Cycas nathorstii

Cycas nathorstii is a tree-like cycad of northern Sri Lanka and the eastern plain of Tamil Nadu, in India, where it grows in rather dry inland and upland forest. Long confused with Cycas circinalis, this species of the genus Cycas was described in 1932 by the German historian and botanist Julius Schuster, then overlooked for decades until it was reinstated in 2007. It is recognised by its bright green new leaves, its narrow, dull leaflets and its large male cones. The IUCN lists it as Vulnerable.

Key facts about Cycas nathorstii

  • Accepted name: Cycas nathorstii J.Schust. (1932), accepted by The World List of Cycads (version 2026.08.15) and by GBIF; POWO could not be consulted
  • Former names and synonyms: no synonym; long referred to Cycas circinalis, and placed in the synonymy of Cycas sphaerica by de Laubenfels and Adema (1998)
  • Family: Cycadaceae, order Cycadales
  • Common names: no English name attested; “madu” in Sinhala (Sri Lanka)
  • Natural range: northern Sri Lanka and eastern Tamil Nadu (India)
  • IUCN status: Vulnerable (VU A2cd+4cd), assessment by J.D. Bösenberg dated 2020 (Red List version 2022-1)
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union
  • Documented hardiness: no data (see Cold hardiness)
  • Light and soil: in the wild, inland and upland forest and flat land, usually on rather dry sites; no cultivation data
  • Habit and adult size: trunk up to 4.5 m tall and 11 to 20 cm in diameter; leaves 1.6 to 1.8 m long
  • In the UK, US and Australia: Montgomery Botanical Center (Florida) holds one accession from 2016; declared in BGCI by the Adelaide Botanic Garden; no British record found
  • Toxicity: no data for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas nathorstii

Among the cycads of South Asia, Cycas nathorstii is identified by a combination of characters: a robust habit, bright green (not bluish) new leaves, narrow, dull leaflets and large male cones whose scales end in a long, upturned spine. The description below follows Lindström and Hill (2007).

The trunk is aerial and reaches 4.5 m in height and 11 to 20 cm in diameter; its base is not strongly swollen and the thick bark stays covered in the persistent bases of leaves and cataphylls (the scale leaves that protect the growing point). The leaves are bright green and semi-glossy, 1.6 to 1.8 m long, flat in section, with 140 to 170 leaflets. The hairless petiole, 45 to 55 cm long, is spiny along 90 to 95% of its length. The median leaflets measure 19 to 31 cm by 9 to 14 mm, with a midrib raised on both surfaces and a soft, non-spiny tip. The down on the young leaves is shed early.

The male cones are narrowly ovoid and orange, about 45 cm long and 15 cm in diameter; each microsporophyll ends in a prominent spine about 1 cm long. The megasporophylls (the fertile leaves of female plants), 15 to 30 cm long and covered in a persistent brown down, carry 6 to 10 hairless ovules; their lanceolate blade, 4 to 6.5 cm long, is edged with 26 to 40 small teeth 1 to 4 mm long and ends in a distinct spine 10 to 14 mm long. The seeds are flattened-ovoid, up to 55 mm by 40 mm; the fleshy outer coat is yellow, there is no fibrous layer and no spongy tissue.

Hybrids

No hybrid is documented for this species.

Possible confusion

Historically, the commonest confusion has been with Cycas circinalis, the cycad of the Western Ghats, under whose name the Sri Lankan plants were filed for a long time. According to Lindström and Hill (2007), Cycas nathorstii differs in its bright green new growth (bluish in Cycas circinalis), its more robust habit, its narrower, dull leaflets and its larger male cones with longer, more curved spines. The same characters separate it from Cycas sphaerica, of eastern India.

In Sri Lanka it shares the island with Cycas zeylanica, a coastal cycad. That species has more widely spaced and more leathery leaflets, longer, harder and hairier cataphylls and, above all, seeds with a spongy layer that lets them float, which Cycas nathorstii lacks.

Taxonomy

Cycas nathorstii is a name accepted by The World List of Cycads and by GBIF; POWO could not be consulted. Following the key of Lindström and Hill (2007), it belongs to section Cycas, the group with hairless ovules and megasporophylls that are toothed but not deeply comb-like; the authors do not, however, state this placement in so many words for the species.

Its story is that of a forgotten name brought back. Julius Schuster separated it from Cycas circinalis in 1932, in his monograph of the Cycadaceae for Engler’s Pflanzenreich. His work was afterwards “largely (rightly) ignored”, write Lindström and Hill, except on this point, where the distinction was valid. In their revision of the genus, de Laubenfels and Adema (1998) placed Cycas nathorstii in the synonymy of Cycas sphaerica, while filing other Sri Lankan collections of the same plant under Cycas circinalis. Lindström and Hill (2007) reinstated it as a species in its own right, a view followed today by The World List of Cycads. For the reader, this means that plants from Sri Lanka and Tamil Nadu sold or recorded as Cycas circinalis may belong to this species.

