Zamia inermis

Zamia inermis is a cycad endemic to central Veracruz, in eastern Mexico, known from a single wild population made up of three small subpopulations in seasonally dry tropical forest. This species of the genus Zamia, described in 1983 by Andrew P. Vovides, J.D. Rees and Mario Vázquez Torres in the Flora de Veracruz, owes its name, “unarmed”, to its petiole and rachis without prickles, a rarity in the genus. The IUCN rates it Critically Endangered, and the specialists who studied its last population in 2017 call it the most threatened cycad in Mexico. It should not be confused with Cycas inermis, an unrelated Vietnamese cycad that shares the same epithet.

Key facts about Zamia inermis

  • Accepted name: Zamia inermis Vovides, J.D.Rees & Vázq.Torres (1983), accepted by The World List of Cycads (version 2026.08.15) and by GBIF; POWO could not be consulted directly
  • Former names and synonyms: none
  • Family: Zamiaceae, order Cycadales
  • Common names: no name attested, in English or in Spanish
  • Natural range: Mexico, central Veracruz; a single wild population of three subpopulations, in the Sierra de Manuel Díaz at Monzomboa, between 150 and 300 m above sea level
  • IUCN status: Critically Endangered (CR A2acd+4acd; B1ab(i,ii,iii,v)), 2022 assessment; listed as endangered (P) under the Mexican standard NOM-059-SEMARNAT-2010
  • CITES and other protection: CITES Appendix II (whole genus, since 1977; seeds exempt under annotation #4); Annex B in the European Union
  • Documented hardiness: no dated record; commercial estimates diverge (see Cold hardiness)
  • Light and soil: in the wild, seasonally dry tropical forest, now fragmented and surrounded by grassland; in cultivation, a free-draining compost kept fairly dry in winter is advised for its group
  • Habit and adult size: stem partly above ground, sometimes with several heads; leaves without prickles, with many narrow, entire leaflets about 25 cm long (nursery description)
  • In the UK, US and Australia: Glasgow Botanic Gardens (BGCI); 15 American gardens, including Montgomery Botanical Center (nine accession numbers), Fairchild, Huntington, Lotusland and San Diego Botanic Garden; Royal Botanic Garden Sydney
  • Toxicity: no data specific to the species; treat it as poisonous, like all cycads (see Toxicity and precautions)

How to recognise Zamia inermis

The decisive character is in the name: the petiole and rachis are completely free of prickles, whereas most Zamia carry them (Haynes, 2022, as given by The World List of Cycads). In their survey of the Zamia of “Mega-Mexico”, Nicolalde-Morejón and colleagues (2011) place it, with Zamia tuerckheimii of Guatemala and Zamia soconuscensis of Chiapas, among the species with above-ground stems and leaflets with entire margins; they add that its linear-lanceolate, leathery, entire leaflets mean that herbarium specimens, which usually lack cones, could be mistaken for Zamia encephalartoides.

The American nursery Jungle Music describes it as a small to medium-sized cycad whose stems can reach about 3 ft (90 cm), with a good number of green leaves 2 to 4 ft (60 cm to 1.2 m) long, paired, narrow leaflets about 10 in (25 cm) long with smooth edges, and light-coloured male and female cones. The same nursery notes that seedlings have toothed leaflets, a character lost as the plant matures. These figures come from a nursery, not from the original description.

On the French Fous de palmiers forum, a grower noted in February 2015 that Zamia inermis forms several heads on a kind of platform while keeping a single root system, which makes it harder to divide than a suckering plant.

Hybrids

No natural hybrid is documented: the only wild population is isolated from other Zamia. In cultivation, the online catalogue of Montgomery Botanical Center lists, alongside its Zamia inermis, an entry recorded as a hybrid involving Zamia vazquezii (accession of 2017), without further detail.

