Dioon caputoi

Dioon caputoi is a small cycad from Mexico that grows only on a few dry limestone hills on the border between southern Puebla and northern Oaxaca, at about 2,000 m (6,600 ft), within the Tehuacán-Cuicatlán Biosphere Reserve. This species of the genus Dioon is recognised by its flat leaves with very narrow leaflets, 4 to 5 mm wide, evenly spaced along the axis, which give the leaf an airy look. Collected as early as 1907–1908 by Carl Albert Purpus but long confused with Dioon purpusii, it was only described in 1980. It is one of the most narrowly distributed cycads in Mexico and is listed as Endangered on the IUCN Red List.

Key facts about Dioon caputoi

  • Accepted name: Dioon caputoi De Luca, Sabato & Vázq.Torres (1980), 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; old specimens wrongly labelled Dioon purpusii
  • Family: Zamiaceae, order Cycadales
  • Common names: no English name is attested; “palma real” in Spanish in its home region (original description, 1980; NOM-059)
  • Natural range: Mexico, southern Puebla and northern Oaxaca (Sierra de Zapotitlán, Tehuacán-Cuicatlán Biosphere Reserve), at about 1,800 to 2,000 m
  • IUCN status: Endangered (EN A2acd), assessment by J. Chemnick and T. Gregory dated December 2020 and published in 2022; Critically Endangered (CR) in the IUCN action plan of 2003
  • CITES and other protection: CITES Appendix II (annotation #4); Annex B in the European Union; “in danger of extinction” (category P) in Mexico under the standard NOM-059-SEMARNAT-2010
  • Documented hardiness: no dated observation; a Californian nursery claims about −7 °C (20 °F), without details (see Cold hardiness)
  • Light and soil: in the wild, steep, open slopes on very poor limestone soil; full sun according to a specialist nursery
  • Habit and adult size: trunk 1 m or more tall and 20 to 25 cm (8 to 10 in) across, reclining beyond 80 to 100 cm; leaves 75 to 90 cm long or more
  • In the UK, US and Australia: Montgomery Botanical Center (Florida, three accessions, two from 2004) and the Fairchild Tropical Botanic Garden (Miami); declared to BGCI by Lotusland, the Huntington, San Diego Botanic Garden and three other American gardens; no British or Australian garden listed
  • Toxicity: no data for the species; toxins known in other cycads (see Toxicity and precautions)

How to recognise Dioon caputoi

Dioon caputoi is recognised by its flat leaves with very narrow leaflets, set at an acute angle and separated by regular gaps along the whole length of the axis. The original description by Paolo De Luca, Sergio Sabato and Mario Vázquez Torres (1980) gives the following characters:

  • Trunk: cylindrical, up to 1 m or more, 20 to 25 cm across; plants more than 80 to 100 cm tall have a reclining trunk.
  • Scales (cataphylls): woolly, 12 to 14 cm long.
  • Leaves: numerous, flat, leathery, upright, smooth, 75 to 90 cm long or more; petiole 12 to 15 cm.
  • Leaflets: 50 to 70 or more on each side, linear-lanceolate, sharp-pointed, with rolled margins, 4 to 5 mm wide and 5 to 7 mm apart; those in the middle of the leaf 6 to 8 cm long, sometimes 10 cm; upper margin entire or, rarely, with one or two spines 2 to 3 mm long, lower margin entire.
  • Female cones: ovoid-cylindrical, 30 to 40 cm long and 20 to 25 cm across, with densely woolly scales.
  • Male cones: elongated and cylindrical, about 40 cm long and 9 to 10 cm wide.
  • Seeds: almost spherical, 3 to 4 cm across.

The identification keys published since use the same characters. That of Gregory, Haynes and Chemnick (2008) relies on leaflets less than 7 mm wide, separated by a gap of at least 0.7 times their width, set at 45 to 60°, dull but not glaucous, with few spines but long relative to their width. That of Gutiérrez-Ortega and co-authors (2021) separates the species by its widely spaced leaflets 4 to 5 mm wide, and that of Martínez-Domínguez and co-authors (2026) by its linear leaflets no more than 6 mm wide.

