Ceratozamia robusta

Ceratozamia robusta is a large cycad of Chiapas, in southern Mexico, and of northern Guatemala, where it grows on humus-covered limestone rocks in evergreen tropical forest between 400 and 1,300 m (about 1,310 to 4,270 ft). Described in 1847 from a plant grown in Amsterdam, it is the most widespread species of the genus Ceratozamia and one of the largest, with male cones up to 70 cm long. Long treated as a variety, Ceratozamia mexicana var. robusta, it is listed as Endangered by the IUCN. The World List of Cycads does not record it in Belize, whose plants were described in 2022 as Ceratozamia osbornei.

Key facts about Ceratozamia robusta

  • Accepted name: Ceratozamia robusta Miq. (1847), accepted by The World List of Cycads (version 2026.08.15), by the 2022 monograph of the genus and by the World Checklist of Vascular Plants (WCVP, the database behind POWO, read via GBIF)
  • Former names and synonyms: Ceratozamia mexicana var. robusta (Miq.) Dyer (1884)
  • Family: Zamiaceae, order Cycadales
  • Common names: no English name; in Chiapas, “amendu” and “piña del tlacoache”
  • Natural range: Mexico (Chiapas) and Guatemala (Alta Verapaz, Petén, Quiché, Huehuetenango, Izabal), 400 to 1,300 m; not recorded in Belize by The World List of Cycads
  • IUCN status: Endangered (EN), assessment published in 2022 (criterion A2acd)
  • CITES and other protection: CITES Appendix I (whole genus, since 1985); Annex A in the European Union, seeds included
  • Documented hardiness: no reliable data (see Cold hardiness)
  • Light and soil: in the wild, karst rocks covered in humus, in evergreen tropical forest; no growing advice published by a reliable source
  • Habit and adult size: trunk 0.3 to 1 m (up to 2.5 m according to another passage of the 2022 monograph); 10 to 50 leaves, 1.4 to 2.7 m long; male cone 50 to 70 cm
  • In the UK, US and Australia: declared to BGCI PlantSearch by 23 gardens in these three countries, including Kew, Edinburgh, Fairchild, Montgomery, Sydney and Melbourne (see In cultivation)
  • Toxicity: seeds eaten locally, but no analysis; treat it as poisonous (see Toxicity and precautions)

How to recognise Ceratozamia robusta

Ceratozamia robusta is a massive plant, with long leaves that are dark brown when they emerge, a petiole armed with long, stout prickles, and lance-shaped leaflets that are bluish-white (glaucous) underneath. According to the 2022 monograph of the genus (Martínez-Domínguez and colleagues), its ripe female cone is dark green with sparse blackish hairs, and its scales have a prominent outer face with two straight horns set at a right angle. The monograph describes it as follows:

  • Trunk: above ground, upright then lying down, 30 to 100 cm long and 20 to 40 cm across; persistent, long-triangular, reddish-brown, woolly cataphylls. Elsewhere, the monograph counts it among the four tree-like species of the genus, with trunks up to 2.5 m long.
  • Leaves: 10 to 50, ascending, 138 to 266 cm long; dark brown when they emerge, then green and hairless. The petiole, 56 to 85 cm long, brown then green, carries 27 to 55 stout prickles 5 to 7 mm long.
  • Leaflets: 20 to 45 pairs, lance-shaped, flat, papery, green above and glaucous beneath, with a drawn-out, asymmetrical tip; the middle ones measure 28 to 42 cm by 2.5 to 4 cm and are spaced 3 to 4.5 cm apart.
  • Male cones: single, cylindrical, upright, 50 to 70 cm long and 7 to 8.5 cm across, light green to yellowish green with blackish hairs when young, then creamy yellow with reddish-brown hairs; stalk 10 to 15 cm long. The scales end in curved horns.
  • Female cones: single, cylindrical, upright, 26 to 40 cm long and 11 to 14.5 cm across, dark green, with a drawn-out tip; stalk 5 to 11 cm long. They carry 153 to 280 scales with straight horns 4 to 5 mm long.
  • Seeds: oval, 2.5 to 3.5 cm long, with whitish-yellow to yellow flesh before ripening, light brown when ripe.

The monograph describes the male cone of Ceratozamia robusta, up to 70 cm long, as “the largest in the genus”; in the same work, the description of Ceratozamia osbornei gives male cones 60 to 80 cm long. The two statements are not reconciled.

Hybrids

No natural or garden hybrid has been documented.