Possible confusion

The absence of prickles on the petiole and rachis, together with the linear-lanceolate, entire leaflets, separates it from most Mexican Zamia:

  • Zamia fischeri, of the Sierra Madre Oriental, also has an unarmed petiole, but it is a much smaller plant with an underground stem and small, strongly toothed leaflets;
  • Zamia vazquezii, the other small Zamia endemic to Veracruz and a close relative, has an underground stem and broad, toothed leaflets;
  • Zamia furfuracea, also from Veracruz but from dunes and coastal areas, has thick, leathery leaflets covered in scurfy down: no confusion is possible;
  • Zamia loddigesii, found in several Mexican states including Veracruz, usually has prickles on the petiole and rachis;
  • Zamia encephalartoides, of Colombia, whose narrow, leathery, entire leaflets can make sterile herbarium specimens look alike (Nicolalde-Morejón and colleagues, 2011);
  • Cycas inermis, a Vietnamese cycad of another family that merely shares the epithet: a search for “inermis” among cycads brings up both.

Taxonomy

Zamia inermis is an accepted name according to The World List of Cycads and GBIF; POWO could not be consulted directly. The species was described in 1983 by Andrew P. Vovides, J.D. Rees and Mario Vázquez Torres in fascicle 26 (Zamiaceae) of the Flora de Veracruz, pages 22 to 24, figure 3. The type is the collection A. Vovides 666, made in Veracruz on 6 June 1981; the holotype is kept at the herbarium of the Instituto de Ecología in Xalapa (XAL), with an isotype at the Field Museum (F) (Nicolalde-Morejón and colleagues, 2011). The name has never changed and has no synonym.

Relationships. The transcriptome phylogeny of Lindstrom and colleagues (2024), which included a sample from Veracruz, strongly supports a distinct Fischeri clade made up of Zamia vazquezii, Zamia fischeri and Zamia inermis, first recognised by Calonje and colleagues (2019); most of its analyses place this clade as sister to the Caribbean Zamia rather than to the other mainland species, as the 2019 study had found. The species of this clade also have some of the smallest genome sizes in the genus. Gómez Díaz (2025), following Calonje and colleagues (2019), stresses that the possible extinction of Zamia inermis and Zamia vazquezii would threaten an entire evolutionary lineage.

Etymology and history

The epithet comes from the Latin inermis, “unarmed”, a reference to the petiole and rachis without prickles (Haynes, 2022, as given by The World List of Cycads).

According to Octavio-Aguilar and colleagues (2017, Cuadernos de Biodiversidad), the species was discovered in 1973 on private land and only formally described in 1983; by then hundreds, perhaps thousands, of plants had already been removed for the ornamental trade, mainly in the 1970s and 1980s. In 1998 Sosa, Vovides and Castillo-Campos, who searched again for six endemic plants of Veracruz feared extinct, found it in fragments of tropical and dry forest, but saw no juvenile plants. Local people now raise the species from seed in backyard nurseries, and viable seed obtained by hand pollination has produced adult plants in several nurseries.

Common names

No common name is attested for this species, in English or in Spanish.

In the wild

Zamia inermis is known from a single wild population of three subpopulations. According to Octavio-Aguilar and colleagues (2017, Cuadernos de Biodiversidad), repeated surveys of the Sierra de Manuel Díaz, at Monzomboa in Veracruz, located them over less than 2.5 km², with 654 plants in all, most of them non-reproductive adults; the genetic study by the same team gives an area of less than 10 km² and recalls the 75 per cent decline over fifty years on which the IUCN listing is based (Iglesias-Andreu and colleagues, 2017). Gómez Díaz (2025) gives an extent of occurrence of 50 km², a single location and municipality, 74 per cent loss of suitable habitat and no part of its range inside a protected area. The same authors estimate the present population at 300 to 700 individuals.

