Cycas collina

Cycas collina is a trunkless cycad of the mountain forests of north-western Vietnam, chiefly Sơn La province, and of southern Yunnan, in China, where it grows in the shade of evergreen forest or on steep slopes, mostly above about 500 m. Described in 2004 by Ken Hill, Nguyễn Tiến Hiệp and Phan Kế Lộc, this species of the genus Cycas had earlier been called Cycas siamensis, then Cycas simplicipinna or Cycas balansae, by Chinese authors. Its name refers to the hills and mountains where it lives. The IUCN lists it as Critically Endangered.

Key facts about Cycas collina

  • Accepted name: Cycas collina K.D.Hill, T.H.Nguyên & P.K.Lôc (2004), accepted by The World List of Cycads (version 2026.08.15); POWO could not be consulted directly
  • Former names and synonyms: no formal synonym; names misapplied in China: Cycas siamensis (Cheng and colleagues 1975), Cycas balansae and Cycas simplicipinna (1990s)
  • Family: Cycadaceae, order Cycadales
  • Common names: none in English; four Chinese names published under Cycas simplicipinna (see Common names)
  • Natural range: north-western Vietnam (mainly Sơn La province) and southern China (Yunnan, Xishuangbanna region); probably also Laos and Myanmar according to Hill (2008)
  • IUCN status: Critically Endangered (CR), reassessment by T. H. Nguyễn and A. Lindström (Red List version 2023-1), CR according to GBIF; criteria shown by The World List of Cycads: A2ace+4ace; Hill (2008) still cited the Vulnerable (VU) status of Donaldson (2003)
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; first-class protected wild plant in China, like all Chinese Cycas
  • Documented hardiness: no measured value; a British nursery gives USDA zone 9b without growing data (see Cold hardiness)
  • Light and soil: in the wild, deep shade of tall closed evergreen forest, or woodland and bamboo thickets on steep slopes; red clays over limestone or loams over metasedimentary rocks
  • Habit and adult size: underground stem 10 to 20 cm across; 2 to 10 leaves, 1.8 to 3.3 m long
  • In the UK, US and Australia: no record in any botanic garden
  • Toxicity: not studied for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas collina

This is a Cycas with no visible trunk and few but very long leaves, up to 3.3 m, carried on long spiny petioles, with broad, undivided leaflets that are dark green and glossy above. Male plants stand out by their large yellow cones, whose soft, rounded microsporophylls have no apical spine. The description below follows Ken Hill’s revision of the Cycas of China (2008), read in full:

  • Stem: underground, 10 to 20 cm across at the narrowest point; 2 to 10 leaves in the crown.
  • Leaves: dark green, highly glossy to semi-glossy, 180 to 330 cm long, barely keeled, with 90 to 190 leaflets and an orange and white down that falls as the leaf expands; rachis usually ending in a pair of leaflets.
  • Petiole: 70 to 190 cm (35 to 55% of the leaf), hairless, spiny for almost its whole length, with spines 1 to 3 mm long; the basal leaflets do not grade into spines.
  • Median leaflets: simple, clearly two-toned, 250 to 410 mm by 15 to 23 mm, narrowed to 2.5–4 mm at the base, 16 to 27 mm apart on the rachis; margins flat, often wavy; tip softly pointed, not pungent; midrib raised above, flat or slightly raised beneath.
  • Cataphylls (the scales that protect the growing point): narrowly triangular, soft, hairy, 50 to 80 mm long.
  • Male cones: narrowly ovoid or spindle-shaped, yellow, 25 to 60 cm by 6 to 10 cm; microsporophylls soft, with a 25 to 40 mm blade and no apical spine.
  • Megasporophylls (the fertile leaves of female plants): 8 to 14 cm long, with yellow felt that falls early, bearing 2 to 4 hairless ovules; blade oval, 50 to 70 mm, deeply comb-like, with 12 to 22 soft lateral spines 15 to 35 mm long; the apical spine is not distinct from the lateral ones.
  • Seeds: ovoid, 25 to 27 mm by 20 to 22 mm; fleshy coat (sarcotesta) yellow, without bloom, 2 mm thick, without a fibrous layer; stony inner coat warty.

Earlier descriptions circulating online gave it an “upright or short trunk”. Hill, on the contrary, describes it as trunkless, and that is precisely the character that singles it out in his key to the Chinese species, together with an unswollen apical spine on the megasporophyll, microsporophylls without a spine and petiole spines of 1 to 3 mm.

