Ceratozamia tenuis

Ceratozamia tenuis is a cycad of central Veracruz, Mexico, that grows in the cloud forests of the Sierra de Chiconquiaco, north of Xalapa, between about 1,200 and 1,920 m (about 3,940 to 6,300 ft). This species of the genus Ceratozamia was long confused with Ceratozamia mexicana: described in 1884 as a mere variety, Ceratozamia mexicana var. tenuis, it was raised to species rank only in 2016. Many plants once called Ceratozamia mexicana in the Xalapa region are in fact Ceratozamia tenuis. It is listed as Endangered by the IUCN.

Key facts about Ceratozamia tenuis

  • Accepted name: Ceratozamia tenuis (Dyer) D.W.Stev. & Vovides (2016), 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. tenuis Dyer (1884), the basionym; Ceratozamia mexicana f. tenuis (Dyer) J.Schust. (1932); Ceratozamia mexicana var. vulgaris J.Schust. (1932), according to the 2022 monograph; often grown as Ceratozamia mexicana
  • Family: Zamiaceae, order Cycadales
  • Common names: none in English; in Veracruz “tepezmaite” or “palmita” (a name shared with two neighbouring species), “costilla de león”, “palma del monte”
  • Natural range: Mexico, mountains of central Veracruz (Sierra de Chiconquiaco, around Xalapa), 1,200 to 1,920 m
  • IUCN status: Endangered (EN, criteria A2c; B1ab(i,ii,iii)), 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: no data for the species (see Cold hardiness)
  • Light and soil: in the wild, cloud forest on volcanic soils with basalt rocks; no published growing advice
  • Habit and adult size: trunk 20 cm to 1 m long and 30 to 45 cm across; up to 56 leaves 85 to 225 cm long
  • In the UK, US and Australia: declared by five American gardens; none in the UK or Australia (see In cultivation)
  • Toxicity: no data for the species; treat it as poisonous, like all cycads (see Toxicity and precautions)

How to recognise Ceratozamia tenuis

It is recognised by its long, narrow, linear leaflets, slightly channelled, by its green new leaves and by its large dark green female cones covered in blackish hairs. The 2022 monograph describes it as follows:

  • Trunk: above ground, upright then lying down, 20 to 100 cm long and 30 to 45 cm across.
  • Leaves: 6 to 56, 85 to 225 cm long, ascending; petiole 30 to 93 cm long, armed with 10 to 55 slender prickles 2 to 5 mm long.
  • Leaflets: 30 to 56 pairs, linear, papery, rolled inwards, green and hairless, 23 to 50.5 cm long and 1 to 2.1 cm wide.
  • Male cones: cylindrical, 25 to 50 cm long and 4 to 8 cm across, greenish yellow, with curved horns on the scales.
  • Female cones: cylindrical, 22 to 35 cm long and 10 to 14 cm across, dark green with blackish hairs, on an upright or hanging stalk.
  • Seeds: oval, 2.5 to 3 cm long, with whitish-yellow flesh turning light brown.

The sources do not describe the new leaves in the same way: green to light green according to Vovides and colleagues (2016), dark green, almost blackish, with brown hairs according to Martínez-Domínguez and colleagues (2018, 2022). All agree in contrasting them with the reddish-brown new leaves of Ceratozamia mexicana.

Hybrids

No hybrid has been documented. Vovides and colleagues (2016) merely suggest that the Ceratozamia mexicana complex, to which the species belongs, might be of hybrid origin; this has not been demonstrated.

Possible confusion

The main confusion, historical and still common in collections, is with Ceratozamia mexicana in the strict sense. According to Vovides and colleagues (2016):

  • Ceratozamia tenuis: linear-lanceolate leaflets, slightly channelled, 1.3 to 1.8 cm wide; green new leaves; no girder-like sclerenchyma in the leaflet.
  • Ceratozamia mexicana: oblong-lanceolate, flat leaflets, 2 to 3.4 cm wide; reddish-brown new leaves; incipient girder-like sclerenchyma.

The other species of the complex, Ceratozamia morettii and Ceratozamia brevifrons, live only about ten kilometres away in the same Sierra de Chiconquiaco, but each occupies a distinct climatic niche (Gómez-Díaz and colleagues, 2024). Thiselton-Dyer already noted in 1884 that its leaflets recall those of Ceratozamia kuesteriana, but that the habit is different. Without a cone, a Ceratozamia is hard to tell from a Zamia.

