Cycas macrocarpa

Cycas macrocarpa is a large cycad of the rainforests of Peninsular Malaysia and Thailand, also reported from Laos, which can grow more than 10 m tall and lives in the forest understorey, often on slopes and ridges. Described in 1854 by the British botanist William Griffith from a plant collected in Malacca, this member of the genus Cycas takes its name from its large seeds, compared to duck eggs. Long confused with Cycas rumphii in Malaysia and with Cycas circinalis in Thailand, it is listed as Vulnerable by the IUCN. Two previously unknown populations were discovered on Penang Island in 2025.

Key facts about Cycas macrocarpa

  • Accepted name: Cycas macrocarpa Griff. (1854), accepted by The World List of Cycads (version 2026.08.15); POWO could not be consulted directly
  • Former names and synonyms: no synonym; wrongly called Cycas rumphii (Ridley 1911, 1925) and Cycas circinalis (Smitinand 1971, 1972)
  • Family: Cycadaceae, order Cycadales
  • Common names: no English common name attested; “bogak” in Malay, “prong pa” (ปรงป่า) in Thai
  • Natural range: Peninsular Malaysia (Kelantan, Pahang, Penang, Perak, Malacca, Terengganu), Thailand (east, west and south), Laos (Vientiane province; presence considered doubtful by those who reported it)
  • IUCN status: Vulnerable (VU, criteria A2cd+4cd), assessment published in 2023
  • 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: understorey of humid lowland and hill forest (100 to 500 m in Thailand), on slopes and ridges, on granite, silty clay or limestone; in Laos, on limestone rocks between 300 and 1,000 m
  • Habit and adult size: trunk up to 12 m tall and 13 to 34 cm in diameter; arching leaves up to 2.9 m long
  • In the UK, US and Australia: Montgomery Botanical Center (Florida) lists accessions from 1995 to 1998; declared in BGCI by the Royal Botanic Garden Sydney, the Hunter Region Botanic Gardens (New South Wales) and The John Fairey Garden (Texas); no British garden record found
  • Toxicity: no data for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas macrocarpa

Cycas macrocarpa stands out by its large size; its long, arching leaves with broad, soft, glossy dark green leaflets, the new growth flushed bluish green; its petiole, spiny right down to the base; and its very large seeds, which lack a spongy layer. Its megasporophylls carry a comb-like blade with 8 to 10 spines on each side. The updated description by Liew and Chacko (2026), based on the Penang plants and specimens in the Kepong herbarium, reads:

  • Trunk: upright, sometimes leaning or decumbent, up to 12 m tall and 34 cm in diameter, sometimes branched, not swollen at the base; bark grey-brown.
  • Leaves: arching, up to 290 cm long; buds covered in brown woolly hairs that fall as the leaf unfurls; new flush bluish green; petiole 25 to 100 cm long, thickened at the base, spiny right to the base (spines 3 mm long at most).
  • Leaflets: 25 to 118 pairs, linear, up to 50 cm long and 2.2 cm wide, set at 60–80°, thin and soft, glossy dark green above, paler and matt beneath; base narrowed and twisted; margins often wavy, not rolled; tip acute and soft; midrib raised, pale green.
  • Cataphylls: up to 14 cm long and 1 cm wide, with brown down.
  • Male cones: usually single, ovoid, up to 32 cm long; microsporophylls up to 45 mm by 17 mm, orange, with a linear, sharply upturned apical spine up to 28 mm long.
  • Megasporophylls: up to 20 cm long, densely covered in reddish-brown hairs, bearing 2 to 6 ovules; blade lanceolate and comb-like, with 8 to 10 sharp spines on each side; terminal spine up to 6.5 cm.
  • Seeds: obovoid, flattened, 50 to 60 mm long and 40 mm wide, reddish brown when ripe; sarcotesta 4 mm thick, without a fibrous layer; no spongy layer.

De Laubenfels and Adema (1998) gave slightly different figures: trunk up to 9 m, leaves 100 to 250 cm, leaflets 19 to 39 cm by 1.2 to 1.7 cm, yellow seeds 50 to 75 mm long. According to Liew and Chacko, the Penang plants exceed the leaf lengths and leaflet numbers published until then; yet the description by Averyanov and colleagues (2014), in their account of the gymnosperms of Laos, already gave a trunk up to 12 m tall and 14 to 24 cm thick, a crown of 30 to 40 leaves, leaves 2.2 to 3.2 m long with 90 to 120 pairs of leaflets 15 to 25 cm long, yellowish-orange ovoid male cones 16 to 22 cm by 9 to 12 cm, megasporophylls 10 to 20 cm long with 2 to 4 ovules, and yellow seeds 4.5 to 5 cm long. In their key to the Cycas of Laos, it is its stiff, pungent cataphylls, 8 to 17 cm long and densely covered in rusty down, and its 4.5 to 5 cm seeds that set it apart from its neighbours. The 2019 report of the Thai Department of Agriculture compares the seed, in shape and size, to a duck egg.