Schuster’s types, kept in Berlin, were destroyed during the Second World War. Lindström and Hill therefore chose a lectotype: a sheet collected by George Thwaites (no. 3689, 1866) and held in Geneva in the Barbey-Boissier herbarium, with duplicates at Harvard (A), Kew, St Petersburg and Paris. First designated in 2002, it combined male and female parts from different plants; in 2007 the authors restricted the lectotype to the female part alone.

Etymology and history

The epithet honours the Swedish palaeobotanist Alfred Gabriel Nathorst (1850–1921), professor at the Natural History Museum in Stockholm, according to Lindström and Hill (2007) and Haynes (2022).

The hill cycad of Sri Lanka was known to botanists long before it had a name of its own: it was one of the elements on which Linnaeus based Cycas circinalis in 1753, through his Flora Zeylanica, and Trimen still called it so in 1898. The specimens behind Schuster’s name came from George Thwaites (1812–1882), superintendent of the Royal Botanic Garden at Peradeniya from 1849 to 1880, and had been distributed to European herbaria by the Swiss botanist William Barbey-Boissier. No history of its introduction into cultivation is documented.

Common names

No English common name is attested. In Sinhala the plant is called “madu” (Schuster 1932, cited by Lindström and Hill 2007); this name covers the cycads of Sri Lanka in general and does not distinguish between the island’s species.

In the wild

Cycas nathorstii grows in inland and upland forest in the north of Sri Lanka and on flat land in the east of Tamil Nadu, in India, usually on rather dry sites (Lindström and Hill 2007). The specimens cited by these authors range, in Sri Lanka, from Wilpattu National Park (North Western Province) to the Bibile area and Gal Oya National Park and, in India, include plants near Chengalpattu, south of Chennai, recorded at less than 25 m above sea level in 2002. Pollination, phenology and seed dispersal are not documented.

Conservation status and regulation

The IUCN lists Cycas nathorstii as Vulnerable (VU, criteria A2cd+4cd), in the assessment by J.D. Bösenberg dated 2020 and published in version 2022-1 of the Red List; an earlier assessment (2010) already existed, and the Red List data relayed by GBIF confirm the current category (consulted on 21 October 2026). These criteria reflect a past and projected decline in population size linked to loss of habitat and exploitation.

Lindström and Hill (2007) described two contrasting situations. In Tamil Nadu, the species has suffered greatly from the cutting of stems for local medicine, several populations being reduced to a few scattered plants, and the lowlands, much sought after for farming, have been cleared; they regarded it as Endangered there. In Sri Lanka it remained locally frequent, though not in great numbers, and was known from reserves, but political instability made assessment difficult; they regarded it as Vulnerable on the island.

Like every species in the genus except Cycas beddomei, Cycas nathorstii 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 exempt, 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 (search of 3 October 2026).

This general information does not replace the official texts: check the rules in force before buying or exchanging plants, ask the seller for proof of origin and prefer plants raised from cultivated seed.

Growing Cycas nathorstii

In short: no institution has published growing advice for Cycas nathorstii, and no grower’s report was found. Its habitat, tropical lowlands and hills with rather dry sites, suggests a frost-free plant for full light and a free-draining mix, watered sparingly in the cool season, as for most cycads; this is a deduction, not a published growing result.

Outdoor and in-ground cultivation

No planting result has been published outside its native range. Only frost-free tropical and near-tropical climates can reasonably be considered for planting out. Montgomery Botanical Center in Florida, which grows its collection outdoors, holds an accession of the species (see below), but has published no observation on it.

Container cultivation

In temperate climates it would be a plant for a pot under heated glass. No container-growing report has been found: searches of the French forum Fous de palmiers and the Italian forum Tropicamente returned nothing for this species, and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on it.

In cultivation in the UK, US and Australia

In the United States, the online catalogue of Montgomery Botanical Center (Coral Gables, Florida) lists Cycas nathorstii under one accession number, 20160146, which by the garden’s numbering dates from 2016 (search of 21 October 2026); the catalogue does not say how many plants it covers. In Australia, the species is declared in BGCI PlantSearch by the Botanic Garden and State Herbarium of South Australia, in Adelaide (search of 21 October 2026); a BGCI entry shows that a garden has declared a plant, not that it is alive today, and it does not say whether the plant grows outdoors or under glass.