Taxonomy

Ceratozamia tenuis 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 the Gulf of Mexico region and lists Ceratozamia mexicana var. tenuis and Ceratozamia mexicana f. tenuis as its synonyms. Its story is that of the splitting of Ceratozamia mexicana, the type species of the genus.

In 1884, William Thiselton-Dyer, of Kew, described in the Biologia Centrali-Americana a variety tenuis of Ceratozamia mexicana in a single line: leaflets a foot long, half an inch wide, spaced, from a plant grown at Kew, of supposed Mexican origin, without a locality. In 1932, Schuster reduced it to the rank of form. With no specimen known, the name remained enigmatic until Dennis Stevenson found in 1999, in the Kew herbarium, three oversized sheets of a leaf collected in 1881 from the plant in the Palm House, labelled in Thiselton-Dyer’s hand.

In 2016, Andrew Vovides, Dennis Stevenson and their colleagues published the article “What is Ceratozamia mexicana?” in Botanical Sciences. They compared two populations of central Veracruz: one in the municipality of Totutla, north-east of Huatusco, which matches Brongniart’s type, and one north of Xalapa that Charles Chamberlain had taken for Ceratozamia mexicana in 1919. Eleven anatomical characters of the leaflets separate them clearly; the population north of Xalapa matches Thiselton-Dyer’s variety. They raised it to species rank, designated the Kew sheets as the lectotype and a collection made by Vovides in the municipality of Jilotepec in 1976 as the epitype. In 2018, Martínez-Domínguez and colleagues corrected this designation and also placed Ceratozamia mexicana var. vulgaris J.Schust. under the species.

For the reader, the consequence is concrete: fine-leaved Ceratozamia mexicana in collections are often Ceratozamia tenuis. The integrative study by Medina-Villarreal and colleagues (2025) confirms the lineage, within a complex of seven lineages that also includes a cryptic species still to be named, close to Ceratozamia tenuis. In the phylogeny by Habib and colleagues (2023), the species falls in the latifolia subclade of the large Mexicana clade.

Etymology and history

The epithet comes from the Latin tenuis, “thin, fine”, referring to the narrow leaflets (Haynes, 2022). The species was therefore in cultivation in Europe in the 19th century: the plant that served as the type grew in the Palm House at Kew in 1881. The populations north of Xalapa have been studied since Chamberlain in the early 20th century, and the species is grown at the Francisco Javier Clavijero Botanic Garden in Xalapa, where the plants of the 2016 study were observed, and at Nong Nooch Tropical Botanical Garden in Thailand, which supplied the material for the 2023 phylogenetic study. The chromosome number, 2n = 16, was established in 2016.

Common names

No common name is recorded in English. In Veracruz, local people call Ceratozamia tenuis, Ceratozamia brevifrons and Ceratozamia morettii by the same local name, “tepezmaite” or “palmita” (Gómez-Díaz and colleagues, 2024). The 2022 monograph also records “costilla de león” (“lion’s rib”) and “palma del monte” (“mountain palm”), from herbarium labels.

In the wild

Ceratozamia tenuis is endemic to the mountains of central Veracruz. It grows in cloud forest between 1,200 and 1,920 m, on volcanic soils with basalt rocks (Martínez-Domínguez and colleagues, 2022). Collections come from the municipalities of Jilotepec, Coacoatzintla, Chiconquiaco, Tepetlán, Tlacolulan, Banderilla and Xalapa. Populations are small and isolated, but the plants can be locally abundant (Vovides and colleagues, 2016).

Its pollination has been partly studied. From 2015 to 2017, researchers of the University of Veracruz found in the cones of a population in the municipality of Coacoatzintla two beetles new to science, Pharaxonotha mexicana and Pharaxonotha tenuis, mostly in the male cones; it was the first record of this genus of insects, regarded as a pollinator of many American cycads, on a Ceratozamia (Santiago-Jiménez and colleagues, 2019).