An account of the rediscovery of the species, reproduced on the wiki of the Palm and Cycad Societies of Australia (PACSOA), gives a simple field key against the coastal Thai plants then called Cycas rumphii: in Cycas macrocarpa the cataphylls are narrowly triangular, up to 110 mm long, with a thick, woolly, rusty red-brown down; new growth is distinctly blue; mature leaflets are dark green, narrow at the base (2 to 4 mm) and have a narrow, raised green midrib. The same account describes the seeds found under young plants as oblong, about 60 by 35 mm, and without the spongy layer typical of the Cycas rumphii group.

Hybrids

No natural or cultivated hybrid is documented for this species.

Possible confusion

  • Cycas edentata, the cycad of beaches and mangroves, found on the same coasts: megasporophylls almost without teeth, seeds with a spongy layer that lets them float;
  • Cycas clivicola, from limestone cliffs in Thailand and Malaysia: a rock-dwelling plant with narrower leaflets (5 to 9 mm);
  • Cycas cantafolia, from the granite cliffs of Johor: another large cycad of the Malay Peninsula, with a very restricted range;
  • Cycas inermis, from Vietnam and Laos, its closest relative according to Hill and Stanberg (2009).

Taxonomy

Cycas macrocarpa is a name accepted by The World List of Cycads; POWO could not be consulted directly. William Griffith described it in his Notulae ad Plantas Asiaticas (volume 4, 1854, pp. 11–14, plate 362), from a specimen collected near Tabong, in what is now the state of Malacca (no. 6361 of the East India Company herbarium, holotype at Kew). The name was then forgotten: Ridley applied the name Cycas rumphii to the Malayan plants (1911, 1925), and Smitinand that of Cycas circinalis to the plants of Thailand (1971; Flora of Thailand, 1972).

The PACSOA account explains how the name resurfaced. Griffith (1810–1845) never published his notes, which were compiled and printed in Calcutta in 1854, nine years after his death; Miquel mentioned the name in 1868 as a species unknown to him and doubtfully distinct, and the Index Kewensis placed it in the synonymy of Cycas rumphii in 1893. The type sheet at Kew bears the label “Pakoo Galouwe / Cycas sp. / Crew near Tabong”, and the seeds and sporophylls belonging to it were found in Kew’s Museum of Economic Botany; they matched seeds collected in southern Thailand. According to the same account, the specimen was gathered in September 1842 by J.B. Westerhout, Assistant Resident of Malacca, and the locality is now Keru, in Melaka.

Ken Hill treated the species in Palms & Cycads (1995), then in the revision of the Cycas of Thailand he wrote with S.L. Yang (Brittonia, 1999). De Laubenfels and Adema (1998) also accept it. According to Hill and Stanberg (2009), its closest relative is Cycas inermis, from Vietnam. By its characters (glabrous ovules, seeds without a spongy layer) it belongs to section Cycas; the molecular phylogeny of Liu and colleagues (2018) nonetheless places it in the clade of section Indosinenses, with Cycas pranburiensis, as noted on the genus page.

Etymology and history

The epithet comes from the Greek makros, “large”, and karpos, “fruit”, a reference to the large seeds (Haynes 2022, as cited by The World List of Cycads).

According to the PACSOA account, the species was rediscovered in the field around Sungai Padi, near Sungai Kolok in the far south of Thailand, where large plants grew in village gardens and in old rubber plantations that were being cleared and deep-ploughed for replanting, destroying the old cycads. The same text reports a plant identified from photographs in the Durban Botanic Gardens, in South Africa, and seedlings from Thai seed in collections in Florida.

In 2025 two members of the Malaysian Nature Society discovered two small populations on Penang Island, the first record of the genus Cycas in that state, even though it had been thoroughly explored since colonial times; their identification was confirmed by the specialist Jutta Poetz (Liew and Chacko 2026).

Common names

No English common name is attested. In Malay the species is commonly called “bogak” (Liew and Chacko 2026). In Thailand the Department of Agriculture calls it “prong pa” (ปรงป่า), literally “forest cycad”; “prong” refers to cycads in general. The IUCN Red List uses the name “pakoo galowe”, whose language is not stated in the sources consulted; it echoes the “Pakoo Galouwe” written on the label of the type collected in 1842.

