Cycas platyphylla

Cycas platyphylla is a cycad of the grassy ironbark woodlands of inland north-eastern Queensland, in Australia, known from the Petford district on the north-western Atherton Tableland and from an isolated population some 250 km further south. This species of the genus Cycas was described in 1992 by the Australian botanist Ken Hill. Its bluish new leaves, which turn yellowish green as they age, and the broad tip of its megasporophylls, which gave it its name, set it apart from the other Australian cycads. For years it was grown and illustrated under the misapplied name Cycas cairnsiana. The IUCN lists it as Endangered.

Key facts about Cycas platyphylla

  • Accepted name: Cycas platyphylla K.D.Hill (1992), 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; the name Cycas cairnsiana was long misapplied to this species; placed in the synonymy of Cycas angulata by de Laubenfels and Adema (1998), a view not followed
  • Family: Cycadaceae, order Cycadales
  • Common names: none attested, in English or in any other language
  • Natural range: Australia, north-eastern Queensland (Petford district and Wandovale station)
  • IUCN status: Endangered (EN, criterion A4d), assessment by J.D. Bösenberg published in Red List version 2022-1; EN according to GBIF
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; Vulnerable under Australia’s federal EPBC Act and under Queensland law
  • Documented hardiness: no measured value; grown in the open ground at least as far south as Sydney (see Cold hardiness)
  • Light and soil: in the wild, open grassy woodland on shallow, stony loams over volcanic rocks; in cultivation, sun and good drainage
  • Habit and adult size: trunk to 2 m, rarely 4 m, 10 to 15 cm across (Hill 1992), although plants over 1.5 m are rare in the field (Forster and Gray 2017); leaves 55 to 110 cm long
  • In the UK, US and Australia: declared by four gardens in the United States, including Montgomery Botanical Center, and five in Australia; no British garden record found
  • Toxicity: all parts should be treated as poisonous, as in other Cycas (see Toxicity and precautions)

How to recognise Cycas platyphylla

Cycas platyphylla is recognised by its new leaves, bluish at first and then yellowish green, by leaflets that are fairly broad for an Australian cycad (4 to 6 mm) with recurved margins, by the thick orange down around the cataphylls and by the broad blade of its megasporophylls. These are the characters Hill (1992, 1996) used to separate it from the other Australian species. The description below follows the original description (Hill 1992) and the online Flora of Australia.

  • Trunk: up to 2 m tall, rarely 4 m, 10 to 15 cm in diameter. Forster and Gray (2017) add that plants more than 1.5 m tall are rare, that the 2 m records usually include the leaves, and that they have never seen a 4 m plant.
  • Leaves: 55 to 110 cm long, sharply keeled in section (opposite leaflets set at 45 to 60° on the rachis), with 120 to 260 leaflets; the rachis usually ends in a spine; petiole hairless, 12 to 24 cm long.
  • Median leaflets: 9 to 17 cm long and 4 to 6 mm wide, semi-glossy, mid-green to yellowish green, 5 to 10 mm apart; the midrib is flat or slightly raised above and prominent beneath.
  • Young growth: covered in a thick rusty down that does not persist; the cataphylls (the scale leaves that protect the growing point) are slender, with a thick orange-brown down.
  • Male cones: ovoid, 15 to 20 cm long and 8 to 11 cm in diameter; each microsporophyll ends in a sharply upturned spine 6 to 9 mm long.
  • Megasporophylls (the fertile leaves of female plants): 16 to 32 cm long, with a loose rusty down, bearing 4 to 6 ovules; the blade is narrowly triangular, 50 to 80 mm long and 16 to 37 mm wide, finely and regularly toothed, with an apical spine 20 to 25 mm long.
  • Seeds: ovoid, green turning yellowish and strongly bloomed, 30 to 40 mm long and 27 to 38 mm in diameter, with a fleshy coat 3 to 4 mm thick.

Hybrids

A large and very variable population in the Irvinebank, Ravenshoe and Mount Garnet district, on the western Atherton Tableland, is intermediate in every respect between Cycas platyphylla and Cycas media. Hill (1992, 1996) interprets it as a population of hybrid origin between the two species that now breeds on its own, with little scope for exchange with its parents; the Flora of Australia treats it as a hybrid swarm. No garden hybrid is documented.

Possible confusion

The most frequent confusion is historical. Until the type locality of Cycas cairnsiana, in the Newcastle Range, was rediscovered, botanists and growers alike applied that name to the Petford plants (Hill 1992). The true Cycas cairnsiana has much narrower leaflets (2 to 3 mm, rarely 4 mm), of an intense waxy blue, with strongly rolled margins. Old plants labelled “Cycas cairnsiana” in collections are therefore worth checking.