Possible confusion

Several large Ceratozamia look like it; according to the 2022 monograph, cones and origin separate them:

  • Ceratozamia osbornei, of Belize: cone scales covered in abundant purple to wine-red hairs; the Belizean plants were previously identified as Ceratozamia robusta.
  • Ceratozamia subroseophylla, of southern Veracruz (the 2022 monograph also included plants from Tabasco, assigned to Ceratozamia gigantea since 2024): female cone with a short point, scales with a pinkish base and dark brown to reddish-brown hairs.
  • Ceratozamia oliversacksii, of southern Oaxaca: green new leaves and linear leaflets.
  • Ceratozamia sancheziae, of the Chiapas Highlands, its geographical neighbour: linear leaflets, new leaves light green or glaucous reddish brown.

In collections, the name has also long been used for plants sold as Ceratozamia mexicana or Ceratozamia latifolia. In 2009, Italian growers on the Tropicamente forum were already debating the identity of their plants, some believing that many commercial “mexicana” were in fact robusta; in 2013, a grower on the French Fous de palmiers forum summed up the situation of plants sold as latifolia, robusta, mexicana and microstrobila as “un bazar monstre”, a complete mess. Without cones or a documented origin, a reliable identification is impossible.

Taxonomy

Ceratozamia robusta is accepted by The World List of Cycads, by the 2022 monograph and by the WCVP, the database behind POWO (read via GBIF on 30 October 2026), which records it from Guatemala and south-eastern Mexico and dates its publication to 1848, the date printed on the issue.

An 1847 description

Friedrich Anton Wilhelm Miquel described the species in an article in Dutch and Latin, “Over eenige nieuwe of zeldzame Cycadeën” (“On some new or rare cycads”), dated Amsterdam, December 1846, in the first volume of a journal of the Royal Netherlands Institute, the Tijdschrift voor de Wis- en Natuurkundige Wetenschappen (pages 42–43). According to The World List of Cycads, the issue bears the date 1848 but was published in the second half of 1847. Miquel describes a Mexican plant grown in the Amsterdam botanic garden: a trunk 27 cm tall and 18 to 19 cm across, a petiole 25 to 30 cm long, a rachis 80 to 100 cm long, and 30 to 32 pairs of leathery leaflets 15 to 25 cm long and 2 to 2.5 cm wide. He calls it a remarkable species, recognisable at once by its petiole and rachis, thicker than in the other species, and by its leaflets, short in relation to the leaf. He adds that the Amsterdam garden held a large number of Ceratozamia, all original plants collected in Mexico in recent years by Belgian travellers.

Neotype and rank

No specimen of the Amsterdam plant is known. In 1986, Dennis Stevenson and Sergio Sabato designated a neotype: a plant collected by Stevenson on 9 July 1983 north-west of Tuxtla Gutiérrez, Chiapas, at about 1,000 m (collection 549A, held at the New York Botanical Garden herbarium, NY).

In 1884, Dyer reduced it to a variety, Ceratozamia mexicana var. robusta, in the Biologia Centrali-Americana. The World List of Cycads and the WCVP now treat that name as a synonym of Ceratozamia robusta, accepted as a species.

Limits under discussion

According to the 2022 monograph, herbarium specimens from Guatemala are sterile and few, which has led to ambiguous or conflicting identifications, and populations once included in Ceratozamia robusta have been assigned to other species over the last ten years. In 2021, a study by José Said Gutiérrez-Ortega and colleagues measured ten leaf and trunk traits on 97 adult plants from six populations then attributed to Ceratozamia robusta. It separated three groups: populations similar to the neotype, at mid elevations in Chiapas; a large form at low elevations in Belize; and the populations of the Chiapas Highlands, described in the same paper as a new species, now Ceratozamia sancheziae. The following year, the monograph described the Belizean plants as Ceratozamia osbornei, on the basis of their cones, and called for population studies to measure gene flow between Ceratozamia robusta and Ceratozamia osbornei.

The species as now understood is therefore narrower than in older literature and collections: a plant labelled Ceratozamia robusta before 2021 may belong to one of these species.

Etymology and history

The epithet comes from the Latin robustus, “sturdy, large”, and apparently refers to the size of the plant (The World List of Cycads, after Haynes’s etymological compendium, 2022); the monograph mentions its “robust appearance”.

The plant described by Miquel was among the Ceratozamia introduced into Europe shortly before 1846; Miquel gives no locality beyond Mexico, so the exact origin of the type plant remains unknown.

Common names

No English common name is recorded. The 2022 monograph records, from herbarium labels in Chiapas, the names “amendu” and “piña del tlacoache”. A similar name, “amenduai”, is recorded for Ceratozamia mirandae. No Guatemalan name is recorded.