Habitat. It grows in tropical deciduous forest (Nicolalde-Morejón and colleagues, 2011), between 150 and 300 m above sea level, in the Gulf of Mexico biogeographic province (Nicolalde-Morejón and colleagues, 2014), now reduced to fragments of seasonally dry forest within grassland (Octavio-Aguilar and colleagues, 2017). Jungle Music adds, without giving a source, that it grows under trees in dry, poor soil. Like all cycads, it forms coralloid roots that host nitrogen-fixing cyanobacteria.

Reproduction and decline. The demographic study confirms that the population is declining (growth rate λ = 0.963 ± 0.011): there are few juveniles, no seedling survived in the field, and the female cones produce few viable seeds (Octavio-Aguilar and colleagues, 2017, Biodiversity and Conservation). The natural pollinator is a beetle, but none has been found in the male cones of the population, and agrochemicals sprayed on neighbouring land kill pollinators. Over eleven years about 20 per cent of the plants, male and female, produced cones, but most seeds are infertile; the germination rate of seed collected on site has fallen from 100 per cent to 10 per cent in twenty years. The few seedlings grow within 3 m of a male plant and almost all die before they are a year old, which the authors read as a sign that pollen is scarce or unavailable; they estimate that the species could disappear from the wild within 70 years (Octavio-Aguilar and colleagues, 2017, Cuadernos de Biodiversidad).

Conservation status and regulation

Zamia inermis is rated Critically Endangered (CR) on the IUCN Red List under criteria A2acd+4acd; B1ab(i,ii,iii,v), in the 2022 assessment by J.D. Bösenberg (category and criteria from The World List of Cycads, author and reference checked on Crossref; GBIF gives the same category; the Red List itself could not be consulted). The species already appeared as Critically Endangered on the Red List consulted in 2016 by Octavio-Aguilar and colleagues; the previous assessment, by Andrew Vovides, Jeff Chemnick and Tim Gregory, dates from 2010. The criteria reflect a severe observed and projected reduction of the population and a tiny range in which the habitat is deteriorating. In Mexico, the species is listed as endangered (category P) under the standard NOM-059-SEMARNAT-2010 (Gómez Díaz, 2025).

The threats named by the specialists are the agricultural use of the land on which the plants grow, the loss of the pollinator to pesticides and other agrochemicals used nearby, and past collecting for the ornamental trade. Internal factors add to them: poor natural regeneration and very low genetic diversity. The genetic study measured an observed heterozygosity of 0.151, the lowest genetic diversity reported for any Mexican cycad, and showed that an ex situ population established five years earlier by a local community in a rural nursery was genetically much less varied than the wild population, because the seed collected to found it did not represent the diversity of the species (Iglesias-Andreu and colleagues, 2017). The authors recommend hand pollination, in vitro propagation and assisted germination, and either moving most plants to protected sites shared with other cycads that still have healthy pollinator populations, or creating a protected area on the property (Octavio-Aguilar and colleagues, 2017). Gómez Díaz (2025), who ranks it second only to Zamia vazquezii among the cycads of Veracruz at risk of extinction, suggests moving the most threatened Zamia to CITES Appendix I.

Like all Zamia except Zamia restrepoi, which is in Appendix I, Zamia inermis is currently covered by the listing of the genus in CITES Appendix II, in force since 4 February 1977. Annotation #4 exempts in particular seeds, pollen, seedlings or tissue cultures obtained in vitro and transported in sterile containers, and cut flowers of artificially propagated plants; international trade in the plants themselves requires an export permit. In the European Union the species falls under Annex B of Regulation (EC) No 338/97, whose current list is set by Regulation (EU) 2026/1383, applicable since 29 June 2026.

This general information does not replace the official texts: check the regulations in force before buying or exchanging plants or seeds, ask the seller for proof of origin and buy only plants raised from cultivated seed.

Growing Zamia inermis

Zamia inermis is grown in a good number of botanical gardens and by specialist collectors, and the American nursery Jungle Music calls it an excellent growing cycad. No growing guide based on trials has been published; the pointers below come from nurseries and from its natural habitat, and should be read as such.