In the wild

Cycas macrocarpa occurs in Peninsular Malaysia, where it was known from Perak, Malacca, Kelantan, Terengganu and Pahang before its discovery on Penang; in southern and western Thailand and in the east of the country (Chanthaburi province); and in Laos, in Vientiane province, where Averyanov and colleagues first reported it in 2014, from three collections made in March 2013 in Vang Vieng district, between 300 and 900 m. De Laubenfels and Adema describe it as an understorey plant of humid lowland forest, often on limestone hills. In Thailand it grows in humid evergreen forest between 100 and 500 m; a survey by the Department of Agriculture (2015–2019) counted 110 plants at three sites, in Makham district (Chanthaburi) and at Khura and Kapong (Phang Nga), with no sign of illegal collecting.

In Laos these authors found it growing on limestone rock between 300 and 1,000 m, in primary or secondary lowland evergreen broadleaved forest and in secondary scrub on limestone, sometimes in damp, half-shaded places. They found fairly large subpopulations on the Vang Vieng limestone massif, where the plant regenerates more or less well. They stress, however, that these localities lie more than 1,000 km north of the place where the species was first found, which makes the presence of a “Malaysian” species in northern Indochina doubtful; only further collections will settle the matter. The World List of Cycads nevertheless includes Laos in the species’ range.

On Penang the two populations grow in hill dipterocarp forest at 200 to 250 m, on steep west-facing slopes, firmly anchored on granite boulders and sometimes on silty clay. They form isolated, very dense groups and include only 15 adult plants. A dry male cone was seen there in February 2025 and a developing megasporophyll in October 2025; one female was surrounded by seedlings, evidence of recent reproduction. The authors note that cycads are pollinated by small weevils that spend almost their whole life in the male cones; their absence from the male cone examined raises concern for the viability of this population.

Conservation status and regulation

Cycas macrocarpa is listed as Vulnerable (VU) by the IUCN, under criteria A2cd+4cd, in the assessment by John Donald Bösenberg published in 2023: its population is thought to have fallen by more than 30% over fifty years through forest clearance, with a further decline of 30 to 50% expected over the next two generations (Liew and Chacko 2026); an earlier assessment by Ken Hill dated from 2010. The Red List itself could not be consulted. The threats cited are habitat destruction for agriculture and collection for ornament.

It is also listed as Vulnerable nationally: in Malaysia, under criterion B1b(iii)+c(iv) (Jutta 2012, Flora of Peninsular Malaysia), and in Thailand, according to the Department of Agriculture report (2019). In Laos, Averyanov and colleagues (2014) did not consider the species threatened in the short term in the areas studied, but recommended a national Vulnerable listing because of the continuing decline of its populations, and priority protection; following Hill and Yang (1999), they note that rubber plantations have probably greatly reduced its range. The Penang populations have no protection; in September 2025 a plant beside a hiking trail was heavily cut back, probably by walkers bothered by its spiny petioles.

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

In short: no growing advice specific to Cycas macrocarpa has been published by a scientific source. In Laos, Averyanov and colleagues (2014) describe it as easily cultivated, without saying under what conditions, and the PACSOA wiki sums up its needs as warm, sheltered and moist but well drained. Its habitat, the understorey of tropical rainforest, suggests a plant for warmth, humidity and partial shade; this is a deduction, not a published trial, and its adult size limits it to large glasshouses outside the tropics.

Outdoor and in-ground cultivation

Only frost-free, humid tropical and near-tropical climates can be considered. The Montgomery Botanical Center, at Coral Gables in Florida, whose collection is grown outdoors, lists the species under accessions dating back to 1995 (see below), and the PACSOA account mentions a plant in the Durban Botanic Gardens, in South Africa; neither source describes how the plants have grown. In Thailand, the species was seen growing in village gardens in the far south.

Container cultivation

In temperate climates it can only be grown in a warm, humid glasshouse or conservatory, and young plants are the only realistic option given the size of the adults. No container-growing report has been found. The plant does circulate in the European trade: on the French Fous de palmiers forum, a post from June 2011 announced a delivery of plants sold under this name at a garden centre near Bordeaux, with no later report on how they fared. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on this species.

In cultivation in the UK, US and Australia

In the United States, the online catalogue of Montgomery Botanical Center (Florida) lists four accessions: 95380 and 95381, which by the garden’s numbering date from 1995, 96733 (1996) and 98974 (1998) (search of 21 October 2026); the catalogue does not say whether the plants are still alive. BGCI PlantSearch (search of 21 October 2026) also lists The John Fairey Garden, in Texas. In Australia, the species is declared in BGCI by the Royal Botanic Garden Sydney, where it also appears in the garden’s online catalogue according to the inventory compiled for this site (19 October 2026), and by the Hunter Region Botanic Gardens at Heatherbrae, in New South Wales. A BGCI entry shows that a garden has declared the species, not that a plant is alive today, and these sources do not say whether the plants grow 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.

