In the far northwest of Uganda, where the White Nile country meets the southern border of South Sudan, a range of low, rocky hills rises from the dry savanna woodland of Moyo District. This is Madi territory — homeland of the Madi people — and it is the only place on Earth where Encephalartos macrostrobilus grows wild. A 2018 population census found exactly 181 mature individuals. Of those, fewer than one in three was female. The baboons that share the hillside routinely destroy the cones before the seeds can mature. The land on which this Encephalartos grows is unprotected community land, used for cattle grazing, stone quarrying, and firewood collection. No formal conservation measures are in place.
Despite these bleak statistics, Encephalartos macrostrobilus possesses one of the most extraordinary morphological features in the genus: its female cones can reach 80 cm in length and 30 cm in width — among the largest reproductive structures produced by any cycad, and vastly disproportionate to the modest, 2.5 m trunk that bears them. The species name says it all: macrostrobilus, from the Latin macro- (“large”) and strobilus (“cone”). It is the cycad world’s answer to the question: what happens when a medium-sized plant produces a giant’s reproductive apparatus?
Taxonomy and nomenclature
Encephalartos macrostrobilus S. Jones & Wynants was first published in 1997 in the journal Encephalartos (volume 50: 13–17, figs. 1–2). The species was described by Scott Jones and Jeff Wynants from material they collected personally (collection number S. Jones & J. Wynants 01) in the Madi area of northwestern Uganda, at coordinates 3°35’N, 31°40’E, between 900 and 1400 m elevation. The holotype is deposited at the National Botanic Garden of Belgium in Meise (BR).
The epithet macrostrobilus refers to the exceptionally large megastrobili (female cones) — up to 80 cm long — which immediately distinguish this species from its closest relative, Encephalartos septentrionalis Schweinfurth, the Nile cycad. Encephalartos septentrionalis is a widespread but poorly known species distributed across South Sudan, northern Uganda, the DRC (within the Okapi Faunal Reserve), and the interior of the Central African Republic. It is essentially stemless or develops only a very short trunk, and its cones are markedly smaller. The PACSOA entry for Encephalartos septentrionalis notes that the colony they visited at Moyo in northern Uganda occurs “less than 100 km from the newly described E. macrostrobilus” — confirming the close geographic relationship between the two species.
In the original description, Jones & Wynants distinguished Encephalartos macrostrobilus from Encephalartos septentrionalis principally by its arborescent habit (a well-developed trunk reaching 2.5 m, vs. an essentially acaulescent or very short-stemmed plant), its much larger female cones, and its more robust vegetative features. The two species are clearly sister taxa, separated by a relatively short geographic distance but occupying different ecological niches — septentrionalis in drier, more open grassland and macrostrobilus on rocky hill slopes with a mix of exposed and sheltered microsites.
Before its formal description, seed from the Moyo population was distributed in 1995 under the name Encephalartos septentrionalis, creating some early confusion in the horticultural community. The recognition of macrostrobilus as a distinct species clarified the situation: the Moyo plants are not septentrionalis but a separate, arborescent taxon with disproportionately large female cones.
Common names: Madi cycad (informal, after the Madi people); giant-coned cycad (descriptive).
Morphological description
Habit and caudex: Encephalartos macrostrobilus is a medium-sized, arborescent cycad. The trunk is erect when young but often becomes somewhat procumbent (sprawling) with age, reaching up to 2.5 m in height and 30–45 cm in diameter. The trunk is usually unbranched but occasionally produces basal offsets. In exposed sites, the trunk is densely covered with persistent leaf bases; in shadier locations, only a few remnant leaf bases remain, leaving the trunk smoother. The base of the leaf is strongly bulbous — a character noted in the original description that contributes to the sturdy, compact architecture of the crown.
