatic contrast unusual in the genus, where both sexes typically produce cones of similar colour. This dimorphism in cone colour is one of the more distinctive features of the species.
Distribution and natural habitat
Encephalartos barteri is native to four countries in West Africa: Nigeria (Kwara and Plateau States), Ghana, Benin (Atakora, Borgou, Collines, Donga, and Zou Departments), and Togo. This is an extraordinary range for an Encephalartos species — spanning approximately 1500 km from eastern Nigeria to Ghana, across the Dahomey Gap (the interruption of the West African forest belt between Ghana and Nigeria), and through some of the most densely populated agricultural landscapes in sub-Saharan Africa.
The habitat is seasonally dry tropical forests and woodlands on sandy soils over granite and sandstone — the Guinea-Sudanian savanna zone that stretches across West Africa between the moist forests of the coast and the dry Sahel to the north. PACSOA describes the habitat as “seasonally dry tropical forests and woodlands on sandy soils over granites and sandstones.” In Ghana, the species occurs sporadically on rocky hillsides. In Benin, populations are distributed across a latitudinal gradient from approximately 7°34’N (Zou Department, in the southern savanna-forest mosaic) to 10°20’N (Atakora Department, in the dry Sudanian zone).
The climate is seasonally dry tropical, with a pronounced rainy season (April–October in the south, June–September further north) and a long dry season dominated by the Harmattan — the dry, dusty trade wind from the Sahara. Annual rainfall ranges from approximately 800 mm in the northern populations to 1200 mm in the south. Temperatures are high year-round (25–35 °C), with the hottest periods occurring during the dry season (March–April) before the onset of the rains. The dry season can be severe, with months of near-zero rainfall, intense sunshine, and relative humidity dropping below 20%.
Fire is a dominant ecological force across the Guinea-Sudanian savanna. Annual or biennial grass fires, both natural and anthropogenic (set by farmers and pastoralists for land clearing and grazing management), sweep through the landscape during the late dry season. Encephalartos barteri is fire-adapted: its thick trunk, protected by persistent leaf bases, insulates the apical meristem from heat, and the species resprouts vigorously after burning. In Ghana, fire is identified as the major threat to the species — paradoxically, because while moderate fire maintains the open habitat the cycad requires, frequent intense fires can kill seedlings and prevent recruitment.
A biogeographic enigma
The presence of an Encephalartos species in West Africa is one of the most puzzling biogeographic patterns in the Cycadales. The genus is otherwise confined to eastern and southern Africa, with a centre of diversity in South Africa and outliers in central Africa (DRC, Angola, Uganda, CAR, South Sudan). Encephalartos barteri is separated from the nearest congener — Encephalartos septentrionalis in the CAR — by over 1500 km of continuous forest and savanna, with no known intermediate populations.
How did a cycad reach West Africa? Several hypotheses have been proposed. The most widely accepted is that Encephalartos barteri represents a relict of a formerly more continuous distribution that existed during drier climatic periods of the Pleistocene, when savanna corridors connected West and Central Africa across what is now the Congo Basin forest. During these dry phases, savanna-adapted cycads could have dispersed westward along the corridor. When the climate became wetter and the forest expanded, the corridor closed, isolating the West African populations from their central African relatives. The result is a species marooned in West Africa — a living fossil of a vanished ecological connection.
The Ekué et al. (2008) population genetics study supports this interpretation: the high genetic differentiation among populations (Gst = 0.23, Φst = 0.32) and the presence of population-specific genetic markers are consistent with long-term isolation and limited gene flow — exactly what one would expect of a relict species persisting in fragmented populations.
Conservation status
Encephalartos barteri is assessed as Vulnerable (VU) on the IUCN Red List, under criteria A2cd+4cd — indicating a population decline of at least 30% over the past three generations, inferred from ongoing reduction of habitat area and number of locations. The species is listed on CITES Appendix I. The subspecies allochrous has been assessed separately.
Ekué et al. (2008) recommended that the IUCN status be upgraded to Endangered, citing “the ongoing decline of the habitat of the species and the continued removal of individuals from the wild.” Whether this recommendation has been adopted for the most recent assessment is unclear.