Hybrids

No hybrid of Dioon caputoi has been reported.

Possible confusion

The historical confusion is with Dioon purpusii, under whose name Purpus’s collections circulated for seventy years. According to the 1980 description, Dioon purpusii differs in its slightly keeled leaves and its broader leaflets (8 to 10 mm instead of 4 to 5 mm), crowded in the middle and upper part of the leaf instead of evenly spaced. Gregory and co-authors (2003) note that Dioon caputoi differs from the three species of the Dioon purpusii complex (Dioon purpusii, Dioon califanoi, Dioon argenteum) in its smaller leaves and much narrower, more widely spaced leaflets.

The 2008 key places it next to Dioon sonorense, a species of north-western Mexico with similarly narrow leaflets, which differs in a wider angle of insertion (65 to 90°), an often glaucous upper surface and more frequent spines. Provenance should be enough to separate them, but a plant sold without origin remains hard to identify. A grower reports on the French Fous de palmiers forum, in August 2014, that seeds bought as Dioon caputoi turned out to belong to another species.

Taxonomy

Dioon caputoi is an accepted name with no synonyms. Paolo De Luca and Sergio Sabato, of the University of Naples, and Mario Vázquez Torres, of the Universidad Veracruzana, described it in 1980 in the journal Brittonia (32: 43–46). The type was collected by Vázquez Torres on 27 December 1978 at the Loma de la Grana, 6 km south-west of San Luis Atolotitlán (formerly San Luis Tultitlanapa), in the municipality of Caltepec (Puebla), at about 2,000 m (holotype in the herbarium of the Universidad Veracruzana, isotypes at ENCB, FI, MEXU and NAP). The World List of Cycads gives 1995 as the year of publication in its data export, but the article, IPNI and volume 32 of Brittonia all date from 1980.

The history of the name explains the confusion. In 1909 Joseph Nelson Rose described Dioon purpusii from plants in the Tomellín canyon, in Oaxaca, and attached to it the seeds and cone scales collected in 1908 by Carl Albert Purpus in the Sierra Mixteca of Puebla. Purpus’s specimens, collected in 1907 and 1908 near San Luis Tultitlanapa and distributed to many herbaria as Dioon purpusii, proved very different from Rose’s type. J. Schuster, in 1932, even described Dioon purpusii mainly from these collections. Vázquez Torres went back to the site and collected new material, whose study led to the description of a new species.

Gregory and co-authors (2003) consider that Dioon caputoi is not close to any other species of the canyons draining to the Gulf of Mexico and rather shares some characters with populations of the Pacific-facing río Balsas basin. Gutiérrez-Ortega and co-authors (2021) nevertheless place it in the “Purpusii clade”, with Dioon purpusii, Dioon argenteum, Dioon califanoi and Dioon planifolium among others, on the basis of the phylogenies published in 2018.

Etymology and history

The species is named after Giuseppe Caputo (1926–2013), professor of botany and director of the Institute and Botanic Garden of the University of Naples, as the original description and Haynes (2022) state. The first name “Ugo” given on some websites is wrong.

The first collections date from 1907 and 1908 and are due to Carl Albert Purpus, one of the leading plant collectors in Mexico at the turn of the twentieth century. After the rediscovery of 1978, a male plant collected near San Luis Atolotitlán was established in the Naples botanic garden, according to the authors. Seeds long remained unobtainable in the trade: the San Diego nursery Jungle Music wrote in 2024 that local people prohibited viewing the plants or collecting seeds, and that seeds only became available about twenty years earlier. On the French Fous de palmiers forum, a grower reported in December 2012 the first offer of seeds he had seen from a specialist seed merchant. In 2022, Nong Nooch Tropical Botanical Garden, in Thailand, reported that seed-grown plants had produced cones there in less than ten years.