Its closest relative is Cycas distans, described in 2017 from the Mitchell River catchment in southern Cape York Peninsula, further west and at lower altitude. According to Forster and Gray (2017), Cycas distans has a much sturdier trunk (up to 3.5 m tall and 15 to 30 cm across), longer median leaflets (13 to 23.6 cm), very small, narrowly ovoid male cones (12 to 20 cm by 4 to 8 cm) and much smaller megasporophylls (9 to 16 cm long, blade 25 to 35 mm long, apical spine 5 to 10 mm).

In the same group, Cycas ophiolitica, from the Rockhampton area, recalls both Cycas platyphylla and Cycas couttsiana; Hill (1992) gives the characters that separate them, Cycas ophiolitica having somewhat longer and broader leaflets on longer leaves, with longer petioles and less orange down around the cataphylls. Cycas media, widespread in eastern Queensland, has green leaves that are never bluish and more pungent cataphylls. Montgomery Botanical Center (2025) notes that the morphological similarities between the species of the “Cycas cairnsiana group” make accurate identification difficult.

Taxonomy

Cycas platyphylla is a name accepted by The World List of Cycads and by GBIF; POWO could not be consulted. Hill described it in 1992 in his preliminary account of the Cycas of Queensland (Telopea 5(1): 193–194, fig. 9), from a type collected 4.3 km from Petford on the Herberton road (Hill 3764 and L. Stanberg, 1 August 1990).

In his revision of the Australian Cycas, Hill (1996) placed the species in section Cycas, subsection Endemicae, series Cairnsianosae, with Cycas cairnsiana, Cycas couttsiana, Cycas desolata and Cycas ophiolitica: cycads with grey or blue leaves, a continuous hypodermis beneath the leaflet epidermis and small to medium male cones. Montgomery Botanical Center (2025) now groups it with Cycas cairnsiana, Cycas couttsiana, Cycas cupida and Cycas desolata in a “Cycas cairnsiana group” of pale-blue cycads of northern Queensland, whose species concepts a genomic study is to clarify.

De Laubenfels and Adema (1998), with their very broad species concept, placed Cycas platyphylla in the synonymy of Cycas angulata (Blumea 43: 363), together with Cycas ophiolitica, Cycas couttsiana and other northern Australian species. Neither the Flora of Australia nor The World List of Cycads follows this treatment, so the name has not changed since 1992.

Etymology and history

The epithet comes from the Greek platys, “broad”, and phyllon, “leaf”, referring to the broad sterile tip of the megasporophylls, which are modified leaves (Hill 1992; Haynes 2022).

The holotype is kept at the herbarium of the Royal Botanic Garden Sydney (NSW), with isotypes in Brisbane (BRI), Canberra (CANB), Darwin (DNA) and Melbourne (MEL). Before it was described, the plant was already grown as Cycas cairnsiana: Elliot and Jones’s Encyclopaedia of Australian Plants (1984, p. 147) illustrates it under that name, according to Hill (1992). The earliest herbarium collections Hill cites date from April 1965 (Lappa Junction) and August 1973 (between Lappa and Petford, 80 km west of Mareeba).

Common names

No common name is attested for this species. The botanical sources consulted (Flora of Australia, Hill 1992 and 1996) give no English or Aboriginal vernacular name, and the British nursery Trebrown knows of none.

In the wild

Cycas platyphylla is known from only two areas of north-eastern Queensland: the Petford district, on the north-western Atherton Tableland about 80 km west of Mareeba, and an isolated population some 250 km to the south, on Wandovale station in the Montgomery Range. In both places it grows in open grassy woodland dominated by ironbark eucalypts, on shallow loamy soils on stony slopes over acid to intermediate volcanic rocks (Hill 1992; Flora of Australia).

Forster and Gray (2017) describe it as always growing in “skeletal soils on rocky slopes (metasediments and volcanics such as granites and rhyolites)”, in the far eastern upper catchment of the Walsh River, a tributary of the Mitchell River, at altitudes of 500 to 840 m. Pollination and phenology are not documented in the sources consulted.

Conservation status and regulation

The IUCN lists Cycas platyphylla as Endangered (EN) under criterion A4d, which refers to a population decline caused by the exploitation of the plants, in the assessment by J.D. Bösenberg published in version 2022-1 of the Red List; the Red List data relayed by GBIF confirm the EN category (consulted on 24 October 2026). As early as 1992, Hill pointed out that its range is small, that none of its habitat is protected and that it is threatened by commercial collectors. Montgomery Botanical Center (2025) adds that the horticultural appeal of the blue cycads of this group has increased global demand and led to significant population declines through plant and seed collection. The Red List itself could not be consulted directly.