Simon Lavaud, of the French specialist nursery Cycadales.eu, places it among the Zamia of Mexico and northern Central America, which he rates of medium difficulty, most of them being used to a marked dry season (Lavaud, 2023). For this group he recommends:

  • a free-draining compost, neutral or slightly alkaline; any kind of water;
  • in winter, 5 to 10 °C (41 to 50 °F), with daytime rises to 20 to 25 °C (68 to 77 °F), and a compost kept fairly dry but never parched;
  • in summer, 15 to 20 °C (59 to 68 °F) at night and 25 to 30 °C (77 to 86 °F) by day, and at least four to six months of summer temperatures a year.

These are recommendations for a group of species, not measurements made on Zamia inermis.

Outdoor and in-ground cultivation

Jungle Music suggests part-day sun in gardens, or perhaps full sun near the coast. In-ground planting is only conceivable in a climate without significant frost; BGCI lists the species in several gardens of coastal southern California and southern Florida, but does not say whether these plants are outdoors.

Container cultivation

In temperate climates it is a plant for a pot kept frost-free in winter, in a cool glasshouse or a bright room, in a very free-draining compost watered generously in the warm season and sparingly in winter, as Lavaud (2023) advises for its group. Its moderate size suits container growing.

In cultivation in the UK, US and Australia

In short: widely held in American gardens, declared by one Scottish garden and by Sydney.

  • United States: Montgomery Botanical Center (Coral Gables, Florida) lists nine accession numbers in its online catalogue, four older numbers and five from 2001 to 2006 (20010058, 20020021, 20020052, 20020622, 20060648). BGCI also records the species at Fairchild Tropical Botanic Garden (Miami), Naples Botanical Garden and Marie Selby Botanical Gardens (Sarasota) in Florida; the Huntington (San Marino), Ganna Walska Lotusland (Santa Barbara), San Diego Botanic Garden (Encinitas), San Diego Zoo and the University of California Botanical Garden at Berkeley in California; Missouri Botanical Garden (St Louis), the New York Botanical Garden, Mercer Arboretum and Botanic Gardens and the John Fairey Garden in Texas, and the University of Hawaii at Hilo and the National Tropical Botanical Garden in Hawaii (queried on 25 October 2026).
  • United Kingdom: Glasgow Botanic Gardens declares it to BGCI; no other British record.
  • Australia: the Royal Botanic Garden Sydney lists it in its online catalogue (Garden Explorer, updated on 1 October 2026) and declares it to BGCI.

Elsewhere in Europe, the Orto Botanico di Napoli offered material of the species in its Index Seminum 2012–2013 (IPEN number XX-0-NAP-1720), from its Califano glasshouses; BGCI also lists the botanic gardens of Ghent, Prague and Teplice. A BGCI declaration shows that a garden held the plant at some point, not that it is alive there today, and the sources rarely say whether the plants are outdoors or under glass.

Propagation

The species is propagated from seed. It has separate male and female plants, so adults of both sexes and, in cultivation, hand pollination are needed. Hand pollination, with pollen suspended in water and injected into the female cone, or dry pollen blown onto receptive cones with compressed air, has proved effective in botanical gardens and private collections; it is practised at the Clavijero Botanical Garden in Xalapa (Octavio-Aguilar and colleagues, 2017, Cuadernos de Biodiversidad). In the backyard nurseries of the region, by contrast, only 92 of 954 seeds had reached the juvenile stage (Octavio-Aguilar and colleagues, 2017, Biodiversity and Conservation). Clean off the fleshy seed coat wearing gloves and sow fresh seed in a free-draining compost, moist but not wet, in warmth.

Plants grown for conservation should come from parents of known, varied origin: the genetic study showed how easily a nursery population can lose diversity. Gómez Díaz (2025) also warns that ex situ propagation must not harm the wild population, for example by removing male cones that serve as pollinator breeding sites for artificial pollination.