Common names

No English common name is attested. The original description gives “palma real” as the local name, also used by Species+, by the Enciclovida database of CONABIO, by the Mexican standard NOM-059 and by a conservation project funded by the Rufford Foundation in 2011. The same name is applied to other Dioon of Oaxaca, such as Dioon purpusii and Dioon argenteum. The English names “Caputo’s cycad” and “Caputo’s dioon” are not supported by any reference source.

In the wild

Dioon caputoi grows on the border between southern Puebla and northern Oaxaca, in the Sierra de Zapotitlán, south of Tehuacán. In 1980 the authors described a population made up of two small groups of at most 50 plants, scattered over a very steep, open slope of about 1 km², on limestone with a very poor soil. The habitat is a transition between tropical dry forest and oak woodland; seedlings are very rare there. Gregory and co-authors (2003) add that this high desert, covered mainly by thorny vegetation and succulents, offers the species a suitable habitat only in the remnants of oak woodland on the highest points.

The climate is semi-arid: an ethnobotanical review of 2019 gives about 300 mm of rain a year, citing Gutiérrez-Ortega and co-authors (2018). The site lies 90 km in a straight line from the populations of Dioon purpusii at Santa Catarina and 70 km from those of Dioon califanoi, between Teotitlán and Huautla.

Other localities have been found since: in 2008, Cabrera-Toledo, González-Astorga and Vovides counted four populations of 50 to 120 individuals, mostly adults, all within the Tehuacán-Cuicatlán Biosphere Reserve and spread over less than 10 km, the smallest range of any Dioon.

The male cones host a small pollen-eating beetle, Pharaxonotha bicolor, collected in particular at Coatepec (Puebla) at about 1,840 m, together with a weevil, Parallocorynus bicolor (Skelley and co-authors, 2022). Their exact role in the pollination of the species has not been demonstrated.

Conservation status and regulation

Dioon caputoi is listed as Endangered (EN) on the IUCN Red List under criterion A2acd. The assessment, by J. Chemnick and T. Gregory, is dated 3 December 2020 and was published in 2022 (The World List of Cycads, GBIF and Crossref); the criterion refers to a past population decline estimated from observation, loss of habitat and exploitation. The IUCN cycad action plan (Donaldson, 2003) then listed it as Critically Endangered (CR), with 200 to 400 plants, a high rate of decline and its presence in a protected area. The higher figures (2,000 to 2,500 adults) that circulate online have not been found in any verifiable source.

The documented threats are illegal trade, reported “for several decades” in a 2011 research project, and changes in land use. This project describes populations made up mostly of adults, with few juveniles and seedlings, the latter being the easiest to dig up. On the genetic side, Cabrera-Toledo and co-authors (2010) find lower diversity in Dioon caputoi than in Dioon merolae and attribute its rarity to relatively recent local ecological factors.

The species is listed in CITES Appendix II, with annotation #4, which exempts seeds in particular, and in Annex B of the European Union regulation (Regulation (EU) 2026/1383, in force since 29 June 2026), according to Species+. In Mexico, Enciclovida lists it as “en peligro de extinción” (category P) under the standard NOM-059-SEMARNAT-2010, a category confirmed by the text published in the Diario Oficial de la Federación on 30 December 2010. Any plant bought must be seed-grown in cultivation and come with the required documents. Databases checked on 26 October 2026: check the regulations in force.

Growing Dioon caputoi

Cultivation data are very thin: the species is known to grow in full sun in a dry, limestone habitat, but no trial is documented in Europe. Jungle Music, in San Diego, described it in 2024 as a full-sun species for most areas. Its native habitat, with low rainfall and very poor, free-draining soil, calls for a mineral mix and careful watering, without standing water.

Outdoor and in-ground cultivation

A tropical botanic garden adds a nuance: at Nong Nooch, in Thailand, in a hot and very wet climate, the Dioon seem to cope with excess rain and humidity, and Dioon caputoi has coned there in less than ten years from seed (Lindstrom, 2022). This tolerance does not extend to a cold, wet winter. In Mediterranean-type climates, a sunny slope or raised bed of mineral soil follows the logic of its habitat; no such trial has been published.