Threats: Habitat loss is the primary threat. The Guinea-Sudanian savanna of West Africa is among the most agriculturally transformed landscapes on the continent. Population growth, farmland expansion, and charcoal production are progressively eliminating the rocky woodland habitats on which the cycad depends. Fire management is a double-edged sword: too little fire allows woody vegetation to encroach and shade out the cycad; too much fire kills seedlings and prevents recruitment. Collection for medicinal or ornamental use is a secondary threat. In Benin, the study identified two populations (Gangamou and Doh) with unique genetic variants that lack any legal protection — their loss would represent an irreversible diminution of the species’ genetic diversity.
Conservation efforts: A Rufford Foundation project led by Alex Asase targeted the ecology and conservation of Encephalartos barteri in Ghana, aiming to improve understanding of the species’ biology and promote awareness of its conservation status. The Ekué et al. genetics study provided the first detailed population-level data for the species and recommended community-based nursery management as a conservation strategy.
Cold hardiness
The West African habitat (7–11°N, 200–800 m estimated altitude) is uniformly warm year-round. Daytime temperatures rarely drop below 25 °C; nighttime temperatures during the cool Harmattan season (December–February) may drop to 15–18 °C in the northern populations and even lower on exposed hilltops, but frost does not occur anywhere in the species’ range.
Practical cold hardiness estimate: USDA Zone 10a–10b (−1 to +2 °C) as a conservative estimate. This is a genuinely tropical species with no evolutionary exposure to frost. Brief, light frost may be tolerated by established plants if conditions are dry, but sustained cold is likely to cause serious damage. In Mediterranean climates (Côte d’Azur, coastal California), outdoor cultivation requires a warm, frost-free microclimate. In cooler climates, a heated greenhouse is essential.
Cultivation guide
Difficulty: 2/5. PACSOA describes the species as a vigorous grower that likes a sunny, well-drained position. The species’ adaptation to the harsh West African dry season — months of intense heat and drought — makes it inherently tough in cultivation.
Light: Full sun. The open savanna woodland and rocky hillside habitat is fully exposed to equatorial sun. In cultivation, full sun promotes compact growth and vigorous leaf production.
Soil: Well-drained, sandy to loamy, over granite or sandstone. The natural substrate is sandy soil derived from granite and sandstone weathering — well-drained, mineral-rich, and moderately fertile. In cultivation, a free-draining mix of coarse sand, loam, and pumice works well.
Watering: Regular during the growing season (spring to autumn), reduced during winter. The species is adapted to a pronounced wet/dry cycle — generous moisture during the rains, near-total drought during the Harmattan. In cultivation, replicate this rhythm: water freely when in active growth, reduce dramatically in winter.
Feeding: Balanced NPK with trace elements during the growing season. The species responds well to regular fertilisation.
Growth rate: Slow for the trunk, but vigorous suckering means that clumps develop relatively quickly. PACSOA describes it as a vigorously suckering species.
Container culture: Well-suited. The moderate trunk height (to 2.6 m) and vigorous suckering habit make this species a viable long-term container subject. In temperate climates, a large container in a greenhouse or conservatory, moved outdoors during summer, is the most practical approach.
Landscape use: In frost-free tropical and subtropical gardens, Encephalartos barteri makes an attractive specimen or group planting. The bright green foliage, multi-stemmed habit, and contrasting yellow male / green female cones create a plant of considerable visual interest. The species is described as doing well in humid tropical climates (Florida, northern Australia, Southeast Asia) as well as in drier subtropical conditions.
