Cycas arenicola

Cycas arenicola is a small cycad of the sandstone escarpments of Arnhem Land, in the north of Australia’s Northern Territory, where it grows on the sandy screes of the upper East Alligator and Liverpool rivers. Described by Ken Hill in 1993, this species of the genus Cycas is, with Cycas calcicola, the only Australian species to keep a brown felt beneath its leaflets. Collected in a very remote region, it remains one of the least studied Australian Cycas.

Key facts about Cycas arenicola

  • Accepted name: Cycas arenicola K.D.Hill (1993), accepted by The World List of Cycads (version 2026.08.15); POWO could not be consulted directly
  • Former names and synonyms: no synonym of its own; placed under Cycas furfuracea by de Laubenfels and Adema (1998)
  • Family: Cycadaceae, order Cycadales
  • Common names: no name attested, in English or any other language
  • Natural range: Australia, northern Northern Territory (Arnhem Land: upper East Alligator and Liverpool rivers)
  • IUCN status: Least Concern (LC); reassessment by Helen Ottley and David Liddle published in Red List version 2023-1, LC according to GBIF; the Flora of Australia gives Near Threatened (NT, 2022) (see Conservation status)
  • 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: sandy screes derived from siliceous sandstone, in rugged, broken country
  • Habit and adult size: trunk to 1.5 m, rarely 2 to 2.5 m, 15 to 20 cm across; leaves 0.9 to 1.6 m long
  • In the UK, US and Australia: photographed at the George Brown Darwin Botanic Gardens (2016); declared by three gardens in Florida and Hawaii in BGCI PlantSearch; no British record
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas arenicola

The most reliable character of Cycas arenicola is the dense, persistent brown felt beneath the adult leaflets, which stay dark green and glossy above. Add to this flat, unkeeled leaves and a narrow, spindle-shaped male cone. According to the original description (Hill 1993) and the Flora of Australia:

  • Trunk: up to 1.5 m, rarely 2 m (2.5 m according to the Flora of Australia), 15 to 20 cm across.
  • Leaves: 90 to 160 cm long, flat (the two rows of leaflets at 160 to 180°), ending in a spine; 180 to 200 leaflets according to the original description, 180 to 270 according to the 1996 revision; petiole 25 to 35 cm long, loosely brown-hairy, spiny.
  • Median leaflets: 9 to 19 cm by 4.5 to 6.5 mm, narrowly lanceolate and slightly curved, inserted at 60 to 90°, 9 to 14 mm apart without overlapping; glossy dark green above, not glaucous, densely brown-felted beneath; margins recurved, tip finely drawn out.
  • Young growth: densely covered in brown hairs; cataphylls (the scales protecting the growing point) soft, 4 to 7 cm long, with orange felt.
  • Male cones: spindle-shaped to elongated-ovoid, about 25 cm long and 5 to 9 cm across; terminal spine of the microsporophylls short (about 5 mm).
  • Megasporophylls (the fertile leaves of female plants): 15 to 20 cm long, with grey and orange down, carrying 4 to 6 ovules; sterile blade 30 to 40 mm by 14 to 18 mm, regularly toothed; terminal spine about 8 mm.
  • Seeds: flattened-ovoid, green then orange, with a bloom, 28 to 32 mm by 25 to 29 mm.

The leaflets have the anatomy of a dry-country plant: a continuous layer of cells beneath the epidermis, stomata sunk in deep, closed crypts and a very thick cuticle (Hill 1996).

Hybrids

No natural or garden hybrid is documented.

Possible confusion

  • Cycas calcicola, also from the Northern Territory and its closest relative: the same small, narrow male cone and the same persistent felt beneath the leaflets, but many more leaflets (210 to 410), narrower (2 to 4 mm), more crowded (4 to 6 mm apart) and abruptly narrowed at the tip;
  • Cycas pruinosa, from Western Australia: narrow leaflets with recurved margins and a narrow male cone, but leaflets hairless when mature and male cones much longer (35 to 45 cm);
  • Cycas arnhemica, from central Arnhem Land: leaves also flat, but leaflets hairless or loosely hairy beneath, never covered with the dense, persistent brown felt of Cycas arenicola.

Taxonomy

Cycas arenicola is accepted by The World List of Cycads; POWO could not be consulted directly. Ken Hill described it in 1993 in a short paper in Telopea (volume 5, pages 419 to 422), so that a name would be available for volume 48 of the Flora of Australia, then in preparation. He noted that the Cycas of the Northern Territory were still poorly known, but that this group of populations was clearly distinct.

