Cycas megacarpa

Cycas megacarpa is a slender-trunked cycad from central-eastern Queensland, Australia, where it grows from Mount Morgan to the Goomeri area in moist eucalypt forest or rainforest. Described in 1992 by Ken Hill, this member of the genus Cycas owes its name to its seeds, the largest of the Australian cycads at up to 5 cm long. Its populations, fragmented by land clearing, are listed as Vulnerable by the IUCN (2022) and as Endangered under Australian federal law. Before 1992 these plants were included in Cycas media, and they were grown in Australia under the misapplied name Cycas kennedyana.

Key facts about Cycas megacarpa

  • Accepted name: Cycas megacarpa K.D.Hill (1992), accepted by The World List of Cycads (version 2026.08.15); 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: no synonym of its own; plants included in Cycas media before 1992 and grown in Australia under the misapplied name Cycas kennedyana; de Laubenfels and Adema (1998) placed it in the synonymy of Cycas media (see Taxonomy)
  • Family: Cycadaceae, order Cycadales; section Cycas, subsection Endemicae (Hill 1996)
  • Common names: no common name attested
  • Natural range: Australia, central-eastern Queensland, from Mount Morgan to the Goomeri area
  • IUCN status: Vulnerable (VU A2c), assessment by J. D. Bösenberg published in 2022; Endangered under the Australian federal EPBC Act (since 2000) and Queensland legislation
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union
  • Documented hardiness: no measured value; “frost tolerant” according to PACSOA, without a threshold (see Cold hardiness)
  • Light and soil: in the wild, sandy to clay-loam soils over various substrates, on slopes, in moist forest; in cultivation, sun and a moist but well-drained soil (PACSOA)
  • Habit and adult size: trunk up to 3 m, rarely 6 m, 8 to 14 cm in diameter; leaves 70 to 110 cm long
  • In the UK, US and Australia: Royal Botanic Garden Sydney and Australian Botanic Garden Mount Annan (plants of wild origin), Adelaide and Townsville; San Diego Botanic Garden, UC Berkeley and Moore Farms in the United States; RHS Wisley in the United Kingdom (BGCI)
  • Toxicity: no analysis specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas megacarpa

Among the Australian cycads, Cycas megacarpa is recognised by the combination of green leaves with broad leaflets and very large, non-glaucous seeds (Hill 1992). Its slender trunk and its fairly short, keeled leaves also separate it from Cycas media, its closest relative.

The trunk reaches 3 m, rarely 6 m, and is 8 to 14 cm in diameter. The leaves, 70 to 110 cm long, are openly keeled: opposite leaflets meet on the rachis at an angle of 90 to 135°. Each carries 120 to 170 leaflets and ends in a pair of leaflets or a spine. The petiole, 20 to 36 cm long, is hairless or covered in grey down, and spiny along 20 to 100% of its length. The median leaflets measure 12 to 20 cm by 5 to 7.5 mm; they are hairless, glossy mid to dark green, flat or slightly keeled, with slightly rolled margins according to the Flora of Australia, and 5 to 12 mm apart. Young leaves are covered in a thick down of orange-brown hairs that does not persist. The cataphylls, narrow and sharp, are up to 7 cm long (Hill 1992; Hill 1998).

The male cones are ovoid, orange, about 18 cm by 7 cm, and their microsporophylls end in an upturned spine of 5 to 8 mm. The megasporophylls, 14 to 25 cm long and covered in brown and grey down, bear 2 to 4 ovules; their blade, narrowly triangular and 4 to 7 cm long, is evenly toothed with 18 to 26 lateral spines and ends in a spine of 8 to 20 mm. The seeds, ovoid, green turning yellowish, not or barely glaucous, measure 38 to 50 mm by 35 to 45 mm, with a flesh (sarcotesta) 4 to 5 mm thick (Hill 1992; Hill 1998).

Hybrids

Hill (1992) describes a broad zone of intergradation with Cycas ophiolitica between Rockhampton and Mount Morgan, at the northern limit of the range: the plants there show characters of both species, but also have larger seeds than those of the southern populations. For the Cycas media complex as a whole, he sees this as the result of species that diverged from an ancestor whose range had been fragmented by climatic change meeting again after a period of isolation. No cultivated hybrid is documented.

