Cycas hainanensis

Cycas hainanensis is a cycad with an aerial trunk from Hainan Island in southern China, where it grows mainly in the humid forests of the east and centre of the island. Described in 1975 and still accepted as a species in Ken Hill’s 2008 revision, this member of the genus Cycas is now treated by The World List of Cycads, the reference checklist for cycads, as a synonym of Cycas taiwaniana: botanically, that is the name to use. The name Cycas hainanensis nevertheless remains in wide use, in the Flora of China, in the CITES database, in Chinese publications and among collectors and botanic gardens, so this page describes the Hainan plant as it was defined under that name and explains the debate over its classification.

Key facts about Cycas hainanensis

  • Name: Cycas hainanensis C.J.Chen (1975); a synonym of Cycas taiwaniana Carruth. for The World List of Cycads (version 2026.08.15); a distinct species for the Flora of China (1999) and for Hill (2008); the World Checklist of Vascular Plants (WCVP), on which POWO is based, treats it as a synonym of Cycas taiwaniana (consulted through GBIF on 31 October 2026)
  • Synonyms: Cycas lingshuiensis G.A.Fu (2004, published with the spelling “lingshuigensis”), which Hill (2008) placed under Cycas hainanensis
  • Family: Cycadaceae, order Cycadales; section Stangerioides according to Hill (2008)
  • Common names: no English name attested; in Chinese 海南苏铁 (hai nan su tie, “Hainan cycad”), also ci-bing su-tie and feng-huang-dan
  • Natural range: China, Hainan Island
  • IUCN status: Endangered (EN); the Red List now places this name under Cycas taiwaniana, assessed as EN in the reassessment published in version 2023-1; Hill (2008) already gave EN for Cycas hainanensis (see Conservation status)
  • CITES and other protection: CITES Appendix II; Annex B in the European Union; first-class state protection in China for all Cycas
  • Documented hardiness: a single report, from Brittany (France): plant defoliated, trunk apparently sound, after a minimum of −5 °C (23 °F) in the winter of 2011–2012 (see Cold hardiness)
  • Light and soil: in the wild, humid forest and open scrub, on soils derived from limestone or volcanic rock
  • Habit and adult size: trunk usually up to 1.5 m (rarely 2.5 to 3.5 m), 30 to 40 cm across and swollen at the base; 50 to 80 leaves 1 to 2.2 m long
  • In the UK, US and Australia: Montgomery Botanical Center (three accessions under this name); Royal Botanic Garden Sydney (under Cycas taiwaniana, one plant of wild origin); six other American gardens and Cairns in BGCI PlantSearch; no British record under this name
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas hainanensis

This is a cycad with a true aerial trunk, swollen at the base, carrying a large crown of 50 to 80 glossy leaves with narrow leaflets; female plants have megasporophylls with a deeply comb-like blade. The Flora of China (1999) describes it as follows:

  • Trunk: up to 1.5 m (rarely 2.5 m) and about 40 cm in diameter, swollen towards the base; bark dark grey and scaly near the top, greyish white and almost smooth lower down.
  • Leaves: 50 to 80, pinnate, 1 to 2.2 m by 30 to 50 cm, with a flat blade; petiole diamond-shaped in section, 20 to 70 cm, armed with 50 to 80 spines on each side.
  • Leaflets: 50 to 80 pairs, inserted at 40–50° on the rachis and 0.8 to 1.5 cm apart, straight, leathery, 15 to 30 cm by 6 to 9 mm (up to 11 mm), with a decurrent base, a flat or barely recurved margin and a sharp, acuminate tip.
  • Cataphylls (the scales that protect the growing point): triangular, 5 to 5.5 cm by 2 to 2.3 cm, densely brown-felted, ending in a long point that is soft and curved when fresh, hard and straight when dry.
  • Megasporophylls (the fertile leaves of female plants): more than 30, crowded, 14 to 20 cm, brown-felted; sterile blade greenish, oval, 6.5 to 9 cm, cut into 13 to 27 lobes 1 to 3 cm long; one or two glabrous ovules on each side.
  • Seeds: greenish to yellowish, broadly ovoid to almost round, 3.5 to 4.5 cm by 2.8 to 3.6 cm; sclerotesta finely warty.

