Ceratozamia reesii

Ceratozamia reesii is a cycad of south-eastern San Luis Potosí, in Mexico, known only from the municipality of Xilitla, in the Sierra Madre Oriental, where it grows on rocks between 580 and 1,300 m (about 1,900 to 4,270 ft). Described in 2022, this species of the genus Ceratozamia corresponds to populations that had been identified as Ceratozamia latifolia since the 1980s, so plants grown under that name may in fact be Ceratozamia reesii. Its new leaves are light green and its female cone turns brown when ripe. It is named after the American botanist John David Rees and has not yet been assessed by the IUCN.

Key facts about Ceratozamia reesii

  • Accepted name: Ceratozamia reesii Vovides, Pérez-Farr. & Gut.Ortega (2022), accepted by The World List of Cycads (version 2026.08.15) and by the World Checklist of Vascular Plants (WCVP, the database behind POWO, read via GBIF)
  • Former names and synonyms: no synonym; its populations were long identified as Ceratozamia latifolia
  • Family: Zamiaceae, order Cycadales
  • Common names: none recorded
  • Natural range: Mexico, San Luis Potosí (municipality of Xilitla), 580 to 1,300 m according to published collections
  • IUCN status: Not Evaluated
  • CITES and other protection: CITES Appendix I (whole genus, since 1985); Annex A in the European Union, seeds included
  • Documented hardiness: no data (see Cold hardiness)
  • Light and soil: a rock-dwelling (rupicolous) plant in the wild; no published growing advice
  • Habit and adult size: short, unbranched trunk 12 to 33 cm tall; 4 to 12 leaves, 0.7 to 2 m long
  • In the UK, US and Australia: no garden declares it under this name (see In cultivation)
  • Toxicity: no data for the species; treat it as poisonous (see Toxicity and precautions)

How to recognise Ceratozamia reesii

According to its original description (Vovides and colleagues, 2022), Ceratozamia reesii is recognised by a combination of features: 4 to 12 leaves per crown, light green when they emerge; a petiole armed with slender prickles; 11 to 23 pairs of leathery, elliptic to lance-shaped or oblanceolate leaflets; and a single, upright female cone that is brown when ripe, on a stalk 4.2 to 6 cm long. The description, published in full by the Plazi treatment database, gives:

  • Trunk: rock-dwelling, unbranched, short, cylindrical and upright, 12 to 33 cm tall and 10.5 to 17 cm across, covered in old leaf bases; persistent brown cataphylls, densely woolly when young.
  • Leaves: 4 to 12 per crown, forming a semi-open crown, upright, 69.5 to 201 cm long and 40 to 71 cm wide; light green when they emerge, then olive green. The petiole, 34 to 68 cm long, carries slender prickles; the green rachis, 34.5 to 138 cm long, carries sparse prickles.
  • Leaflets: 11 to 23 pairs, linear to oblanceolate, leathery, slightly sickle-shaped towards the tip, with an acute to drawn-out, asymmetrical tip; the point of attachment is yellow on the upper side; 28 to 37 faint veins. The middle leaflets measure 19.8 to 35.5 cm by 1.5 to 5.1 cm and are spaced 1.2 to 7.2 cm apart.
  • Male cones: single, conical, upright, light brown when ripe, 33 to 35 cm long and 4.8 to 5 cm across, on a light brown, densely woolly stalk 14 to 15 cm long.
  • Female cones: single, cylindrical, upright, about 16 cm long and 6.5 to 8 cm across, with a short point and a brown down when ripe, on a brown stalk 4.2 to 6 cm long. The scales are light brown to brown in the centre, fading to reddish brown at the edges.
  • Seeds: egg-shaped, 2 to 2.3 cm long, with cream flesh before ripening and a beige stony layer when ripe. The diagnosis gives a seed length of up to 2.8 cm, slightly more than the detailed description.

Hybrids

No natural or garden hybrid has been documented.

