Cycas clivicola

Cycas clivicola is a cycad of the limestone cliffs of South-East Asia, clinging to the almost vertical faces of karst towers in southern and eastern Thailand, northern Peninsular Malaysia, Cambodia and southern Vietnam. This species of the genus Cycas was described in 1999 by the Australian botanist Ken Hill from plants on the beach at Pak Meng, in the Thai province of Trang, and its Latin name means “cliff-dweller”. Widespread and often out of reach, it is listed as Least Concern by the IUCN, although the typical subspecies is considered Endangered on the Red List of Peninsular Malaysia because of collecting.

Key facts about Cycas clivicola

  • Accepted name: Cycas clivicola K.D.Hill (1999), accepted by The World List of Cycads (version 2026.08.15); POWO could not be consulted directly
  • Former names and synonyms: Cycas clivicola subsp. lutea K.D.Hill (1999), now included in the species; plants formerly referred to Cycas siamensis, Cycas pectinata or Cycas rumphii; the neotype chosen in 1998 for the name Cycas miquelii belongs to this species (see Taxonomy)
  • Family: Cycadaceae, order Cycadales
  • Common names: no established English name; ปรงเขาใต้ (prong khao tai) in Thai; paku aji in Malay
  • Natural range: southern and eastern Thailand, northern Peninsular Malaysia (Kedah, Perak, Selangor; Perlis according to MyBIS), Cambodia, southern Vietnam (An Giang, Kiên Giang)
  • IUCN status: Least Concern (LC), reassessment by J. D. Bösenberg and T. H. Nguyễn (Red List version 2023-1), LC according to GBIF; Endangered (EN) for the typical subspecies on the Red List of Peninsular Malaysia (2021)
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union
  • Documented hardiness: no measured value; a tropical species to be kept frost-free (see Cold hardiness)
  • Light and soil: in the wild, full sun in cracks in limestone cliffs, often with no soil; in cultivation, full sun and a free-draining, alkaline soil or potting mix (Palm and Cycad Society of Australia)
  • Habit and adult size: trunk upright, leaning or hanging down cliff faces, up to 7 or 8 m, swollen at the base; leaf blade 70 to 165 cm long (Thai Department of Agriculture)
  • In the UK, US and Australia: Paignton Zoo (Devon); Montgomery Botanical Center (Florida) and three other American gardens; Royal Botanic Garden Sydney (see In cultivation in the UK, US and Australia)
  • Toxicity: not studied for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas clivicola

The first clue is the setting: a Cycas rooted in a limestone cliff in full sun. Close up, it has a smooth, grey to yellowish trunk swollen at the base, flat leaves with stiff, crowded leaflets and, on female plants, a closed head of fertile leaves packed together like a cabbage. The original description by Hill and Yang (1999) could not be consulted; the characters below come from the species account of the Thai Department of Agriculture (2019), from the original description of Cycas cantafolia (Jutta and colleagues 2010), which compares the two species in detail, and from the Malaysian biodiversity portal MyBIS:

  • Trunk: up to 7 or 8 m, upright, leaning or hanging down the rock face, 30 cm across or more, clearly swollen at the base (up to 60 cm); bark pale grey to yellowish, almost smooth, cracking with age.
  • Leaves: 50 or more in the crown, glossy green to glaucous green, flat (not keeled); petiole 15 to 25 cm with short spines; blade 70 to 165 cm long, with 45 to 110 leaflets on each side; young leaves covered in pale yellow wool.
  • Leaflets: 9 to 20 cm long and 5 to 9 mm wide, stiff, crowded and regular, with flat margins; the lowest leaflets are not reduced to spines.
  • Cataphylls (the scales that protect the growing point): triangular, soft, 4 to 8 cm long, with light brown or grey hairs.
  • Male cones: narrowly ovoid, brownish yellow. The Thai account gives 8 to 15 cm, whereas MyBIS cites a cone of 68 cm by 17.5 cm for Malaysia; this large discrepancy remains unexplained.
  • Megasporophylls (the fertile leaves of female plants): 12 to 22 cm long, with yellow to grey felt, packed into a closed head; blade rounded, deeply comb-like, with 26 to 54 lateral spines up to 40 mm long; 1 to 4 ovules.
  • Seeds: flattened ovoid, 33 to 39 mm by 26 to 35 mm; fleshy coat yellow, light brown when dry, with a fibrous layer.

Ken Hill (2008) notes that the thin, smooth bark, shared with Cycas elongata, is probably a consequence of wetter surroundings: the old leaf bases and cataphylls that form an armour on the trunks of other species decay quickly there.

