Encephalartos hildebrandtii

Encephalartos hildebrandtii is a large cycad of the East African coast, growing in evergreen coastal bushland and coastal forest in Kenya and Tanzania, including the island of Zanzibar. This species of the genus Encephalartos was discovered in 1873 near Mombasa by the German explorer Johann Maria Hildebrandt and described the following year in Berlin; in English it is known as the Mombasa cycad. It can form a trunk 6 m tall bearing glossy dark green leaves 2 to 3 m long, with spiny-toothed leaflets, and its new leaves often emerge orange. The IUCN lists it as Least Concern (assessment published in 2024), although tourist development has destroyed populations on the coast of Zanzibar. Outside the tropics it is a plant for a frost-free glasshouse or conservatory.

Key facts about Encephalartos hildebrandtii

  • Accepted name: Encephalartos hildebrandtii A.Braun & C.D.Bouché (1874), accepted by The World List of Cycads (version 2026.08.15) and Species+
  • Former names and synonyms: Encephalartos hildebrandtii var. dentatus Melville (1957), a synonym according to The World List of Cycads; Encephalartos villosus f. hildebrandtii (A.Braun & C.D.Bouché) Henn. (1890); Zamia hildebrandtii, a horticultural name (Prain, 1917; Species+)
  • Family: Zamiaceae, order Cycadales
  • Common names: Mombasa cycad (English); msapo and mtsapu (Swahili), according to Species+
  • Natural range: coast of Kenya and Tanzania (Tanga and Lushoto districts, Zanzibar Island) according to The World List of Cycads; Species+ also lists Mozambique, a record the Flora of Mozambique considers doubtful
  • IUCN status: Least Concern (LC), assessment dated 13 March 2020 and published in the IUCN Red List 2024-1, as in the previous assessment (October 2009, published in 2010); Near Threatened (NT) in the IUCN action plan of 2003
  • CITES and other protection: CITES Appendix I (whole genus, since 1977); Annex A in the European Union, with a positive EU opinion for artificially propagated plants from South Africa with a caudex up to 7 cm in diameter and a negative opinion above that size
  • Documented hardiness: no rigorously measured value; in the Salento (southern Italy), plants came through a single night at −1 °C (30.2 °F) undamaged in December 2009 (see Cold hardiness)
  • Light and soil: in the wild, evergreen coastal bushland from sea level to 450 m (Melville, 1957); in cultivation, bright light or part shade and a free-draining soil, frost-free in winter
  • Habit and adult size: trunk up to 6 m tall and 30 cm in diameter; leaves 2 to 3 m long; male cones 20 to 50 cm, female cones 28 to 60 cm long (Melville, 1957)
  • In the UK, US and Australia: Kew, the Royal Botanic Garden Edinburgh and the Millennium Seed Bank (BGCI); Montgomery (six accessions), Fairchild, the Huntington, Lotusland, the San Diego Botanic Garden and some fifteen other US gardens; Royal Botanic Garden Sydney, Brisbane, Melbourne, Adelaide and Townsville in Australia
  • Toxicity: no data specific to the species; seeds toxic as in all cycads (see Toxicity and precautions)

How to recognise Encephalartos hildebrandtii

Look for very long, glossy dark green leaves, lance-shaped leaflets armed with a few spiny teeth on each margin and often ending in two or three spines, lower leaflets reduced to prickles down to the base of the petiole, and greenish, reddish or yellowish cones. The fullest description is that of R. Melville (1957), in his revision of the Encephalartos of Central and East Africa:

  • Trunk: up to 6 m tall and 30 cm in diameter; cataphylls linear to narrowly triangular, 10 to 15 cm long, covered outside with a thick tawny felt
  • Leaves: linear-oblanceolate, 2 to 3 m long and 30 to 65 cm wide; rachis rounded above; swollen base of the petiole at first woolly and tawny, later hairless
  • Leaflets: median leaflets linear-lanceolate, 15 to 35 cm long and 13 to 45 mm wide, with a long-pointed, sharp tip or two or three spiny teeth at the apex, and one to four, up to nine, spreading spiny teeth on each margin, often grouped towards the base; leathery, glossy dark green above, paler beneath, with 26 to 40 parallel veins; the lower leaflets become palmately spiny, then three- and two-pronged and finally simple prickles down to the base of the petiole
  • Male cones: cylindrical to subconical or spindle-shaped, 20 to 50 cm long and 5 to 9 cm across, greenish to dull red, on a stalk 5 to 25 cm long; Prain (1917) counts up to seven per crown
  • Female cones: cylindrical, 28 to 60 cm long and 15 to 25 cm across, dull yellow, on a stalk 4 to 6 cm long
  • Seeds: ovoid, truncate, vermilion, 20 to 38 mm long and 16 to 26 mm across