Hybrids

No garden hybrid is documented, but there is a natural transition zone. Hill (2008) reports, west of the town of Mộc Châu in Sơn La province, a population of Cycas dolichophylla with narrow leaflets, short to medium petioles and small seeds, which he interprets as a zone of intergradation with Cycas collina, common on the higher ground to the west (specimen from Chieng Hac, Chieng Pan, at about 500 m). No published genetic study confirms gene flow between the two species.

Possible confusion

Cycas collina belongs to a group of closely related trunkless species with soft male cones, a fleshy seed coat that comes away easily and a warty inner coat (section Stangerioides), spread across northern Vietnam, Laos, northern Thailand, Yunnan and Guangxi. According to Hill (2008):

  • its larger and often more numerous leaves, with more leaflets, and its larger male cones with rounded microsporophylls separate it from Cycas simplicipinna and Cycas balansae;
  • the lack of a distinct apical spine on the microsporophylls sets it apart from the other species of the group;
  • with Cycas dolichophylla, which also has very long leaves, the boundary is blurred around Mộc Châu (see Hybrids);
  • Cycas ferruginea, a plant of bare limestone cliffs, keys out by the broadened apical spine of its megasporophylls.

The species of the same region with divided leaflets, such as Cycas micholitzii or Cycas multipinnata, cannot be mistaken for it: its leaflets are simple.

Taxonomy

Cycas collina is accepted by The World List of Cycads; POWO could not be consulted directly. Ken Hill, Nguyễn Tiến Hiệp and Phan Kế Lộc described it in “The genus Cycas (Cycadaceae) in Vietnam”, The Botanical Review 70(2): 142–144, fig. 2 (2004); its IPNI identifier is 60436305-2. The type was collected on 5 April 1996 by S. L. Yang and H. T. Nguyễn (no. 777) in Mai Sơn district, between Hát Lót and Bắc Yên, at 400 to 900 m; the holotype is in Hanoi (HN). Hill described it again in his revision of the Cycas of China (2008), which extended its known range to Yunnan.

The history of the name explains why the species appears under other labels in the Chinese literature. According to Hill (2008), Cheng and colleagues (1975) wrongly applied to it the name Cycas siamensis, and later authors used Cycas simplicipinna and Cycas balansae (Wang 1996; Chen and Stevenson 1999). These are not synonyms in the strict sense, but names of other species used for these plants. Hill places Cycas collina in section Stangerioides, the group of continental Sino-Vietnamese Cycas with soft male cones, hairless ovules and a warty inner seed coat.

Etymology and history

The epithet is Latin: collinus, “of the hills”, according to Hill (2008), or collis, “hill”, according to the etymological compendium of Haynes (2022) cited by The World List of Cycads. Both sources link it to the occurrence of the species at middle and higher altitudes, in mountainous country.

The type was collected in Vietnam in 1996 and the species described eight years later, but Hill (2008) refers to it much older herbarium specimens from Yunnan: a collection by Cavalerie from 1913 and two by Joseph Rock from 1922, in the Nam Ha valley and between Keng Hung and Muang Hing. One of Rock’s 1922 sheets is held at the Royal Botanic Garden Edinburgh (GBIF).

Common names

No English common name is attested, and the British nursery Trebrown knows of none. Hill (2008) cites four Chinese names, kong-que-bao-dan, shan-ba-buo, shen-xian-mi and xiang-wei-cai, taken from Walters and Yang (1994) and from Bonta and Osborne (2007), who gave them for Cycas simplicipinna. Under Hill’s taxonomy they should therefore refer to Cycas collina, but no source has checked this in the field. No Vietnamese name specific to the species has been found.

In the wild

According to Hill (2008), Cycas collina is locally frequent but never forms dense stands. In China it grows mainly in the Xishuangbanna region of southern Yunnan, in the most sheltered sites, in the deep shade of tall closed evergreen forest. In Vietnam it occupies mountainous country, chiefly in Sơn La province, above about 500 m, in evergreen or partly deciduous forest, woodland or bamboo thickets on steep ridge slopes. The substrate ranges from red clays over limestone to loams over metasedimentary rocks. Hill considers it probably present in Laos and Myanmar as well.

The Vietnamese localities cited by Hill include the Chieng Dong pass (Yên Châu district), the Phang pass (Thuận Châu district) and Phong Lai, all at about 800 to 900 m; in China, the Menglun nature reserve (Mengla county) and a reserve in Jinghong county. Herbarium labels published through GBIF add two localities collected in 2006 in Sơn La province: Chieng Hac commune, in Mộc Châu district, at 1,250 m, and Na Lang village, in Yên Châu district, at 950 m, showing that the species climbs well above the 800–900 m quoted by Hill.