Hybrids

No natural or garden hybrid is documented in the sources consulted.

Possible confusion

Before 1999, plants of Cycas clivicola were taken for forms of Cycas pectinata or Cycas siamensis, and the older floras of Malaysia and Thailand placed them under Cycas siamensis or Cycas rumphii (Jutta and colleagues 2010). The species most likely to be confused with it today are:

  • Cycas cantafolia, from Johor: it shares the closed female cone, but grows on granite and has much less deeply cut megasporophylls, with 25 to 30 spines no longer than 18 mm.
  • Cycas tansachana, from the limestone hills of Saraburi, and Cycas chamaoensis, from Khao Chamao: both also have a closed cone and a rounded megasporophyll blade, but each is known from a single small area.
  • The Cycas of the coast and lowland forests of the Malay Peninsula, Cycas edentata (of which Cycas litoralis is a synonym according to The World List of Cycads) and Cycas macrocarpa: their female cones are open.

Taxonomy

Cycas clivicola is accepted by The World List of Cycads; POWO could not be consulted directly. Ken Hill described it in “The genus Cycas (Cycadaceae) in Thailand”, written with S. L. Yang, Brittonia 51(1): 62–63 (1999). The type was collected on 22 April 1994 by Hill and Vatcharakorn (no. 4633) at Pak Meng beach, west of Trang; the holotype is in Sydney (NSW), with isotypes in Bangkok (BKF), at Kew, in Leiden and in Beijing. At the same time Hill described a subspecies lutea, with a yellowish trunk; The World List of Cycads now treats it as a synonym, and the study behind this decision could not be identified.

The species belongs to section Indosinenses, which Hill (2008) defines by its firm male cones, hairless ovules, large comb-like megasporophyll blade and a fibrous layer in the fleshy coat of the seed.

Cycas clivicola also plays a part in a long-running muddle over the name Cycas miquelii. Warburg described Cycas miquelii in 1900 without citing a type, giving only “Süd-China” as its origin. In their 1998 revision, de Laubenfels and Adema transferred the name to their genus Epicycas as Epicycas miquelii and, Warburg’s material having been destroyed in Berlin, chose a neotype: a specimen collected by A. F. G. Kerr in Chumphon province, in southern Thailand (Kerr 11873, at Kew). Ten years later, Hill (2008) pointed out that this specimen belongs to “a quite different species from southern Thailand”, Cycas clivicola. He rejected the neotype as redundant, since two sheets at Utrecht from a plant grown in the Amsterdam botanic garden can serve as original material, and as contrary to the original description, the specimen not being from southern China. He designated those Utrecht sheets as lectotype; as they show a somewhat aberrant form of Cycas revoluta without petiole spines, Cycas miquelii is now a synonym of Cycas revoluta. In practice, plants or texts labelled “miquelii” after the 1998 revision may refer to Cycas clivicola, to Cycas sexseminifera or to other species, not to Cycas revoluta.

Etymology and history

According to Haynes (2022, as cited by The World List of Cycads) and MyBIS, the epithet is formed from the Latin clivis, “cliff”, and -cola, “dweller”, after the cliff habitat of the species. According to the account reproduced by the online encyclopedia Llifle from Ken Hill’s Cycad Pages, this abundant plant remained unnamed until the late 1990s and was grown outside Thailand as “species Araipathet”. William Tang devoted an article to it in 2001 in the journal Encephalartos, which could not be consulted.

Common names

No English common name is established in the botanical literature. The Royal Botanic Garden Sydney labels its plant “Mountain Sago”, and Llifle gives “cliff cycad” and “mountain cycad”, without a primary source: these are labels, not attested vernacular names. In Thailand, the Department of Agriculture calls the species ปรงเขาใต้ (prong khao tai); prong is the Thai name for Cycas. In Malaysia, MyBIS gives the Malay name paku aji for the typical subspecies; the word paku also appears in the names of other Cycas of the peninsula.

In the wild

Cycas clivicola has a wide range, over 300,000 km² according to the account reproduced by Llifle. The World List of Cycads records it in nine Thai provinces (Chumphon, Krabi, Narathiwat, Phang Nga, Phuket, Prachin Buri, Rayong, Ranong and Trang), in the Malaysian states of Kedah, Perak and Selangor, in Cambodia, and in the Vietnamese provinces of An Giang and Kiên Giang. MyBIS also cites the state of Perlis, and Llifle the island of Langkawi.