Possible confusion

  • Cycas media: longer (110 cm or more) and flatter leaves, more leaflets, a thicker trunk (over 17 cm), longer cataphylls and smaller seeds (31 to 38 mm); it grows further north (Hill 1992, 1996).
  • Cycas ophiolitica: narrower, more crowded and more or less glaucous leaflets, petiole covered in grey or white down, smaller seeds (29 to 33 mm) (Hill 1992).
  • Cycas silvestris, from north Queensland: flat leaves with broader leaflets and smaller seeds (Hill 1992).
  • Cycas candida: also has keeled leaves, but leaflets with rolled margins, soft cataphylls with a thick orange down and waxy white seeds (Hill 2004).

Without seeds, telling it from Cycas media depends on habit: a slender trunk and short, keeled leaves in Cycas megacarpa. Plants from the Mount Morgan area, intermediate with Cycas ophiolitica, are hard to assign to either species.

Taxonomy

Ken Hill described Cycas megacarpa in 1992 in a preliminary account of the Cycas of Queensland, from a collection made on 1 October 1991 at Blackmans Gap, 20.9 km from the Bruce Highway, from Miriam Vale, on the road to Manypeaks (Hill and Stanberg 4142; holotype in Sydney, NSW, isotypes at BRI, CANB and DNA). These plants had previously been included in Cycas media: the Flora of South-eastern Queensland (1989) still illustrates them under that name.

In his revision of the Australian cycads, Hill (1996) places the species in section Cycas, subsection Endemicae, series Endemicosae, with Cycas media and Cycas silvestris. In 2004, when describing Cycas candida, he related it instead to a small group of species with keeled, often green leaves, including Cycas ophiolitica and Cycas candida, allied to Cycas cairnsiana.

De Laubenfels and Adema (1998) did not recognise the species and placed it in the synonymy of Cycas media, suggesting that the large-seeded southern populations might form a variety. The World List of Cycads, the Flora of Australia and Species+ accept it as a species, and this site follows The World List of Cycads.

Hill’s protologue gives Blackmans Gap as the type locality and a range from Mount Morgan to Goomeri.

Etymology and history

The epithet comes from the Greek mega-, “large”, and karpos, “fruit”, in reference to the large seeds (Hill 1992). Before its description, the species was grown in Australia under the name Cycas kennedyana, but the type of that name belongs to Cycas media (Hill 1992, 1996).

Seed was offered in Europe from the end of the 2000s: members of the French forum Fous de palmiers placed a group order with a seed merchant in September 2010.

Common names

No common name is attested.

In the wild

Cycas megacarpa is endemic to central-eastern Queensland, from Mount Morgan, near Rockhampton, to the Goomeri area in the south. It grows scattered on sandy to clay-loam soils over various substrates, usually on slopes, in moist eucalypt forest or rainforest. It favours locally cooler, moister sites and becomes more sporadic and further from the coast in the south of its range (Hill 1992; Hill 1998).

A demographic study of a population of about 5,600 plants over 96 ha found equal numbers of male and female plants, males half a metre shorter on average and fertile at a smaller size, and plants grouped in clusters, with young plants close to females (Etherington and colleagues 2018).

Hill describes the habitat as moist forest and locally moist sites.

Conservation status and regulation

The IUCN lists Cycas megacarpa as Vulnerable (VU A2c), in the assessment by J. D. Bösenberg published in 2022 and carried out in September 2020 (category confirmed by GBIF, consulted on 21 October 2026); an earlier assessment, by Paul Forster, dates from 2010. Criterion A2c indicates a population decline linked to loss of habitat. The “Endangered” status sometimes quoted for the species is its status under Australian law, not the IUCN category. In Australia the species has been listed as Endangered under the federal Environment Protection and Biodiversity Conservation Act (EPBC Act) since 16 July 2000, and under Queensland legislation (Flora of Australia).

The threats are well established. A genetic study of 992 plants from 33 populations (James and colleagues 2018) estimates that 69% of suitable habitat was lost between the 1960s and 2009, and that only 29% of the remaining habitat is protected; clearing for urban development, agriculture and coal-seam gas infrastructure continues. Many populations are small, recruitment of young plants appears to be declining, and the growing isolation of populations reduces the species’ viability. Some plants have been moved to make way for development (Etherington and colleagues 2018). Forster (1995) already reported the plundering of populations of this species, sought after by collectors.

Like the whole family Cycadaceae, the species has been listed in CITES Appendix II since 4 February 1977. The listing carries annotation #4 (CoP20 version, in force since 5 March 2026): seeds, pollen, seedlings and tissue cultures obtained in vitro and transported in sterile containers, and cut flowers of artificially propagated plants are not covered by CITES. In the European Union the species falls under Annex B of Regulation (EC) No 338/97, whose annexes in force are set by Regulation (EU) 2026/1383, applicable since 29 June 2026. Species+ confirms this status and gives Australia as the only range country.

