Cycas curranii

Cycas curranii is a large understorey cycad endemic to the island of Palawan, in the Philippines, where it grows in dense forest on the ultramafic soils of the hills of Puerto Princesa, Aborlan and Narra. This species of the genus Cycas was first described in 1932 as a mere variety of Cycas circinalis, under the name Cycas circinalis var. curranii, before the Australian botanist Ken Hill raised it to species rank in 1995. Its seeds, among the largest in the genus, have a shell marked with lengthwise ribs, a feature it shares with only two other Philippine cycads. The IUCN lists it as Critically Endangered.

Key facts about Cycas curranii

  • Accepted name: Cycas curranii (J.Schust.) K.D.Hill (1995), according to The World List of Cycads; POWO could not be consulted directly
  • Former names and synonyms: Cycas circinalis var. curranii J.Schust. (1932), the basionym, published as Cycas circinalis subsp. riuminiana var. curranii; included in Cycas silvestris by de Laubenfels and Adema (1998), a view not followed
  • Family: Cycadaceae, order Cycadales
  • Common names: no established English name; in the Philippines, pitogo, a local name for the broad-leaflet cycads; garden label “Curran’s Pitago” at the Royal Botanic Garden Sydney
  • Natural range: Philippines, island of Palawan (municipalities of Puerto Princesa, Aborlan and Narra); a presence on Mindoro is disputed
  • IUCN status: Critically Endangered (CR), reassessment by J. D. Bösenberg (Red List version 2023-1), CR according to GBIF; previous assessment by E. M. G. Agoo and colleagues (2014), criteria A2acd+4acd
  • 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 forest species to be kept frost-free (see Cold hardiness)
  • Light and soil: in the wild, the understorey of dense forest on steep ultramafic slopes; in cultivation, light shade to full sun and a moist, well-drained position (Palm and Cycad Society of Australia)
  • Habit and adult size: trunk 1 to 8 m tall and 14 to 25 cm across; leaves 180 to 260 cm long; about 3 m in cultivation according to the Palm and Cycad Society of Australia
  • In the UK, US and Australia: Montgomery Botanical Center (Florida), San Diego Botanic Garden and San Diego Zoo (California), National Tropical Botanical Garden (Hawaii); Royal Botanic Garden Sydney; no British record
  • Toxicity: not studied for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas curranii

Two characters together identify it: broad leaflets (10 to 14 mm) on very long, glossy leaves, and large yellow seeds whose shell bears regular lengthwise ribs. The revision of the Philippine Cycas by Lindström, Hill and Stanberg (2008) gives the following characters:

  • Trunk: 1 to 8 m tall and 14 to 25 cm in diameter, barely swollen at the base, with thick, corky bark; 30 to 120 leaves in the crown.
  • Leaves: dark green or grey-green, highly glossy to semi-glossy, 180 to 260 cm long, flat or barely keeled, with 150 to 360 leaflets; white or orange down that soon falls; the leaf axis ends in a pair of leaflets; petiole 35 to 55 cm long, hairless, spiny along 70 to 100% of its length.
  • Leaflets: 210 to 310 mm long and 10 to 14 mm wide, paler beneath, flat, sharply narrowed at the base (2.5 to 3 mm), with an acute but not spiny tip; midrib raised above, flat below.
  • Cataphylls (the scales that protect the growing point): narrowly triangular, soft, hairy, 100 to 130 mm long.
  • Male cones: spindle-shaped, green or cream; microsporophylls soft, with no apical spine or only a rudimentary, downward-pointing one.
  • Female organs: a head that stays closed both at pollination and when the seeds are ripe; megasporophylls about 21 cm long, with grey down and 2 to 6 ovules; blade rounded, about 100 mm by 70 mm, deeply comb-like, with some 30 soft lateral spines about 20 mm long.
  • Seeds: almost round to ovoid, about 48 mm by 40 mm; fleshy coat yellow, without bloom and without a fibrous layer; shell with lengthwise ribs.

Hybrids

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

Possible confusion

Only two other cycads, both Philippine, have a seed shell with lengthwise ribs (Lindström and colleagues 2008):

  • Cycas wadei, from the island of Culion, has seeds half the size and leaflets half as wide (3 to 8 mm), and grows in dry grassland that is often burnt.
  • Cycas saxatilis, also from Palawan, hangs from the limestone cliffs of St Paul’s Bay and has narrower, more elongated male cones.

The other Philippine cycads, such as Cycas riuminiana or Cycas edentata, have firm male cones and an unornamented seed shell. The old records of Cycas circinalis or Cycas rumphii from the Philippines referred to other species.

Taxonomy

Cycas curranii is accepted by The World List of Cycads; POWO could not be consulted directly. The German botanist Julius Schuster described it in 1932 in Engler’s Das Pflanzenreich (volume 99, page 69) as a variety of Cycas circinalis, placed under subspecies riuminiana. Ken Hill raised it to species rank in 1995, in the proceedings of the Third International Conference on Cycad Biology (page 150). The type was collected in March 1906 by H. M. Curran (no. 3842) on the bank of the Molinao River, on Palawan; the Manila holotype (PNH) has been lost, probably destroyed during the Second World War, and duplicates are kept at Kew and in Paris.

