Cycas tansachana

Cycas tansachana is a tree-like cycad of central Thailand, confined to the limestone hills of Saraburi province and, according to the Thai Department of Agriculture, neighbouring Lopburi, where it clings to cliffs and bare rock outcrops. Described in 1999 by Ken Hill and S.L. Yang, this species of the genus Cycas is named after Kampon Tansacha, director of Nong Nooch Tropical Botanical Garden. It has the stoutest trunk of any Thai cycad. Threatened by limestone quarrying and the removal of wild plants, it is listed as Critically Endangered.

Key facts about Cycas tansachana

  • Accepted name: Cycas tansachana K.D.Hill & S.L.Yang (1999), accepted by The World List of Cycads (version 2026.08.15) and by GBIF; 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: none
  • Family: Cycadaceae, order Cycadales
  • Common names: no traditional English name; in Thai ปรงสระบุรี (prong Saraburi, “Saraburi cycad”) and มะพร้าวลิง (maphrao ling, “monkey coconut”); “Kampon’s sago” is a trade name used by a British nursery
  • Natural range: Thailand, Saraburi province (The World List of Cycads); also neighbouring Lopburi province according to the Thai Department of Agriculture
  • IUCN status: Critically Endangered (CR A3cd+4cd; B1ab(i,ii,iii,v)), assessment by A. Lindström dated 2020 and published in Red List version 2022-1; also Critically Endangered on the Thai national red list (ONEP 2006)
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; protected plant in Thailand (Plant Act of 1975)
  • Documented hardiness: no data (see Cold hardiness)
  • Light and soil: bare limestone cliffs and outcrops, in full sun or part shade, at 100 to 400 m
  • Habit and adult size: trunk 5 m or more, with a strongly swollen base that can exceed 1 m across, branching with age; leaves 1 to 1.7 m long
  • In the UK, US and Australia: Montgomery Botanical Center (Florida), 13 accessions from 1995 to 2008; several American gardens, the National Botanic Garden of Wales and the Botanic Garden of Adelaide declared to BGCI
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas tansachana

By its enormous trunk and its V-shaped leaves. The Thai Department of Agriculture (DOA 2019) describes it as the Thai cycad with the thickest trunk and the only one whose leaves form a V, their bases covered in dense golden hairs. Its female cones are “closed”, as in the other species of section Indosinenses, and its megasporophylls carry a rounded, deeply comb-like blade. The description below follows the DOA report (in Thai) and the comparative table of Jutta, Chew and Saw (2010); the original description could not be consulted.

  • Trunk: 5 m or more, with a much swollen base 1 m or more in diameter; grey, deeply fissured bark; old plants branch, and some carry up to fifteen heads.
  • Leaves: erect to spreading, green, keeled into a V; petiole 30 to 45 cm, edged with short spines; blade 1 to 1.7 m, with 65 to 100 leaflets on each side, crowded and regular, with a blunt, non-pungent tip; midrib flat above and raised below.
  • Cataphylls: narrowly triangular, soft, 5 to 6 cm long, with short yellowish-brown or grey hairs.
  • Male cones: narrowly ovoid, yellow, 11 to 13 cm long according to the DOA; microsporophylls 1.2 to 1.4 by 3.3 to 4.5 cm, ending in a spine of 1 to 3 mm.
  • Female cones and megasporophylls: a rounded, flattened, closed cone; megasporophylls 20 to 22 cm long, with brown to yellow felt; blade orbicular and deeply pectinate, with 40 to 60 lateral spines 18 to 25 mm long (Jutta et al. 2010).
  • Seeds: flattened-ovoid, 45 to 50 mm by 35 to 40 mm, with a yellow sarcotesta. The DOA describes them without a fibrous layer, whereas Jutta and colleagues (2010) record one: the sources disagree.

The male cone length given by the DOA (11 to 13 cm) seems small for a plant of this size; it could not be checked against the original description.