The Flora of China states that the male cones are unknown. Hill (2008), who examined more material, describes them as spindle-shaped, green or cream, about 40 cm long and 8 cm wide. His leaf measurements differ slightly: leaves bright green and very glossy, 70 to 230 cm long, moderately keeled, with 100 to 280 leaflets 6 to 10 mm wide, twisted where they join the rachis; trunk 0.3 to 1.5 m, exceptionally 3.5 m. According to him, the seeds, 35 to 40 mm long, have a yellow sarcotesta, not glaucous, without a fibrous layer.

Hybrids

No named hybrid, wild or cultivated, is documented. The close resemblance between the Hainan cycads is a question of how the species are delimited (see Taxonomy), not of hybridisation.

Possible confusion

The risk of confusion lies mainly with the other members of the “Cycas taiwaniana complex”, a group of very similar cycads from southern China:

  • Cycas taiwaniana in Hill’s sense (2008), that is, the mainland plants: according to him, Cycas hainanensis differs in its more strongly keeled leaves, with narrower, more crowded leaflets, a smaller megasporophyll blade with fewer but longer lateral spines and an often much broadened terminal spine, and markedly larger seeds;
  • Cycas changjiangensis, from western Hainan, a dwarf plant with a mostly underground trunk, growing on grassy hills with a marked dry season;
  • Cycas shanyaensis, described in 2006 from Sanya in the south of the island, which Hill (2008) considered close to Cycas hainanensis;
  • Cycas szechuanensis, from south-eastern mainland China, with which The World List of Cycads now merges Cycas fairylakea.

There is also a trap in the name itself: for more than a century, Cycas taiwaniana was wrongly applied to the cycad of Taiwan, now called Cycas taitungensis (Hill 2008). A plant sold or described as “taiwaniana” is therefore not necessarily a Hainan plant.

Taxonomy

The name Cycas hainanensis was published by C. J. Chen in 1975 in Acta Phytotaxonomica Sinica 13(4): 82 (plate 2, figures 5–6). The type was collected by Y. Zhong (no. 4706) on 16 October 1961 at Luilianling, in Wanning district, Hainan, where the plants were scattered in humid forest; the holotype is kept in Beijing (PE), an isotype in Guangzhou (IBSC) (Hill 2008; The World List of Cycads). The plant was first compared with Cycas rumphii, from which, according to Hill (2008), it is in fact far removed.

The Flora of China (1999) and Ken Hill’s revision of the Cycas of China (2008) kept it as a species, in section Stangerioides, defined by soft male cones, comb-like megasporophylls and seeds without a fibrous layer. Hill included in it Cycas lingshuiensis, described in 2004 from Lingshui in the south of the island under the incorrect spelling “lingshuigensis”. As early as 1998, however, the revision of the genus by de Laubenfels and Adema had already placed Cycas hainanensis in the synonymy of Cycas taiwaniana (reference given by The World List of Cycads).

In 2021, Feng and colleagues (Taxon) combined morphology, plastid DNA, nuclear genes and microsatellites to delimit the six taxa of the complex. They recognise only two species: Cycas szechuanensis (including Cycas fairylakea) and Cycas taiwaniana, which absorbs Cycas hainanensis, Cycas lingshuiensis and Cycas changjiangensis. A 2019 study (Wang and colleagues, Frontiers in Genetics) reached a similar conclusion, and Zheng and colleagues (2017) already mentioned work treating Cycas hainanensis as a subspecies of Cycas taiwaniana. The World List of Cycads has followed Feng and colleagues for Cycas hainanensis, citing page 488 of their paper, but not for Cycas changjiangensis, which it still accepts.

In practice, recent publications often present the Hainan plant as Cycas taiwaniana. A 2022 genetic study (Wu and colleagues, Ecology and Evolution) thus describes Cycas taiwaniana as “endemic to Hainan Island”, an origin it attributes to the work of Feng and colleagues. Species+, the CITES database, by contrast still lists Cycas hainanensis as an accepted name, with Cycas lingshuiensis as a synonym. This site keeps the historical name, which is still widely searched, and gives Cycas taiwaniana as the name accepted by the world checklist.

Etymology and history

The epithet refers to the plant’s origin: the island province of Hainan, with the Latin suffix -ensis, “from” (Hill 2008).

According to Hill (2008), Chinese floras long recorded the species only from Hainan, but later work (Zhou and colleagues, 1990) reported it in cultivation in Fujian, Guangdong and Sichuan as well. It was then suggested that at least the Guangdong plants were distinct, and Hill concluded that the mainland plants belong to another species, to which he referred the type of Cycas taiwaniana. It is this separation that the study by Feng and colleagues (2021) called into question. In 1998 the South African journal Encephalartos published an article by William Tang, “Focus on Cycas hainanensis”.

