Ceratozamia mexicana

Ceratozamia mexicana is a cycad of central Veracruz, Mexico, where it grows in cloud forest on limestone rocks between 500 and 1,100 m (about 1,640 to 3,610 ft). It is the type species of the genus Ceratozamia: the French botanist Adolphe Brongniart described it in 1846 from plants grown at the Jardin des Plantes in Paris, and for a long time its name was used for most of the Ceratozamia of Veracruz. It has also been described as Ceratozamia longifolia and Ceratozamia intermedia, names now treated as synonyms. In the strict sense it is a rare plant, assessed as Critically Endangered by the IUCN, and many plants sold under this name belong to other species.

Key facts about Ceratozamia mexicana

  • Accepted name: Ceratozamia mexicana Brongn. (1846), type species of the genus, accepted by The World List of Cycads (version 2026.08.15), by Species+ and by the World Checklist of Vascular Plants (WCVP, the database behind POWO, read via GBIF)
  • Former names and synonyms: Ceratozamia longifolia Miq., Ceratozamia intermedia Miq., Ceratozamia longifolia var. minor Miq., Ceratozamia mexicana var. longifolia (Miq.) Dyer; the WCVP adds older names such as Zamia mexicana (Brongn.) G.Don and Dipsacozamia mexicana (Brongn.) Liebm. ex Dyer (see Taxonomy)
  • Family: Zamiaceae, order Cycadales
  • Common names: no English name; “palma imperial” in Spanish (Species+)
  • Natural range: Mexico, central Veracruz, from the La Antigua river basin to the southern end of the Sierra Madre Oriental, 500 to 1,100 m
  • IUCN status: Critically Endangered (CR A2acd), assessment published in 2022
  • CITES and other protection: CITES Appendix I (whole genus, since 1985); Annex A in the European Union, seeds included
  • Documented hardiness: in-ground plants in France came through −5 to −9.5 °C (23 to 14.9 °F) in February 2012, nearly always under protection; a plant in Ravenna (Italy) took −7 °C (19.4 °F) unharmed; amateur observations, indicative only (see Cold hardiness)
  • Light and soil: in the wild, cloud forest understorey on karst; in cultivation, bright partial shade and humus-rich, very free-draining soil
  • Habit and adult size: trunk 20 to 80 cm long and 20 to 45 cm across, upright or leaning; 5 to 55 leaves, 1 to 2.7 m long
  • In the UK, US and Australia: declared by 7 British, 28 American and 5 Australian gardens to BGCI PlantSearch, identifications not checked (see In cultivation)
  • Toxicity: no data for the species; treat it as poisonous, like all cycads (see Toxicity and precautions)

How to recognise Ceratozamia mexicana

Ceratozamia mexicana is recognised by its large, drooping leaves and its lance-shaped, leathery leaflets, 29 to 51 cm long and 2.3 to 3.7 cm wide in the middle of the leaf. The description below follows the 2022 monograph of the genus by Lilí Martínez-Domínguez and colleagues:

  • Trunk: above ground, 20 to 80 cm long and 20 to 45 cm in diameter, upright and often leaning with age; persistent, triangular, reddish-brown cataphylls, densely brown-woolly when they emerge.
  • Leaves: 5 to 55, 1 to 2.7 m long, drooping; green with brown hairs when they emerge according to the monograph, then hairless. The petiole, 30 to 93 cm long, carries 8 to 30 thin prickles 0.6 to 2 mm long.
  • Leaflets: 25 to 42 pairs, opposite to nearly opposite, set in one plane, lance-shaped, leathery and flat, with a pointed, symmetrical tip and prominent light-green veins.
  • Male cones: one or two, cylindrical and upright, 20 to 40 cm long and 4.5 to 7.6 cm across, greenish yellow with blackish hairs when ripe.
  • Female cones: usually single, cylindrical and upright, 23.5 to 40 cm long and 8 to 15 cm across, dark green with black and grey hairs; the scales carry two straight horns 5 to 12 mm long.
  • Seeds: egg-shaped, 2 to 3.3 cm long, with a whitish-yellow to yellow fleshy coat before ripening, light brown when ripe.

The colour of the young leaves does not settle identity on its own, because the sources disagree. The 2022 monograph describes them as green when they emerge, whereas Andrew Vovides and colleagues (2016), who fixed the identity of the species, describe reddish-brown emerging leaflets in a population of the municipality of Totutla, where the type material is reported to have come from, and light-green ones in Ceratozamia tenuis. The same study gives Ceratozamia mexicana oblong-lanceolate, flat leaflets 2 to 3.4 cm wide and 2n = 16 chromosomes. French and Italian growers note that many plants sold under this name produce red or coppery new leaves; without a known origin, this feature proves nothing.