Leaves: The crown carries an impressive 35–60 leaves simultaneously — one of the highest leaf counts in the genus, giving the plant a dense, full-crowned appearance disproportionate to its modest trunk height. The fronds are spreading-erect, rigid, straight, and dark green, somewhat recurved near the apex. In sheltered locations, leaves reach 1.9–2.2 m in length and 39–59 cm in width; in more exposed sites, they are shorter (1.4–2.0 m). The petiole is 12–15 cm long. The basal leaflets are abruptly reduced to 1–3 pairs of bifid (two-pointed) spines. The rachis bears a longitudinal groove along its upper surface.
The leaflets are lanceolate, tough, and leathery, each up to 25 cm long, arranged at approximate right angles to the rachis — giving the fronds a flat, symmetrical, fern-like appearance. The leaflets are dentate (toothed) with pungent apices. This rigid, well-armed foliage resembles that of Encephalartos septentrionalis and, more distantly, Encephalartos hildebrandtii — the original description notes a resemblance to both species in the stiff, dentate, pungent green leaves.
Reproductive structures — the defining feature: It is in reproduction that Encephalartos macrostrobilus reveals its most remarkable character.
Male plants are prolific cone producers, bearing 6–14 closely packed, erect, ovoid cones per stem — a number far exceeding that of most Encephalartos species, where 1–5 male cones per stem is typical. Each male cone measures 18–20 cm long and approximately 5 cm wide, initially olive green and darkening to deep green as it matures.
Female plants produce 1–3 cones per stem, but these are extraordinary in their dimensions. Each female cone is cylindrical-ovoid, reaching up to 80 cm in length and 30 cm in width — comparable in size to the cones of the largest South African species (Encephalartos transvenosus, Encephalartos longifolius) but produced on a plant that is less than half their stature. The cones are initially dark green, turning olive green as they ripen. The seeds are enclosed in an orange-red sarcotesta.
The contrast between the relatively modest vegetative structure (trunk to 2.5 m) and the colossal female cones (to 80 cm) is the species’ signature: a mid-sized cycad with the reproductive apparatus of a giant.
Distribution and natural habitat
Encephalartos macrostrobilus is endemic to Moyo District in the far northwest of Uganda, in the region known as the Madi area (or Madi Opei — the administrative designation used by POWO). The type locality lies at approximately 3°35’N, 31°40’E, at elevations between 900 and 1400 m above sea level. This places the species in the northernmost reaches of the East African Encephalartos range — at a latitude comparable to northern South Sudan, and only about 100 km from populations of Encephalartos septentrionalis in the same region.
The habitat is classified by POWO as seasonally dry tropical biome. The cycads grow on low, rocky hill slopes — outcrops of granite and gneiss that project above the surrounding savanna woodland and grassland. The vegetation is open dry woodland and thicket, with scattered trees of Dalbergia melanoxylon (African blackwood), Afzelia africana, and Vitellaria paradoxa (shea) — all three of which are themselves threatened species, as noted during the 2018 population survey. The climate is seasonally arid, with a pronounced dry season (November–March) and a wet season (April–October), total annual rainfall of approximately 800–1200 mm, and temperatures of 20–35 °C. Brief, mild frosts are conceivable during the dry season at 1400 m elevation, though unlikely at the lower end of the range.
The land on which the cycads grow is community land belonging to the Madi people. It has no formal legal protection — no national park, no reserve, no gazetted conservation area. The site is actively used for cattle and goat grazing, stone quarrying, firewood and timber collection. Trails criss-cross the cycad habitat. The cycads coexist with human land use, but their long-term survival depends on the goodwill of the communities that use the land.
Conservation status
Encephalartos macrostrobilus is assessed as Endangered (EN) on the IUCN Red List. The World List of Cycads confirms this assessment. The species is listed on CITES Appendix I, prohibiting international commercial trade.
