Dioon oaxacensis

Dioon oaxacensis is a cycad endemic to the Mexican state of Oaxaca, where it grows on rocky hillsides in arid regions, among plants adapted to drought. This species of the genus Dioon was described in 2020 from populations previously included in Dioon merolae, which genetic studies had shown to form a distinct lineage. It is recognised by its flat, stiff, straight leaflets and its large cones. In the seed trade it circulated for years as Dioon sp. “El Camarón”. Still little studied, it has not been assessed by the IUCN, and its cultivation is barely documented.

Key facts about Dioon oaxacensis

  • Accepted name: Dioon oaxacensis Gut.Ortega, Pérez-Farr. & Vovides (2020), accepted by The World List of Cycads (version 2026.08.15), GBIF and Kew’s World Checklist of Vascular Plants, the database behind POWO (June 2026 version, published on GBIF)
  • Former names and synonyms: no synonym; populations formerly included in Dioon merolae; sold earlier under the trade name Dioon sp. “El Camarón”, according to a seed merchant
  • Family: Zamiaceae, order Cycadales
  • Common names: none attested; “El Camaron Cycad” is a trade name
  • Natural range: Mexico, Oaxaca; type locality in the Sierra Sur; arid regions of the east of the state according to the authors
  • IUCN status: Not Evaluated (NE)
  • CITES and other protection: CITES Appendix II, through the listing of the whole family Zamiaceae (annotation #4); Annex B in the European Union; not covered by the Mexican standard NOM-059-SEMARNAT-2010, whose list predates its description
  • Documented hardiness: no measured value; a seed merchant states that it “can withstand moderate freezes” (see Cold hardiness)
  • Light and soil: in the wild, rocky hillsides in dry habitats; full sun from an early age, with light shade when young or in hot, dry climates, according to a seed merchant
  • Habit and adult size: tree-like (Enciclovida); detailed measurements are given in the original description (2020)
  • In the UK, US and Australia: Ganna Walska Lotusland (California, among its notable species), Montgomery Botanical Center (eight accessions from 2004), the San Diego Zoo and the John Fairey Garden (BGCI); Royal Botanic Garden Sydney (catalogue); no British garden listed
  • Toxicity: no data for the species; toxins known in other cycads (see Toxicity and precautions)

How to recognise Dioon oaxacensis

According to the abstract of its original description, Dioon oaxacensis “can be easily identified by its flat, stiff, straight leaflets obliquely inserted to rachis, and by its large reproductive structures”. The detailed measurements (number of leaves, leaflet length, cone size) are given in the full text of the description, in Phytotaxa.

The keys published since then add some pointers. That of Gutiérrez-Ortega and co-authors (2021) separates the species, within its group, by flat leaflets, strongly overlapping and not bent downwards at the tip, on a leaf that is often moderately keeled. That of Martínez-Domínguez and co-authors (2026), on the other hand, places it among the species with flat leaves and non-overlapping leaflets, and separates it from Dioon salas-moralesiae by leaflets not arched at the tip. The two keys do not agree on whether the leaflets overlap: a single plant without known provenance remains hard to identify.

The seed merchant Rarepalmseeds describes bluish-green, flat leaves, similar to those of Dioon merolae, on a plant larger, more robust and more vigorous; this commercial description has not been checked against the scientific literature.

Hybrids

No hybrid of Dioon oaxacensis has been reported.

Possible confusion

The most likely confusion is with Dioon merolae, its sister species, whose overlapping leaflets are clearly bent downwards at the tip (2021 key) and form a regular pattern (2008 key of Gregory, Haynes and Chemnick). Dioon salas-moralesiae, described in 2021 from south-eastern Oaxaca, differs in leaflets slightly arched downwards at the tip. José Said Gutiérrez-Ortega, first author of the description, also notes similarities with Dioon purpusii, whose leaves are keeled and whose leaflets overlap little or not at all.

Seeds sold as Dioon sp. “El Camarón” are presented by Rarepalmseeds as belonging to this species. On the French Fous de palmiers forum, in 2013, a grower in the Gard reported that this form was regarded as a “more imposing” Dioon merolae. No scientific source links this trade name to the species, and without a precise origin the identity of plants sold under it cannot be guaranteed.

Taxonomy

Dioon oaxacensis is an accepted name, without synonyms. José Said Gutiérrez-Ortega, Miguel Ángel Pérez-Farrera, Andrew P. Vovides, Silvia H. Salas-Morales and Jeffrey Chemnick described it in 2020 in the journal Phytotaxa (474: 51–61), under the title “a new cycad species from the arid central valleys of Oaxaca”. The name is attributed to the first three authors. The holotype (Pérez-Farrera and Gutiérrez-Ortega 3467) comes from the Sierra Sur of Oaxaca and is kept in the Eizi Matuda herbarium (HEM) of the Universidad de Ciencias y Artes de Chiapas.