Hybrids

No natural hybrid has been documented. European amateurs report seedlings sold as Ceratozamia mexicana × Ceratozamia robusta (Fous de palmiers forum, 2015), but their origin cannot be checked.

Possible confusion

Confusion is common, because the name Ceratozamia mexicana long covered almost every Ceratozamia of central Veracruz. The 2022 monograph and the 2016 study give the following criteria:

  • Ceratozamia tenuis: linear-lanceolate, narrower leaflets, 1.3 to 1.8 cm wide and slightly channelled (Vovides and colleagues, 2016); reinstated as a species in 2016;
  • Ceratozamia morettii: oblong leaflets;
  • Ceratozamia brevifrons: keeled leaflets and a petiole armed with sturdy prickles;
  • Ceratozamia latifolia, from San Luis Potosí: reddish-brown young leaves, oblong, paper-thin leaflets and an almost unarmed petiole. It is the species growers most often mistake for Ceratozamia mexicana.

Plants sold as “Palma Sola” belong to Ceratozamia brevifrons. Montgomery Botanical Center itself lists one plant received as Ceratozamia mexicana under Ceratozamia brevifrons in its online catalogue.

Taxonomy

Ceratozamia mexicana is accepted by The World List of Cycads, which treats it as the type species of the genus, by Species+ and by the WCVP, the database behind POWO (read via GBIF on 30 October 2026), which places it in the Gulf region of Mexico. The history of the name explains the confusion that still surrounds it. According to the 2022 monograph, the Dutch botanist Friedrich Miquel described five new species using only vegetative characters, including Ceratozamia longifolia and Ceratozamia intermedia, before lumping all of them into Ceratozamia mexicana, which became a very broad name. These two names, together with Ceratozamia longifolia var. minor and Ceratozamia mexicana var. longifolia, are now synonyms, and neotypes were designated for them in 2018. The World List of Cycads dates Miquel’s names to 1847, the WCVP to 1848.

The WCVP also lists under this name several old names not mentioned by The World List of Cycads: Zamia mexicana (Brongn.) G.Don (1855), Dipsacozamia mexicana (Brongn.) Liebm. ex Dyer (1884), Ceratozamia mexicana var. vulgaris J.Schust. (1932), Ceratozamia purpurea Matte (1904), Macrozamia breviformis J.Schust. (1932), Zamia atropurpurea J.Parm. (1853) and Zamia macrophylla J.Parm. ex Miq. (1861).

The species was narrowed down in 2016. In an article in Botanical Sciences entitled “What is Ceratozamia mexicana (Zamiaceae)?”, Andrew Vovides and colleagues compared two populations of central Veracruz: one north of Xalapa, long treated as Ceratozamia mexicana by Charles Chamberlain and later authors, and one in the municipality of Totutla, where Ghiesbreght had collected the plants described by Brongniart. Only the Totutla plants matched the type; the plants from north of Xalapa corresponded to a variety described in 1884 from a plant at Kew, which they raised to species rank as Ceratozamia tenuis. An analysis of eleven anatomical characters of the leaflets supported the separation, and they designated an epitype to fix the identity of Ceratozamia mexicana: a plant collected in 1982 in the municipality of Totutla, at about 900 m (XAL herbarium).

In 2025, an integrative study in Plant Species Biology by Medina-Villarreal and colleagues, based on 196 plants from 13 populations, recognised seven lineages in the Ceratozamia mexicana complex, supported by DNA, leaf measurements and climate niches: Ceratozamia brevifrons, Ceratozamia delucana, Ceratozamia decumbens, Ceratozamia mexicana, Ceratozamia morettii, Ceratozamia tenuis and a still unnamed cryptic species, sister to Ceratozamia tenuis. In the 2023 phylogeny of the genus by Habib and colleagues, the species gives its name to one of the three major clades, the Mexicana clade, where it falls in the latifolia subclade; the old “Ceratozamia mexicana complex” did not form a natural group there. For the reader, the consequence is simple: a plant labelled Ceratozamia mexicana before this work, or sold without a known origin, may belong to another species.

Etymology and history

The epithet mexicana refers to the country of origin of the material used to describe the species (The World List of Cycads; 2022 monograph). It was the first species described in the genus.