The 2018 Ojelel census — the most detailed population data for any central-east African Encephalartos:
In May 2018, Samuel Ojelel of Makerere University, Kampala, conducted a thorough population survey as part of a Mohamed bin Zayed Species Conservation Fund (MBZF) project. This census — the first comprehensive field survey of the species — produced the following results:
Total mature individuals documented: 181. All individuals were georeferenced with GPS and a specimen deposited at the Makerere University Herbarium — the first time the species was formally vouchered in a Ugandan institution.
Sex ratio: 2:5, female to male (28.6% female). This heavily male-skewed ratio has profound implications for the species’ reproductive capacity. With fewer than 52 female plants in the entire known population, seed production is severely constrained — particularly given the additional obstacle of baboon predation on cones.
Threats identified during the survey:
Habitat degradation: the cycad site is unprotected community land used for stone quarrying, cattle grazing, and firewood collection. No buffer zone or conservation management exists.
Cone predation by baboons: baboons persistently destroy female cones before seed maturation, dramatically reducing the already limited seed crop. This biological bottleneck, combined with the low proportion of female plants, creates a reproductive crisis. Only 21 seedlings were raised from the limited seed available — a meagre recruitment rate for a species with 181 mature individuals.
Associated threatened species: the same community land supports populations of Dalbergia melanoxylon (VU), Afzelia africana (VU), and Vitellaria paradoxa — species whose timber and products are subject to government trade bans in Uganda, highlighting the broader conservation significance of the site.
The Ojelel project included community sensitisation (awareness-raising), propagation training, and the establishment of a local monitoring team led by community member Mzee Ewoko Angelico. The project generated a scientific manuscript on population size and sex ratio, submitted to the Encephalartos journal. However, as Ojelel noted, there remains “a need to consolidate the gains in this project” — additional surveys in suspected cycad areas, expanded seedling multiplication, and formal habitat protection remain urgent priorities.
The septentrionalis connection — two species, one landscape
The relationship between Encephalartos macrostrobilus and Encephalartos septentrionalis deserves attention. Encephalartos septentrionalis — the Nile cycad, first described by Georg Schweinfurth in 1871 — is one of the most widely distributed Encephalartos species in central-east Africa, recorded from South Sudan, northern Uganda, the northeastern DRC, and the Central African Republic. It is essentially stemless (acaulescent) or develops only a very short subterranean trunk, and its cones are considerably smaller than those of macrostrobilus.
The two species occur within 100 km of each other in the Moyo/Madi region of northwestern Uganda. They are clearly closely related — sharing the same general morphological template of stiff, dark green, dentate, pungent-tipped leaves — but separated by a consistent suite of characters: trunk development (arborescent vs. acaulescent), cone size (80 cm female cones vs. much smaller), and the number of male cones per stem (6–14 in macrostrobilus vs. typically fewer in septentrionalis).
Whether these two taxa represent true biological species, incipient species, or the extremes of a clinal continuum remains unresolved. No molecular phylogenetic study has been published comparing the two. The original description by Jones & Wynants (1997) treated them as distinct species on the basis of consistent morphological differences, and this treatment is accepted by POWO, the World List of Cycads, and all current authorities. The relationship between the macrostrobilus and septentrionalis populations in the Moyo/Madi region — their precise distribution, zone of contact (if any), ecological segregation, and genetic divergence — represents one of the most interesting open questions in Encephalartos systematics.
Cold hardiness
The type locality (3°35’N, 900–1400 m) experiences a seasonally dry tropical climate with warm days and mild to cool nights. At 1400 m, dry-season nighttime temperatures may occasionally approach 10 °C, and brief, light ground frost is not impossible on exposed hilltops during clear nights in January — though it would be exceptional. The lower altitudinal limit (900 m) is warmer and frost-free.
No published cold-hardiness data exist specifically for Encephalartos macrostrobilus. By analogy:
— Encephalartos septentrionalis is grown in similar climates with some reported frost tolerance (it extends into seasonally cool, dry savannas in South Sudan).
— Encephalartos tegulaneus (1200–2300 m, Kenya) tolerates cool montane conditions.