No British garden declares the species. No report from an English-speaking grower could be read; PalmTalk and Dave’s Garden could not be consulted. Plants labelled Cycas circinalis in older collections may include this species, but no garden has published such a re-identification.

Propagation

The plant is dioecious: a male and a female plant are needed to obtain seed. No germination data specific to the species have been published; its seeds have no spongy layer. Seeds are exempt from CITES under annotation #4, but Sri Lankan and Indian rules on collection and export apply in the countries of origin.

Pests and diseases

No pest or disease specific to the species is documented. The main recorded damage is human: the cutting of stems for traditional medicine in Tamil Nadu (Lindström and Hill 2007). Cycad scale insects, including the Asian cycad scale, Aulacaspis yasumatsui, can attack all cultivated species.

Cold hardiness

No cold-tolerance data exist for Cycas nathorstii. Its range, in northern Sri Lanka and on the coastal plain of Tamil Nadu, is frost-free, and nothing allows us to say that the plant tolerates frost.

Mediterranean experience

No growing result has been published in Europe, in the ground or in a pot, and no dated frost event concerns the species; the Jardin zoologique tropical in the Var has published nothing on it. Readers in comparable climates, such as California or southern Australia, have no European result to go on.

United Kingdom, United States and Australia

No cold reading or dated growing report was found, either on forums or from botanic gardens; Montgomery, in southern Florida, has published no observation. No USDA zone can be given. In the UK, and in most of the United States and Australia outside the tropics, keep it under heated glass.

Toxicity and precautions

No toxicity analysis specific to Cycas nathorstii 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. The ASPCA lists the sago palm (Cycas revoluta) as poisonous to dogs, cats and horses. Until proven otherwise, treat the plant as poisonous: keep seeds and leaves out of reach of children and pets, and wear gloves to clean the seeds. If any part is swallowed, contact a poison centre, a doctor or a vet straight away.

Traditional uses

In Tamil Nadu, the stems of Cycas nathorstii are cut for local medicine, to the point of having depleted several populations (Lindström and Hill 2007). The preparations and their precise uses are not described in the sources consulted.

Frequently asked questions

Where does Cycas nathorstii grow?

In northern Sri Lanka and in eastern Tamil Nadu, in India. It lives in inland and upland forest or on flat land, usually on rather dry sites.

Is Cycas nathorstii the same as Cycas circinalis?

No. The Sri Lankan plants long went under that name, but Lindström and Hill (2007) showed that they form a distinct species, with bright green rather than bluish new leaves, narrower leaflets and larger male cones.

Where does the name nathorstii come from?

It honours the Swedish palaeobotanist Alfred Gabriel Nathorst (1850–1921), professor at the Natural History Museum in Stockholm.

How can it be told from Cycas zeylanica?

By the seeds and the leaflets. Cycas zeylanica, the coastal cycad of Sri Lanka, has seeds with a spongy layer that float and more widely spaced, more leathery leaflets; Cycas nathorstii has no spongy tissue in its seeds.

Is it endangered?

Yes. The IUCN lists it as Vulnerable: in Tamil Nadu, stem cutting for local medicine and land clearance have reduced several populations to a few plants.

Can it be grown outdoors in the UK?

Almost certainly not. No cold data exist and its range is frost-free; outside the tropics it is a plant for a pot under heated glass.

Is it poisonous?

It must be assumed so. No analysis exists for the species, but all the cycads studied contain serious toxins, especially in the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Lindström, A.J. & Hill, K.D. (2007). The genus Cycas (Cycadaceae) in India. Telopea 11(4): 463–488. doi:10.7751/telopea20075745 [Revision of the cycads of India and Sri Lanka; lectotype, description, range, status, Sinhala name; full text consulted.]
  • Schuster, J. (1932). Cycadaceae. In: Engler, A. (ed.), Das Pflanzenreich IV.1 (Heft 99): 1–168. Wilhelm Engelmann, Leipzig. [Original description (p. 76, fig. 10E); not consulted directly, cited after Lindström and Hill (2007) and The World List of Cycads.]
  • Bösenberg, J.D. (2022). Cycas nathorstii. The IUCN Red List of Threatened Species 2022: e.T42094A68906510. doi:10.2305/IUCN.UK.2022-1.RLTS.T42094A68906510.en [Red List assessment (dated 2020); reference found on The World List of Cycads and Crossref, category VU relayed by GBIF, page not consulted (access blocked).]
  • Laubenfels, D.J. de & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Very broad species concepts; cited after The World List of Cycads and Lindström and Hill (2007).]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Source of the etymologies given by The World List of Cycads; not consulted directly.]
  • 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.]