Container cultivation

A contributor to the Italian Tropicamente forum considered in March 2009 that his plant grew faster than Dioon edule and was starting to produce offsets; he gave no location, age or growing conditions. Until its cold tolerance is known, a pot with a very free-draining mix, kept frost-free and dry in winter, remains the prudent option.

In cultivation in the UK, US and Australia

  • United Kingdom: no British garden declares the species to BGCI PlantSearch, and no cultivation is documented.
  • United States: the Montgomery Botanical Center (Coral Gables, Florida) lists three accessions in its online catalogue, two of them from 2004 (20040522 and 20041201), and the Fairchild Tropical Botanic Garden (Miami) lists the species in its online catalogue. BGCI PlantSearch also lists Lotusland, the Huntington, San Diego Botanic Garden, Moore Farms Botanical Garden and the botanic garden of the University of Hawaii at Hilo. A BGCI listing is a declaration by the garden, not proof that the plant is alive today.
  • Australia: no Australian garden declares the species to BGCI.

Propagation

The species is propagated from seed, and germination seems erratic. On the French Fous de palmiers forum, a grower in the Gard reported in February 2013 that 3 seeds out of 10 had germinated and the others had rotted; another French grower reported a similar result with seeds bought at the same time from the same merchant, without knowing whether too much water during germination was to blame. These two trials concern seeds of the same origin and cannot be generalised. Separation of offsets has not been described.

Pests and diseases

No disease specific to Dioon caputoi is documented in cultivation. The 1980 description mentions plants “threatened by worms” in the wild, without saying which. The cones host specialised insects, such as Pharaxonotha bicolor and the weevil Parallocorynus bicolor. In cultivation, the main risk for a species from a dry habitat remains root rot in a mix that stays too wet.

Cold hardiness

No dated observation of the cold tolerance of Dioon caputoi has been published. The only figures available come from nurseries and amateurs, without place or precise episode.

Mediterranean and European experience

No report of Dioon caputoi grown in the ground or in a pot is documented in France or Italy. The French Fous de palmiers forum contains only discussions about buying and germinating seeds, and the Italian contributor quoted above considers the species hardier than Dioon edule, without giving any temperature. Without data, no climate can be recommended for planting out; a pot sheltered from frost and rain in winter is the prudent solution.

United Kingdom, United States and Australia

No dated report from a British, American or Australian grower has been found. The San Diego nursery Jungle Music claims a cold hardiness of “about 20 degrees F”, about −7 °C; this is a nursery’s assessment. The altitude of its habitat, at about 2,000 m, suggests that the species experiences cool nights, but no temperature records from its sites are documented.

Toxicity and precautions

No toxicity data have been published for Dioon caputoi. 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 caputoi has been documented. The 2011 research project aims, on the contrary, to encourage seed collection, sowing and the sale of cultivated plants by the communities of the reserve, to reduce collecting from the wild.

Frequently asked questions

How can Dioon caputoi be recognised?

By its very narrow leaflets, 4 to 5 mm wide, evenly spaced along the whole length of the leaf. The leaves are flat and about 75 to 90 cm long. No other Dioon of Oaxaca or Puebla combines such fine and widely spaced leaflets.

What is the difference from Dioon purpusii?

It lies in the leaves and leaflets. Dioon purpusii has keeled leaves and leaflets 8 to 10 mm wide, crowded in the upper part of the leaf; Dioon caputoi has flat leaves and leaflets 4 to 5 mm wide, evenly spaced. The two species were confused until 1980.

Is Dioon caputoi hardy?

Nobody knows. No dated trial has been published. A Californian nursery claims about −7 °C (20 °F), without details. Until observations are available, grow it in a pot and protect it from frost and rain in winter.

Why is it so rare?

Because its range is tiny and its populations are small. In 1980 no more than about a hundred plants were known, over 1 km²; in 2003 the IUCN estimated 200 to 400. Illegal trade and changes in land use have reduced the number of young plants, and seeds long remained unobtainable.

Is it protected?