David Prain (1917), in the Flora of Tropical Africa, gives comparable figures: a trunk up to 20 ft (6 m), leaves of 8 to 9 ft (2.4 to 2.7 m) and 50 to 70 pairs of leaflets about 9 in (23 cm) long, usually with two or three teeth on each margin. The original description of 1874, based on young plants brought back by Hildebrandt and grown in Berlin, is more modest: trunks of wild plants sometimes 1.5 m tall, but no more than 20 cm on cultivated plants, often suckering at the base; leaves 0.5 to 1 m long; 36 to 50 pairs of leaflets 8 to 10 cm long and 14 to 16 mm wide, most often with four teeth on each margin.

In cultivation, the young leaves often emerge orange, turn olive green as they unfold and then become dark green and glossy, as a grower in the Var (south-eastern France) described on the Fous de palmiers forum in June 2009; another member of the forum noted in 2012 that the species regularly produces coloured flushes. The San Diego County nursery Jungle Music describes it as fast-growing, with spiny leaflets that remain somewhat flexible, and gives cone colours that differ from Melville’s: very pale yellow, almost white, female cones and yellow male cones.

Hybrids

No natural hybrid of Encephalartos hildebrandtii is documented. Melville’s var. dentatus, now a synonym, was known only from plants cultivated in Dar es Salaam (see Taxonomy), and no hybrid origin was suggested for it. In collections, cross-pollination with other Encephalartos is possible: to obtain pure seed, isolate the female cones and control the origin of the pollen.

Possible confusion

The most frequent confusion is with Encephalartos kisambo, from the Taita Hills of south-eastern Kenya (The World List of Cycads also records it from the Kilimanjaro region of Tanzania), which its authors, R. B. Faden and H. J. Beentje (1989), considered perhaps the closest species. They separate Encephalartos kisambo by its sickle-shaped leaflets with fewer teeth, its generally larger male cones with less strongly deflexed scales, its shallower female cone scales and its orange-yellow, not red, seeds. Young seedlings of the two species look very much alike (Holzman, 2009), so a reliable label matters. Encephalartos equatorialis, from Uganda, differs according to its authors (Hurter and Glen, 1995) in its straight, hard leaflets pointing towards the leaf tip and strongly overlapping towards the top of the leaf, whereas those of Encephalartos hildebrandtii are arched, flexible, point towards the base and often end in two or three spines.

Prain (1917) placed it closest to Encephalartos laurentianus, from the Congo, and Encephalartos gratus, from Malawi, from which it differs in the shape of the cone scales and in narrower, less sickle-shaped leaflets. It is less close to Encephalartos villosus, from South Africa, which some authors had treated it as a geographical form of: the foliage of the two species can look alike at certain stages, but the scales of the female cones, bossed in Encephalartos hildebrandtii and flattened in Encephalartos villosus, separate them clearly. Braun and Bouché (1874) already distinguished it from Encephalartos septentrionalis, with its almost entirely buried, globular trunk.

The history of the species shows how easily mistakes are made: a collection made in 1911 in the Mathews Range of northern Kenya had been identified as Encephalartos hildebrandtii but belongs to Encephalartos tegulaneus, described only in 1957 (Faden and Beentje, 1989). Melville also included in Encephalartos hildebrandtii the plants of the Mpanga River in western Uganda, which he considered intermediate towards Encephalartos laurentianus; it was at the Mpanga Falls that Hurter described Encephalartos whitelockii in 1995. Under the present taxonomy those Ugandan plants would therefore belong to that species, a deduction that no published source states in so many words.

Taxonomy

Alexander Braun and Carl David Bouché published the name in 1874 in the Index Seminum of the Berlin botanic garden (p. 18), among the “new plants brought back from East Africa by Mr Hildebrandt and grown in 1874 in the Berlin garden”. The Latin diagnosis states that Hildebrandt discovered it in 1873 on the bushy hills of the “Zanzibar coast”, that is the mainland coast then under the sultanate: The World List of Cycads and Melville (1957) give as type a collection by Hildebrandt without number, from Mombasa in Kenya, kept in Berlin (holotype, B), with an isotype at Kew.