Adolphe Brongniart published it in 1846 in the Annales des Sciences Naturelles (Botanique, series 3, volume 5, pages 7–8, plate 1), together with the genus. He did not describe a wild plant collected by a botanist: the plants were grown at the Jardin des Plantes in Paris, from material sent from Mexico in 1845 by the collector Ghiesbreght. The type specimen is kept in the herbarium of the Muséum national d’histoire naturelle in Paris; The World List of Cycads calls it a lectotype, the 2022 monograph and the 2016 study a holotype.

Common names

No English name is recorded. The 2022 monograph lists no local name for the species in the strict sense. Species+ gives the Spanish name “palma imperial”, without saying where it is used.

In the wild

Ceratozamia mexicana is endemic to the state of Veracruz. According to the 2022 monograph, it occupies a fairly narrow band from the La Antigua river basin to the southern end of the Sierra Madre Oriental, in cloud forest on karst rocks between 500 and 1,100 m. The specimens studied come from the municipalities of Coatepec, Comapa, Puente Nacional, Sochiapa, Teocelo, Tlaltetela, Totutla and Xico.

The populations visited by the authors of the monograph had only 30 to 50 adult plants each, in a region where forest cover has declined sharply. Plants are male or female, and, as in other Ceratozamia, the cones are pollinated by insects.

A study of reproductive timing published in 2000 by Sánchez-Tinoco, Engleman and Vovides, under the name Ceratozamia mexicana in its broad sense of the time, shows a very long cycle: 24 months pass between the formation of the ovules, in August, and the full development of the embryo. Pollination probably takes place in February and March, seeds fall in September, fertilisation happens at about the time they fall, and the embryo then develops for about nine months, detached from the mother plant.

Conservation status and regulation

Ceratozamia mexicana is assessed as Critically Endangered (CR, criterion A2acd) on the IUCN Red List, in an assessment by J.D. Bösenberg published in 2022, reflecting a large past decline of its populations. The category is given by The World List of Cycads and by the Red List data distributed through GBIF (checked on 30 October 2026). The 2022 monograph, which still cited the earlier Vulnerable listing, recommended the Critically Endangered category (under criterion B1), given the very small range of the species in the strict sense and the small size of its populations.

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.

In practice, buy only cultivated plants or seeds with their paperwork. For such a threatened and often misidentified species, the origin of the seed matters as much as the label: plants raised from parents of known wild origin are the only guarantee of having a true Ceratozamia mexicana.

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

Growing Ceratozamia mexicana

Ceratozamia mexicana is grown as an understorey cycad: filtered light, humus-rich but very free-draining soil, regular watering in summer and much less in winter. It is the species of the genus most often tried in the ground in France, with encouraging results in sheltered gardens.

  • Light: bright partial shade or light shade, like its cloud forest home. Reports on full sun differ: a grower on the Côte Bleue, near Marseille, grows it in sun facing the sea, while a grower in the Tarn (south-west France) lost scorched leaves in spring 2014, shortly after planting. A plant raised under glass should be hardened to sun gradually.
  • Soil: humus-rich and free-draining. On the Fous de palmiers forum, a grower in Nantes uses good potting compost mixed with coarse sand; a grower in the Gard uses about 50% citrus compost, 20% loam and 30% perlite.
  • Watering: regular during growth, without leaving the soil sodden; much reduced in winter. Standing water rots roots and trunk: on the Tropicamente forum, an Italian grower reported in April 2011 that a very small plant, only scorched by the cold, later died of rot from excess moisture.
  • Wind: leaves snap easily at the base. A grower in the Tarn had many leaves broken by a 100 km/h (62 mph) wind in May 2014; a sheltered spot is better.
  • Growth: slow in young plants, about one leaf a year according to a grower in Nantes; older plants produce a crown of several leaves at once.

Outdoor and in-ground cultivation

In France, a few amateurs have grown it in the ground for several winters (see Cold hardiness). In Nantes, one grower planted his under the dense canopy of Brahea armata palms against a south-east-facing wall, a spot that limits radiative frost and scorching sun. In Italy, an article on the Naples Botanic Garden published in Delpinoa (2007 volume, issued in 2011) mentions a plant growing outdoors in the gymnosperm area, with its coralloid roots visible at the soil surface. In climates with dry, hot summers, partial shade and summer watering are needed.

Container cultivation

In pots, it is easy to overwinter frost-free in cold regions, and young plants are usually grown this way. Use a deep container: the young taproot is fragile. Leaves on mature plants can exceed 2 m, so older plants need room.