In Australia, the species has been listed as Vulnerable under the federal Environment Protection and Biodiversity Conservation Act 1999 since 16 July 2000, and as Vulnerable in Queensland (Nature Conservation (Plants) Regulation 2020, list of November 2022), according to the Flora of Australia.

Like every species in the genus except Cycas beddomei, Cycas platyphylla is listed in CITES Appendix II, where the family Cycadaceae has been 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, ask the seller for proof of provenance and prefer plants raised from seed in cultivation.

Growing Cycas platyphylla

In short: it is rare in cultivation for lack of material, but it can be grown. The Australian Native Plants Society (ANPSA) notes that it withstands extended dry periods once established, prefers a sunny position with good drainage and grows slowly, taking five years or more to make a feature plant; it has been established in the open ground at least as far south as Sydney.

Outdoor and in-ground cultivation

Outdoors, its establishment as far south as Sydney suggests that it can be grown in tropical and subtropical climates with mild winters. ANPSA describes it as an attractive plant for a garden or a container, while warning that its tropical origin may make it unsuitable for cold areas. Its habitat, shallow stony soils on rocky slopes under open woodland, points to full sun and a lean, very free-draining soil, but this is a deduction from the wild, not a tested recommendation. No outdoor trial has been published in a Mediterranean or temperate climate.

Container cultivation

In the United Kingdom and other temperate regions, it is a plant for a heated glasshouse or conservatory. In a 2021 note on growing Australian Cycas in a European climate, the French nurseryman Simon Lavaud (Cycadales.eu) does not name Cycas platyphylla, but his general advice for the group applies: a strongly mineral substrate, full sun or the brightest place in the glasshouse, and generous, frequent watering when nights are at 18 to 20 °C (64.4 to 68 °F) and days at 30 °C (86 °F), reduced below 20 °C (68 °F) and stopped when nights fall below 10 °C (50 °F), because watering in cool weather carries a very high risk of root rot. These are a grower’s recommendations for the group, not results for this species.

The experience of Mediterranean growers points the same way. A grower in the Ain and Hérault (France) reports on the Fous de palmiers forum, in August 2016, that the Australian Cycas grow slowly outside a tropical climate and rot quickly when cold is combined with wet; he recommends a very mineral, free-draining substrate and warmth all year round. Seed of the species circulated among French collectors through group orders in 2010, and a grower reports on the same forum that seeds germinated indoors in December 2010. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on Cycas platyphylla.

In cultivation in the UK, US and Australia

In short: grown in a few botanic gardens in the United States and Australia, but not recorded in any British garden.

  • United States: the online catalogue of Montgomery Botanical Center (Coral Gables, Florida) lists an older accession (8525), six accessions of 2004 (20040282 to 20040287) and ten of 2024 (numbered between 20240069 and 20240081). In 2025 the garden reported that it had collected more than 1,800 seeds of Cycas cairnsiana, Cycas cupida, Cycas desolata and Cycas platyphylla in northern Queensland, from various maternal lines; half are being raised in Australia and half are now in its living collections, to build assurance colonies. The Huntington (San Marino, California), Naples Botanical Garden (Florida) and the University of California Botanical Garden at Berkeley also declare the species in the BGCI PlantSearch database.
  • Australia: the Royal Botanic Garden Sydney and the Australian Botanic Garden Mount Annan list it in their online catalogues (Garden Explorer, consulted on 19 October 2026; out of service on 24 October); BGCI also lists the Australian National Botanic Gardens (Canberra), Brisbane Botanic Gardens Mount Coot-tha and James Cook University in Townsville.
  • United Kingdom: no garden declares it in BGCI, and no other record was found.

A BGCI entry shows that a garden has declared the species at some point, not that a plant is alive there today. No first-hand report from a private grower in these countries could be read; PalmTalk and Dave’s Garden could not be consulted.

Propagation

Like all Cycas, Cycas platyphylla is dioecious: a male and a female plant are needed for fertile seed. According to ANPSA, fresh seed germinates easily without any pretreatment. Seeds are exempt from CITES under annotation #4; given the pressure from collecting, ask for seed from cultivated plants.

Pests and diseases

No pest or disease specific to the species is documented. Outside the tropics, the main risk growers report for the Australian Cycas is rot of the collar and roots in a cold, wet substrate. Scale insects, including Aulacaspis yasumatsui, can attack any Cycas in cultivation.