It grows both on inland limestone massifs and on limestone islets along the coast, usually rooted in cracks and fissures in near-vertical rock faces, in full sun, often with no soil around the roots. Herbarium labels published through GBIF confirm this range of settings: the slopes of a limestone cliff on an island in Temenggor Lake, in the Belum forest reserve (Perak, 1994); Ko Tao, an island in the Gulf of Thailand about 100 km east of Chumphon (1996); and a seashore site on Ko Ngai, off the Andaman coast (1966). According to the account reproduced by Llifle, the plants rise above the monsoon forest around the karst towers and do not establish in shade; on the coast they come down to the foot of the cliffs, stopped only by mangrove or the tides. Weevils found in the male cones are thought to pollinate them.

Conservation status and regulation

Cycas clivicola is listed as Least Concern (LC) by the IUCN. The first global assessment, by Ken Hill, was published in 2010, with separate assessments of the two subspecies then recognised; a reassessment by J. D. Bösenberg and T. H. Nguyễn was published in Red List version 2023-1 (references checked on Crossref), and the IUCN data relayed by GBIF give it the LC category (consulted on 21 October 2026). The Red List itself could not be consulted directly.

National assessments are more cautious. The Red List of the plants of Peninsular Malaysia (Yong and colleagues 2021) lists the typical subspecies as Endangered because of collecting for the ornamental trade (MyBIS). The 2006 Thai red list (ONEP) placed the species in the Near Threatened category, whereas the 2019 study of the Thai Department of Agriculture regards it as Least Concern, while noting illegal collecting from the wild for all Cycas in the country.

Like every species in the genus except Cycas beddomei, Cycas clivicola 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+, the official CITES database, 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 ask for proof that the plant was raised in cultivation.

Growing Cycas clivicola

In short: a sun-loving tropical Cycas that needs very sharp drainage and, according to the Palm and Cycad Society of Australia, an alkaline soil; it is grown outdoors in tropical and frost-free subtropical gardens, and under glass elsewhere. No detailed growing account has been published.

Outdoor and in-ground cultivation

According to the account reproduced by Llifle, the species is common in gardens in its home region, and a plant grown at the Nong Nooch Tropical Botanical Garden, in Thailand, was collected for the Vienna herbarium in 2011 (GBIF). The Palm and Cycad Society of Australia (PACSOA) recommends full sun and a well-drained, alkaline soil or potting mix, in keeping with its limestone habitat. Outside the tropics, the American and Australian gardens listed below are the only documented plantings; whether their plants grow outdoors is stated only for Sydney, where the plant stands in a garden bed.

Container cultivation

In the United Kingdom and other temperate regions, it is a plant for a heated glasshouse or conservatory: a deep pot, a very free-draining mineral mix with some limestone grit (by analogy with its habitat; not a tested recipe), as much light as possible and sparing watering in winter. No account of pot culture specific to the species has been found, and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on Cycas clivicola. On the French forum Fous de palmiers, the name appears only as a possible identification for a young plant of uncertain Thai origin (2010), with no growing report.

In cultivation in the UK, US and Australia

The species is present in a handful of gardens in the three countries; each source below is a declaration or a catalogue entry, not proof of a plant alive today.

  • United Kingdom: Paignton Zoo, in Devon, declares one accession in BGCI PlantSearch, without saying whether it grows indoors or out.
  • United States: the online catalogue of Montgomery Botanical Center (Coral Gables, Florida), which grows its cycads in the open, lists 16 accessions under Cycas clivicola, whose numbers date from 1994 and 1995, and one under subsp. lutea (1998). BGCI PlantSearch also lists The Huntington (San Marino, California), Brooklyn Botanic Garden (New York) and Mercer Arboretum and Botanic Gardens (Humble, Texas), one accession each; BGCI does not say whether these plants grow outdoors or under glass.
  • Australia: the Royal Botanic Garden Sydney grows one plant of wild origin from Malaysia (accession S1994-0062/1) in garden bed 65b, labelled “Mountain Sago” (Garden Explorer, updated 1 October 2026).

Outside these countries, BGCI lists among others the Singapore Botanic Gardens and the Jardim Botânico da Madeira. 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 clivicola 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. Seeds are exempt from CITES under annotation #4; ask for seed from cultivated plants.

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 clivicola, and no outdoor growing report outside the tropics has been found. An online plant retailer (Araflora) states that the plant tolerates about −4 °C (24.8 °F), without saying how this figure was obtained; the same page recommends shade or partial shade, contrary to the plant’s natural habitat, so the figure should be treated as a sales claim, not as a growing result.

European experience

No growing result has been published in Europe, in the open ground or in a pot. The species does not appear on the Italian forum Tropicamente, and on the French forum Fous de palmiers only as a doubtful identification. In the absence of data, grow it under glass, frost-free.