Pests and diseases

No pest or disease specific to the species is documented. The risks are those of cultivated cycads: scale insects, and root and stem rot in a compost that stays too wet, which Lavaud (2023) suggests preventing by keeping the compost fairly dry in winter.

Cold hardiness

No dated cold record has been published for Zamia inermis, and the commercial estimates diverge. The American nursery Jungle Music believes that its hardiness “appears to be into the mid to low twenties F”, that is roughly −7 to −4 °C (20 to 25 °F), and suggests, from a native range lying further north than that of Zamia furfuracea, that it might take colder weather than that species; this is the nursery’s inference, not an observation. The British nursery Trebrown places it in USDA zone 10a, which implies much less frost tolerance. Both are commercial classifications.

Mediterranean and European experience

No in-ground planting has been reported in France or elsewhere in Europe, and no dated frost episode concerns the species. The French growers who mention it on the Fous de palmiers forum (2010, 2015) keep it in their collections without cold data, and the plants at Naples were grown in a glasshouse. For readers in Mediterranean-type climates such as California or southern Australia, it is a candidate for a sheltered, frost-free spot rather than a proven outdoor plant.

United Kingdom, United States and Australia

No cold record exists. In the US it is held by several gardens of coastal southern California and southern Florida, but without information on whether the plants are outdoors or how they behave in cold spells. In the UK it needs a frost-free glasshouse; BGCI does not say how Glasgow, the only British garden to declare it, grows its plant.

Toxicity and precautions

No toxicity study specific to Zamia inermis has been published. The risk is, however, well documented in cycads: Zamia contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived, a compound toxic to the liver and nervous system, and the ASPCA cites cycasin and BMAA, a neurotoxic amino acid, for Zamia furfuracea, which it lists as toxic to dogs, cats and horses; the seeds are the most dangerous part. In the absence of evidence to the contrary, treat the plant as poisonous: keep seeds and leaves out of reach of children and animals, and wear gloves to clean seeds. If any part is swallowed, contact a poison centre, a doctor or a vet straight away.

Traditional uses

No traditional use is documented for this species. Its interest today is ornamental and, above all, for conservation: plants in the trade should come only from cultivated seed of verified origin.

Frequently asked questions

Why is it called “inermis”?

Because it is “unarmed”: in Latin inermis means “without weapons”, and its petiole and rachis have no prickles, unlike those of most Zamia.

Is Zamia inermis the same plant as Cycas inermis?

No. Cycas inermis is a Vietnamese cycad of the family Cycadaceae, described by Loureiro in a work dated 1790; Zamia inermis is a Mexican species of the family Zamiaceae described in 1983. They simply share an epithet meaning “unarmed”.

How can it be told from Zamia fischeri, which also lacks prickles?

By size and leaflets. Zamia fischeri is much smaller, with an underground stem and small, strongly toothed leaflets; Zamia inermis has a stem partly above ground and long, narrow leaflets with entire margins. The two species also grow in different regions.

Where does it grow in the wild?

Only in central Veracruz, Mexico, in a single population of three subpopulations in the Sierra de Manuel Díaz, between 150 and 300 m, in fragments of seasonally dry forest.

Why is it so threatened?

Because of its tiny range, the agricultural use of its habitat, the loss of its pollinator to agrochemicals, past collecting for the trade, almost no natural regeneration and very low genetic diversity. Its authors estimate that it could disappear from the wild within 70 years.

Is it hardy?

Not reliably. No dated record exists; one American nursery suggests it may tolerate about −4 to −7 °C (20 to 25 °F), while a British nursery rates it zone 10a. Keep it frost-free until trials are published.

Is it easy to grow?

Reasonably, according to nurseries: Jungle Music calls it an excellent growing cycad, and Cycadales.eu rates its group of medium difficulty. The difficulty lies rather in obtaining plants of legal, cultivated origin.

Are the seeds poisonous?

