Cycas tuckeri

Cycas tuckeri is a tree-like cycad of central Cape York Peninsula, in Queensland, Australia, known from a single population in the Coen district, on granite slopes covered with open savanna woodland. Described in 1996 by Ken Hill, this species of the genus Cycas is recognised by its very short megasporophylls, the shortest of any Australian cycad. It is named after Robert Tucker, the Townsville naturalist who first noticed it. The IUCN lists it as Vulnerable, and Queensland now lists it as Critically Endangered.

Key facts about Cycas tuckeri

  • Accepted name: Cycas tuckeri K.D.Hill (1996), accepted by The World List of Cycads (version 2026.08.15) and by GBIF; POWO could not be consulted
  • Former names and synonyms: none; de Laubenfels and Adema (1998) sank it into Cycas angulata, a treatment not followed
  • Family: Cycadaceae, order Cycadales
  • Common names: none attested
  • Natural range: Australia, Queensland: one population in the Coen district, Cape York Peninsula
  • IUCN status: Vulnerable (VU D2), assessment by J.D. Bösenberg dated 2020 and published in Red List version 2023-1, following K.D. Hill’s assessment of 2010
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; Critically Endangered in Queensland since May 2026, according to WildNet (previously Vulnerable)
  • Documented hardiness: no data (see Cold hardiness)
  • Light and soil: low open savanna woodland, gritty soils on stony granite slopes
  • Habit and adult size: trunk to 4 or 5 m depending on the source, rarely 6 m, 16 to 24 cm across; leaves 0.9 to 1.5 m long
  • In the UK, US and Australia: Montgomery Botanical Center (Florida), three accessions from 2004 and 2019; James Cook University, Townsville (declared to BGCI)
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas tuckeri

By its very short megasporophylls: only 10 to 14 cm long, with a short, broad blade. Its short, soft cataphylls, covered in a fine, silky grey-white down, are also distinctive (Hill 1996). The description below combines Hill (1996) and the Flora of Australia, whose figures differ slightly.

  • Trunk: to 4 m, rarely 6 m (Hill), or to 5 m (Flora of Australia), 16 to 24 cm in diameter.
  • Leaves: 90 to 150 cm long, openly keeled (opposite leaflets set at 90 to 140° to each other), glossy or semi-glossy dark green, with 100 to 200 leaflets; petiole 20 to 45 cm, loosely covered in orange-brown down, unarmed according to the Flora.
  • Mid-leaf leaflets: 15 to 25 cm long and 7 to 9 mm wide, narrowed to 2.5 to 4 mm at the base, 10 to 17 mm apart, hairless or loosely woolly, with slightly recurved margins; new growth loosely covered in orange-brown hairs.
  • Cataphylls: narrowly triangular, soft, not pungent, 4 to 8 cm long, finely silky and grey-white.
  • Male cones: ovoid, brown, about 20 to 30 cm long and 7 to 11 cm across according to Hill, 30 to 35 cm by 13 to 15 cm according to the Flora; microsporophylls 35 to 45 mm long, ending in a slender, sharply upturned spine of 10 to 16 mm.
  • Megasporophylls: 10 to 14 cm long, grey-felted, with 2 to 6 ovules; blade broadly triangular to ovate, 50 to 65 mm long and 38 to 50 mm wide, regularly toothed with 22 to 36 teeth 1 to 4 mm long; apical spine 19 to 30 mm.
  • Seeds: flattened-ovoid, green turning orange, not bloomed, 28 to 34 mm long and 26 to 32 mm across; sarcotesta 2 to 3 mm thick.

Hybrids

No hybrid has been documented for this species.

Possible confusion

  • Cycas semota, from the far north of Cape York: the only other Australian species with short megasporophylls, but they are distinctly longer, with a longer and narrower blade (Hill 1996; Flora of Australia).
  • Cycas yorkiana and Cycas badensis, of the same series: crown and cataphylls densely orange-woolly or floccose, whereas those of Cycas tuckeri carry very short grey to white silky hairs (key of Hill 1996).
  • Cycas xipholepis, which shares the Coen region: long, hard, pungent cataphylls and flat leaves.