Common names

No English common name is attested: the British specialist nursery Trebrown gives “None known”. The Flora of China gives the Chinese name 海南苏铁 (hai nan su tie, “Hainan cycad”); Hill (2008) also cites ci-bing su-tie (“spiny-petioled cycad”) and feng-huang-dan (“phoenix egg”), taken from earlier sources. The Royal Botanic Garden Sydney labels its plants “Hai nan su-tie”, a transliteration of the Chinese name rather than an English name.

In the wild

According to Hill (2008), Cycas hainanensis is known only from the wettest parts of eastern Hainan; the specimens he examined come from the districts of Wanning, Qiongdong, Baoting, Lingshui (Mount Diaolou) and Changjiang (Bawangling). It grows from sea level to about 1,200 m, on soils derived from limestone or volcanic rock, in a very wet subtropical climate (about 2,000 mm of rain a year), most often in tropical rainforest. The Flora of China gives tropical forest and open scrub between 100 and 1,000 m, pollination from March to May and seeds ripening from September to October.

Hill noted in 2008 that wild populations were much reduced and that the species survived mainly in cultivation. Zheng and colleagues (2017) record it in four protected areas of Hainan: Wuzhishan National Nature Reserve, Yinggeling Provincial Nature Reserve, Ganshiling Nature Reserve and Sanya Municipal Mangrove Reserve. The study by Wu and colleagues (2022), which treats these plants as Cycas taiwaniana, sampled twelve wild populations around the Wuzhi and Yingge mountains: genetic diversity is relatively low and differentiation between populations strong, with three distinct groups that the authors propose as separate conservation units.

No published source reports wild populations on the Chinese mainland; the mainland records concern cultivated plants.

Conservation status and regulation

The Hainan plant is listed as Endangered (EN), whichever name is used, but the history of its assessments is tangled. Hill (2008) gave the category EN for Cycas hainanensis, from the 2003 IUCN action plan. The World List of Cycads then cites an assessment by Anders Lindström published under the name Cycas hainanensis in the 2022 Red List (reference checked on Crossref). The current Red List data relayed by GBIF (consulted on 21 October 2026), however, treat Cycas hainanensis, Cycas lingshuigensis and Cycas shanyaensis as synonyms of Cycas taiwaniana, listed as Endangered in the reassessment by J. D. Bösenberg published in version 2023-1.

In China, all Cycas species are on the list of first-class protected plants (Zheng and colleagues 2017; Wu and colleagues 2022). Like every species of the genus except Cycas beddomei, the plant falls under CITES Appendix II, where the family Cycadaceae has been listed since 4 February 1977. The listing carries annotation #4 (version in force since 5 March 2026): seeds, pollen, and seedlings or tissue cultures obtained in vitro in sterile containers are exempt, whereas international trade in plants requires an export permit. In the European Union it is listed in Annex B of Regulation (EC) No 338/97, in the version set by Regulation (EU) 2026/1383, applicable since 29 June 2026; Species+ confirms this status for Cycas hainanensis.

This information does not replace the official texts: check the regulations in force before any purchase or exchange, ask the seller for proof of origin and prefer plants raised from seed in cultivation.

Growing Cycas hainanensis

No growing recommendations specific to Cycas hainanensis have been published. The plant has nevertheless long been cultivated in China: Hill (2008) mentions plants grown at a forestry institute in Guangxi and in the People’s Park in Haikou, the capital of Hainan, besides the records of cultivation in Fujian, Guangdong and Sichuan, and Wu and colleagues (2022) studied a cultivated population in Fujian. Its natural habitat, a warm, very wet forest, suggests a plant that needs steady warmth and a free-draining substrate; this is a deduction from its habitat, not a recommendation from a published source.

Outdoor and in-ground cultivation

No in-ground trial has been published in a frost-free climate. The only outdoor report found comes from the Atlantic coast of France: a grower in Concarneau (Finistère, Brittany) reports on the Fous de palmiers forum, in April 2012, that his Cycas hainanensis, grown in the garden, lost all its leaves during the winter of 2011–2012, when the lowest temperature he recorded was −5 °C (23 °F), but that its trunk seemed sound; he does not say whether it later recovered. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published nothing on the species.