In cultivation in the UK, US and Australia

The name is widely used in gardens, but identifications are those of each garden and may cover other species. Under this name, 114 gardens worldwide declare the species to BGCI PlantSearch (queried on 30 October 2026). In the United Kingdom, these are the Royal Botanic Gardens, Kew, RHS Garden Wisley, Oxford Botanic Garden, the University of Bristol Botanic Garden, Birmingham Botanical Gardens, Treborth Botanic Garden (Bangor) and Paignton Zoo. In the United States, 28 gardens declare it, among them Fairchild Tropical Botanic Garden, the Huntington, Lotusland, San Diego Botanic Garden, the Missouri Botanical Garden, the New York Botanical Garden and the University of California Botanical Garden at Berkeley; the online catalogue of Montgomery Botanical Center (Coral Gables, Florida) lists no accession under the accepted name. In Australia, Brisbane Botanic Gardens Mount Coot-tha, Royal Botanic Gardens Victoria (Melbourne), the Cairns Botanic Gardens, the Botanic Garden of Adelaide and the Hunter Region Botanic Gardens declare it; in Melbourne, the Royal Botanic Gardens Victoria census places it in the Tropical House.

Propagation

Propagation is almost entirely from seed, since offsets are rare. A male and a female plant are needed, and in cultivation pollination is usually done by hand. In the wild, seeds fall in September and the embryo finishes developing after they fall, over several months. Sow fresh seed, cleaned of its fleshy coat wearing gloves, in a warm, free-draining mix, in a deep pot for the fragile taproot.

Pests and diseases

No pest specific to the species has been documented. In cultivation, the main danger is rot of the trunk and roots in cold, wet soil. As with other cycads, watch for armoured scale insects: an amateur in the Deux-Sèvres (western France) found some in 2010 on a Ceratozamia hildae received from a seller.

Cold hardiness

Ceratozamia mexicana takes moderate frosts, especially when protected and planted under cover. No botanic garden or institution has published hardiness results; the data come from amateur growers in France and Italy. Remember that many plants grown under this name may not be Ceratozamia mexicana in the strict sense.

Mediterranean and European experience

A grower in Ravenna (Emilia-Romagna, Italy; USDA zone 8a/8b according to him) reports on the Tropicamente forum that his small Ceratozamia mexicana took −7 °C (19.4 °F) at the end of 2009 and the whole following winter “without a scratch”, sheltered only from snow and rain; whether it was in a pot or in the ground is not stated, and the identification rests on the sale name.

A grower in the Gard (southern France) reports on the Fous de palmiers forum that his in-ground plant, with a trunk 4 to 5 cm across, did not flinch in winter 2012–2013 after brief frosts down to −4 °C (24.8 °F).

A grower in the south-eastern suburbs of Paris (banks of the Marne, France) reports on the same forum that his in-ground plant, set out in 2009 in a free-draining bed, came through winter 2010–2011 without trouble at −7 to −8 °C (19.4 to 17.6 °F) at the lowest, under horticultural fleece and bubble wrap. In February 2012 it survived −8.5 °C (16.7 °F), after about a week without thaw, under basic protection: it lost its leaves, but its trunk stayed sound and it produced a new leaf in July 2012. He considers a peak of −10 °C (14 °F) the limit of the species in a dry Mediterranean climate.

A grower in Nantes (Loire-Atlantique, western France) reports that his two young in-ground plants, set out in spring 2010 under Brahea armata against a south-east-facing wall, kept intact foliage after many frosts of −6 °C (21.2 °F) in November and December 2010 under simple fleece. In February 2012, protected by a cloche, his plant stayed intact apart from very slight burns on an old leaf while the garden fell to −9.5 °C (14.9 °F) with 3 or 4 days without thaw; the thermometer under the cloche showed at least −6 °C (21.2 °F).

A grower in Concarneau (Finistère, Brittany, France) reports that his in-ground plant suffered no damage in February 2012 at −5 °C (23 °F), reached for a few hours; protection is not stated.

The documented failures did not come from cold: in the Tarn, a newly planted Ceratozamia mexicana in partial shade had leaves snapped by wind and then lost two leaves to sun in spring 2014. The Jardin zoologique tropical in La Londe-les-Maures (Var, on the French Riviera) has published no observation of the species; its “Palma Sola” plant belongs to Ceratozamia brevifrons. These French results, from short frosts and nearly always under protection, are a useful guide for gardens with similar winters, such as coastal California, southern Australia or the mildest parts of southern England.

