Cycas hongheensis

Cycas hongheensis is a trunked cycad from south-eastern Yunnan, in China, known only from a short stretch of the Red River valley (Hong He) in Gejiu district, where it grows on hot, dry limestone cliffs. This member of the genus Cycas, described in 1996, is recognised by its smooth grey trunk and its strongly keeled, grey-green leaves, which keep a white down for a long time. It is the only species of section Indosinenses, the group of Cycas pectinata, that is confined to China, and one of the most threatened Chinese cycads: the IUCN lists it as Critically Endangered, collection for the ornamental trade having almost emptied its habitat.

Key facts about Cycas hongheensis

  • Accepted name: Cycas hongheensis S.Y.Yang & S.L.Yang ex D.Yue Wang (1996), accepted by The World List of Cycads (version 2026.08.15); the World Checklist of Vascular Plants (WCVP), on which POWO is based, also accepts it (consulted through GBIF on 31 October 2026)
  • Former names and synonyms: Cycas pectinata f. hongheensis (S.Y.Yang & S.L.Yang ex D.Yue Wang) Z.T.Guan, cited by the Flora of China
  • Family: Cycadaceae, order Cycadales; section Indosinenses
  • Common names: no English name attested; in Chinese 灰干苏铁 (hui gan su tie), hong-he su-tie and ba-he su-tie
  • Natural range: China, south-eastern Yunnan, Red River valley in Gejiu district
  • IUCN status: Critically Endangered (CR); reassessment by J. Liu, A. Lindström and X. Gong published in version 2023-1 of the Red List, after that of 2010 (criteria A2cd+4cd; B2ab(iii,v))
  • CITES and other protection: CITES Appendix II; Annex B in the European Union; first-class state protection in China for all Cycas since 1999
  • Documented hardiness: no data (see Cold hardiness)
  • Light and soil: in the wild, full sun on deeply eroded limestone slopes, roots in rock fissures with very little soil
  • Habit and adult size: trunk 1 to 3 m tall and 12 to 15 cm across according to Hill (2008), up to 8 m by 60 cm according to the Flora of China; leaves 50 to 120 cm
  • In the UK, US and Australia: Montgomery Botanical Center (Florida), five accessions; no British or Australian record
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas hongheensis

Three characters are enough to separate it from the other Chinese cycads: a smooth grey trunk whose apex is not woolly, clearly keeled leaves whose two ranks of leaflets rise in a V, and dull grey-green adult foliage covered in a persistent white down. This is the combination used in Ken Hill’s key (2008) to distinguish it from the two other Chinese cycads with keeled leaves, Cycas revoluta and Cycas taitungensis, which have a densely woolly trunk apex, a rough trunk and dark green adult leaves.

The Flora of China (1999) describes it as follows:

  • Trunk: cylindrical, sometimes branched, up to 8 m tall and 60 cm in diameter, without wool at the apex; bark grey, smooth towards the base, with fine longitudinal cracks.
  • Leaves: 20 to 50 (up to 60), pinnate, 50 to 120 cm by 15 to 35 cm, strongly V-shaped in section and arching, covered in a pale brown felt when young; petiole almost cylindrical, 10 to 25 cm, armed with 25 to 50 spines on each side.
  • Leaflets: 50 to 70 pairs, inserted at 45–50° on the rachis, glaucous when mature, 8 to 18 cm by 6 to 8 mm, leathery, densely hairy at first, with a decurrent base, a more or less rolled margin and a sharp, acuminate tip.
  • Cataphylls (the scales that protect the growing point): lanceolate, 3 to 5 cm by 1 to 1.5 cm, densely pale-brown-felted on the upper side, with a sharp tip.

Hill’s measurements, taken from the material he examined, are more modest: trunk 1 to 3 m tall and 12 to 15 cm across, 12 to 25 leaves per crown, grey-green leaves 70 to 100 cm long carrying 120 to 140 leaflets 15 to 20 cm by 7 to 8 mm, petiole about 26 cm, and persistent white down on both surfaces. No published source explains the gap with the Flora of China, especially in trunk height.