Lindström, Hill and Stanberg (2008) created section Wadeae for this species, Cycas wadei and Cycas saxatilis, defined by soft, waxy male cones, comb-like megasporophylls, hairless ovules and yellow seeds with a strongly ribbed shell. They regard it as an isolated relict group, related to groups on the Asian mainland and probably separated from them by the drift of fragments of the Earth’s crust early in the Tertiary. In their view, Schuster’s placement under Cycas circinalis reflects no real relationship. De Laubenfels and Adema (1998), for their part, included these plants in a broad concept of Cycas silvestris, a species that The World List of Cycads treats as endemic to Australia.

Etymology and history

The epithet honours the collector of the type, the American forester Hugh M. Curran (1875–1960), who worked for the Bureau of Forestry in Manila (Haynes 2022, as cited by The World List of Cycads). Lindström and colleagues (2008) call him “Hugo M. Curran”.

The American botanist E. D. Merrill was the first to report, in 1911 and again in 1923, an unnamed cycad from Palawan, based on Curran’s collection. After Schuster’s description the plant was largely ignored until 1995; in 1986, Zamora and Co still placed the Palawan plants under Cycas wadei. In the early 1990s, large quantities of seed collected in the wild were distributed, and the resulting plants are now widespread in cultivation (Lindström and colleagues 2008).

Common names

No English vernacular name is established in the botanical literature. The Palm and Cycad Society of Australia gives pitogo as the local name for the broad-leaflet cycads; the same word refers in Tagalog to the seeds of Cycas wadei (Lindström and colleagues 2008). The Royal Botanic Garden Sydney labels its plants “Curran’s Pitago”: this is a garden label, not an attested vernacular name.

In the wild

According to Lindström and colleagues (2008), Cycas curranii is known only from Palawan, where it seems to be tied to ultramafic rocks: it grows mainly on steep slopes of these rocks, sometimes on the fans of debris below them, in the understorey of dense, rich mixed forest. It has been collected in the municipalities of Puerto Princesa, Aborlan and Narra, notably at the foot of Mount Victoria; a set of herbarium sheets published through GBIF records a 1984 collection from Narra, on Mount Victoria, in a mining company’s area. Some secondary sources, probably derived from the IUCN assessment, also report a subpopulation at Bongabon and Mansalay, in Oriental Mindoro province; Lindström and colleagues attribute the Mansalay record to Cycas wadei, and no specimen supports it. Its presence on Mindoro therefore remains unconfirmed.

Conservation status and regulation

Cycas curranii is listed as Critically Endangered (CR) by the IUCN: J. D. Bösenberg’s reassessment was published in Red List version 2023-1 (reference checked on Crossref), and the IUCN data relayed by GBIF give it the CR category (consulted on 21 October 2026). The previous assessment, by E. M. G. Agoo, D. A. Madulid, V. C. Linis and E. Sambale (2014), cited by The World List of Cycads, used criteria A2acd+4acd, which correspond to an estimated decline of at least 80% of the population, past and future, linked to habitat loss and collecting. The Red List itself could not be consulted directly.

This status contrasts with the view of Lindström and colleagues (2008), who described a species scattered over a wide area at low densities, whose forest is degraded at low altitude and near the coastal plain but more intact inland; they then recommended the category Near Threatened. The sources consulted do not explain the gap between these two assessments.

Like every species in the genus except Cycas beddomei, Cycas curranii 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 curranii

In short: a handsome tropical forest cycad, fairly widespread in tropical collections, that wants warmth, moisture and good drainage, and tolerates more shade than most Cycas. Outside the tropics it is a plant for a heated glasshouse.

Outdoor and in-ground cultivation

Cycas curranii is fairly common in tropical collections, thanks to the seed distributed in the early 1990s (Lindström and colleagues 2008). The Palm and Cycad Society of Australia describes it as an attractive cycad of about 3 m in cultivation, with glossy deep green leaves, to be planted in a moist, well-drained position, in light shade to full sun. This advice matches its forest-understorey habitat, which is moister than that of most cycads. Outdoors, it belongs in frost-free tropical and humid subtropical gardens, such as those of South Florida and Hawaii where it is grown (see below); no garden has published how its plants are placed or how they fare.

Container cultivation

In the United Kingdom and other temperate regions, it is a plant for a large pot in a heated glasshouse or conservatory, with a free-draining but moisture-retentive mix and bright, filtered light; these are general recommendations drawn from its habitat and from the Palm and Cycad Society of Australia, not a tested recipe for the species. No first-hand growing report has been found on the English, French or Italian forums consulted, and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on it, so no Mediterranean experience can be passed on.