The sources disagree on the range. Species+, the CITES database, gives China and Vietnam, whereas The World List of Cycads lists only Vietnam (Sơn La province). Some older descriptions called the species endemic to north-western Vietnam, which Hill’s revision contradicts.

Conservation status and regulation

Cycas collina is listed as Critically Endangered (CR) by the IUCN, a category confirmed by the IUCN data relayed by GBIF (consulted on 21 October 2026). A reassessment by T. H. Nguyễn and A. Lindström was published in Red List version 2023-1 (reference checked on Crossref), following a first assessment by H. T. Nguyễn published in 2010. The World List of Cycads shows the criteria A2ace+4ace, which point to a steep population decline, observed and projected, and links to the 2023 assessment while citing the 2010 one as its reference: which of the two these criteria belong to could not be checked, and the Red List itself could not be consulted.

Judgements have changed over time. Hill (2008) described a widespread species, never in large or dense populations, whose habitat was steadily shrinking but of which many populations survived, and he cited the Vulnerable (VU) status given by Donaldson (2003). The precise causes of decline recorded by the IUCN could not be read.

In China, all species of Cycas are first-class protected wild plants on the national list (Xi and colleagues 2022). Like every species in the genus except Cycas beddomei, Cycas collina is listed in CITES Appendix II, through the listing of the family Cycadaceae, included since 4 February 1977. The listing carries annotation #4 (CoP20 version, in force since 5 March 2026): seeds, pollen, seedlings or tissue cultures obtained in vitro and transported in sterile containers, and cut flowers of artificially propagated plants, are not subject to CITES, whereas international trade in the plants themselves requires an export permit. Australia, the United Kingdom and the United States apply CITES through their own national legislation; in the European Union the species is in Annex B of Regulation (EC) No 338/97, whose annexes in force are set by Commission Regulation (EU) 2026/1383, applicable since 29 June 2026. Species+ names the species and confirms this status. This general information does not replace the official texts: check the rules in force before buying or exchanging plants, and only accept seed or plants of documented legal origin.

Growing Cycas collina

In short: no growing account has been published and the species is rare in collections. Its habitat suggests a shade-loving plant for warm, frost-free gardens or for the glasshouse.

Outdoor and in-ground cultivation

Hill (2008) mentions a plant grown at the nursery of the forestry research centre in Nanning, Guangxi, taken from Xishuangbanna, and a plant cultivated at the Nong Nooch Tropical Botanical Garden, in Thailand (accession 144 A), was collected for the Vienna herbarium in 2011 (GBIF). Its natural setting, shaded evergreen forest on clay or loam, points to a plant for partial or full shade in a fertile but free-draining soil; the Palm and Cycad Society of Australia likewise recommends “a shady, well drained position in the tropics/sub-tropics”. These are recommendations and deductions from the habitat, not results of trials.

Container cultivation

In the United Kingdom and other temperate regions, the only realistic option is a large pot in a heated glasshouse or conservatory, in bright shade, given the length of the leaves (up to 3.3 m in the wild). No account of pot culture specific to the species has been found. In Mediterranean Europe, no grower has reported it: neither the French forum Fous de palmiers nor the Italian forum Tropicamente has a message on the species, and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published nothing on it.

In cultivation in the UK, US and Australia

No record. The species does not appear in BGCI PlantSearch for any garden (consulted on 21 October 2026), nor in the online catalogues of Montgomery Botanical Center, Fairchild Tropical Botanic Garden, the Royal Botanic Garden Sydney, the Australian Botanic Garden Mount Annan or the Royal Botanic Gardens Victoria. The British nursery Trebrown lists the name. No report from a private grower in the UK, US or Australia could be read; PalmTalk and Dave’s Garden could not be consulted.

Propagation

Like all Cycas, Cycas collina is dioecious and is raised from seed: a male and a female plant are needed for fertile seed. No germination data specific to the species have been published. Given its IUCN status and its protection in China, only seed of documented legal origin is acceptable; seeds are exempt from CITES under annotation #4.

Pests and diseases

No pest or disease specific to the species is documented. Like all Cycas, it is exposed to the Asian cycad scale, Aulacaspis yasumatsui, and to root rot in waterlogged substrate.