In the wild

According to the 2022 monograph, Ceratozamia robusta is the most widespread species of the genus, occurring continuously from central Chiapas to northern Guatemala. It grows in evergreen tropical forest, on karst rocks covered in humus-rich soil, between 400 and 1,300 m. The World List of Cycads records it in Chiapas and in five departments of Guatemala: Alta Verapaz, Petén, Quiché, Huehuetenango and Izabal. It does not list Belize.

No study of the pollination, phenology or population dynamics of the species has been published.

Conservation status and regulation

Ceratozamia robusta is listed as Endangered (EN) on the IUCN Red List, in an assessment by J.D. Bösenberg published in 2022, under criterion A2acd (The World List of Cycads; category confirmed by the Red List data distributed through GBIF, 30 October 2026): an observed population decline linked to habitat loss and exploitation. The 2022 monograph considers a reassessment necessary: the range is wide, but some populations once attributed to the species now belong to other species.

Like the whole genus, it has been covered by CITES Appendix I since 1 August 1985 (the genus had been in Appendix II since 1977), and by Annex A of Regulation (EC) No 338/97 in the European Union (annexes now set by Regulation (EU) 2026/1383, applicable since 29 June 2026), seeds included (Species+, checked on 30 October 2026). International trade in wild-collected plants for commercial purposes is banned; only artificially propagated plants with the required permits can be traded.

This general information does not replace the official texts: check the regulations in force before buying, importing or exchanging plants, and ask for proof of origin.

Growing Ceratozamia robusta

No reliable source describes how to grow Ceratozamia robusta. Growers have discussed it since at least 2009, but the identity of plants sold under this name is doubtful, as they acknowledge themselves.

Its habitat, humus-covered limestone rocks in mid-elevation tropical rainforest, points to partial shade, warmth and a free-draining, humus-rich mix. Its size, with leaves over 2.5 m long, needs a lot of room. These pointers are drawn from the habitat and have not been confirmed by published trials.

Outdoor and in-ground cultivation

The species is held by several gardens in frost-free climates, such as southern Florida and Hawaii, but none publishes whether its plants grow outdoors or under glass, or how they behave in cold spells.

Container cultivation

Young plants can be grown in a large, deep pot with a free-draining mix rich in organic matter; adults, with their very long leaves, are better planted out in a heated glasshouse or a tropical garden.

In cultivation in the UK, US and Australia

Ceratozamia robusta is one of the most widely declared species of the genus. BGCI PlantSearch (queried on 30 October 2026) lists 42 gardens under this name, including in the United Kingdom the Royal Botanic Gardens, Kew, the Royal Botanic Garden Edinburgh and Oxford Botanic Garden; in the United States 16 gardens, among them Fairchild Tropical Botanic Garden, Montgomery Botanical Center, the Huntington, Lotusland, San Diego Zoo, Naples Botanical Garden and the New York Botanical Garden; and in Australia the Royal Botanic Garden Sydney, Royal Botanic Gardens Victoria (Melbourne), Cairns and Adelaide. The online catalogue of Montgomery Botanical Center lists 12 accessions; Edinburgh’s Garden Explorer lists the species, but its glasshouses are closed for restoration. A separate BGCI entry, “Ceratozamia robusta ‘Santiago Tuxtla’”, is declared by three gardens, including Honolulu and Melbourne: Santiago Tuxtla is the municipality of Veracruz where the type of Ceratozamia subroseophylla was collected, so these plants deserve checking.

Given the history of the name, the identity of these garden plants has not been verified against the current definition of the species, and no garden states whether its plants grow outdoors.

Propagation

No data exist for the species. Like all Ceratozamia, it has separate male and female plants; it is propagated from fresh seed after pollination, by hand in cultivation. Handle seeds wearing gloves.

Pests and diseases

No pest or disease specific to the species has been documented. In cultivated Ceratozamia, growers mainly report rot in cold, sodden soil and leaf scorch after sudden exposure to full sun.

Cold hardiness

No reliable cold-hardiness data exist for Ceratozamia robusta. The few reports found concern commercial plants whose identity is uncertain.

Mediterranean and European experience

No cultivation result has been published for plants of known origin in Europe, and the Jardin zoologique tropical in La Londe-les-Maures (Var, on the French Riviera) has published no observation of this species. A grower reported on the Italian Tropicamente forum in September 2012 that seedlings labelled robusta had overwintered under a porch while it was −8.4 °C (17 °F) outside, without giving the region; the identity of the plants is not documented. Until trials on plants of known origin exist, keep it frost-free.

United Kingdom, United States and Australia

No dated cold record and no hardiness rating from a reliable source have been published. In the UK it is a plant for a heated glasshouse.