The split from Dioon merolae rests on genetics. In a study published the same year in New Phytologist, Gutiérrez-Ortega and co-authors analysed chloroplast DNA, markers spread across the whole genome, the morphology and the climate of the populations attributed to Dioon merolae. They found clearly distinct geographical groups, separated by areas unsuitable for cycads but each faithful to the same type of habitat. The 2020 description states that the delimitation of Dioon oaxacensis is consistent with these results. In 2021 a second study separated the populations of south-eastern Oaxaca as Dioon salas-moralesiae, the name Dioon merolae now covering the remaining populations. For the grower, this means that a plant from Oaxaca labelled Dioon merolae before 2020 may belong to either of these species.

Gutiérrez-Ortega and co-authors (2021) place Dioon oaxacensis in the “Purpusii clade”, with Dioon merolae, Dioon salas-moralesiae, Dioon purpusii, Dioon argenteum, Dioon califanoi, Dioon caputoi, Dioon holmgrenii and Dioon planifolium.

Etymology and history

The epithet oaxacensis means “of Oaxaca” and refers to the species being endemic to that state (Haynes, 2022, as given by The World List of Cycads). The history of its introduction into cultivation is not documented in detail. The Montgomery Botanical Center catalogue lists eight accessions from 2004, sixteen years before the species was described, and the form sold as Dioon sp. “El Camarón” was offered by a European seed merchant at least from 2012, according to the Fous de palmiers forum.

Common names

No common name is attested for Dioon oaxacensis, in English or in Spanish: the Enciclovida database of CONABIO gives none. “El Camarón”, used by the seed trade (“El Camaron Cycad”), is a trade name referring to a provenance, not a vernacular name.

In the wild

Dioon oaxacensis is endemic to Oaxaca. According to the abstract of the description, its populations usually occur in dry habitats, growing on rocky hillsides, together with plants well known for their adaptation to aridity. The title of the article places the species in the arid central valleys of the state, the type locality lies in the Sierra Sur, and the first author writes that the lineage evolved in the arid environments of eastern Oaxaca. The exact localities, altitude and population sizes are not given in the sources available without subscription.

Earlier studies showed that the aridification of Mexico, in the Miocene, encouraged the diversification of Dioon and the adaptation of the leaf epidermis in species of arid habitats (Gutiérrez-Ortega and co-authors, 2018); these studies concerned the genus, not this species in particular.

Conservation status and regulation

Dioon oaxacensis has not yet been assessed by the IUCN (category NE, according to The World List of Cycads and GBIF). No published estimate of its numbers or threats is documented.

Species+ does not list the species by name, but the listing of the whole family Zamiaceae in CITES Appendix II (with annotation #4, which exempts seeds in particular) and in Annex B of the European regulation (Regulation (EU) 2026/1383, in force since 29 June 2026) applies to it; Enciclovida also records it in Appendix II. The Mexican standard NOM-059-SEMARNAT-2010, whose list predates its description, does not cover it, and Enciclovida assigns it no category. Any plant bought must come from cultivation and carry the required documents. Databases checked on 26 October 2026: check the regulations in force.

Growing Dioon oaxacensis

No scientific publication describes the cultivation of Dioon oaxacensis, and the only growing advice comes from a seed merchant. Its natural habitat, rocky hillsides in dry regions, calls for a mineral, free-draining soil and moderate watering, but these are precautions deduced from the habitat.

  • Light: Rarepalmseeds recommends full sun from an early age, with light shade when young and in dry, hot climates.
  • Water: moderate needs, drought-tolerant, according to the same merchant; it also rates its wind tolerance as high and its growth as slow.
  • Climate: according to Rarepalmseeds, it grows best in a warm temperate climate.

At Nong Nooch Tropical Botanical Garden, in Thailand, the cycad curator wrote in 2022 that all described Dioon are grown there and produce cones, without detail on this species.

Outdoor and in-ground cultivation

In California, Ganna Walska Lotusland, at Montecito (Santa Barbara), counts Dioon oaxacensis among the notable species of its outdoor cycad garden; Jeffrey Chemnick, one of the authors of the species, is affiliated with Lotusland. No Mediterranean trial is documented, and no observation of the species has been published for the Jardin zoologique tropical at La Londe-les-Maures, in the Var. A sunny, sharply drained position, sheltered from winter wet, follows the logic of its habitat.

Container cultivation

In climates with frost, a pot with a gritty mineral mix, kept dry and frost-free in winter, is the prudent option until cold tolerance has been documented.

In cultivation in the UK, US and Australia

  • United Kingdom: no British garden declares the species to BGCI PlantSearch.
  • United States: Ganna Walska Lotusland (California) lists it among the notable species of its cycad garden; the Montgomery Botanical Center (Coral Gables, Florida) lists eight accessions in its online catalogue, all from 2004; the San Diego Zoo and the John Fairey Garden (Texas) declare it to BGCI PlantSearch. A BGCI listing is a declaration by the garden, not proof that the plant is alive today.
  • Australia: the Royal Botanic Garden Sydney lists it in its online Garden Explorer and declares it to BGCI.

Propagation

Seed is the only means of propagation mentioned. On the French Fous de palmiers forum, a grower whose profile gives Belley (Ain) and Montpellier (Hérault) reported in January and February 2013 that none of his seeds of Dioon sp. “El Camarón” had germinated, whereas seeds of another species sown at the same time had come up. A single trial does not allow any conclusion.

