Cycas silvestris: the forest cycad of Cape York, Queensland

Cycas silvestris is a tree-like cycad from the far north-east of Cape York Peninsula, in Queensland (Australia), where it grows in closed forest on old white sand dunes. Described in 1992 by Ken Hill, this species of the genus Cycas is the only Australian cycad of closed forest: its name means “of the forests” in Latin. It is recognised by its broad, glossy leaflets and its smooth trunk, which sheds its old leaf bases. Its status differs between sources: Near Threatened for the IUCN according to The World List of Cycads and GBIF, Vulnerable under Australian federal law and Queensland law.

Key facts about Cycas silvestris

Accepted name: Cycas silvestris 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; recorded before 1992 as Cycas rumphii (Bailey 1913, according to Hill 1996)
Family: Cycadaceae, order Cycadales
Common names: none attested; the British nursery Trebrown knows of none
Natural range: Australia, Queensland: north-eastern Cape York Peninsula (Temple Bay, Olive River estuary)
IUCN status: Near Threatened (NT, criteria B1a; D2) in the assessment by K.D. Hill (2010) cited by The World List of Cycads; reassessed by J.D. Bösenberg in Red List version 2023-1, NT according to GBIF; the Flora of Australia gives “Vulnerable, 2022” (see Conservation status)
CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; Vulnerable under the Australian Environment Protection and Biodiversity Conservation Act 1999 and under the Queensland Nature Conservation (Animals/Plants) Regulation 2020 (WildNet)
Documented hardiness: no data (see Cold hardiness)
Light and soil: closed forests (Araucaria dry rainforest, Melaleuca forest) on white siliceous sand of old dunes; tolerates shade as well as full sun in the wild
Habit and adult size: trunk 3 to 4 m according to the flora, up to 7 m observed in the field; leaves 1 to 2 m long
In the UK, US and Australia: Royal Botanic Garden Sydney; no British or American record (see In cultivation)
Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas silvestris

Among the Australian cycads, Cycas silvestris is distinguished by its adult leaflets, broader and relatively thinner than in any other species, and by its smooth trunk: leaf bases and cataphylls older than about four years fall, whereas the neighbouring species keep them (Hill 1996; Flora of Australia). The description below follows the Flora of Australia online and the original description (Hill 1992), with field observations by Paul Forster (1996).

Trunk: up to 3 m, rarely 4 m, 10 to 15 cm in diameter; plants up to 7 m tall, usually single-headed, sometimes leaning or partly fallen, are not uncommon in the field (Forster 1996).
Leaves: 100 to 200 cm long, flat in section, pale to mid-green and highly glossy, with 90 to 200 leaflets; petiole 30 to 50 cm, spiny along 10 to 90% of its length.
Median leaflets: 15 to 37 cm long and 9 to 15 mm wide, narrowed to 3.5 to 5 mm at the base, set 11 to 17 mm apart, hairless, with slightly recurved margins; midrib flat above, raised below.
Cataphylls (the scale leaves that protect the growing point): linear, pungent, about 13 cm long.
Male cones: not seen by Hill in 1992 and still recorded as “not seen” by the Flora of Australia; Forster (1996) describes them as very small for a Queensland cycad, 11 to 13 cm long and about 5 cm across, with microsporophylls 20 to 22 mm long.
Megasporophylls: 25 to 38 cm long, with 2 to 10 ovules; narrowly triangular blade 30 to 85 mm long and 15 to 45 mm wide, regularly toothed with 20 to 36 lateral spines 2 to 4 mm long; apical spine 8 to 26 mm long.
Seeds: ovoid, green turning yellowish, 30 to 35 mm long and 25 to 30 mm wide according to the flora; 30 to 39 mm by 25 to 32 mm, some almost spherical, in about two hundred seeds measured in the field (Forster 1996). They have no spongy layer.

Hybrids

No hybrid has been described. Hill (1992) nevertheless reports, near Cooktown, plants of Cycas media with broader, more distinctly sickle-shaped leaflets, which may indicate introgression from Cycas silvestris.

Possible confusion

Cycas media and Cycas megacarpa, of the same series: narrower leaflets and a trunk covered with persistent leaf bases.
The Cycas rumphii complex, coastal cycads of New Guinea and the western Pacific: same habit, same broad, sickle-shaped leaflets, same megasporophyll with a clear apical spine, but larger seeds with a spongy layer (Hill 1992, 1996). Forster (1996) also notes that the plants recall many members of this complex.
Cycas seemannii, from the islands of the South Pacific: petiole spineless or nearly so, much larger seeds (Hill 1992).