Hybrids

No hybrid has been documented for this species.

Possible confusion

  • Cycas chamaoensis, from the granite cliffs of Khao Chamao (Rayong), and Cycas clivicola, from the limestone hills of southern Thailand and Malaysia: two close relatives that also have closed female cones and an orbicular megasporophyll blade, and differ in habitat and in details of the leaves and sporophylls (Jutta et al. 2010).
  • Cycas cantafolia, from Johor in Peninsular Malaysia, whose megasporophyll blade is oval rather than orbicular.
  • Cycas elephantipes, from Chaiyaphum, another Thai cycad with a very swollen, “elephant-foot” trunk base, which grows on sandstone cliffs and in open forest instead (DOA 2019).
  • Cycas pranburiensis and Cycas petraea, other Thai cycads of limestone hills (DOA 2019).

Taxonomy

Cycas tansachana is an accepted name in 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). Ken Hill and S.L. Yang described it in 1999 in their account of the genus in Thailand (Brittonia 51(1): 65–66). That paper could not be consulted, so the description given here comes from later sources. Jutta, Chew and Saw (2010) place the species in section Indosinenses, the Indochinese Cycas with closed female cones. It has never been known under another name.

Etymology and history

The epithet honours Kampon Tansacha, director of Nong Nooch Tropical Botanical Garden, near Pattaya in Chonburi province, who was instrumental in the discovery of the species (Haynes 2022, quoted by The World List of Cycads).

The type was collected on 3 March 1997 by Ken Hill and P. Vatcharakorn in the hills north-east of Khong Khi Sua, in Saraburi province; the holotype is at the National Herbarium of New South Wales in Sydney, with isotypes in Bangkok, at Kew, in Leiden and in Beijing. In the year of its description, the journal of the Cycad Society of South Africa ran a feature on the species (Tang 1999).

Common names

No traditional English name is recorded. In Thai the species is called ปรงสระบุรี (prong Saraburi, “Saraburi cycad”) by the Department of Agriculture (DOA 2019) and by the Thai biodiversity database TH-BIF; Species+ gives “Prong”, the general Thai word for cycads. A Thai forestry study reports the local name มะพร้าวลิง (maphrao ling, literally “monkey coconut”) (Iadthong 2005), which is not necessarily restricted to this species. The British nursery Trebrown lists it as “Kampon’s sago”, a trade name built on the epithet rather than a name in use in Thailand.

In the wild

Cycas tansachana grows on the cliffs and bare outcrops of limestone hills, between 100 and 400 m according to TH-BIF. In surveys carried out from 2015 to 2019, the Department of Agriculture counted about 300 plants at three sites: the Phra Phutthabat Noi community forest (Song Khon subdistrict) and Khao Wong village, both in Kaeng Khoi district (Saraburi), and Lam Sonthi district in neighbouring Lopburi province. The World List of Cycads gives Saraburi only.

In the Phra Phutthabat Noi community forest, which covers about 4.8 km², a transect study estimated a density of 231 to 312 plants per km², all age classes included; long-tailed macaques (Macaca fascicularis) destroy young seeds and the new leaves of seedlings there (Iadthong 2005). Pollination has not been documented.

Conservation status and regulation

The IUCN lists Cycas tansachana as Critically Endangered (CR) under two sets of criteria: a past, ongoing or projected population decline linked to habitat loss and exploitation (A3cd+4cd), and a tiny range in continuing decline (B1ab(i,ii,iii,v)). The assessment is by Anders Lindström, dated 2020 and published in Red List version 2022-1 (reference checked on Crossref, which also records a second version issued the same year); The World List of Cycads gives the same criteria and GBIF relays the CR category. The Thai national red list (ONEP 2006) also rates it Critically Endangered.