Taxonomy

Cycas tuckeri is an accepted name in The World List of Cycads; POWO could not be consulted. Ken Hill described it in his revision of the Australian Cycas (Telopea 7(1): 20–23, fig. 10), placing it in subsection Endemicae and series Yorkianosae, a tropical group of about five species from Cape York and New Guinea with flat or weakly keeled leaves and short, soft cataphylls, alongside Cycas yorkiana, Cycas badensis and Cycas semota.

De Laubenfels and Adema (1998), who took a very broad view of species, placed it, like Cycas yorkiana, in the synonymy of Cycas angulata. The World List of Cycads, like the Flora of Australia, keeps it as a species.

Etymology and history

The epithet honours Robert Tucker (1955–1992), former director of the Parks and Gardens Department in Townsville, a keen naturalist and horticulturist who spotted the plant and recognised its distinctive nature (Hill 1996; Haynes 2022).

The type was collected on 7 July 1994 in the Coen district by Ken Hill and Leonie Stanberg (Hill & Stanberg 4683; holotype in Sydney, isotypes in Brisbane, Canberra, Darwin, at Kew, in Leiden, Melbourne and New York). An older specimen, collected by J.R. Maconochie, dates from 15 June 1981. The precise localities are withheld.

Common names

No common name is attested for this species, in English or in any other language, in the sources consulted.

In the wild

Cycas tuckeri is known only from one population, at the type locality in the Coen district, in the centre of Cape York Peninsula. It grows in low open savanna woodland dominated by Eucalyptus cullenii, on gritty soils on stony granite slopes (Hill 1996; Flora of Australia). Population size, pollination and dispersal are not documented.

Conservation status and regulation

The World List of Cycads lists Cycas tuckeri as Vulnerable (VU, criterion D2: a very small or restricted population), citing K.D. Hill’s assessment published in 2010. According to Crossref, a reassessment by J.D. Bösenberg, dated 17 September 2020, was published in Red List version 2023-1, and GBIF relays the VU category. The Red List itself could not be consulted. As early as 1996, Hill considered the species rare and potentially at risk, and called for urgent study of its status.

In Queensland, the Flora of Australia gives the species as Vulnerable under the Nature Conservation (Plants) Regulation 2020 (November 2022 list). The state’s WildNet database now lists it as Critically Endangered under the Nature Conservation (Animals/Plants) Regulation 2020, a status recorded on 24 May 2026, as well as a restricted plant and a confidential taxon whose locations are not published; it also flags the species as recorded within a protected area, without naming it. No listing under the national EPBC Act appears in WildNet.

Like every species in the genus except Cycas beddomei, Cycas tuckeri is listed in CITES Appendix II, where the family Cycadaceae has appeared since 4 February 1977. The listing carries annotation #4 (the version adopted at CoP20, in force since 5 March 2026): seeds, pollen, seedlings and tissue cultures obtained in vitro and transported in sterile containers, as well as cut flowers of artificially propagated plants, are not covered by CITES; international trade in the plants themselves requires an export permit. In the European Union the species falls under Annex B of Regulation (EC) No 338/97, whose current annexes are set by Regulation (EU) 2026/1383, applicable since 29 June 2026. Species+, the official CITES database, lists the species and confirms this status (consulted on 24 October 2026).

This summary does not replace the official texts: check the regulations in force before any purchase or exchange, ask the seller for proof of origin and choose nursery-raised plants grown from seed.

Growing Cycas tuckeri

No cultivation guidance specific to Cycas tuckeri has been published, and no dated cultivation report was found on English-, French- or Italian-language forums. Its natural setting, tropical savanna on gritty granite soil with a monsoon climate, suggests a very free-draining mineral mix and full light: these are cautious inferences, not tested results.

Outdoor and in-ground cultivation

Only frost-free tropical climates, such as that of northern Queensland, can reasonably be considered for planting out. No planted specimen with a documented history outside its range has been found.