Possible confusion

The main confusion is historical: the Xilitla populations were taken for Ceratozamia latifolia from the 1980s onwards. The key to the latifolia species complex published with the description separates them from their neighbours:

  • Ceratozamia latifolia, of San Luis Potosí (Ciudad del Maíz, Rayón, Tamasopo): reddish-brown new leaves, papery leaflets, petiole unarmed or almost so; a very short trunk, 2 to 6 leaves, and a smaller female cone (8 to 13.5 cm) on a longer stalk (6.5 to 10 cm).
  • Ceratozamia huastecorum, of northern Veracruz: also light green new leaves and oblanceolate leaflets, but an olive-green female cone when ripe.
  • Ceratozamia morettii, of central Veracruz: light green new leaves, but oblong leaflets.
  • Ceratozamia chamberlainii and Ceratozamia fuscoviridis: brown or reddish new leaves. The authors of Ceratozamia reesii call them its southern neighbours and checked that the Xilitla plants did not match them either.

A plant without a documented origin cannot be identified with certainty: young leaf colour, leaflet texture and the colour of the ripe female cone have to be checked together.

Taxonomy

Ceratozamia reesii is accepted by The World List of Cycads and by the WCVP, the database behind POWO (read via GBIF on 30 October 2026), which records it from north-eastern Mexico and dates its publication to 2022. It was described in December 2022 in the journal Phytotaxa (575(3): 224–252; name published on page 241), in an article by Andrew Vovides, Miguel Ángel Pérez-Farrera, María Magdalena Salinas-Rodríguez, Sonia Galicia, Pedro Díaz-Jiménez, Michael Calonje and José Said Gutiérrez-Ortega.

Untangling Ceratozamia latifolia

The article sets out the origin of the problem. Ceratozamia latifolia was described by Miquel in 1847 from a young plant of unknown origin, grown in the Amsterdam botanic garden and obtained from Belgium, without a type specimen or illustration. The name long remained doubtful, usually applied to a plant probably from Veracruz. In 1986, the designation of a neotype tied it to a population in San Luis Potosí that belonged to Ceratozamia microstrobila, described shortly before, which therefore fell into synonymy. But this designation, made in a paper on nomenclature, came with no description, and taxonomists and horticulturists went on to call “latifolia” plants from several clearly different populations in San Luis Potosí.

The authors compared the morphology and anatomy of wild Ceratozamia latifolia with those of the Xilitla plants, considered latifolia since the 1980s. They differ in many leaf and cone characters and do not match Ceratozamia chamberlainii or Ceratozamia fuscoviridis either, hence the description of a new species. For the reader, an old “latifolia” from Xilitla may be a Ceratozamia reesii, while a plant labelled Ceratozamia microstrobila is now a Ceratozamia latifolia.

The 2022 monograph of the genus, published a few months before the description, predates the name. Its only specimens from the municipality of Xilitla are listed under Ceratozamia chamberlainii, whose type was collected there, and the type of Ceratozamia hildae came from plants originally collected north of Xilitla: several species of the genus therefore grow in or near this municipality.

Type

The holotype is a female plant collected on 31 July 2021 in the municipality of Xilitla, at about 790 m, by M.A. Pérez-Farrera, P. Díaz and M.M. Salinas (no. 4017). It is held at the Eizi Matuda herbarium (HEM) in Tuxtla Gutiérrez, with an isotype at the XAL herbarium in Xalapa.

Etymology and history

The epithet honours the memory of John David Rees (1932–2021), an American botanist and the principal author’s mentor in the study of cycads. According to the description, his guidance and knowledge of Mexican cycads were invaluable to the later creation of the Mexican National Cycad Collection at the Francisco Javier Clavijero Botanic Garden of INECOL, in Xalapa (Veracruz). Rees was also a co-author of Ceratozamia microstrobila (1983), the name now placed under Ceratozamia latifolia.

The species is grown in that garden: the description cites a plant of the collection (accession 2001-110A), raised from a collection made in the municipality of Xilitla by S. Avendaño.

Common names

No common name is recorded for the species, in English or in any other language.

In the wild

Ceratozamia reesii is known only from the municipality of Xilitla, in San Luis Potosí (The World List of Cycads), in the Sierra Madre Oriental. It is a rock-dwelling plant. The published collections range from 580 m to 1,300 m, with the type at about 790 m. No source documents the size of its populations.