Container cultivation

No source describes container cultivation of this species. Its size, a trunk of 1.5 m carrying leaves up to 2.2 m long, makes it a large tub plant once mature. The general advice given for tropical Cycas in pots, a very free-draining mix and a frost-free winter shelter, applies by default; it is not backed by data for Cycas hainanensis itself.

In cultivation in the UK, US and Australia

The species is grown in a handful of public collections, often under the name Cycas taiwaniana, which makes the records hard to compare.

  • Montgomery Botanical Center (Coral Gables, Florida), where cycads are grown outdoors: its living collection catalogue lists Cycas hainanensis under that name, with three accessions whose numbers date them to 1993, 1995 and 2000.
  • Other American gardens: BGCI PlantSearch lists the name Cycas hainanensis for Brooklyn Botanic Garden, the Huntington (California), Fairchild Tropical Botanic Garden (Florida), the National Tropical Botanical Garden (Hawaii) and San Diego Botanic Garden, besides Montgomery. A BGCI listing records that a garden has declared the plant at some point; it does not prove that the plant is alive today, and it says nothing about whether it grows outdoors.
  • Royal Botanic Garden Sydney: its Garden Explorer catalogue files the plant under Cycas taiwaniana, with Cycas hainanensis as a synonym and the name “Hai nan su-tie”: one plant of wild origin from China (accession of 1993) in bed 51f, and four plants of garden origin (accession of 2021).
  • Cairns Botanic Gardens (Queensland) declares the name in BGCI PlantSearch.
  • United Kingdom: no garden declares Cycas hainanensis. Oxford and Birmingham list “Cycas taiwaniana” in BGCI, but since that name was long misapplied to Cycas taitungensis, these records cannot be equated with the Hainan plant.

No growing report from an English-language forum or gardening site is documented for this species.

Propagation

The plant is dioecious: a male and a female plant are needed for fertile seed. No germination data specific to the species have been published; the general method for Cycas seed applies. Seeds are exempt from CITES under annotation #4; ask for seed from cultivated plants. Propagation from offsets is not documented for this species.

Pests and diseases

No pest or disease specific to the species is documented. Like all Cycas, it can be attacked by the Asian cycad scale, Aulacaspis yasumatsui, and a substrate that stays wet for long periods encourages root rot.

Cold hardiness

The cold data come down to a single growing report: a plant defoliated but with an apparently intact trunk after −5 °C (23 °F) in Brittany. No scientific source states how much cold the species tolerates; it lives in a very wet subtropical climate, mostly at low altitude. The British nursery Trebrown rates it USDA zone 9b (average annual minimum of −3.9 to −1.1 °C, or 25 to 30 °F), a commercial rating not backed by observations.

In the same Concarneau garden, during the same winter, Cycas revoluta, Cycas panzhihuaensis and Cycas guizhouensis came through without damage, according to the same grower. Neither the age of the Cycas hainanensis nor any protection is stated, and the identity of the plant cannot be checked: this is an isolated report, not a rule. For readers in comparable mild, wet maritime climates, such as south-west England, it nevertheless suggests that the foliage will not survive a frost of this order.

One warning is essential: hardiness figures published under the name “Cycas taiwaniana” may in fact refer to Cycas taitungensis, the cycad of Taiwan, to which that name was long misapplied (Hill 2008). They should not be transferred to the Hainan plants.

Toxicity and precautions

No toxicity analysis specific to Cycas hainanensis is documented, but the risk is well documented in the genus: Cycas tissues, and the seeds above all, contain cycasin, which is converted during digestion into methylazoxymethanol, toxic to the liver and nervous system, along with a neurotoxic amino acid, BMAA. The ASPCA lists the sago palm (Cycas revoluta) among plants poisonous to dogs, cats and horses, with vomiting, diarrhoea and liver damage that can be fatal. Without evidence to the contrary, treat the plant as poisonous: keep seeds and leaves out of reach of children and pets, wear gloves to clean seeds and, if any part is swallowed, contact a poison centre, a doctor or a vet straight away.

Traditional uses

No traditional use specific to Cycas hainanensis is documented; the Chinese names recorded by Hill show only that the plant is known and grown in China.

Frequently asked questions

Is Cycas hainanensis a valid species?

It depends on the source. The World List of Cycads treats it as a synonym of Cycas taiwaniana following Feng and colleagues (2021), and so do the current IUCN Red List data; the Flora of China, Hill (2008) and the CITES database still use the name Cycas hainanensis.

Where does it come from?

From Hainan Island in southern China. It grows mainly in the island’s humid forests, from sea level to about 1,200 m.