Toxicity and precautions

No toxicity study specific to Ceratozamia robusta has been published. The risk is well documented in other cycads: their tissues, and above all their seeds, contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived, a compound harmful to the liver and nervous system. Dogs, livestock and people can be seriously poisoned. According to the 2022 monograph, the seeds of this species are nevertheless eaten locally; no source describes how they are prepared, and this use does not prove that they are safe. In the absence of evidence to the contrary, treat the plant as poisonous: keep seeds and leaves out of reach of children and animals, wear gloves to clean seeds, and if any part is swallowed, call a poison centre, a doctor or a vet straight away.

Traditional uses

The 2022 monograph records two uses: the seeds are eaten, and the leaves are used to decorate altars. It gives neither places nor the preparation of the seeds.

Frequently asked questions

Does Ceratozamia robusta grow in Belize?

No, according to The World List of Cycads and the WCVP, which limit it to Chiapas and Guatemala. The Ceratozamia of Belize, identified as Ceratozamia robusta in 2009 and still attributed to it in 2021, were described in 2022 as a distinct species, Ceratozamia osbornei.

Is it a variety of Ceratozamia mexicana?

No. The rank of variety (Ceratozamia mexicana var. robusta), proposed in 1884, is no longer followed: The World List of Cycads, the WCVP and the 2022 monograph accept it as a species.

Is it the largest Ceratozamia?

Not clearly. The 2022 monograph calls its male cone, up to 70 cm, “the largest in the genus”, but gives 60 to 80 cm for that of Ceratozamia osbornei, and counts four tree-like species with trunks up to 2.5 m.

How can I recognise Ceratozamia robusta?

By its large size, its dark brown new leaves and its petiole bristling with stout prickles. Its ripe female cone is dark green and almost hairless, and its male cone can reach 70 cm.

Are plants sold under this name really robusta?

Not always. The name has long been applied to large Ceratozamia of uncertain identity, and part of the former species is now Ceratozamia sancheziae or Ceratozamia osbornei; only a plant of known origin, or one with cones, can be identified.

Is it hardy?

Nobody really knows. The figures that circulate rest on no reliable trial; keep it frost-free.

Is it endangered?

Yes. The IUCN has listed it as Endangered since the assessment published in 2022, and the monograph calls for a reassessment now that the species has been split.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Miquel, F.A.W. (1847). Over eenige nieuwe of zeldzame Cycadeën. Tijdschr. Wis- Natuurk. Wetensch. Eerste Kl. Kon. Ned. Inst. Wetensch. 1(1): 42–43. [Original description.]
  • Dyer, W.T. (1884). Biologia Centrali-Americana, Botany 3: 193. [Combination Ceratozamia mexicana var. robusta; reference cited by The World List of Cycads.]
  • Stevenson, D.W. & Sabato, S. (1986). Typification of names in Ceratozamia Brongn., Dioon Lindl. and Microcycas A.DC. (Zamiaceae). Taxon 35(3): 578–584. [Designation of the neotype; reference cited by The World List of Cycads and the monograph.]
  • Gutiérrez-Ortega, J.S., Pérez-Farrera, M.A., Vovides, A.P., Chávez-Cortázar, A., López, S., Santos-Hernández, N.G. & Ruíz-Roblero, S.K. (2021). Ceratozamia sanchezae (Zamiaceae): a new cycad species from Chiapas Highlands (Mexico). Phytotaxa 500(3): 201–216. https://doi.org/10.11646/phytotaxa.500.3.4 [Variation of Ceratozamia robusta across six populations; the three groups are given here from its abstract.]
  • Martínez-Domínguez, L., Nicolalde-Morejón, F., Vergara-Silva, F. & Stevenson, D.W. (2022). Monograph of Ceratozamia (Zamiaceae, Cycadales): an endangered genus. PhytoKeys 208: 1–102. https://doi.org/10.3897/phytokeys.208.80382 [Monograph of the genus; open access.]
  • Calonje, M.A., Meerman, J., Griffith, M.P. & Hoese, G. (2009). A new species of Zamia (Zamiaceae) from the Maya Mountains of Belize. Journal of the Botanical Research Institute of Texas 3(1): 31–41. [Identification of the Belizean Ceratozamia as Ceratozamia robusta at the time.]
  • Bösenberg, J.D. (2022). Ceratozamia robusta. The IUCN Red List of Threatened Species 2022: e.T42144A69866877. https://doi.org/10.2305/IUCN.UK.2022-1.RLTS.T42144A69866877.en [Red List assessment; category confirmed by GBIF.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. https://doi.org/10.11646/phytotaxa.550.1.1 [Source of the etymologies given 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 [Reference checklist.]