Pests and diseases

No disease or pest specific to Dioon oaxacensis is documented. As in other Dioon of dry habitats, root rot in a mix that stays wet is the main risk in cultivation.

Cold hardiness

No measurement of the cold tolerance of Dioon oaxacensis has been published.

Mediterranean and European experience

No cultivation report is documented in France or elsewhere in Mediterranean Europe. The temperatures documented for Dioon merolae cannot be transferred to this species, which lives in a different habitat.

United Kingdom, United States and Australia

  • Seed trade: Rarepalmseeds states that Dioon oaxacensis “can withstand moderate freezes” and rates its frost tolerance as moderate, without giving any temperature; this is a commercial assessment.
  • No dated report from a British, American or Australian grower has been found, and Lotusland has published no cold data for the species.

Toxicity and precautions

No toxicity data have been published for Dioon oaxacensis. The risk is documented in other cycads, which contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived, a toxin affecting the liver and the nervous system, dangerous to people, livestock and pets. Treat the species as potentially toxic, keep the seeds out of reach of children and animals, and wear gloves to clean them. If any part has been eaten, contact a poison centre, a doctor or a vet.

Traditional uses

No traditional use specific to Dioon oaxacensis has been documented.

Frequently asked questions

Is Dioon oaxacensis a former Dioon merolae?

Yes, in part. Its populations were included in Dioon merolae until 2020. Genetic analyses showed that they form a distinct lineage, described as a new species. A plant from Oaxaca labelled Dioon merolae before that date may therefore be Dioon oaxacensis.

How can it be told from Dioon merolae?

By the shape of the leaflets. Those of Dioon oaxacensis are flat, stiff and straight; those of Dioon merolae bend clearly downwards at the tip. The authors also stress the large size of its cones.

Are Dioon oaxacensis and Dioon sp. “El Camarón” the same plant?

That is what a seed merchant states, but no scientific source confirms it. Without a precise provenance, the identity of plants sold under this name cannot be guaranteed.

Is it endangered?

Nobody knows yet. The species has not been assessed by the IUCN and no published data describe its numbers. It is nonetheless protected by CITES, like all Zamiaceae.

Is it hardy?

Not known. No observation has been published; a seed merchant speaks only of “moderate freezes”. Grow it in a pot and protect it from frost and rain in winter.

Is it toxic?

It should be treated as such. There are no data for the species, but other cycads contain toxins dangerous to people and animals.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Gutiérrez-Ortega, J.S., Pérez-Farrera, M.A., Vovides, A.P., Salas-Morales, S.H. & Chemnick, J. (2020). Dioon oaxacensis (Zamiaceae): a new cycad species from the arid central valleys of Oaxaca (Mexico). Phytotaxa 474(1): 51–61. doi:10.11646/phytotaxa.474.1.5 [Protologue; abstract and reference list.]
  • Gutiérrez-Ortega, J.S., Salinas-Rodríguez, M.M., Ito, T. et al. (2020). Niche conservatism promotes speciation in cycads: the case of Dioon merolae (Zamiaceae) in Mexico. New Phytologist 227(6): 1872–1884. doi:10.1111/nph.16647 [Lineages of the former Dioon merolae; abstract.]
  • Gutiérrez-Ortega, J.S., Pérez-Farrera, M.A., Chemnick, J. & Gregory, T.J. (2021). A reassessment of Dioon merolae (Zamiaceae) leads to the description of Dioon salas-moralesae, a new cycad species from Southeastern Oaxaca, Mexico. Phytotaxa 528(2): 93–110. doi:10.11646/phytotaxa.528.2.3 [Three lineages within the former Dioon merolae, Purpusii clade and key; abstract and key (Plazi).]
  • Gutiérrez-Ortega, J.S., Yamamoto, T., Vovides, A.P. et al. (2018). Aridification as a driver of biodiversity: a case study for the cycad genus Dioon (Zamiaceae). Annals of Botany 121(1): 47–60. doi:10.1093/aob/mcx123 [Diversification linked to aridification; abstract.]
  • Gregory, T., Haynes, J. & Chemnick, J. (2008). Key to the species of Dioon. The Cycad Newsletter 31: 16–17. [Leaflet pattern of Dioon merolae.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology, as given by The World List of Cycads.]
  • Lindstrom, A. (2022). The cycad collection at Nong Nooch Tropical Botanical Garden, Thailand. CYCADS 6(1). [Cultivation of Dioon in a tropical climate.]
  • Martínez-Domínguez, L., Nicolalde-Morejón, F., Stevenson, D.W., Lorea-Hernández, F.G. & Vergara-Silva, F. (2026). A striking new species of Dioon (Zamiaceae) from pine and pine-oak forest of Guerrero, Mexico. PhytoKeys 274: 229–245. doi:10.3897/phytokeys.274.173907 [Key including Dioon oaxacensis.]
  • Calonje, M., Stevenson, D.W. & Osborne, R. (2026). The World List of Cycads, version 2026.08.15. Montgomery Botanical Center, Coral Gables. doi:10.5281/zenodo.21958524 [Reference checklist.]