How big does it get?

It is a trunked cycad. The trunk usually reaches 1.5 m, rarely 2.5 to 3.5 m, and carries a crown of 50 to 80 leaves 1 to 2.2 m long.

How does it differ from Cycas changjiangensis?

Mainly in habit. Cycas changjiangensis is a dwarf plant with an almost entirely underground trunk, from the dry grassy hills of western Hainan; Cycas hainanensis has a true trunk and grows in humid forest.

Is it hardy?

Not very, on the only evidence available. In Brittany, a plant lost all its leaves at −5 °C (23 °F) in the winter of 2011–2012 while keeping an apparently sound trunk; this is an isolated report that should not be generalised.

Is it the same plant as the “Cycas taiwaniana” sold in nurseries?

Not necessarily. The name Cycas taiwaniana was long applied to the cycad of Taiwan, now Cycas taitungensis, and plants sold under that name should be identified with care.

Is it poisonous?

It must be assumed so. There is no analysis for the species, but all the cycads studied contain dangerous toxins, especially in the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Chen, C.J. (1975). In: Cheng, W.C. et al., Acta Phytotaxonomica Sinica 13(4): 82, pl. 2, figs 5–6. [Original description; reference taken from The World List of Cycads, the Flora of China and Hill (2008).]
  • Chen, C.J. & Stevenson, D.W. (1999). Cycadaceae. In Wu, Z.Y. & Raven, P.H. (eds), Flora of China 4: 1–7. Science Press, Beijing; Missouri Botanical Garden Press, St Louis. [Description, Chinese name, habitat and phenology; online version.]
  • Laubenfels, D.J. de & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Cycas hainanensis in the synonymy of Cycas taiwaniana (p. 378); reference taken from The World List of Cycads.]
  • Tang, W. (1998). Focus on Cycas hainanensis. Encephalartos 54: 4–10. [Reference taken from The World List of Cycads.]
  • Hill, K.D. (2008). The genus Cycas (Cycadaceae) in China. Telopea 12(1): 71–118. doi:10.7751/telopea20085804 [Type, synonymy, description (pp. 99–100), history, range, habitat, Chinese names, status, cultivated plants.]
  • Zheng, Y., Liu, J., Feng, X. & Gong, X. (2017). The distribution, diversity, and conservation status of Cycas in China. Ecology and Evolution 7(9): 3212–3224. doi:10.1002/ece3.2910 [Protected areas of Hainan, earlier work on the complex, national protection.]
  • Wang, X.-H., Li, J., Zhang, L.-M., He, Z.-W., Mei, Q.-M., Gong, X. & Jian, S.-G. (2019). Population differentiation and demographic history of the Cycas taiwaniana complex (Cycadaceae) endemic to South China as indicated by DNA sequences and microsatellite markers. Frontiers in Genetics 10: 1238. doi:10.3389/fgene.2019.01238 [Two lineages in the complex, the Hainan populations forming one.]
  • Feng, X.-Y., Wang, X.-H., Chiang, Y.-C., Jian, S.-G. & Gong, X. (2021). Species delimitation with distinct methods based on molecular data to elucidate species boundaries in the Cycas taiwaniana complex (Cycadaceae). Taxon 70(3): 477–491. doi:10.1002/tax.12457 [Two species recognised in the complex, Cycas hainanensis included in Cycas taiwaniana.]
  • Wu, L.X., Xu, H.Y., Jian, S.G., Gong, X. & Feng, X.Y. (2022). Geographic factors and climatic fluctuation drive the genetic structure and demographic history of Cycas taiwaniana (Cycadaceae), an endemic endangered species to Hainan Island in China. Ecology and Evolution 12: e9508. doi:10.1002/ece3.9508 [Twelve wild populations, structure, cultivated population in Fujian.]
  • Lindström, A. (2022). Cycas hainanensis. The IUCN Red List of Threatened Species 2022: e.T216174412A68902177. doi:10.2305/IUCN.UK.2022-1.RLTS.T216174412A68902177.en [Reference checked on Crossref.]
  • Bösenberg, J.D. (2023). Cycas taiwaniana. The IUCN Red List of Threatened Species 2023: e.T238708222A69827031. doi:10.2305/IUCN.UK.2023-1.RLTS.T238708222A69827031.en [Current assessment of the accepted name, with Cycas hainanensis as a synonym; reference checked on Crossref, category EN confirmed by GBIF.]
  • 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.]