Practical cold hardiness estimate: USDA Zone 9b–10a (−1 to −4 °C) as a provisional estimate. The moderate altitude (up to 1400 m) and seasonally dry climate suggest some tolerance for cool, dry conditions — more than the truly equatorial, low-altitude species (hildebrandtii, laurentianus) but less than the South African montane species (ghellinckii, cycadifolius). Brief frost, if dry, may be tolerated; prolonged or wet frost would likely cause serious damage.
Cultivation guide
Difficulty: 3/5. Cultural requirements are straightforward for a seasonally dry tropical cycad, but the extreme rarity of the species in cultivation means that practical growing experience is almost non-existent outside Uganda. Virtually no cultivated specimens exist in Western collections.
Light: Full sun to partial shade. The rocky hill-slope habitat is exposed to strong tropical sun, but the mix of open and sheltered microsites in the natural habitat suggests adaptability. In cultivation, full sun promotes compact growth and abundant leaf production.
Soil: Well-drained, mineral-rich. The granite and gneiss substrate of the natural habitat produces thin, well-drained, slightly acidic soils. In cultivation, a free-draining mix of coarse sand, loam, and pumice with minimal organic matter would replicate the natural conditions. Good drainage is essential — the species experiences a pronounced dry season and is adapted to periodic drought, not constant moisture.
Watering: Regular during the growing (wet) season, reduced to minimal during winter or the dry season. The seasonally dry tropical climate — 800–1200 mm concentrated in the wet season, with a long, pronounced dry season — means the species is adapted to alternating wet and dry cycles. In cultivation, water generously from spring to autumn and keep nearly dry through winter. This pattern resembles the watering regime for the South African summer-rainfall species.
Feeding: Balanced NPK with trace elements during the growing season. The species produces a high number of leaves (35–60 per crown) and a prolific number of male cones (6–14 per stem), both of which place significant nutrient demands on the plant.
Growth rate: Not well documented. The trunk height of 2.5 m suggests moderate growth by Encephalartos standards — faster than the stemless or dwarf species but slower than the central African giants (laurentianus, hildebrandtii). The high leaf count (35–60) suggests active, sustained growth in suitable conditions.
Container culture: Feasible and appropriate for the first decade or more. The moderate eventual size (trunk to 2.5 m, leaves to 2.2 m) makes Encephalartos macrostrobilus a viable long-term container subject — large enough to be impressive, small enough to be manageable. In temperate climates, a large container in a greenhouse or conservatory, moved outdoors during summer, would be the most practical approach.
Comparison with related northern species
| Character | E. macrostrobilus | E. septentrionalis | E. whitelockii | E. equatorialis |
|---|---|---|---|---|
| Distribution | NW Uganda (Moyo District) | S. Sudan / N. Uganda / NE DRC / CAR | SW Uganda (Mpanga Gorge) | SE Uganda (Lake Victoria) |
| Altitude | 900–1400 m | 600–1200 m | 1000–1300 m | ~1000 m |
| Trunk | Erect → procumbent, to 2.5 m × 30–45 cm | Acaulescent or very short | Erect, 3–4 m × 35–40 cm, clumping | Erect, 3.5–4 m × 35–45 cm |
| Leaf count | 35–60 (high) | 15–30 | 20–40 | Not well documented |
| Leaf length | 1.4–2.2 m | 1.0–1.8 m | 3.1–4.1 m | 3–4 m |
| Leaflet apex | Pungent, dentate | Pungent, dentate | Pungent, heavily toothed | Bifurcate/trifurcate + pungent |
| Male cones/stem | 6–14 (extremely high) | 1–5 | Up to 5, pendulous | Not well documented |
| Female cone size | Up to 80 × 30 cm (largest vs. plant size) | Much smaller | Bluish-green, medium | 35–40 × 18–20 cm |
| Seed sarcotesta | Orange-red | Red | Red | Orange-red |
| Biome | Seasonally dry tropical | Seasonally dry tropical | Tropical gorge forest | Seasonally dry tropical |
| Cold hardiness | Zone 9b–10a (estimated) | Zone 9b–10a (estimated) | Zone 10a–10b | Zone 10a–10b (estimated) |
| IUCN status | EN (181 mature plants) | NT (widespread but poorly documented) | CR (8000–12 000 plants) | CR (~300 plants) |
| Key diagnostic | Giant female cones on modest trunk | Acaulescent habit | Pendulous male cones, glossy fronds | Imbricate leaflets |
Propagation
Seed: Seed availability is the critical bottleneck. The 2018 census documented a sex ratio of only 28.6% female, and baboons routinely destroy the cones before seed maturation. Only 21 seedlings were raised from the entire known population during the MBZF conservation project. When seed is obtainable, standard Encephalartos germination protocols apply: clean the sarcotesta (gloves — toxic), sow on free-draining medium at 27–28 °C. The original description notes that seed from Moyo was distributed in 1995 (under the name E. septentrionalis), suggesting that germination is feasible under standard conditions.