A model of its climatic niche (Gómez-Díaz and colleagues, 2024), based on 21 localities, shows that its distribution depends mainly on the rainfall of the driest month, the mean temperature of the coldest quarter and summer rainfall. Its suitable range would have expanded greatly since the Last Glacial Maximum, but could shrink by 83% by 2080 under climate change.

Conservation status and regulation

Ceratozamia tenuis is listed as Endangered (EN, criteria A2c; B1ab(i,ii,iii)) on the IUCN Red List, in an assessment by J.D. Bösenberg published in 2022 (status given by The World List of Cycads and confirmed by the Red List data distributed through GBIF, 30 October 2026). The 2022 monograph, for its part, states that the species had not been assessed and proposes Endangered under criteria A1acd; B1ab(iii), citing populations of 100 to 300 adults in a narrow range much affected by land-use change. An analysis of the extinction risk of the cycads of Veracruz (Gómez Díaz, 2025) places it among the most threatened species of the state: 8 localities, an extent of occurrence of 313 km², 87% of the habitat transformed and 98% of the range outside protected areas. The author proposes listing it as “in danger of extinction” in the Mexican NOM-059 standard, where the species, described after 2010, does not yet appear under this name.

Like the whole genus, it has been covered by CITES Appendix I since 1 August 1985 (cycads 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+ does not list the species under its own name (checked on 30 October 2026), but the listing covers the entire genus. International trade in wild-collected plants for commercial purposes is banned; only artificially propagated plants with the required permits can be traded.

In practice, ask for seed-grown plants with documents of origin, and check the exact identity: a plant sold as Ceratozamia mexicana may be a Ceratozamia tenuis, and vice versa. This general information does not replace the official texts: check the regulations in force before buying, importing or exchanging plants.

Growing Ceratozamia tenuis

No source describes the cultivation of Ceratozamia tenuis specifically. The pointers below are drawn from its cloud-forest habitat and from the general rules for the genus; they have not been confirmed by published trials.

  • Light: bright partial shade or light shade; in hot, dry summers, shade in the afternoon.
  • Soil: rich in humus but very free-draining, like the volcanic soils of its habitat.
  • Watering: regular during growth, avoiding standing water; less in winter. Its habitat receives regular rain, and its distribution depends on dry-season rainfall.
  • Space: it is a large species, with leaves 2 m long or more in adults; allow room.

Outdoor and in-ground cultivation

No outdoor planting of a plant identified as Ceratozamia tenuis has been documented with a dated result. The American gardens that declare it, in southern Florida and California, do not say whether their plants grow outdoors or under glass.

Container cultivation

Young plants grow well in a pot in a humus-rich, free-draining mix, which allows them to be moved under cover in winter; adults soon outgrow most containers.

In cultivation in the UK, US and Australia

In the United States, BGCI PlantSearch (queried on 30 October 2026) lists five gardens: Fairchild Tropical Botanic Garden (Miami), Miami Beach Botanical Garden and Montgomery Botanical Center (Coral Gables) in Florida, the Huntington (San Marino) and the University of California Botanical Garden at Berkeley in California. The online catalogue of Montgomery Botanical Center lists one accession. No garden in the United Kingdom or Australia declares it under this name. Outside these countries, BGCI lists the Francisco Javier Clavijero Botanic Garden in Xalapa, the Marimurtra botanic garden in Blanes (Catalonia, Spain) and a garden in China.

Because the species was long confused with Ceratozamia mexicana, some garden plants labelled Ceratozamia mexicana may belong to it; no garden states whether its plants grow outdoors.

Propagation

Propagation is from seed. The plants are male or female: both sexes and, in cultivation, hand pollination are needed to obtain fertile seed. No germination data specific to the species have been published. Handle seeds wearing gloves.

Pests and diseases

No pest or disease specific to Ceratozamia tenuis 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 hardiness data exist for Ceratozamia tenuis under this name. The published cultivation reports concern plants called Ceratozamia mexicana, some of which might belong to this species, but none allows this to be confirmed.

Mediterranean and European experience

No cultivation of Ceratozamia tenuis identified as such has been reported in Europe, and the Jardin zoologique tropical in La Londe-les-Maures (Var, on the French Riviera) has published no observation of it. The Ceratozamia mexicana that came through the cold spell of February 2012 in the ground, with protection, in western France and near Paris were not identified with certainty: their results cannot be transferred to Ceratozamia tenuis.