Yes. As in all cycads, the seeds contain dangerous toxins; handle them with gloves and keep them out of reach of children and animals.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Vovides, A.P., Rees, J.D. & Vázquez Torres, M. (1983). Zamiaceae. Flora de Veracruz 26: 22–24, fig. 3. Instituto Nacional de Investigaciones sobre Recursos Bióticos, Xalapa. [Original description; reference given by The World List of Cycads, text not consulted.]
  • Octavio-Aguilar, P., Iglesias-Andreu, L.G., Vovides, A.P. & Rivera-Fernández, A. (2017). Zamia inermis, la cícada más amenazada de México. Cuadernos de Biodiversidad 52: 1–5. https://doi.org/10.14198/cdbio.2017.52.01 [Synthesis by the authors of the 2017 studies; full text read (open access).]
  • Octavio-Aguilar, P., Rivera-Fernández, A., Iglesias-Andreu, L.G., Vovides, A.P. & Núñez de Cáceres-González, F.F. (2017). Extinction risk of Zamia inermis: a demographic study in its single natural population. Biodiversity and Conservation 26(4): 787–800. https://doi.org/10.1007/s10531-016-1270-z [Demographic study; abstract read, reference checked on Crossref.]
  • Iglesias-Andreu, L.G., Octavio-Aguilar, P., Vovides, A.P., Meerow, A.W., de Cáceres-González, F.N. & Galván-Hernández, D.M. (2017). Extinction risk of Zamia inermis (Zamiaceae): a genetic approach for the conservation of its single natural population. International Journal of Plant Sciences 178(9): 715–723. https://doi.org/10.1086/694080 [Genetic study; abstract read, reference checked on Crossref.]
  • Sosa, V., Vovides, A.P. & Castillo-Campos, G. (1998). Monitoring endemic plant extinction in Veracruz, Mexico. Biodiversity and Conservation 7(11): 1521–1527. https://doi.org/10.1023/A:1008809332490 [Field search for endemic species; abstract read.]
  • 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 [Full text read.]
  • Nicolalde-Morejón, F., González-Astorga, J., Vergara-Silva, F. & Vovides, A.P. (2011). Perspectivas sistemáticas de Zamia (Zamiaceae) en Megaméxico: de la taxonomía alfa a los códigos de barras genéticos. Revista Mexicana de Biodiversidad 82(2): 341–355. [Regional systematic survey; read.]
  • Nicolalde-Morejón, F., González-Astorga, J., Vergara-Silva, F., Stevenson, D.W., Rojas-Soto, O. & Medina-Villarreal, A. (2014). Biodiversidad de Zamiaceae en México. Revista Mexicana de Biodiversidad, suppl. 85: S114–S125. https://doi.org/10.7550/rmb.38114 [National inventory of Zamiaceae; full text read.]
  • Lindstrom, A., Habib, S., Dong, S., Gong, Y., Liu, J., Calonje, M., Stevenson, D. & Zhang, S. (2024). Transcriptome sequencing data provide a solid base to understand the phylogenetic relationships, biogeography and reticulated evolution of the genus Zamia L. (Cycadales: Zamiaceae). Annals of Botany 134(5): 747–768. https://doi.org/10.1093/aob/mcae065 [Sample from Veracruz; Fischeri clade; full text consulted.]
  • Bösenberg, J.D. (2022). Zamia inermis. The IUCN Red List of Threatened Species 2022: e.T42111A69833031. https://doi.org/10.2305/IUCN.UK.2022-1.RLTS.T42111A69833031.en [CR assessment; reference checked on Crossref, category and criteria confirmed by The World List of Cycads; Red List page not consulted.]
  • Vovides, A., Chemnick, J. & Gregory, T. (2010). Zamia inermis. The IUCN Red List of Threatened Species 2010: e.T42111A10649971. https://doi.org/10.2305/IUCN.UK.2010-3.RLTS.T42111A10649971.en [Previous assessment; reference checked on Crossref, not consulted.]
  • 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; not consulted directly.]
  • 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; consulted directly.]