Neither the Flora of China nor Hill had seen the cones. The reproductive organs were described only in 2016 by Jian Liu, Anders Lindström and Xun Gong, in the journal Phytotaxa, after fertile material was found at the type locality. According to the abstract of that study, the only part that could be read, the ovules are glabrous and the megasporophylls carry a distinct apical spine, as in section Indosinenses, while the microsporophylls have a soft, rudimentary apical spine and the seed’s sarcotesta lacks a fibrous layer, two characters that recall other groups.

Hybrids

No hybrid, wild or cultivated, is documented.

Possible confusion

The closest species is Cycas pectinata, of the same section, which Hill (2008) and Zheng and colleagues (2017) also record in Yunnan; The World List of Cycads now restricts it to South Asia, from Nepal to Bangladesh. According to Hill, the tall smooth trunk of Cycas hongheensis closely resembles that of Cycas pectinata and of the related species of Thailand, but its keeled leaves, with their fairly persistent white down, set it apart at once from every species of that group. The Flora of China in fact cites a combination that makes it a mere form of Cycas pectinata.

Among the Chinese cycads with keeled leaves, Cycas revoluta and Cycas taitungensis are recognised by their woolly trunk apex, rough trunk and dark green adult leaves (Hill’s key, 2008).

Other cycads grow in the Red River region, but they belong to section Stangerioides, with soft male cones and seeds without a fibrous layer: such is the case of Cycas diannanensis and Cycas multipinnata, protected alongside it in the Mount Dawei nature reserve (Zheng and colleagues 2017). Its keeled grey-green leaves and smooth trunk are enough to tell it apart.

Taxonomy

Cycas hongheensis is a name accepted by The World List of Cycads; the World Checklist of Vascular Plants (WCVP), on which POWO is based, also accepts it (consulted through GBIF on 31 October 2026). The plant was first proposed as a species in 1994, without a type specimen or Latin description, which did not amount to valid publication (Vorster 1997, cited by Wu and colleagues 2021). The name was validly published in 1996 in the book Cycads in China, edited by F. X. Wang and H. B. Liang, on page 62 of the chapter by D. Y. Wang, hence the author citation “S.Y.Yang & S.L.Yang ex D.Yue Wang”. That description was based on vegetative material only (Liu and colleagues 2016; Hill 2008).

The type is the specimen S. Y. Yang 9301, collected in the wild at Gejiu on 17 May 1993; the holotype is kept at the Panzhihua Institute of Horticulture, with isotypes at the FTG, HWA and PE herbaria (Hill 2008).

In Hill’s classification (2008), the species belongs to section Indosinenses, defined by stiff or woody male cones, glabrous ovules, a large, deeply comb-like megasporophyll blade and a fibrous layer in the sarcotesta. In China the section has only two species, Cycas pectinata and Cycas hongheensis; the other Chinese cycads belong to sections Stangerioides, Asiorientales (Cycas revoluta and Cycas taitungensis) and Panzhihuaenses (Cycas panzhihuaensis) (Zheng and colleagues 2017).

The 2016 study confirmed this placement, with a caveat: chloroplast DNA, inherited from the mother, and nuclear DNA, inherited from both parents, give conflicting results, which match the plant’s unusual combination of characters. The authors keep it in section Indosinenses on the characters of the megasporophyll and ovule and on the nuclear data, which they consider more complete. In 2021 the complete chloroplast genome of the species was sequenced from a plant from Gejiu: in that analysis, limited to the eight Cycas whose chloroplast genome had then been published, it sits as the sister group of all the others (Wu and colleagues 2021).

Etymology and history

The epithet refers to the Hong He, the Red River, near which the species grows in south-eastern Yunnan, with the Latin suffix -ensis, “from” (Hill 2008; Haynes 2022). According to Hill, Chinese botanists noticed the plant as a distinct taxon in 1993, and it was described in 1996 without cones, although local people reported that its seeds were large. Cones were first observed in 2015 (Zheng and colleagues 2017) and described the following year. No history of its introduction into cultivation outside China is documented.

Common names

No English common name is attested: the British specialist nursery Trebrown gives “None known”. The Flora of China gives the Chinese name 灰干苏铁 (hui gan su tie), which can be rendered as “grey-trunked cycad”; Hill (2008) also cites hong-he su-tie (“Red River cycad”, a Chinese name) and ba-he su-tie, taken from earlier sources.