United Kingdom, United States and Australia

No dated cold record and no commercial hardiness rating have been published. Its cloud-forest habitat, where the temperature of the coldest quarter is one of the factors limiting its distribution, provides no measured frost tolerance. Overwinter it frost-free until documented trials exist.

Toxicity and precautions

No toxicity study specific to Ceratozamia tenuis 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. 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 reports a local use of the female cones as an insecticide: cut in half and mixed with milk or sugar, they are used to kill flies. This use, recorded on a herbarium label, suggests that the cones contain toxic substances, but no analysis has tested it. No food or medicinal use has been reported.

Frequently asked questions

What is the difference between Ceratozamia tenuis and Ceratozamia mexicana?

Mainly the leaflets. Those of Ceratozamia tenuis are narrow (1.3 to 1.8 cm) and slightly channelled, those of Ceratozamia mexicana broader (2 to 3.4 cm) and flat. The new leaves are green in the former and reddish brown in the latter, according to the 2016 study.

Is my Ceratozamia mexicana a Ceratozamia tenuis?

Possibly, if it has fine leaflets. Many plants from the Xalapa region were grown as Ceratozamia mexicana before 2016. Only a known wild origin, or the opinion of a specialist, can settle the question.

Since when has it been a species?

Since 2016. Described in 1884 as a variety of Ceratozamia mexicana, it was raised to species rank by Stevenson and Vovides on the basis of leaflet anatomy and the rediscovery of the type sheets at Kew.

Where does it grow?

In central Veracruz, Mexico. It is found in cloud forest north of Xalapa, in the Sierra de Chiconquiaco, between about 1,200 and 1,920 m.

Is it endangered?

Yes. The IUCN lists it as Endangered, and a 2025 study ranks it among the most threatened cycads of Veracruz. Climate models predict a sharp reduction of its range by 2080.

Can it take frost?

Nobody knows. No documented trial concerns a plant identified as Ceratozamia tenuis. Overwinter it frost-free until data exist.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Thiselton-Dyer, W.T. (1884). Cycadaceae. In: Hemsley, W.B., Biologia Centrali-Americana, Botany 3: 193. [Description of Ceratozamia mexicana var. tenuis; primary source.]
  • 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 [New combination, lectotype, epitypes; open access.]
  • Martínez-Domínguez, L., Nicolalde-Morejón, F., Vergara-Silva, F. & Stevenson, D.W. (2018). Taxonomic review of Ceratozamia (Zamiaceae) in the Sierra Madre Oriental, Mexico. PhytoKeys 100: 91–124. https://doi.org/10.3897/phytokeys.100.23152 [Synonymy, corrected epitype; 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 [Monograph of the genus; open access.]
  • Medina-Villarreal, A. and colleagues (2025). Integrative taxonomy of the Ceratozamia mexicana Brongn. (Zamiaceae) species complex from a phylogeographic perspective. Plant Species Biology. https://doi.org/10.1111/1442-1984.70008 [Seven lineages in the complex.]
  • Gómez-Díaz, J.A., Carvajal-Hernández, C.I. & Dáttilo, W. (2024). Past, present and future in the geographical distribution of Mexican Tepezmaite cycads: genus Ceratozamia. PLOS ONE. https://doi.org/10.1371/journal.pone.0284007 [Climatic niche and projections; open access.]
  • Gómez Díaz, J.A. (2025). Assessing the extinction risk of Veracruz cycads. Cambridge Prisms: Extinction 3: e7. https://doi.org/10.1017/ext.2025.5 [Risk indicators; open access.]
  • Santiago-Jiménez, Q.J., Martínez-Domínguez, L. & Nicolalde-Morejón, F. (2019). Two new Mexican species of Pharaxonotha Reitter, 1875 (Coleoptera: Erotylidae) from Ceratozamia tenuis (Cycadales: Zamiaceae). Dugesiana 26(1): 15–25. https://doi.org/10.32870/dugesiana.v26i1.7054 [Insects of the cones.]
  • 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 tenuis. The IUCN Red List of Threatened Species 2022: e.T103632135A103632280. https://doi.org/10.2305/IUCN.UK.2022-1.RLTS.T103632135A103632280.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.]