This general information does not replace the official texts: check the regulations in force before any purchase or exchange, and prefer plants raised from seed in cultivation.

Growing Cycas megacarpa

No growing recommendations specific to Cycas megacarpa have been published by a botanic garden or institution. The Australian society PACSOA advises a sunny position and a moist but well-drained soil, and describes the plant as frost and drought tolerant, without giving a threshold.

The French nurseryman Simon Lavaud (Cycadales.eu), in a 2021 note on growing Australian cycads in a European climate, ranks Cycas megacarpa among the species of “medium” difficulty, the easiest group, together with Cycas media, Cycas ophiolitica and Cycas silvestris.

Outdoor and in-ground cultivation

In Australia the species is grown in botanic gardens from Townsville to Sydney and Adelaide (see below), but no outdoor growing report giving temperatures is documented. In Europe, the few reports concern plants of uncertain position. A grower on the Côte Bleue, in the Bouches-du-Rhône (Mediterranean France), reported on the Fous de palmiers forum in January 2010 that his Cycas megacarpa does not lose its leaves in winter, unlike his Cycas cairnsiana, kept indoors behind a picture window at 15 to 20 °C (59 to 68 °F) in January; he does not say whether the megacarpa was outdoors or what temperatures it met. This Mediterranean experience may interest growers in comparable climates, such as coastal California or southern Australia, but it gives no figure that can be transferred. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on this species.

Container cultivation

An Italian grower reported in February 2013 on the Tropicamente forum that a seedling of Cycas megacarpa with a trunk 7 to 8 cm across produced leaves only every two or three years and sometimes spent a year without leaves; he found the Australian cycads very hard to keep alive. In the United Kingdom, northern Europe and the colder parts of the United States, a pot kept dry and frost-free in a bright glasshouse or conservatory in winter is therefore the prudent approach; this follows from these reports and from Lavaud’s advice, not from a published trial.

In cultivation in the UK, US and Australia

  • Royal Botanic Garden Sydney: its Garden Explorer catalogue lists plants of wild origin received in 1990 and 1991 (accessions S1990-2186 and S1991-2859) and five more of wild origin received in 2021 (S2021-0666 and S2021-0667).
  • Australian Botanic Garden Mount Annan (New South Wales): the species is listed in its Garden Explorer catalogue and in BGCI PlantSearch.
  • Other Australian gardens: the Botanic Garden and State Herbarium of South Australia (Adelaide) and James Cook University in Townsville declare it in BGCI PlantSearch.
  • United States: San Diego Botanic Garden (California), the University of California Botanical Garden at Berkeley and Moore Farms Botanical Garden (South Carolina) declare it in BGCI PlantSearch; it does not appear in the Montgomery Botanical Center catalogue.
  • United Kingdom: RHS Garden Wisley declares it in BGCI PlantSearch, presumably under glass, as are almost all cycads in British gardens.

A BGCI listing records that a garden has declared the plant at some point; it does not prove that the plant is alive today, nor whether it grows outdoors. No dated growing report from an English-language forum is documented.

Propagation

Like all Cycas, Cycas megacarpa is dioecious: a male and a female plant are needed for seed. In the wild, male plants become fertile at a smaller size than females (Etherington and colleagues 2018). No germination data specific to the species are documented. Seeds are exempt from CITES under annotation #4; given the decline of wild populations, ask for seed from cultivated plants.

Pests and diseases

No disease or pest specific to Cycas megacarpa is documented in cultivation. In Europe, the main risk reported for Australian cycads is root rot when the substrate stays damp in cool weather (Lavaud 2021). Scale insects, including the Asian cycad scale Aulacaspis yasumatsui, threaten all cultivated Cycas.

Cold hardiness

No cold-hardiness value has been measured. PACSOA describes the species as frost tolerant without saying down to what temperature.

The only European report, from the Côte Bleue in Mediterranean France (2010), states neither how the plant was wintered nor the temperatures it met, and the Italian report (2013) concerns very slow growth in a pot without any temperature. No USDA zone is given by a reliable source. Until data exist, keep it frost-free and dry in winter wherever frost is regular, and treat the PACSOA statement as a general indication rather than a limit.