Taxonomy

Cycas silvestris is a name accepted by The World List of Cycads and by GBIF; POWO could not be consulted. Ken Hill described it in 1992 in his preliminary account of the cycads of Queensland (Telopea 5(1): 181–182, fig. 1). In his revision of the Australian cycads (Hill 1996), he placed it in subsection Endemicae, which includes all the Australian species, and in the series typified by Cycas media, a series of three species of the east coast of Queensland, with Cycas megacarpa.

The name went through a period of confusion. In their revision of the genus, de Laubenfels and Adema (1998) gave Cycas silvestris a very broad concept, which took in plants from the Philippines now referred to Cycas curranii, Cycas riuminiana and Cycas edentata, as well as the type collection of Cycas lacrimans. Lindström, Hill and Stanberg (2008) rejected this treatment: for them, as for The World List of Cycads, Cycas silvestris is endemic to Australia. In practice, a record of “Cycas silvestris” from the Philippines in a work that follows the 1998 revision refers to one of these Philippine species.

Etymology and history

The epithet comes from the Latin silvestris, “of the forests”, in reference to the closed-forest habitat of the species (Hill 1992; Haynes 2022).

The first specimens were collected on 12 September 1974 near the mouth of the Olive River by CSIRO botanists (B.P.M. Hyland, and L.J. Webb and J.G. Tracey). The type was collected on 14 July 1990 about 0.75 km north-west of Bolt Head by J.R. Clarkson and V.J. Neldner, of the Queensland Herbarium (Clarkson and Neldner 8813; holotype at Sydney, isotypes at Brisbane and Mareeba). The earliest records of Cycas rumphii in Queensland (Bailey 1913) actually refer to this species (Hill 1996). According to Forster (1996), a limited number of seeds and seedlings had reached the market in the years before he wrote, any later offer being subject to Queensland regulations.

Common names

No common name is attested for this species, in English or in any other language, in the sources consulted; WildNet, the Queensland Government’s wildlife database, gives none, and the British nursery Trebrown knows of none.

In the wild

Cycas silvestris is known only from the far north-east of Cape York Peninsula: near Temple Bay and to the north and south of the Olive River estuary (Flora of Australia). It grows in rich, complex subcoastal forests, rainforests and Melaleuca forests, on white siliceous sand of old beach dunes; the Flora of Australia considers it apparently confined to this substrate.

Paul Forster (1996), of the Queensland Herbarium, fills in the picture: the plants form small groups or “cycad groves”, with a few old specimens, younger plants and countless seedlings, almost always under the canopy of a dry rainforest with emergent hoop pines (Araucaria cunninghamii), on the dunes just behind the foredune and up to 2 km inland, where the cycad is patchy but overall quite common. He also reports a disjunct population farther south, near the Nesbit River, of plants that appear identical to those of the type locality, which would extend the range. Pollination and seed dispersal are not documented.

Conservation status and regulation

The sources disagree on the international status. The World List of Cycads lists Cycas silvestris as Near Threatened (NT, criteria B1a; D2), following the assessment by K.D. Hill published in 2010; a reassessment by J.D. Bösenberg, dated 2020, was published in version 2023-1 of the Red List (reference found on Crossref), and the Red List data relayed by GBIF give the category NT (consulted on 24 October 2026). The Flora of Australia online, on the other hand, gives “Vulnerable, 2022” for the Red List, and WildNet also records a Red List status of Vulnerable. The Red List itself could not be consulted to settle the question, so both are given here.

Under Australian law, the status is clear: WildNet lists the species as Vulnerable under the federal Environment Protection and Biodiversity Conservation Act 1999 (since December 2022) and under the Queensland Nature Conservation (Animals/Plants) Regulation 2020, as a restricted plant whose records are kept confidential, with an earlier “Medium” ranking under the state’s Back on Track programme (2008 to 2022). In 1992 Hill gave it the conservation code 2V (vulnerable, with a range under 100 km).

The main threat is collection. In 1996 the species was not in any conservation reserve, and signs of illegal collection had been found in 1991 and 1996 despite the difficult access (Forster 1996); WildNet now records it in at least one protected area, while the Flora of Australia notes that the few small stands are not adequately reserved.

Like every species in the genus except Cycas beddomei, Cycas silvestris falls under CITES Appendix II, where the family Cycadaceae has been included since 4 February 1977. Annotation #4 (CoP20 version, in force since 5 March 2026) exempts seeds, pollen, seedlings and tissue cultures obtained in vitro and transported in sterile containers, and cut flowers of artificially propagated plants; international trade in the plants themselves requires an export permit. The United Kingdom, the United States and Australia apply CITES through their own legislation; in the European Union the species is in Annex B of Regulation (EC) No 338/97, as set by Commission Regulation (EU) 2026/1383, applicable since 29 June 2026. Species+, the official CITES database, lists the species under its own name and confirms this status. This information was checked in October 2026 and does not replace the official texts: check the rules in force, ask for proof of origin and prefer plants raised from seed in cultivation.