Comparison with other geographically isolated Encephalartos
| Character | E. barteri | E. septentrionalis | E. laurentianus |
|---|---|---|---|
| Distribution | West Africa (Nigeria, Ghana, Benin, Togo) | S. Sudan / N. Uganda / NE DRC / CAR | Angola / DRC (Kwango River) |
| Biogeographic position | Western outlier (>1500 km from nearest congener) | Northernmost species | Largest species; Kwango valley endemic |
| Trunk | Erect, to 2.6 m, vigorously suckering | Partly subterranean, 30–200 cm | Erect → prostrate, 4–15 m (largest) |
| Leaf colour | Bright green | Mid green (or silvery in ‘Sudan Silver’) | Dark green, glossy |
| Leaf length | 1–2 m | 0.9–2 m | 4–7 m (longest) |
| Male cone colour | Yellow (distinctive) | Greenish → yellowish brown | Yellowish green |
| Female cone colour | Green (contrast with yellow males) | Yellowish brown | Yellowish green |
| Subspecies | 2 (barteri + allochrous) | None (but ‘Sudan Silver’ form) | None |
| Habitat | Guinea-Sudanian savanna on granite/sandstone | Dry savanna on granite boulders | Gallery forest / sandstone cliffs |
| Fire adaptation | Strong (savanna fire regime) | Strong (semi-deciduous, blackened trunks) | Moderate (gallery forest) |
| Cold hardiness | Zone 10a–10b (tropical, no frost) | Zone 9b–10a | Zone 10a–10b |
| IUCN status | VU A2cd+4cd (recommended upgrade to EN) | NT (widespread) | NT (large but unquantified population) |
Propagation
Seed: The species produces oblong seeds, 20–30 mm × 18–23 mm, with a red sarcotesta. Standard germination protocols apply: clean the sarcotesta (gloves — toxic), sow on free-draining medium at 27–30 °C. Germination is reportedly reliable. The Ekué et al. study recommends community-based nursery management as a conservation-propagation strategy, suggesting that seed-based propagation is practical at a community level.
Offsets: The species’ vigorous suckering habit makes offset propagation the most efficient vegetative method. Well-developed suckers with established roots can be separated from the parent clump.
The last gymnosperm of the Guinea savanna
Encephalartos barteri is an anachronism. It is a gymnosperm — a member of a plant lineage that dominated the world’s forests 200 million years ago — surviving in a landscape now controlled by grasses and flowering trees. It is an Encephalartos — a member of a genus centred on southern and eastern Africa — persisting 1500 km west of any relative. It is a slow-growing, long-lived organism in a landscape defined by fast turnover: annual fires, seasonal floods, and the relentless expansion of human agriculture.
The population genetics data tell a story of survival against the odds: high genetic diversity at the species level (82.7% polymorphic loci), but strong differentiation among populations (Gst = 0.23) — the signature of a species that was once more widespread and is now fragmented into isolated patches, each evolving independently. The populations at Gangamou and Doh in Benin, with their unique genetic variants and no legal protection, represent irreplaceable components of this diversity. Their loss would be permanent.
Whether Encephalartos barteri survives the twenty-first century depends on whether the communities of West Africa — the farmers, pastoralists, and charcoal makers who share its habitat — can find reasons to keep it. The Rufford and Ekué projects have begun this conversation. The cycad, patient as ever, waits for the answer.
Authority websites
POWO — Plants of the World Online: https://powo.science.kew.org/…
IUCN Red List: https://www.iucnredlist.org/species/41900/50823905
World List of Cycads: https://cycadlist.org
Bibliography
Carruthers, W. ex Miquel, F.A.W. (1868). Encephalartos barteri. Archives Néerlandaises des Sciences Exactes et Naturelles 3: 243. [Original description]
Melville, R. (1957). Encephalartos in Central Africa. Kew Bulletin 12(2): 237–257. [Type confirmation, p. 243]
Newton, L.E. Encephalartos barteri subsp. allochrous. [Subspecies description]
Ekué, M.R.M., Gailing, O., Hölscher, D., Sinsin, B. & Finkeldey, R. (2008). Population genetics of the cycad Encephalartos barteri ssp. barteri (Zamiaceae) in Benin with notes on leaflet morphology and implications for conservation. Systematics and Biodiversity. [Key genetics paper]
Asase, A. Ecology and conservation of threatened cycad species (Encephalartos barteri) in Ghana. Rufford Foundation. [Conservation project]
Burkill, H.M. (1985). The Useful Plants of West Tropical Africa, vol. 5.
Whitelock, L.M. (2002). The Cycads. Timber Press, Portland. 374 pp.
Donaldson, J.S. (ed.) (2003). Cycads: Status Survey and Conservation Action Plan. IUCN/SSC Cycad Specialist Group, IUCN, Gland.
Bösenberg, J.D. (2022). Encephalartos barteri. The IUCN Red List of Threatened Species 2022.
Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31.