Propagation

The plant is dioecious: a male and a female plant are needed to obtain seed. In Thailand more than a year passes between pollination and ripe seed (Department of Agriculture 2019). According to Averyanov and colleagues (2014), pollination takes place in June and July and seeds ripen in February and March. On Penang, seeds had germinated in the debris trapped among the leaves of a female plant. No germination data from cultivation 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. Cycad scale insects, including the Asian cycad scale, Aulacaspis yasumatsui, can attack all cultivated species.

Cold hardiness

No cold-tolerance data exist for Cycas macrocarpa. Its range is entirely tropical, from the Malay Peninsula to northern Laos (Vang Vieng district, at about 19° N, with collections up to 900 m); no source says whether 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 only French forum post found on this cycad announces plants for sale in Gironde in 2011, with no growing report, and the Jardin zoologique tropical in the Var has published nothing on it. There is therefore nothing to pass on to readers in comparable climates such as California or southern Australia.

United Kingdom, United States and Australia

No cold reading or dated growing report was found, either on forums or from botanic gardens; the gardens that list it, in southern Florida, Texas and New South Wales, have published no observation. No USDA zone can be given. In the UK, and in most of the United States and Australia outside the tropics, it is a plant for a heated glasshouse.

Toxicity and precautions

No toxicity analysis specific to Cycas macrocarpa 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

No use is documented for this species in the sources consulted. The 2019 Thai report notes in general terms that wild cycads in the country are collected and sold, but found no sign of collecting at the sites of this species.

Frequently asked questions

What does macrocarpa mean?

“Large-fruited” in Greek: the name describes the seeds, 5 to 7 cm long, the size of a duck egg.

Where does Cycas macrocarpa grow?

In Peninsular Malaysia and Thailand, in the understorey of humid forest, often on slopes and ridges. It has also been reported from Laos, on limestone rocks, but those who found it there consider its presence to need confirmation.

Is it a Cycas circinalis or a Cycas rumphii?

No. Those names were wrongly applied to it in Thailand and Malaysia; it is a distinct species, described as early as 1854.

How can it be told from Cycas edentata?

By its comb-like megasporophylls, its seeds without a spongy layer and its inland forest habitat; Cycas edentata lives on beaches.

Does it grow on Penang?

Yes. Two small populations were discovered there in 2025, on granite slopes in hill forest: the first record of the genus in that state.

Is it endangered?

Yes. The IUCN lists it as Vulnerable, as do the national red lists of Malaysia and Thailand, because of forest clearance and collecting.

Is it hardy?

Almost certainly not. No cold data exist; it is a plant of tropical rainforest.

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

  • Griffith, W. (1854). Notulae ad Plantas Asiaticas 4: 11–14, pl. 362, fig. 2. Bishop’s College Press, Calcutta. [Original description; not consulted, cited after Liew and Chacko (2026) and The World List of Cycads.]
  • Liew, H.-H. & Chacko, R.P. (2026). Discovery of Cycas macrocarpa Griff. in Penang: a new locality record for the genus and species. Malayan Nature Journal 78(2): 129–136. doi:10.62613/mnj.26782.04 [Updated description, ecology, status, Penang populations; full text consulted.]
  • Hill, K.D. & Yang, S.L. (1999). The genus Cycas (Cycadaceae) in Thailand. Brittonia 51(1): 48–73. [Thai revision, description pp. 66–68; not consulted (JSTOR), cited after The World List of Cycads.]
  • Averyanov, L.V., Nguyen, T.H., Nguyen, S.K., Pham, T.V., Lamxay, V., Bounphanmy, S., Lorphengsy, S., Phan, L.K., Lanorsavanh, S. & Chantthavongsa, K. (2014). Gymnosperms of Laos. Nordic Journal of Botany 32(6): 765–805. doi:10.1111/njb.00498 [First record from Laos (2013 collections), description, ecology, doubt about the species in northern Indochina, proposed national status, key to the Cycas of Laos; primary source, full text read in the Early View version (pp. 19–20).]
  • Hill, K.D. & Stanberg, L.C. (2009). Notes on Cycas truncata de Laub. and related matters. Telopea 12(3): 447–450. doi:10.7751/telopea20095832 [Relationship with Cycas inermis; full text consulted.]
  • Jutta, M. (2012). Cycadaceae. In: Kiew, R., Chung, R.C.K., Saw, L.G. & Soepadmo, E. (eds), Flora of Peninsular Malaysia, ser. II, vol. 3: 149–160. FRIM, Kepong. [Distribution in Malaysia and national status; not consulted, cited after Liew and Chacko (2026).]
  • Laubenfels, D.J. de & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Description pp. 381–382; very broad species concepts; full text consulted.]
  • Bösenberg, J.D. (2023). Cycas macrocarpa. The IUCN Red List of Threatened Species: e.T42057A68904566. [Red List assessment; reference found on Crossref, Red List 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 [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.]