Conservation status and regulation

Ceratozamia reesii has not been assessed on the IUCN Red List (The World List of Cycads, version 2026.08.15; no category in the Red List data distributed through GBIF, checked on 30 October 2026). No population estimate is available.

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+ does not list the species under its own name, since it was described after the CITES checklist of cycads, but the listing covers the whole genus (“Ceratozamia spp.”) and therefore applies to it (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 reesii

No growing advice has been published under this name. Because its populations were called Ceratozamia latifolia by horticulturists, Xilitla plants grown under that name may belong to it, but no source says which ones.

As a rock-dwelling plant of the mountains, it probably needs a very free-draining mix; light and watering needs are not documented. These pointers are drawn from the description and have not been confirmed by published trials.

Outdoor and in-ground cultivation

No outdoor planting under this name has been documented anywhere, and no cold record exists.

Container cultivation

Its small trunk and few leaves make it suitable for a pot: a deep container, a mineral, very free-draining mix and protection from frost follow the general practice for small Ceratozamia; no trial specific to the species has been published.

In cultivation in the UK, US and Australia

No garden in the United Kingdom, the United States or Australia declares Ceratozamia reesii under this name: BGCI PlantSearch lists only the Francisco Javier Clavijero Botanic Garden in Xalapa, Mexico, and the online catalogue of Montgomery Botanical Center, in Florida, has no accession under it (both queried on 30 October 2026). Some plants declared as Ceratozamia latifolia may come from Xilitla, but no garden documents it.

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. The usual risks for Ceratozamia in cultivation are rot in cold, sodden soil and scale insects.

Cold hardiness

No cold-hardiness data exist for Ceratozamia reesii under this name. Results published for “Ceratozamia latifolia” cannot be transferred to it, since the origin of the plants is not given.

Mediterranean and European experience

No cultivation result has been published in Europe under this name, and the Jardin zoologique tropical in La Londe-les-Maures (Var, on the French Riviera) has published no observation of this species. Until trials on plants of known origin exist, protect it from frost.

United Kingdom, United States and Australia

No dated cold record and no commercial hardiness rating have been published. In the UK it is a plant for a frost-free glasshouse.

Toxicity and precautions

No toxicity study specific to Ceratozamia reesii 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

No use is recorded for this species.

Frequently asked questions

Is Ceratozamia reesii a recognised species?

Yes. The World List of Cycads and the WCVP have accepted it since its description in 2022; it is not a synonym of Ceratozamia latifolia.

Is my “Ceratozamia latifolia” really a reesii?

Possibly, if it comes from Xilitla. The Xilitla populations were called latifolia from the 1980s onwards; a plant with light green new leaves and leathery leaflets is worth checking.

How can I tell Ceratozamia reesii from Ceratozamia latifolia?

By the new leaves and the leaflets. Ceratozamia reesii has light green new leaves and leathery leaflets; Ceratozamia latifolia has reddish-brown new leaves, papery leaflets and a petiole with few or no prickles.

Who was Rees?

John David Rees (1932–2021), an American botanist who studied Mexican cycads and mentored the principal author of the description.

Where does it grow?

In the municipality of Xilitla, in San Luis Potosí, Mexico, on rocks between 580 and 1,300 m according to published collections.

Is it endangered?

Nobody knows yet. The IUCN has not assessed it; like the whole genus, it is listed in CITES Appendix I.

Can it take frost?

Nobody knows. No trial has been published under this name; protect it from frost.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Vovides, A.P., Pérez-Farrera, M.A., Salinas-Rodríguez, M.M., Galicia, S., Díaz-Jiménez, P., Calonje, M. & Gutiérrez-Ortega, J.S. (2022). Morphological and anatomical analyses clarify the species definition of Ceratozamia latifolia Miq. (Zamiaceae) and lead to the description of a new species: Ceratozamia reesii. Phytotaxa 575(3): 224–252. https://doi.org/10.11646/phytotaxa.575.3.2 [Original description; abstract, treatments and key published by Plazi.]
  • 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; Ceratozamia chamberlainii and the Xilitla specimens; open access.]
  • 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.]