The threats are well documented. The Department of Agriculture (DOA 2019) found traces of illegal trunk removal at all three sites, and limestone quarry concessions are destroying the habitat. Locally the sites are promoted as tourist attractions (“thousand-year-old cycads”) with no propagation or conservation programme. The DOA regards Cycas tansachana as the most threatened of the twelve Thai Cycas and recommends that exports should not be authorised. At Phra Phutthabat Noi, too, the main threat recorded is the removal of large trunks for sale (Iadthong 2005).

Like every species in the genus except Cycas beddomei, it is listed in CITES Appendix II, where the family Cycadaceae has appeared since 4 February 1977. The listing carries annotation #4 (the version adopted at CoP20, in force since 5 March 2026): seeds, pollen, seedlings and tissue cultures obtained in vitro and transported in sterile containers, as well as cut flowers of artificially propagated plants, are not covered by CITES; international trade in plants requires an export permit. In the European Union the species falls under Annex B of Regulation (EC) No 338/97, whose current annexes are set by Regulation (EU) 2026/1383, applicable since 29 June 2026. In the United Kingdom, the United States and Australia, CITES is applied through national legislation. Species+, the official CITES database, lists the species under this name and confirms this status (consulted on 24 October 2026). In Thailand all native cycads are protected under the Plant Act of 1975 (B.E. 2518), and their export requires a permit from the Department of Agriculture.

This summary does not replace the official texts: check the regulations in force before any purchase or exchange, ask the seller for proof of origin and choose nursery-raised plants grown from seed.

Growing Cycas tansachana

No cultivation guidance specific to Cycas tansachana has been published, and the few cultivation reports found come from France. Its natural setting, bare limestone in a tropical region with a marked dry season, suggests a very free-draining mineral mix and strong light. These are cautious inferences from the habitat, not tested results.

Outdoor and in-ground cultivation

Only frost-free tropical and subtropical climates can be considered for planting out, and no planted specimen with a documented history is known. Several gardens in southern Florida and coastal southern California hold the species (see below), but no published source says whether their plants grow outdoors or under glass.

Container cultivation

Elsewhere, a pot that spends the winter in a heated glasshouse or conservatory is the prudent choice. A gritty, mineral compost and careful watering in cool weather are the general rules for Cycas from seasonally dry climates; there is no specific data for this species.

In cultivation in the UK, US and Australia

In short: the species is well represented in American collections, while British and Australian records are limited to declarations to BGCI.

  • United States: Montgomery Botanical Center, in Coral Gables (Florida), lists 13 accessions in its online catalogue; their numbers date seven of them to 1995, two to 1996, two to 1998, one to 2005 and one to 2008 (consulted on 24 October 2026). The Huntington (San Marino, California), San Diego Botanic Garden (Encinitas), the San Diego Zoo, Naples Botanical Garden and Pinecrest Gardens (Florida), and the U.S. National Plant Germplasm System also declare it to BGCI PlantSearch.
  • United Kingdom: the National Botanic Garden of Wales declares it to BGCI; such a plant would be grown under glass. The British nursery Trebrown lists it with a USDA zone 9a rating, its own commercial classification, not a documented trial.
  • Australia: the Botanic Garden and State Herbarium of South Australia (Adelaide) declares it to BGCI.

A BGCI declaration shows that a garden held the plant at some point, not that it is alive today. Elsewhere, BGCI lists gardens in Thailand (Queen Sirikit Botanic Garden), Singapore, China, Egypt, Portugal (Madeira) and Sweden. No report from a private grower in these three countries is documented.

Propagation

The plant is dioecious: a male and a female are needed to obtain seed. No germination data specific to the species has been published; Cycas seed is usually sown fresh, in a free-draining mix and in warmth, and the only French report (see Cold hardiness) suggests slow early growth. Seeds are exempt from CITES under annotation #4: ask for seed from cultivated plants. For conservation, the DOA recommends propagation from seed, separation of offsets and reintroduction into the wild.

Pests and diseases

No disease specific to the species has been documented. In the wild, macaques destroy young seeds and the leaves of seedlings (Iadthong 2005).