In 1890 Hennings reduced it to a form of Encephalartos villosus, a combination since abandoned. In 1957 Melville distinguished two varieties: var. hildebrandtii, with untoothed ridges on the cone scales, and var. dentatus, with toothed ridges, described from a plant grown in a garden in Dar es Salaam (Wigg 1044) and then known only in cultivation. The World List of Cycads now treats var. dentatus as a synonym of the species. Some older literature placed Encephalartos hildebrandtii at the centre of an East African group of related species; Moretti and colleagues (1989), for example, described the now synonymous Encephalartos voiensis as a member of the “E. hildebrandtii complex”, but no formal group of that name is recognised today.

Etymology and history

The epithet honours Johann Maria Hildebrandt (1847–1881), German explorer, botanist and collector in East Africa and Madagascar, who collected the type specimen (Haynes, 2022, cited by The World List of Cycads).

The species entered cultivation almost at once: by 1874 the young plants brought back by Hildebrandt were growing in Berlin, where they were described. Prain (1917) cites a long series of horticultural publications of the late nineteenth century in Germany, France (Revue horticole, 1880) and England (The Gardeners’ Chronicle, 1878 and 1900), and two plates in Curtis’s Botanical Magazine. He treated the species in 1917 in the Flora of Tropical Africa, and Melville gave the fullest description of it in 1957.

Common names

In English, Species+ and the Flora of Mozambique call it the Mombasa cycad. Species+ gives two Swahili names, msapo and mtsapu; Prain (1917) had already recorded that the species is called mtsapu in the Rabai Hills near Mombasa, and that Engler called it the “East African sago palm”. Other English names found on some websites are not attested by these sources.

In the wild

Encephalartos hildebrandtii lives on the coast of Kenya and Tanzania: The World List of Cycads cites the Kenyan coast and, in Tanzania, the Lushoto (East Usambara Mountains) and Tanga districts and Zanzibar Island. Prain (1917) lists collections from the hills near Mombasa and Rabai, the coastal belt at Tanga, Bagamoyo and Dar es Salaam, the foot of the Usambara Mountains and Zanzibar, where the species grew “among bushes on recent coral formations”; he describes it as present “from Dar es Salaam to Mombasa”. According to Melville (1957), it grows in evergreen coastal bushland from sea level to 450 m; Prain nevertheless cites a collection by Engler at 2,700 ft (about 820 m), in savanna forest in the upper Bombo valley of the Usambaras. The Flora of Mozambique reports a record for Mozambique in the Flora Zambesiaca, based on sterile material and therefore doubtful; The World List of Cycads does not include that country, and the mention of “northern Mozambique” by Jungle Music is not supported by these sources.

The IUCN cycad action plan (Donaldson, 2003) reports that urban development and tourist resorts have destroyed populations of Encephalartos hildebrandtii along the east coast of Zanzibar, and publishes a photograph of a population cleared to build a holiday village. No study of its pollination has been published.

Conservation status and regulation

Encephalartos hildebrandtii is listed as Least Concern (LC) on the IUCN Red List. The assessment in force, by W. R. Q. Luke and J. D. Bösenberg, is dated 13 March 2020 and was published in the Red List 2024-1 (GBIF, Crossref). It keeps the category of the previous assessment, carried out by the Eastern Arc Mountains and Coastal Forests CEPF Plant Assessment Project and J. D. Bösenberg, dated 31 October 2009 and published in 2010, which is the one still cited by The World List of Cycads. In 2003 the IUCN action plan listed it as Near Threatened (NT), with 10,000 to 20,000 plants, a slight decline, populations in protected areas and habitat destruction as the main threat.