Growing Cycas silvestris

In short: little is published, but a Queensland Herbarium botanist considered it straightforward to grow, and a cultivated plant has been photographed in the Northern Territory.

According to Paul Forster (1996), cultivation of Cycas silvestris should be straightforward and similar to the methods that succeed with the cycads of Asia and the western Pacific. In the wild the plant grows in white beach sand with organic matter and excellent drainage; it tolerates shade, although many plants grow in full sun and seem to cope with it. Root and caudex development is extensive, so seedlings should be given plenty of pot room. Unlike many Australian Cycas from drier habitats, it does not show a marked leaf drop before producing a new flush. A cultivated plant at Katherine, in the Northern Territory, is shown on the PACSOA wiki.

In his 2021 note on growing Australian Cycas in a European climate, the French nurseryman Simon Lavaud places Cycas silvestris in the first of his three difficulty classes, “medium”, with Cycas ophiolitica, Cycas media and Cycas megacarpa, the other classes being “difficult” and “very difficult”; he gives no advice specific to this species. This is a grower’s ranking, not the result of a trial.

Outdoor and in-ground cultivation

The only documented cultivated plant is the one photographed at Katherine, in the tropical monsoon climate of the Northern Territory; no result is published for subtropical or Mediterranean gardens. A deep, sandy, perfectly drained soil enriched with organic matter, in sun or light shade, matches its habitat; this is a deduction, not a documented result.

Container cultivation

In the United Kingdom and other temperate regions, it can only be grown in a pot in a heated glasshouse, in a free-draining mix and in a deep, roomy container, as Forster recommends for seedlings. No European experience exists: searches of the French forum Fous de palmiers and the Italian forum Tropicamente found no reliable report (the only French mention concerns a plant from Thailand whose identity is not established), and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on this cycad.

In cultivation in the UK, US and Australia

In short: one Australian botanic garden, nothing in Britain or the United States.

Australia: the Royal Botanic Garden Sydney lists it in its online catalogue (inventory of 19 October 2026) and declares it to BGCI. A cultivated plant photographed at Katherine, in the Northern Territory, is shown on the PACSOA wiki.
United States: no accession in the online catalogue of Montgomery Botanical Center and no American garden in BGCI (both consulted on 24 October 2026).
United Kingdom: no garden record; the British nursery Trebrown lists the species with a USDA zone 9b rating, its own commercial classification, not a documented trial.

Elsewhere, BGCI lists gardens in China, the Czech Republic and France; 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 in the UK or the US was found; PalmTalk and Dave’s Garden could not be consulted.

Propagation

The plant is dioecious: seed requires a male and a female plant. No germination data specific to the species have been published. In the wild, old plants are surrounded by countless seedlings (Forster 1996), and Forster advises giving seedlings plenty of pot room because of their large roots and caudex. Seeds are exempt from CITES under annotation #4; the species being protected in Australia, look only for seed of legal, documented origin, from cultivated plants.

Pests and diseases

No disease or pest specific to the species is documented. In cultivation, as with any Cycas, scales such as Aulacaspis yasumatsui can attack it, and overwatering or poor drainage rots the trunk and roots.

Cold hardiness

No cold-tolerance data exist for Cycas silvestris. Northern Cape York has a tropical monsoon climate without frost, and nothing suggests that the plant can take 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 this species.

United Kingdom, United States and Australia

No cold reading was found in any country. The plant photographed at Katherine, in a tropical climate, says nothing about cold tolerance, and Trebrown’s zone 9b rating (an average annual minimum of −3.9 to −1.1 °C, 25 to 30 °F) is a commercial classification, not the result of a published trial. Treat it as a frost-tender plant: a heated glasshouse in the UK, frost-free tropical gardens elsewhere.

Toxicity and precautions

No toxicity study specific to Cycas silvestris 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 this species 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 is documented for this species in the sources consulted.

Frequently asked questions

What does silvestris mean?

“Of the forests” in Latin: it is the only Australian cycad that lives in closed forest.

Where does Cycas silvestris grow?

Only in the far north-east of Cape York Peninsula, Queensland, on old white sand dunes covered with forest, between Temple Bay and the Olive River.

How can it be recognised?

By its broad, thin, glossy leaflets and its smooth trunk, which sheds its old leaf bases; its male cones are also unusually small for a Queensland cycad.

Does it grow in the Philippines?

No, according to The World List of Cycads. The Philippine plants placed under this name in 1998 belong to other species.

Is it endangered?

Yes, to a degree that the sources assess differently: Near Threatened for the IUCN according to The World List of Cycads and GBIF, Vulnerable under Australian and Queensland law; illegal collection has been recorded.

Is it easy to grow?

Probably, by the standards of Australian cycads: a Queensland Herbarium botanist considered it straightforward, and the French nurseryman Simon Lavaud ranks it among the less difficult Australian Cycas in Europe; but it needs warmth, perfect drainage and a roomy pot.