Cold hardiness

No cold-tolerance value has been measured for Cycas collina. The British nursery Trebrown gives it USDA zone 9b, that is, an average annual minimum of −3.9 to −1.1 °C (25 to 30 °F), but this is a commercial rating with no growing observation behind it. The species grows in the mountains, above 500 m and up to at least 1,250 m in Vietnam, but in tropical and subtropical regions: altitude alone does not show that it can take frost.

European experience

No growing result has been published in Europe, in the open ground or in a pot, and no dated frost episode concerns the species. In the absence of data, grow it in a pot, frost-free.

United Kingdom, United States and Australia

No cold reading and no growing report were found. No USDA zone can be given without a documented trial; the 9b rating above is the nursery’s, not a tested result.

Toxicity and precautions

No toxicity analysis specific to Cycas collina has been found. The risk is, however, 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. North Carolina State University notes that cycasin is present in all parts of the plant, and the ASPCA lists the sago palm (Cycas revoluta) as poisonous to dogs, cats and horses, with vomiting, sometimes bloody diarrhoea, jaundice and liver damage that can be fatal. Until proven otherwise, treat the plant as poisonous: wear gloves to handle the seeds and their fleshy coat, pick up fallen seeds, and keep plants and seeds out of reach of children and pets. If any part is swallowed, contact a poison centre, a doctor or a vet straight away.

Traditional uses

No traditional use specific to Cycas collina is documented in the sources consulted. The existence of several Chinese names shows that local people know the plant, but the sources do not say what it is used for. Given the toxins of the genus, no part of it should be eaten.

Frequently asked questions

What does “collina” mean?

“Of the hills”. The epithet comes from the Latin collinus (or collis, “hill”) and recalls that the species grows at middle and higher altitudes, in mountainous country.

Where does it grow in the wild?

In north-western Vietnam, mainly Sơn La province, from about 500 m to at least 1,250 m, and in southern Yunnan (Xishuangbanna); probably also in Laos and Myanmar. It is therefore not endemic to Vietnam.

Does it have a trunk?

No. Its stem stays underground; only the very long leaves emerge from the soil.

What is its closest relative?

The sources do not name a single one, but Hill (2008) describes a transition zone with Cycas dolichophylla west of Mộc Châu, and compares it mainly with Cycas simplicipinna and Cycas balansae.

Is it endangered?

Yes. The IUCN lists it as Critically Endangered, a category kept by the reassessment published in 2023, whereas Hill (2008) still considered it widespread. It is protected by CITES, by Annex B in the European Union and, in China, at the highest national level.

Can it be grown outdoors in the UK?

Almost certainly not. No cold-tolerance measurement or trial is documented; in the UK it is a plant for a heated glasshouse.

Is it poisonous?

It must be assumed so. It has not been analysed, but all Cycas studied contain toxins dangerous to people and animals, especially in the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Hill, K.D., Nguyễn, T.H. & Lộc, P.K. (2004). The genus Cycas (Cycadaceae) in Vietnam. The Botanical Review 70(2): 134–193. doi:10.1663/0006-8101(2004)070[0134:TGCCIV]2.0.CO;2 [Original description, pages 142–144, figure 2; text not consulted (paywalled), reference checked through The World List of Cycads.]
  • Hill, K.D. (2008). The genus Cycas (Cycadaceae) in China. Telopea 12(1): 71–118. doi:10.7751/telopea20085804 [Description, key, history of the name, range, habitat, status, specimens; full text consulted.]
  • Nguyễn, H.T. (2010). Cycas collina. The IUCN Red List of Threatened Species 2010: e.T42051A10639008. doi:10.2305/IUCN.UK.2010-3.RLTS.T42051A10639008.en [First assessment; reference checked on Crossref, page not consulted.]
  • Nguyễn, T.H. & Lindström, A. (2023). Cycas collina. The IUCN Red List of Threatened Species 2023: e.T42051A67340335. doi:10.2305/IUCN.UK.2023-1.RLTS.T42051A67340335.en [Current assessment, CR; reference checked on Crossref, category relayed by GBIF; page not consulted (access blocked).]
  • Xi, H.-H., Wang, Y.-Q., Pan, Y.-Z., Xu, T., Zhan, Q.-Q., Liu, J., Feng, X.-Y. & Gong, X. (2022). Resources and protection of Cycas plants in China. Biodiversity Science 30(7): 21495. doi:10.17520/biods.2021495 [First-class national protection of all Chinese Cycas; abstract and tables consulted.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology; cited by 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; consulted directly.]