Cold hardiness

There is no cold-hardiness data for Cycas tansachana. Central Thailand has a frost-free tropical climate, and nothing supports the idea that the plant can withstand frost.

Mediterranean and European experience

The species has reached the French trade: a June 2011 message on the Fous de palmiers forum reports its arrival at a garden centre near Bordeaux, and young plants were already offered for exchange on the same forum in 2007. A grower living between Belley (Ain) and Montpellier (Hérault), in France, reports on the same forum that a seedling sown in February–March 2009 had produced only two leaves and a caudex of barely 1 cm by November, far less than another cycad sown at the same time. That is a growth record, not a cold result: no frost report is documented. The Jardin zoologique tropical at La Londe-les-Maures, in the Var, has published no observation of this species.

United Kingdom, United States and Australia

No cold value and no dated cultivation report is documented, from forums or from botanic gardens. Trebrown’s zone 9a rating is a commercial classification and is not supported by a published trial.

Toxicity and precautions

No toxicity analysis specific to Cycas tansachana has been published, 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) as poisonous to dogs, cats and horses. 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. Its present use is ornamental: trunks taken from the wild are sold for gardens (DOA 2019).

Frequently asked questions

Who was Tansacha?

Kampon Tansacha, director of Nong Nooch Tropical Botanical Garden near Pattaya, who helped to bring the species to light.

Where does Cycas tansachana grow?

On limestone cliffs in Saraburi province, central Thailand, and, according to the Thai Department of Agriculture, in neighbouring Lopburi province.

How can I recognise it?

By its massive trunk, swollen at the base and often branched, and by its leaves, which are keeled into a V.

How many plants are left in the wild?

Few: the Thai Department of Agriculture counted about 300 plants at three sites between 2015 and 2019.

Why is it endangered?

Because of limestone quarrying and the illegal removal of trunks for gardens; the IUCN lists it as Critically Endangered.

Is it hardy in the UK?

Almost certainly not. There is no cold data and its range is tropical: in Britain it is a glasshouse plant.

Is it fast-growing?

Not on the only evidence available: a seedling raised in France had just two leaves after eight or nine months.

Is it poisonous?

It should be assumed so. No analysis exists for this species, but all the Cycas studied contain dangerous toxins, especially in their 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 (pp. 65–66); cited from The World List of Cycads.]
  • Jutta, M., Chew, K.L. & Saw, L.G. (2010). A new species of Cycas (Cycadaceae) from Peninsular Malaysia. Blumea 55: 249–252. doi:10.3767/000651910X544438 [Comparative table (section, cones, megasporophylls, seeds, habitat).]
  • ยอดหญิง สอนสุภาพ, ดวงเดือน ศรีโพทา, พรเทพ ท้วมสมบุญ & สุมาลี ทองดอนแอ [Sonsupap, Y. et al.] (2019). วิจัยสถานภาพพืชอนุรักษ์สกุลปรง (Non-Detriment Findings for Cycas spp.). Final report, Department of Agriculture, Bangkok. [Translated for this page.]
  • วิชาญ เอียดทอง [Iadthong, W.] (2005). Studied on population size of Cycas tansachana K.D. Hill & S.L. Yang in Khao Phra Budhthabat Noi Community Forest, Kaeng Koi District, Saraburi Province. Thai Journal of Forestry 24(1–2): 26–34.
  • Lindström, A. (2022). Cycas tansachana. The IUCN Red List of Threatened Species 2022-1: e.T42042A69827478. doi:10.2305/IUCN.UK.2022-1.RLTS.T42042A69827478.en [Assessment dated 13 November 2020; reference checked on Crossref, CR category relayed by GBIF.]
  • Tang, W. (1999). Focus on Cycas tansachana. Encephalartos 60: 4–7. [Cited from The World List of Cycads.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Source of the etymology given 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.]