Offsets: The species is described as usually single-trunked but occasionally producing basal offsets. Offset propagation is possible in principle but limited by the extreme rarity of cultivated material.
Why Encephalartos macrostrobilus matters
Encephalartos macrostrobilus is not famous. It appears on no “top ten” lists of spectacular cycads. It lacks the blue foliage of the Eastern Cape species, the colossal dimensions of Encephalartos laurentianus, or the tragic celebrity of Encephalartos woodii. What it possesses instead is a quiet, almost accidental vulnerability — the vulnerability of a species that was not even described until 1997, that exists in a single administrative district of a country where cycad conservation is not a national priority, and that faces a demographic profile (181 individuals, 28.6% female, baboons eating the cones) that reads like a textbook case study in small-population biology.
The 2018 Ojelel census is both the best and the worst thing that has happened to Encephalartos macrostrobilus: best, because it provided the first rigorous baseline data; worst, because those data confirm that the species is balanced on a demographic knife-edge. With fewer than 52 female plants producing seed — and baboons intercepting much of what is produced — the effective reproductive population is vanishingly small. Genetic erosion, inbreeding depression, and demographic stochasticity (the random fluctuations that can push tiny populations to extinction) are all immediate risks.
The path forward is clear in principle: protect the habitat, exclude baboons from female cones during seed maturation, collect and germinate seed systematically, establish ex-situ populations in botanical gardens, and work with the Madi communities to create lasting incentives for conservation. The MBZF project has made a start. Whether that start translates into long-term survival for the giant-coned cycad of the Madi Hills depends on sustained effort, funding, and political will in a region where all three are in short supply.
Authority websites
POWO — Plants of the World Online: https://powo.science.kew.org/…
IUCN Red List: https://www.iucnredlist.org/species/41951/121560270
World List of Cycads: https://cycadlist.org
Bibliography
Jones, S. & Wynants, J. (1997). Encephalartos macrostrobilus (Zamiaceae): a new cycad species from northern Uganda. Encephalartos 50: 13–17, figs. 1–2. [Original description]
Schweinfurth, G. (1871). Cycadaceae. Botanische Zeitung. [First description of E. septentrionalis]
Melville, R. (1957). Encephalartos in Central Africa. Kew Bulletin 12: 237–257.
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.
Vorster, P. (2004). Classification concepts in Encephalartos (Zamiaceae). In: Walters, T. & Osborne, R. (eds.), Cycad Classification: Concepts and Recommendations, pp. 69–83. CABI Publishing, Oxfordshire.
Ojelel, S. (2018). Empowering the local community to protect an Endangered cycad (Encephalartos macrostrobilus) in Moyo District, Uganda. MBZF Grant 172516737, Makerere University. [Population census and conservation project report]
Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31.