Cold hardiness

No cold-tolerance value has been published for Cycas platyphylla. The only indication is its cultivation in the open ground as far south as Sydney, reported by ANPSA without a date or a temperature reading: it shows that the plant copes with a subtropical climate with mild winters, not that it tolerates frost.

Mediterranean and European experience

No cultivation result has been published in Europe, in the open ground or in a pot, and no dated frost episode concerns the species. A search of the French forum Fous de palmiers and the Italian forum Tropicamente found no report of cold tolerance for it; the only opinion published in France (2016), a general one, judges the Australian Cycas barely hardy and sensitive to cold combined with wet. In the mildest Mediterranean climates, comparable to coastal California or southern Australia, this means a pot, a dry substrate and a bright, frost-free shelter in winter.

United Kingdom, United States and Australia

No cold reading and no dated growing report were found, either on forums or from botanic gardens. The British nursery Trebrown rates it USDA zone 9b (average annual minimum of −3.9 to −1.1 °C, or 25 to 30 °F), a commercial rating not backed by any published growing observation. In the United Kingdom, treat it as a glasshouse plant.

Toxicity and precautions

ANPSA points out that, as in all cycads, various parts of Cycas platyphylla are toxic; the starchy seeds become safe to eat only after the toxic compounds have been destroyed, and Aboriginal people developed a method of vigorous leaching to remove them from various cycad species. 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. 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 specific to this species is documented. ANPSA mentions only, for cycads in general, the preparation of the seeds by Aboriginal people.

Frequently asked questions

Are Cycas platyphylla and Cycas cairnsiana the same plant?

No. The name Cycas cairnsiana was long applied by mistake to Cycas platyphylla, but they are two distinct species: Cycas cairnsiana has much narrower leaflets, of an intense blue, with rolled margins.

Where does Cycas platyphylla grow?

In north-eastern Queensland, Australia: in the Petford district, on the north-western Atherton Tableland, and on Wandovale station, 250 km further south, in open woodland on stony volcanic soils.

Why is it called a blue cycad?

Because its new leaves are bluish. They turn mid-green to yellowish green as they age, unlike those of Cycas cairnsiana, which stay blue.

How can it be told from Cycas distans?

Mainly by its size and its cones. Cycas distans has a taller, thicker trunk, longer leaflets, very small male cones and much smaller megasporophylls; it also grows further west, in the Mitchell River catchment, at lower altitude.

Is it endangered?

Yes. The IUCN lists it as Endangered, and it is listed as Vulnerable in Australia; its range is small and it suffers from the collecting of plants and seeds.

Can it be grown outdoors in the UK?

No. No outdoor result is documented in Europe, and Australian Cycas dislike cold combined with wet. Grow it in a pot in a heated glasshouse or conservatory.

Do its seeds germinate easily?

Yes, when fresh, without any pretreatment according to ANPSA; a male and a female plant are needed to obtain them.

Is it poisonous?

Yes. As in all Cycas, every part should be treated as toxic, the seeds especially.

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 [Original description (pp. 193–194, fig. 9), intermediate population with Cycas media, misapplication of the name Cycas cairnsiana; full text consulted.]
  • Hill, K.D. (1996). A taxonomic revision of the genus Cycas (Cycadaceae) in Australia. Telopea 7(1): 1–64. doi:10.7751/telopea19963040 [Series Cairnsianosae, leaf anatomy, status; full text consulted.]
  • Hill, K.D. (1998). Cycadaceae. In McCarthy, P.M. (ed.), Flora of Australia 48: 597–635. CSIRO Publishing, Melbourne. [Consulted in its updated online version (profiles.ala.org.au).]
  • Forster, P.I. & Gray, B. (2017). Cycas distans P.I.Forst. & B.Gray (Cycadaceae), a new species from southern Cape York Peninsula, Queensland. Austrobaileya 10(1): 74–84. https://www.qld.gov.au/__data/assets/pdf_file/0023/69026/forster-gray-austrobaileya-v10s1-p74-84.pdf [Comparison with Cycas platyphylla (table 1), field observations on its height, soils and altitude; full text consulted.]
  • Bösenberg, J.D. (2022). Cycas platyphylla. The IUCN Red List of Threatened Species: e.T41952A69154974. doi:10.2305/IUCN.UK.2022-1.RLTS.T41952A69154974.en [Current assessment; reference checked on The World List of Cycads and Crossref, EN category relayed by GBIF; Red List page not consulted (access blocked).]
  • de Laubenfels, D.J. & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Very broad species concept: Cycas platyphylla placed in the synonymy of Cycas angulata (p. 363); full text consulted.]
  • 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 taken up 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.]