Is it hardy in the UK?

No, as far as anyone can tell. No cold data exist and it is a tropical forest plant: grow it in a heated glasshouse.

Is it poisonous?

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

Sources

Reference sites

The World List of Cycads (version 2026.08.15), Cycas silvestris: https://cycadlist.org/scientific_name/215 — authors, original publication, type, range, IUCN status (NT, assessment of 2010), etymology. Checklist of the IUCN Cycad Specialist Group, reliable; consulted on 3, 13 and 24 October 2026.
GBIF (API), Cycas silvestris: https://api.gbif.org/v1/species/2683303/iucnRedListCategory — accepted name, IUCN category NT relayed from the Red List. Reference data infrastructure; consulted on 24 October 2026.
Flora of Australia online (ABRS, from Hill 1998), Cycas silvestris: https://profiles.ala.org.au/opus/foa/profile/Cycas%20silvestris — description, diagnostic features, range, habitat, statuses (Queensland Vulnerable, “IUCN Vulnerable, 2022”). National flora, reliable; consulted on 3 and 24 October 2026.
WildNet (Queensland Government), Cycas silvestris, taxon 8384: https://wildnet-pub.science-data.qld.gov.au/api/v1/taxon-details/8384 — Vulnerable under the EPBC Act and Queensland law, restricted and confidential plant, Back on Track ranking, occurrence in a protected area. Official database; consulted on 24 October 2026.
PACSOA Wiki, Cycas silvestris: https://pacsoa.org.au/wiki/index.php/Cycas_silvestris — reprint of a note by P.I. Forster (Palms & Cycads 52–53, 1996): male cones, seeds, habitat, Nesbit River population, poaching, cultivation, photograph of a plant at Katherine. Note by a Queensland Herbarium botanist on the site of a growers’ society; reliable.
Simon Lavaud, “Quelques données sur les bases de la culture des Cycas australiens en climat Européen” (Cycadales, 2021, in French): https://cycadales.eu/wp-content/uploads/2021/04/Bases-de-la-culture-des-Cycas-australiens.pdf — classification of Australian Cycas by difficulty in European cultivation (Cycas silvestris in the “medium” class). Note by a specialist nurseryman; grower’s experience; consulted on 24 October 2026.
Species+ (UNEP-WCMC), Cycas silvestris: https://speciesplus.net/species#/taxon_concepts/16124/legal — CITES Appendix II (family listed since 4 February 1977, annotation #4), EU Annex B. Official CITES and EU database; consulted on 3 and 13 October 2026.
Commission Regulation (EU) 2026/1383: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=OJ:L_202601383 — annexes to Regulation (EC) No 338/97 in force since 29 June 2026. Official text.
BGCI PlantSearch, Cycas silvestris: https://plantsearch.bgci.org/ — four gardens: Royal Botanic Garden Sydney, Fairy Lake Botanical Garden (Shenzhen), Prague Botanical Garden, SCCV Château Pérouse (France). Global database of garden lists; a declaration is not proof of a living plant today; consulted on 24 October 2026.
Trebrown Nurseries, Cycas silvestris: https://www.trebrown.com/plant_info.php?species=Cycas+silvestris — no common name known, commercial USDA zone 9b rating. British specialist nursery; commercial information; consulted on 24 October 2026.
ASPCA Animal Poison Control, Sago Palm: https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/sago-palm — toxicity of cycads to dogs, cats and horses. Veterinary poison control centre, reliable; genus-level information.

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. 181–183), habitat, conservation code; 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 [Reference revision for Australia, smooth trunk, Bailey’s 1913 record; 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. (1996). [Note on Cycas silvestris, title not recorded]. Palms & Cycads 52–53 (July–December 1996). [Read in its reprint on the PACSOA wiki; original title not recorded.]
Forster, P.I. (1996). A preliminary assessment of cycad conservation and diversity in Queensland, Australia. Encephalartos 46: 8–18. [Not consulted; cited from Forster’s note on the PACSOA wiki.]
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 concepts; 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 [Rejection of de Laubenfels’ broad concept; full text consulted.]
Hill, K.D. (2010). Cycas silvestris. The IUCN Red List of Threatened Species: e.T41960A10585196. doi:10.2305/IUCN.UK.2010-3.RLTS.T41960A10585196.en [Previous assessment (NT); reference found on The World List of Cycads and Crossref; Red List page not consulted (access blocked).]
Bösenberg, J.D. (2023). Cycas silvestris. The IUCN Red List of Threatened Species: e.T41960A69157756. doi:10.2305/IUCN.UK.2023-1.RLTS.T41960A69157756.en [Reassessment dated 2020; reference found on Crossref, NT category relayed by GBIF; 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.]