United Kingdom, United States and Australia

No dated cold record from a named place and no commercial hardiness rating have been published for this species in these countries. Melbourne grows it in a glasshouse, and in the UK it is a plant for a cool or heated glasshouse. Outside frost-free areas, young plants in pots should be kept frost-free in winter.

Toxicity and precautions

No toxicity study specific to Ceratozamia mexicana 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. 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 no use for the species in the strict sense. Other Mexican Ceratozamia are eaten after detoxification or used in religious festivals, but no published source reports this for Ceratozamia mexicana.

Frequently asked questions

Is Ceratozamia mexicana cold-hardy?

Partly, and under conditions. In-ground plants in France took −5 to −9.5 °C (23 to 14.9 °F) in February 2012 in Nantes, Concarneau and near Paris, mostly under fleece or a cloche. These results apply to short frosts, in free-draining soil and under cover; elsewhere, growing it in a pot and keeping it frost-free is safer.

Is my Ceratozamia mexicana really a Ceratozamia mexicana?

Not necessarily. The name long covered several species of Veracruz now separated, such as Ceratozamia tenuis, and plants of Ceratozamia latifolia circulate under this name. Lance-shaped, flat, leathery leaflets 2 to 3.7 cm wide and a petiole with thin prickles point to the right species; the colour of the young leaves is described differently by the sources, and only a known origin makes it certain.

Why are the young leaves of my plant red?

That alone proves nothing. The 2022 monograph describes green young leaves in Ceratozamia mexicana, but the 2016 study that fixed the identity of the species describes reddish-brown emerging leaflets in a population of the municipality of Totutla, close to the type. Red or reddish-brown flushes are also seen in Ceratozamia latifolia, often sold under this name.

Can it take full sun?

It depends on the climate and on acclimatisation. One grower on the coast near Marseille grows it in sun facing the sea, but another in south-west France lost scorched leaves after planting. Bright partial shade is the safest choice, with afternoon shade in summer.

What are its old names?

Ceratozamia longifolia and Ceratozamia intermedia, described by Miquel in the 1840s, and two varieties. All are synonyms of Ceratozamia mexicana; the WCVP adds a few other old names, such as Zamia mexicana.

Can I buy one freely?

No, not without paperwork. The species is in CITES Appendix I and in Annex A of the EU regulation, seeds included. Only artificially propagated plants can be sold, with proof of origin.

Is it toxic?

Assume so. No analysis exists for the species, but the cycads studied contain toxins that are serious for the liver and nervous system, especially in their seeds. Keep it out of reach of children and animals.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Brongniart, A. (1846). [Description of the genus Ceratozamia and of Ceratozamia mexicana.] Annales des Sciences Naturelles, Botanique, ser. 3, 5: 7–8, pl. 1. [Original description; reference given by The World List of Cycads.]
  • Vovides, A.P., Stevenson, D.W., Pérez-Farrera, M.A., López, S. & Avendaño, S. (2016). What is Ceratozamia mexicana (Zamiaceae)? Botanical Sciences 94(2): 419–429. https://doi.org/10.17129/botsci.449 [Epitypification and reinstatement of Ceratozamia tenuis; open access.]
  • 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 [Description, range, status; open access.]
  • Medina-Villarreal, A., González-Astorga, J. & Espinosa de los Monteros, A. (2025). Integrative taxonomy of the Ceratozamia mexicana Brongn. (Zamiaceae) species complex from a phylogeographic perspective. Plant Species Biology 40: 530–546. https://doi.org/10.1111/1442-1984.70008 [Seven lineages in the complex; abstract.]
  • Sánchez-Tinoco, M.Y., Engleman, E.M. & Vovides, A.P. (2000). Reproduction chronology of Ceratozamia mexicana (Cycadales). Boletín de la Sociedad Botánica de México 66: 15–23. [Reproductive timing; abstract.]
  • Habib, S., Gong, Y., Dong, S., Lindstrom, A., Stevenson, D.W., Wu, H. & Zhang, S. (2023). Phylotranscriptomics shed light on intrageneric relationships and historical biogeography of Ceratozamia (Cycadales). Plants 12(3): 478. https://doi.org/10.3390/plants12030478 [Phylogeny of the genus; open access.]
  • Bösenberg, J.D. (2022). Ceratozamia mexicana. The IUCN Red List of Threatened Species 2022: e.T212187667A69866192. https://doi.org/10.2305/IUCN.UK.2022-1.RLTS.T212187667A69866192.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 etymology 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.]