In cultivation in the UK, US and Australia

Each source below is a catalogue entry or a declaration, not proof that a plant is alive today.

  • United States: the online catalogue of Montgomery Botanical Center (Coral Gables, Florida), which grows its cycads in the open, lists one accession, whose number dates from 1995; a herbarium specimen made in Florida in 2006 by D. P. Little, published through GBIF, documents a cultivated plant. BGCI PlantSearch also lists San Diego Botanic Garden (Encinitas) and San Diego Zoo Botanical Gardens (California), and the National Tropical Botanical Garden (Kalāheo, Hawaii), without saying whether the plants grow outdoors or under glass.
  • Australia: the Royal Botanic Garden Sydney grows a plant of wild origin from the Philippines, accession S1993-0435, recorded in two locations and labelled “Curran’s Pitago” (Garden Explorer, updated 1 October 2026).
  • United Kingdom: no record in BGCI PlantSearch or in the British garden catalogues consulted.

Elsewhere, BGCI lists the Hortus Botanicus Amsterdam, the Singapore Botanic Gardens, the Fairy Lake Botanical Garden in Shenzhen and, on Palawan itself, the Katala Foundation in Puerto Princesa. 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 curranii is dioecious and is raised from seed: a male and a female plant are needed for fertile seed. The seeds are large. No published germination data specific to the species have been found. Seeds are exempt from CITES under annotation #4; given the Critically Endangered status and past seed collecting in the wild, ask for seed from cultivated plants.

Pests and diseases

Lindström and colleagues (2008) observed that on Palawan the Asian cycad scale, Aulacaspis yasumatsui, seems to be kept in check by native predators, whereas it devastates cultivated cycads on Luzon, Negros and Panay. It remains a serious threat to Philippine cycads should it reach wild populations without predators. In cultivation, the species is exposed to this scale and to root rot in waterlogged substrate.

Cold hardiness

No cold-tolerance value has been published for Cycas curranii, and no outdoor growing report outside the tropics has been found. It comes from forest on a tropical island, which suggests that it has no tolerance of frost; this is a deduction, not a documented result.

European experience

No growing result has been published in Europe, outdoors 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 passing mention without any growing report. 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 tropical or subtropical settings (South Florida, Hawaii, Sydney) or of unknown placement (San Diego). No USDA zone can be given without a documented trial.

Toxicity and precautions

No toxicity analysis specific to Cycas curranii 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 curranii has been found in the sources consulted.

Frequently asked questions

Where does Cycas curranii come from?

From the island of Palawan, in the Philippines, where it grows in forest understorey on ultramafic rocks; its presence on Mindoro is disputed.

Is it a variety of Cycas circinalis?

No. It was described in 1932 as a variety of Cycas circinalis, but it is not closely related: it belongs to section Wadeae, confined to the Philippines, and was raised to species rank in 1995.

What is special about its seeds?

They are large, about 48 mm long, and their shell bears lengthwise ribs, a feature shared only with Cycas wadei and Cycas saxatilis.

Is it endangered?

Yes. The IUCN lists it as Critically Endangered, a category confirmed by the 2023 reassessment, although a 2008 revision considered it only Near Threatened.

Does it tolerate shade?

Yes, in part. It is a forest-understorey cycad, and the Palm and Cycad Society of Australia recommends light shade to full sun.

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

  • Schuster, J. (1932). Cycadaceae. In A. Engler (ed.), Das Pflanzenreich, Heft 99. [Basionym Cycas circinalis var. curranii, page 69; reference taken from Lindström and colleagues (2008), not consulted.]
  • Hill, K.D. (1995). Infrageneric relationships, phylogeny, and biogeography of the genus Cycas (Cycadaceae). Proceedings of the Third International Conference on Cycad Biology: 139–162. [Combination at species rank, page 150; reference taken from The World List of Cycads, 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. [Inclusion in Cycas silvestris; broad species concept; full text consulted.]
  • Lindström, A.J., Hill, K.D. & Stanberg, L.C. (2008). The genus Cycas (Cycadaceae) in The Philippines. Telopea 12(1): 119–145. doi:10.7751/telopea20085805 [Description, section Wadeae, history, distribution, conservation, cycad scale; full text consulted.]
  • Agoo, E.M.G., Madulid, D.A., Linis, V.C. & Sambale, E. (2014). Cycas curranii. The IUCN Red List of Threatened Species 2014: e.T42090A61490070. doi:10.2305/IUCN.UK.2014-2.RLTS.T42090A61490070.en [Previous assessment, CR A2acd+4acd, cited by The World List of Cycads; reference checked on Crossref, page not consulted.]
  • Bösenberg, J.D. (2023). Cycas curranii. The IUCN Red List of Threatened Species 2023: e.T42090A67341354. doi:10.2305/IUCN.UK.2023-1.RLTS.T42090A67341354.en [Current assessment; reference checked on Crossref, CR category relayed by GBIF; page not consulted (access blocked).]
  • 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.]