Like the whole genus, it has been listed in CITES Appendix I since 4 February 1977 and, in the European Union, in Annex A of the wildlife trade regulations (current list: Regulation (EU) 2026/1383), according to Species+. For artificially propagated plants from South Africa, Species+ records a negative opinion of the EU Scientific Review Group covering the whole genus on 3 December 2010, removed on 11 March 2011; for this species, a positive opinion for plants with a caudex up to 7 cm in diameter has been in force since 20 June 2011, and a negative opinion above 7 cm since 7 February 2013. Species+ also records, for Mozambique, a negative opinion of 2006, EU suspensions of imports of wild plants (2008–2017) and CITES suspensions of all exports of Zamiaceae (2012–2018), none of which is still in force. Seeds are covered too: on the Italian Tropicamente forum, in March 2011, a traveller described collecting Encephalartos seeds in a hotel garden on Zanzibar, where the gardeners were handing them out; another participant identified them as Encephalartos hildebrandtii, and the discussion recalled that importing them without CITES documents is not allowed, even when the parent plant grows in a private garden. Databases consulted on 25 October 2026: buy only nursery-propagated plants with the required documents, and check the current rules before any purchase or import.

Growing Encephalartos hildebrandtii

Reliable sources on cultivation are few, and the dated reports from Europe all concern container plants overwintered under cover. The natural habitat, warm and frost-free coastal bushland, calls for a free-draining soil, bright light, regular watering in the warm season and a drier winter. The original description shows that young plants brought from Africa were already growing in Berlin in 1874 and tended to sucker at the base. Jungle Music, which calls the species fast-growing and in need of space, finds that it tolerates full sun on the coast of southern California but looks better in part sun; inland it recommends part sun or shade, and in desert areas shade, in a loamy, well-drained soil. The nursery notes that basal suckers are produced, but not very often.

Outdoor and in-ground cultivation

Planting out is only realistic in frost-free climates. Jungle Music recommends it for established gardens with a tree canopy or shade in southern California. No planting in the ground is documented in Europe, and the cold reports below do not support one.

Container cultivation

In the Var, south-eastern France, a collector described on Fous de palmiers a potted Encephalartos hildebrandtii that carried 18 leaves at the end of its June 2009 flush; he overwinters his tropical cycads in a heated glasshouse and in 2012 considered it the most vigorous of his East African Encephalartos, ahead of Encephalartos sclavoi and Encephalartos kisambo, while advising against planting it out all year. At Néoules, also in the Var, another grower overwintered two potted plants indoors in 2019; they made their new leaves in spring, before going outside after the last night frosts, and he reported scale insects indoors, on his Encephalartos only. In Poland, a grower rooted within a year a bare stem that had arrived without roots or leaves (first root in March 2010, first leaf in May 2010); sun later scorched some of the leaves and the plant stalled, before producing a new leaf in September 2013 and more in 2014, and it was repotted in January 2015 into a deeper pot (Fous de palmiers). For readers in Mediterranean or cool temperate climates, these reports point to the same practice: a large container kept frost-free in winter, with bright light but protection from scorching sun after a move.

In cultivation in the UK, US and Australia

The species was known to British horticulture early on: Prain cites articles on it in The Gardeners’ Chronicle of 1878 and 1900 and two plates in Curtis’s Botanical Magazine. Today three British institutions declare it to BGCI PlantSearch: the Royal Botanic Gardens, Kew, the Royal Botanic Garden Edinburgh and the Millennium Seed Bank at Wakehurst. In Ireland, a Czech collector named the Encephalartos hildebrandtii of the botanic garden in Dublin in 2010 among the finest in Europe (Fous de palmiers), and the same forum showed an old plant in the Poznań glasshouses, in Poland, in 2009.

In the United States, Montgomery Botanical Center in Coral Gables lists six accessions in its online catalogue, one of them of 2003 according to its number, and Fairchild Tropical Botanic Garden lists the species in its Garden Explorer. Twenty-one US institutions declare it to BGCI, among them Montgomery, Fairchild, the Huntington, Lotusland, the San Diego Botanic Garden, the San Diego Zoo, the Los Angeles County Arboretum, the University of California Botanical Garden at Berkeley, the Missouri Botanical Garden, Naples Botanical Garden, Marie Selby Botanical Gardens, the Atlanta Botanical Garden, the Denver Botanic Gardens, the Edison and Ford Winter Estates, the National Tropical Botanical Garden and Honolulu Botanical Gardens. In Australia, five gardens declare it: the Royal Botanic Garden Sydney, which also lists it in its online Garden Explorer, Brisbane Botanic Gardens Mount Coot-tha, the Royal Botanic Gardens Victoria, the Botanic Garden of South Australia in Adelaide and James Cook University in Townsville; the current census of the Royal Botanic Gardens Victoria does not list it. A BGCI listing shows that a garden has declared the species at some point, not that a plant is alive today.