Toxicity and precautions

No toxicity analysis specific to Cycas megacarpa is documented. The risk is well documented in the genus, however: 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) among plants poisonous to dogs, cats and horses. Treat the plant as poisonous: keep seeds and leaves out of reach of children and pets, 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 use specific to Cycas megacarpa is documented. A study by Beck (1992) deals with the Aboriginal preparation of Cycas seeds in Australia; its text was not consulted, and it is not known whether this species is included.

Frequently asked questions

Where does the name megacarpa come from?

From the Greek mega-, “large”, and karpos, “fruit”: its seeds, up to 5 cm long, are the largest of the Australian cycads.

Where does Cycas megacarpa grow?

In central-eastern Queensland, Australia, from Mount Morgan to the Goomeri area, in moist eucalypt forest or rainforest, often on slopes.

How can it be told from Cycas media?

By its more slender trunk (8 to 14 cm across), its shorter, keeled leaves with fewer leaflets, and its larger seeds.

Is it endangered?

Yes. The IUCN lists it as Vulnerable (2022) and Australian federal law as Endangered: nearly 70% of its habitat has been cleared since the 1960s.

Is it hardy?

Nobody knows precisely. PACSOA calls it frost tolerant without giving a threshold, and no measurement exists; where frost is regular, winter it frost-free and dry.

Is it easy to grow?

It is one of the less difficult Australian cycads according to the nurseryman Simon Lavaud, but its growth remains very slow and it dislikes being watered in cool weather.

Is it poisonous?

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

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Hill, K.D. (1992). A preliminary account of Cycas (Cycadaceae) in Queensland. Telopea 5(1): 177–206. doi:10.7751/telopea19924964 [Protologue (pp. 188–189), description, range, habitat, intergradation with Cycas ophiolitica, etymology, Cycas kennedyana.]
  • Hill, K.D. (1996). A taxonomic revision of the genus Cycas (Cycadaceae) in Australia. Telopea 7(1): 1–64. doi:10.7751/telopea19963040 [Classification (section Cycas, subsection Endemicae), key, anatomy, range.]
  • Hill, K.D. (1998). Cycadaceae. In McCarthy, P.M. (ed.), Flora of Australia 48: 598–635. CSIRO Publishing, Melbourne. [Consulted in its updated online version (profiles.ala.org.au).]
  • Laubenfels, D.J. de & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Synonymy with Cycas media (p. 361).]
  • Hill, K.D. (2004). Cycas candida (Cycadaceae), a new species from Queensland together with an extension of range and amended description of Cycas yorkiana. Telopea 10(2): 607–611. [Affinities of Cycas megacarpa.]
  • Forster, P.I. (1995). Cycas desolata (Cycadaceae), a new species from north Queensland. Austrobaileya 4(3): 345–352. doi:10.5962/p.365826 [Plundering of populations.]
  • James, H.E., Forster, P.I., Lamont, R.W. & Shapcott, A. (2018). Conservation genetics and demographic analysis of the endangered cycad species Cycas megacarpa and the impacts of past habitat fragmentation. Australian Journal of Botany 66: 173–189. doi:10.1071/BT17192 [Habitat loss, threats, genetic structure.]
  • Etherington, R., Jeffers, B., Grigg, L. & Paddock, A. (2018). Investigating the demographics and intrapopulation spatial patterns of the endangered Cycas megacarpa K.D.Hill in central Queensland, Australia. Austral Ecology 43: 110–116. doi:10.1111/aec.12548 [Demography, sex ratio, spatial pattern, transplanting.]
  • Bösenberg, J.D. (2022). Cycas megacarpa. The IUCN Red List of Threatened Species 2022: e.T41951A68905593. doi:10.2305/IUCN.UK.2022-1.RLTS.T41951A68905593.en [Current assessment (VU A2c), carried out on 11 September 2020 according to Crossref; category confirmed by GBIF.]
  • Forster, P.I. (2010). Cycas megacarpa. The IUCN Red List of Threatened Species 2010: e.T41951A10609805. doi:10.2305/IUCN.UK.2010-3.RLTS.T41951A10609805.en [Previous assessment; reference checked on Crossref.]
  • Forster, P.I. (2007). Recovery plans for endangered cycads: a model set of objectives and actions using the example of Cycas megacarpa from Queensland, Australia. In Proceedings of Cycad 2005: The 7th International Conference on Cycad Biology: 3–31. doi:10.21135/893274900.002 [Reference checked on Crossref.]
  • Beck, W. (1992). Aboriginal preparation of Cycas seeds in Australia. Economic Botany 46(2): 133–147. doi:10.1007/BF02930628 [Reference checked on Crossref.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology; used via 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.]