Container cultivation

Elsewhere, grow it in a pot, in a gritty mineral compost and in full light, and keep it in a heated glasshouse or conservatory in winter. Australian Cycas in general have a reputation in Europe for declining on their own roots through root rot in cool, wet spells; there is no documented experience for this species.

In cultivation in the UK, US and Australia

In short: one American and one Australian collection; no British record.

  • United States: Montgomery Botanical Center, in Coral Gables (Florida), lists three accessions in its online catalogue, numbered 20040261 and 20040262 (2004) and 20190253 (2019), and is the only American garden declaring the species to BGCI (both consulted on 24 October 2026).
  • Australia: James Cook University, on its Townsville campus, declares the species to BGCI.
  • United Kingdom: no record in BGCI or in the British catalogues checked in October 2026. The British nursery Trebrown lists the species with a USDA zone 9b rating, its own commercial classification, not a documented trial.

A BGCI declaration shows that a garden held the plant at some point, not that it is alive today. No report from a private grower was found.

Propagation

The plant is dioecious: a male and a female are needed to obtain seed. No germination data specific to the species has been published; Cycas seed is usually sown fresh, in a free-draining mix and in warmth. 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 has been documented.

Cold hardiness

There is no cold-hardiness data for Cycas tuckeri. The Coen district has a tropical climate with a marked dry season: nothing supports the idea that the plant can withstand frost.

Mediterranean and European experience

No cultivation result has been published from southern France or Italy, outdoors or in a pot. No dated cold event concerns the species. The Jardin zoologique tropical at La Londe-les-Maures, in the Var, has published no observation of this species.

United Kingdom, United States and Australia

No cold value and no dated cultivation report was found, from forums or from botanic gardens. Trebrown’s zone 9b rating is a commercial classification, not a measured result.

Toxicity and precautions

No toxicity analysis specific to Cycas tuckeri has been found, but 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. In the absence of evidence to the contrary, treat the plant as poisonous: keep seeds and leaves out of reach of children and animals 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 of this species is documented in the sources consulted.

Frequently asked questions

Who was Tucker?

Robert Tucker (1955–1992), director of Parks and Gardens in Townsville and a naturalist, who spotted the plant.

Where does Cycas tuckeri grow?

At a single locality in the Coen district, in central Cape York Peninsula (Queensland), in savanna on granite slopes.

How can I recognise it?

By its very short megasporophylls, 10 to 14 cm long with a broad blade, and by its short, silky grey-white cataphylls.

Is it endangered?

Yes. The IUCN lists it as Vulnerable, and Queensland as Critically Endangered since 2026: only one population is known.

Is it a form of Cycas angulata?

No, according to The World List of Cycads and the Flora of Australia; only the 1998 revision by de Laubenfels and Adema placed it under that species.

Is it hardy in the UK?

Nothing suggests so. There is no cold data for the species, and its tropical range says nothing of any frost tolerance: in Britain it should be grown under glass.

Is it poisonous?

It should be assumed so. No analysis exists for this species, but all the Cycas studied contain serious toxins, especially in their seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Hill, K.D. (1996). A taxonomic revision of the genus Cycas (Cycadaceae) in Australia. Telopea 7(1): 1–64. doi:10.7751/telopea19963040 [Original description (pp. 20–23), series Yorkianosae; reference revision for Australia; 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).]
  • 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 concept; synonymy under Cycas angulata; full text consulted.]
  • Hill, K.D. (2010). Cycas tuckeri. The IUCN Red List of Threatened Species 2010: e.T41976A10588927. [Reference found on The World List of Cycads; Red List page not consulted (access blocked).]
  • Bösenberg, J.D. (2023). Cycas tuckeri. The IUCN Red List of Threatened Species 2023-1: e.T41976A69828135. doi:10.2305/IUCN.UK.2023-1.RLTS.T41976A69828135.en [Assessment dated 17 September 2020; reference checked on Crossref, VU category relayed by GBIF; Red List page not 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 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.]