In Italy, the Botanic Garden of Naples grew two plants, from Kenya and Tanzania, in 1993–1994 (Gaudio and colleagues, 1997), the species appears in the 2009 cycad list of the Orto Botanico of Messina, and the botanic garden of Catania declares it to BGCI.

Propagation

Seed is the usual method, but germination is slow and irregular. A grower in the Ain and Hérault (France) reported on Fous de palmiers in 2010 that seeds received in April germinated in October, because the embryo of fresh seed is not yet mature, and in 2011 that 30 cheaply bought seeds had given him only two seedlings. On Tropicamente, a collector in the Salento recalled in 2011 that Encephalartos seeds may take 12 to 18 months to germinate, or never do so, depending on their fertility and ripeness. Young plants sucker readily at the base (Braun and Bouché, 1874), although Jungle Music finds suckers uncommon on its plants. Seeds, like plants, fall under CITES Appendix I.

Pests and diseases

No disease or pest specific to Encephalartos hildebrandtii is documented. In cultivation, scale insects can appear on plants overwintered indoors (Fous de palmiers, Var, 2019), and the main risk, as with all Encephalartos, remains root and caudex rot in a cold, waterlogged substrate.

Cold hardiness

Encephalartos hildebrandtii is a species of the tropical coast that does not experience frost in the wild, and no rigorously measured cold tolerance value is documented. As in other Encephalartos, survival in the cold often concerns young plants whose caudex is still underground, protected by the warmth stored in the soil; an adult plant with an aerial trunk, as this species becomes, does not enjoy that protection.

Mediterranean and European experience

In Italy, a collector in the Salento (Apulia) reported on Tropicamente in December 2008, from plants “of a certain size and in good health”, that the group formed by Encephalartos arenarius, Encephalartos bubalinus, Encephalartos sclavoi, Encephalartos hildebrandtii and Encephalartos kisambo loses all its leaves after a frost, with a good chance of recovery. In December 2009 he wrote that after a single night at −1 °C (30.2 °F) between two days close to 20 °C (68 °F), which had marked several other Encephalartos, his Encephalartos sclavoi, Encephalartos kisambo and Encephalartos hildebrandtii had “come through unharmed”, without saying whether they were in pots or in the ground. That was a very brief, very light frost, which does not justify planting out. In France, no temperature record has been published for a plant in cultivation: all the plants mentioned on Fous de palmiers are in containers and overwintered in a heated glasshouse or indoors.

United Kingdom, United States and Australia

No dated cold report with a temperature has been published for the species in these countries. In coastal southern California, Jungle Music grows it in the open without reporting cold damage or a minimum temperature. No USDA zone is published for the species by a botanical source; the zone ratings found on some websites cite no measurement. In Britain it is a plant for a heated glasshouse.

Toxicity and precautions

No study deals with the toxicity of Encephalartos hildebrandtii itself, but the risk is documented in the genus: the toxicity of Encephalartos horridus was demonstrated as early as 1944 (Van der Walt), and Encephalartos, like other cycads, contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived; these substances affect the liver, the digestive tract and the nervous system, and the seeds are the most dangerous part. The ASPCA reports vomiting, diarrhoea, liver damage and deaths in dogs, cats and horses that have eaten cycads. The traditional uses described below do not make the plant safe.

Wear gloves to clean seeds, and keep plants and seeds out of reach of children and pets. If any part is swallowed, contact a poison centre, a doctor or a vet without delay.

Traditional uses

Prain (1917) reports, from Hildebrandt, that near Mombasa the floury seeds were eaten in times of famine and, from Engler, that the trunk yields a kind of meal, as in other species. The IUCN action plan (Donaldson, 2003) also states that on Zanzibar the trunks have been used to make a starchy flour, probably only in times of food shortage. These traditional preparations, which require lengthy treatment to remove the toxins, must not be imitated.

Frequently asked questions

Who was Hildebrandt?

Johann Maria Hildebrandt (1847–1881) was a German explorer and botanist who collected plants in East Africa and Madagascar. He discovered the species in 1873 near Mombasa, and the plants he brought back to Berlin were used to describe it in 1874.

How big does it get?

Large, in the wild: Melville (1957) and Prain (1917) give a trunk up to 6 m and leaves 2 to 3 m long. In containers, young plants remain much smaller for many years.

Why are its new leaves orange?

It is a trait often seen in cultivation: the new leaves emerge orange, then turn olive green and finally glossy dark green as they harden.