Yes. It is listed as Endangered by the IUCN (2022), in CITES Appendix II and in Annex B in the European Union, and it is protected in Mexico. Buy only seed-grown plants, with the required documents.

Do the seeds germinate easily?

Not always. Two French growers obtained only about 3 germinations out of 10 seeds of the same origin in 2013. Seeds sold under this name have also turned out to belong to another species: buy them from a reliable supplier.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Rose, J.N. (1909). Cycadaceae. A new species of Dioon. In: Studies of Mexican and Central American plants. Contributions from the United States National Herbarium 12(7): 260–261. [Description of Dioon purpusii, including Purpus’s 1908 collections; full text on archive.org.]
  • De Luca, P., Sabato, S. & Vázquez Torres, M. (1980). Dioon caputoi (Zamiaceae), a new species from Mexico. Brittonia 32(1): 43–46. doi:10.2307/2806216 [Protologue: description, history of the collections, population, local name, dedication.]
  • Donaldson, J.S. (ed.) (2003). Cycads. Status Survey and Conservation Action Plan. IUCN/SSC Cycad Specialist Group, Gland and Cambridge. [CR status, 200 to 400 plants (table 6.1).]
  • Gregory, T.J., Chemnick, J., Salas-Morales, S. & Vovides, A.P. (2003). A new species in the genus Dioon (Zamiaceae) from north-central Oaxaca, Mexico. Botanical Journal of the Linnean Society 141(4): 471–476. doi:10.1046/j.1095-8339.2003.t01-1-00151.x [Position of Dioon caputoi and its habitat.]
  • Gregory, T., Haynes, J. & Chemnick, J. (2008). Key to the species of Dioon. The Cycad Newsletter 31: 16–17. [Identification key.]
  • Cabrera-Toledo, D., González-Astorga, J. & Vovides, A.P. (2008). Heterozygote excess in ancient populations of the critically endangered Dioon caputoi (Zamiaceae, Cycadales) from central Mexico. Botanical Journal of the Linnean Society 158(3): 436–447. doi:10.1111/j.1095-8339.2008.00868.x [Four populations of 50 to 120 individuals over less than 10 km, heterozygote excess; abstract (OpenAlex).]
  • Cabrera-Toledo, D., González-Astorga, J., Nicolalde-Morejón, F., Vergara-Silva, F. & Vovides, A.P. (2010). Allozyme diversity levels in two congeneric Dioon spp. (Zamiaceae, Cycadales) with contrasting rarities. Plant Systematics and Evolution 290: 115–125. doi:10.1007/s00606-010-0354-6 [Genetic diversity compared with Dioon merolae; abstract (FAO AGRIS).]
  • Bonta, M., Pulido, M.T., Diego Vargas, T., Vite Reyes, A., Vovides, A.P. & Cibrián-Jaramillo, A. (2019). Ethnobotany of Mexican and northern Central American cycads (Zamiaceae). Journal of Ethnobiology and Ethnomedicine 15: 4. doi:10.1186/s13002-018-0282-z [Altitude and rainfall of the habitat.]
  • 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. Phytotaxa 528(2): 93–110. doi:10.11646/phytotaxa.528.2.3 [Purpusii clade and key (Plazi).]
  • Skelley, P.E., Tang, W. & Pérez-Farrera, M.A. (2022). Review of Pharaxonotha Reitter inhabiting the cycad genus Dioon Lindl., with descriptions of nine new species. Insecta Mundi 0908: 1–21. [Insects of the male cones.]
  • Chemnick, J. & Gregory, T. (2022). Dioon caputoi. The IUCN Red List of Threatened Species 2022: e.T42106A69831511. doi:10.2305/IUCN.UK.2022-1.RLTS.T42106A69831511.en [Category EN A2acd; reference taken from The World List of Cycads and checked on Crossref.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Dedicatee and dates, as given by The World List of Cycads.]
  • Lindstrom, A. (2022). The cycad collection at Nong Nooch Tropical Botanical Garden, Thailand. CYCADS 6(1). [Cones on seed-grown plants.]
  • 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 caputoi.]
  • 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.]