United Kingdom, United States and Australia

No cold reading and no growing report were found. The documented plantings are in frost-free or nearly frost-free settings (South Florida, Sydney) or of unknown placement. No USDA zone can be given without a documented trial.

Toxicity and precautions

No toxicity analysis specific to Cycas clivicola 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 clivicola has been found; the Malaysian and Thai sources mention only its trade as an ornamental plant.

Frequently asked questions

What does “clivicola” mean?

“Cliff-dweller”. The Latin name refers to its habit of growing on limestone rock faces.

Where can Cycas clivicola be seen in the wild?

On the limestone hills and islets of southern Thailand, for example around Phang Nga or Pak Meng, and in northern Peninsular Malaysia, notably on Langkawi.

Is it endangered?

Not globally: the IUCN lists it as Least Concern. The typical subspecies is, however, considered Endangered in Peninsular Malaysia because of collecting for the ornamental trade.

How can it be told from Cycas siamensis?

By its habitat and its female plants. Cycas clivicola grows on limestone cliffs and its megasporophylls form a closed head; it was long taken for a form of Cycas siamensis or Cycas pectinata.

What is its link with Cycas miquelii?

In 1998 de Laubenfels and Adema chose a specimen of Cycas clivicola from Chumphon as neotype of the name Cycas miquelii. Hill (2008) rejected that choice and designated older Utrecht sheets, which make Cycas miquelii a synonym of Cycas revoluta.

Does it need limestone?

It depends on the mix, but a free-draining, alkaline soil or potting mix is recommended by the Palm and Cycad Society of Australia, in keeping with its natural habitat.

Can it be grown outdoors in the UK?

No. It is a tropical species with no documented cold tolerance; in the UK it needs a heated glasshouse.

Is it poisonous?

It must be assumed so. It has not been studied, but all parts of Cycas are poisonous, especially the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Hill, K.D. & Yang, S.L. (1999). The genus Cycas (Cycadaceae) in Thailand. Brittonia 51(1): 48–73. doi:10.2307/2666557 [Original description, pages 62–64; reference checked on Crossref, text not consulted.]
  • de Laubenfels, D.J. & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43: 351–400. [Epicycas miquelii and its neotype Kerr 11873 (K), Chumphon, p. 393; full text consulted.]
  • Hill, K.D., Nguyễn, H.T. & Lộc, P.K. (2004). The genus Cycas (Cycadaceae) in Vietnam. The Botanical Review 70(2): 134–193. [Description, pages 173–174; reference taken from The World List of Cycads, text not consulted.]
  • Hill, K.D. (2008). The genus Cycas (Cycadaceae) in China. Telopea 12(1): 71–118. doi:10.7751/telopea20085804 [Section Indosinenses, smooth bark, lectotype of Cycas miquelii and rejection of the 1998 neotype (a specimen of Cycas clivicola); full text consulted.]
  • Jutta, M., Chew, K.L. & Saw, L.G. (2010). A new species of Cycas (Cycadaceae) from Peninsular Malaysia. Blumea 55(3): 249–252. doi:10.3767/000651910X544438 [Comparison with Cycas cantafolia, megasporophyll and seed characters; full text consulted.]
  • Hill, K.D. (2010). Cycas clivicola. The IUCN Red List of Threatened Species 2010: e.T42074A10619321. doi:10.2305/IUCN.UK.2010-3.RLTS.T42074A10619321.en [First global assessment, with separate assessments of subsp. clivicola and subsp. lutea; reference checked on Crossref, page not consulted.]
  • Bösenberg, J.D. & Nguyễn, T.H. (2023). Cycas clivicola. The IUCN Red List of Threatened Species 2023: e.T42074A67339659. doi:10.2305/IUCN.UK.2023-1.RLTS.T42074A67339659.en [Current assessment; reference checked on Crossref, LC category relayed by GBIF; page not consulted (access blocked).]
  • Tang, W. (2001). Focus on Cycas clivicola subsp. clivicola. Encephalartos 67: 8–13. [Specialist society journal; reference taken from The World List of Cycads, text not consulted.]
  • Yong, W.S.Y. et al. (2021). Malaysia Red List: Plants of Peninsular Malaysia, vol. 1, part 2. Forest Research Institute Malaysia, Kepong. [National EN status; cited by MyBIS, not consulted.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology of the epithet; cited by The World List of Cycads, text not consulted.]
  • 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: accepted name, original publication, type, range, synonyms, IUCN status; consulted directly.]