How can I tell it from Encephalartos kisambo?

With difficulty on young plants. According to Faden and Beentje (1989), Encephalartos kisambo has sickle-shaped leaflets with fewer teeth, generally larger male cones and orange-yellow seeds, whereas those of Encephalartos hildebrandtii are red. Seedlings of the two species look very similar.

Is it frost-hardy?

Only to very brief, light frosts, on the little evidence available: plants came through one night at −1 °C (30.2 °F) in the Salento in 2009. Outside frost-free climates, grow it in a container kept above freezing in winter.

Can I bring seeds back from Zanzibar or Kenya?

No, not without permits. All Encephalartos, seeds included, are in CITES Appendix I, and imports require permits from the authorities of both countries.

Is it poisonous?

Treat it as such, like all cycads, and especially its seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Braun, A. & Bouché, C.D. (1874). Encephalartos hildebrandtii. Index Seminum in Horto Botanico Berolinensi 1874: 18. [Original description.]
  • Prain, D. (1917). Cycadaceae. In: Flora of Tropical Africa 6(2): 351–352. [Description, collections, names, uses; copy on the Internet Archive.]
  • Melville, R. (1957). Encephalartos in Central Africa. Kew Bulletin 12(2): 237–257. [Description, var. dentatus, habitat, distribution.]
  • Faden, R.B. & Beentje, H.J. (1989). Encephalartos kisambo, a new cycad from Kenya, with a note on Encephalartos tegulaneus. Utafiti 2(1): 7–10. [Comparison with Encephalartos kisambo; 1911 collection wrongly attributed to the species.]
  • Moretti, A., De Luca, P., Sclavo, J.-P. & Stevenson, D.W. (1989). Encephalartos voiensis (Zamiaceae), a new east central African species in the E. hildebrandtii complex. Annals of the Missouri Botanical Garden 76: 934–938. [Title cited for the informal “complex”.]
  • Osborne, R. (1990). Focus on Encephalartos hildebrandtii. Encephalartos 22: 6–12. [Journal of the Cycad Society of South Africa; cited by The World List of Cycads.]
  • Hurter, P.J.H. & Glen, H. (1995). Encephalartos equatorialis (Zamiaceae): a newly described species from tropical Africa. South African Journal of Botany 61(4): 226–229. [Comparison.]
  • Gaudio, L., Aceto, S., Caputo, P., Cozzolino, S., Siniscalco Gigliano, G., Moretti, A. & De Luca, P. (1997). Enzyme polymorphism in Encephalartos Lehmann (Zamiaceae). Delpinoa n.s. 35–36: 55–64. [Two plants grown in Naples in 1993–1994; table 1.]
  • Donaldson, J.S. (ed.) (2003). Cycads. Status Survey and Conservation Action Plan. IUCN/SSC Cycad Specialist Group, Gland and Cambridge. [NT status in 2003, numbers, destruction of populations on Zanzibar, use of the trunk.]
  • Holzman, G. (2009). Growing kisambos in Hawaii. The Cycad Newsletter 32(1): 19–20. [Similarity of seedlings of the two species.]
  • Eastern Arc Mountains & Coastal Forests CEPF Plant Assessment Project & Bösenberg, J.D. (2010). Encephalartos hildebrandtii. The IUCN Red List of Threatened Species 2010: e.T41931A10603165. [Previous assessment, cited by The World List of Cycads and Crossref.]
  • Luke, W.R.Q. & Bösenberg, J.D. (2024). Encephalartos hildebrandtii. The IUCN Red List of Threatened Species 2024: e.T41931A51056232. https://doi.org/10.2305/IUCN.UK.2024-1.RLTS.T41931A51056232.en [Assessment in force (LC), dated 13 March 2020; authors and date read on Crossref, category on GBIF.]
  • Van der Walt, S.J. (1944). Recent investigations into the toxicity of plants, etc., in the Union of South Africa. Onderstepoort Journal of Veterinary Science and Animal Industry 20(1). [Toxicity of Encephalartos horridus.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. https://doi.org/10.11646/phytotaxa.550.1.1 [Etymology, cited by The World List of Cycads.]
  • Calonje, M., Stevenson, D.W. & Osborne, R. (2026). The World List of Cycads, version 2026.08.15. Montgomery Botanical Center, Coral Gables. https://doi.org/10.5281/zenodo.21958524 [Checklist.]