In the wild

Cycas hongheensis is known only from a small area along the Hong He, in Gejiu district, south-eastern Yunnan (Hill 2008), on the north bank of the river (Wu and colleagues 2021). It grows on steep limestone outcrops at low altitude, between 400 and 600 m according to the Flora of China, in open, hot, dry and sunny woodland. Hill describes it in low, open vine thickets, often with succulent euphorbias, rooted in cracks and fissures of the rock, often with very little soil, and considers it apparently restricted to these limestones that are dry for part of the year. A specimen examined by Hill was collected in July 2000 near the town of Baohe, in a dry side valley north of the Hong He, on “heavily dissected and eroded” limestone.

Only two wild populations remain, together numbering fewer than 1,000 individuals, one in the Mount Dawei nature reserve and the other in a reserve in Gejiu district (Zheng and colleagues 2017). The sources do not agree on the location of the first: Wu and colleagues (2021) restrict the species to Gejiu. Pollinators, phenology and seed dispersal are not documented.

Conservation status and regulation

Cycas hongheensis is listed as Critically Endangered (CR) by the IUCN: this is the current category relayed by GBIF (consulted on 21 October 2026). The assessment by J. D. Bösenberg published in 2010 used the criteria A2cd+4cd; B2ab(iii,v), which The World List of Cycads still displays; a reassessment by Jian Liu, Anders Lindström and Xun Gong was published in version 2023-1 of the Red List (reference checked on Crossref), and the category remained CR. The species was already listed as Endangered in the 1997 Red List of plants and as Critically Endangered in the 2003 IUCN action plan (Hill 2008).

The causes of the decline are well described. The Flora of China reported in 1999 a very rapid disappearance in the wild, due to excessive collection by traders and the destruction of the habitat; Hill (2008) describes populations heavily depleted by collection for sale as an ornamental; Zheng and colleagues (2017) name agricultural clearance as the main current threat.

In China, all Cycas species received first-class state protection in 1999, and the Mount Dawei national nature reserve protects this species together with Cycas multipinnata and Cycas diannanensis (Zheng and colleagues 2017). Like every species of the genus except Cycas beddomei, it 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+, the official CITES database, confirms this status.

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, for a species almost emptied from its habitat by collection, choose only plants raised from seed in cultivation.

Growing Cycas hongheensis

No growing recommendations specific to Cycas hongheensis have been published, and no growing report is documented on the forums. Its natural habitat nevertheless gives clear pointers: limestone cliffs in full sun, in a hot valley with a marked dry season, with roots lodged in fissures almost without soil (Flora of China; Hill 2008). By analogy with the habitat, and without confirmation in cultivation, one can infer a very free-draining mineral substrate, plenty of light and reduced watering when the plant is not growing.

Outdoor and in-ground cultivation

No in-ground cultivation is documented anywhere outside China, apart from the plants of the Montgomery Botanical Center in southern Florida (see below), for which no growing data have been published. With no cold data at all, the plant can only be considered for planting out in frost-free climates; this is a precaution, not a measured limit. In Europe, no cultivation is documented.

Container cultivation

No source describes container cultivation of this species. In the United Kingdom, northern Europe and the colder parts of the United States and Australia, it is to be treated as a plant for a glasshouse, or for a pot brought under cover in winter, in a mineral mix that drains quickly; this follows from the lack of any hardiness data and from its habitat, not from a published trial.

In cultivation in the UK, US and Australia

The species is very rare in public collections.

  • Montgomery Botanical Center (Coral Gables, Florida), where cycads are grown outdoors: its living collection catalogue lists five accessions, four whose numbers date them to 1994 and one to 2026. It is the only garden in the three countries that declares the species in BGCI PlantSearch.
  • United Kingdom and Australia: no garden declares Cycas hongheensis in BGCI PlantSearch, and it does not appear in the online garden catalogues (Royal Botanic Garden Sydney, Cambridge, Edinburgh).

No growing report from an English-language forum or gardening site is documented for this species. On the Italian forum Tropicamente, a member noted in March 2009 that Chinese cycads including “Hongheensis” were then on sale at moderate prices; the identity of those plants cannot be checked.

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; local people only reported that the seeds are large (Hill 2008). Seeds are exempt from CITES under annotation #4; for a Critically Endangered species, sowing legally sourced seed from cultivated plants is the only responsible way to obtain it.

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. For a plant of dry rocks, a substrate that stays wet for long periods is likely to be the main risk of rot, but no source documents this for the species.

Cold hardiness

There are no cold-hardiness data for Cycas hongheensis. Its Chinese origin should not mislead: it lives between 400 and 600 m in a hot, dry valley of southern Yunnan (Flora of China), a habitat very different from that of Cycas panzhihuaensis, the Chinese cycad best known for its cold tolerance. 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, without growing observations to back it.

No in-ground or container result has been published in Europe, in the United States outside Florida or in Australia, and no dated frost episode concerns the species. For gardeners in Mediterranean climates or in the milder parts of California and southern Australia, the only safe assumption is that its tolerance of frost is unknown.

Toxicity and precautions

No toxicity analysis specific to Cycas hongheensis 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 hongheensis is documented. The only use reported is ornamental: according to Hill (2008) and the Flora of China, the collection of wild plants for sale is one of the causes of its decline.

Frequently asked questions

What does hongheensis mean?

“From the Red River”. The Hong He is the river of south-eastern Yunnan along which the species grows, in Gejiu district.

Why is it unusual among Chinese cycads?

Because it is the only species of section Indosinenses confined to China (Liu and colleagues 2016). The other species of the section recorded in China, Cycas pectinata, grows mainly in South Asia.

How big does it get?

It depends on the source. Hill (2008) gives a trunk of 1 to 3 m, the Flora of China up to 8 m tall and 60 cm across; the difference is not explained.

Is it endangered?

Yes, severely. The IUCN lists it as Critically Endangered, and only two wild populations remain, together numbering fewer than 1,000 individuals, because of collection for the ornamental trade, habitat destruction and agricultural clearance.

How can it be told from Cycas pectinata?

Mainly by its leaves. The two species share a tall smooth trunk, but Cycas hongheensis has keeled, grey-green leaves with a persistent white down, a character that Hill (2008) found in no other species of the Cycas pectinata group.

Can it be grown outdoors in the UK or the cooler parts of the US?

Nobody knows. There are no cold data and no growing reports; until there are, it should be treated as a glasshouse plant, or a pot plant brought under cover in winter.

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

  • Wang, D.Y. (1996). Taxonomy of Cycas in China. In Wang, F.X. & Liang, H.B. (eds), Cycads in China: 33–142 (p. 62). [Original description; reference taken from The World List of Cycads 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 threats; online version.]
  • Hill, K.D. (2008). The genus Cycas (Cycadaceae) in China. Telopea 12(1): 71–118. doi:10.7751/telopea20085804 [Key, section Indosinenses, type, description (pp. 114–115), history, habitat, Chinese names, status.]
  • Liu, J., Lindström, A.J. & Gong, X. (2016). Supplementary description of Cycas hongheensis (Cycadaceae) from Yunnan, China and its phylogenetic position. Phytotaxa 257(1). doi:10.11646/phytotaxa.257.1.5 [First description of the cones and seeds, phylogenetic position.]
  • 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 [Sections present in China, remaining populations, reserves, threats, national protection.]
  • Wu, L.X., Wang, Y.H. & Gong, X. (2021). Characterization of the complete chloroplast genome of Cycas hongheensis (Cycadaceae), an endemic species in the red river region of China. Mitochondrial DNA Part B 6: 3513–3514. doi:10.1080/23802359.2021.2005484 [Invalid 1994 proposal, north bank of the Red River, chloroplast position.]
  • Bösenberg, J.D. (2010). Cycas hongheensis. The IUCN Red List of Threatened Species 2010: e.T42040A10635591. [Assessment cited by The World List of Cycads.]
  • Liu, J., Lindström, A. & Gong, X. (2023). Cycas hongheensis. The IUCN Red List of Threatened Species 2023: e.T42040A68902633. doi:10.2305/IUCN.UK.2023-1.RLTS.T42040A68902633.en [Reassessment; reference checked on Crossref, current category CR confirmed by GBIF.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology, via 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. doi:10.5281/zenodo.21958524 [Reference checklist.]