In 1996 he placed the species in series Calcicolosae, which brings together four species of the northern Northern Territory (Cycas calcicola, Cycas arenicola, Cycas arnhemica and Cycas maconochiei): almost flat leaves, leaflets with recurved margins, soft cataphylls and small male cones. He acknowledged that, unlike almost all the other species, he had not been able to study this one in the field. De Laubenfels and Adema (Blumea, 1998) placed it under Cycas furfuracea from the Kimberley, a treatment followed neither by The World List of Cycads nor by the Australian Plant Census.

Etymology and history

The name combines the Latin arenarius, “of sand”, and the suffix -cola, “dweller”: the plant “lives in sand”, a reference to the sandy screes of the sandstone ranges where it grows (original description).

The type was collected on 7 September 1991 by Jeremy Russell-Smith and John Brock on the upper East Alligator River (12°48′ S, 133°21′ E); the holotype is in Sydney (NSW), with an isotype in Darwin (DNA). Ken Hill thanked Kym Brennan, John Brock and Jeremy Russell-Smith for searching for the plant. An earlier collection, made by Lazarides in July 1972 on the same river, had been distributed to several herbaria; the Sydney sheet could not be found in 1993.

Common names

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

In the wild

Cycas arenicola grows on sandy soils, on screes of siliceous sandstone, in the deeply dissected country of the upper East Alligator and Liverpool rivers, in Arnhem Land. Ken Hill noted in 1993 that the species had rarely been collected and was probably more widespread than herbarium records showed. He described it as locally abundant, in remote areas that are difficult to reach.

Pollinators, phenology and seed dispersers are not documented for the species.

Conservation status and regulation

Cycas arenicola is listed as Least Concern (LC) by the IUCN, but the sources do not all agree. The World List of Cycads gives LC, citing the assessment by Ken Hill (2010). A reassessment by Helen Ottley and David Liddle was published in Red List version 2023-1 (reference checked on Crossref), and the IUCN data relayed by GBIF give the LC category (consulted on 21 October 2026). The Flora of Australia, updated in 2025, states instead “Listed as Near Threatened, 2022”; the sources consulted do not explain this difference. The Red List itself could not be consulted directly. In 1993 Ken Hill did not consider the species threatened.

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

In short: no institution has published growing advice for Cycas arenicola. It is grown at the George Brown Darwin Botanic Gardens, in its own tropical climate, and a French specialist nurseryman ranks the Northern Territory Cycas among the hardest to grow in Europe.

Outdoor and in-ground cultivation

Its habitat (very free-draining sandstone screes, a tropical climate with a long dry season) points to a plant for full sun, in a mineral soil, watered with care. In the open it is documented only in Darwin, where a member of the French forum Fous de palmiers living in Thailand photographed it in September 2016. 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. In a 2021 note on growing Australian Cycas in a European climate, the French nurseryman Simon Lavaud (Cycadales.eu) classes all the Northern Territory species except Cycas angulata as “very difficult”; he does not name Cycas arenicola, which falls into that group by its origin. His general advice for the Australian Cycas is a very mineral substrate, full sun, a glasshouse to lengthen the growing season, and generous watering in hot weather, reduced below 20 °C (68 °F) and stopped when nights fall below 10 °C (50 °F), because of the risk of root rot. These are a grower’s recommendations for the group, not results for this species. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on Cycas arenicola.

In cultivation in the UK, US and Australia

In short: very rare in collections. A garden listed in the BGCI PlantSearch database (consulted in October 2026) has declared the species at some point, which does not prove that a living plant is there today.

  • Australia: plants photographed in September 2016 at the George Brown Darwin Botanic Gardens (forum Fous de palmiers). The species does not appear in the Garden Explorer of the Royal Botanic Garden Sydney or of the Australian Botanic Garden Mount Annan, nor in the online census of the Royal Botanic Gardens Victoria.
  • United States: Montgomery Botanical Center, in Coral Gables, Florida, the Honolulu Botanical Gardens and the National Tropical Botanical Garden, in Hawaii, declare it in BGCI PlantSearch; it does not appear in Montgomery’s own online catalogue.
  • United Kingdom: no record.

No first-hand report from a private grower in these countries could be read; PalmTalk and Dave’s Garden could not be consulted, and the PACSOA wiki page for the species is empty.

Propagation

Like all Cycas, Cycas arenicola is dioecious: a male and a female plant are needed for fertile seed. No germination data specific to the species 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. Scale insects, including Aulacaspis yasumatsui, can attack any cultivated Cycas, and root rot in a cold, wet substrate is the cause of failure most often cited for Australian Cycas in Europe (Lavaud 2021).

Cold hardiness

No cold-tolerance data exist for Cycas arenicola. Its whole range is tropical; nothing suggests that it can take frost.

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. In the absence of data, grow it under heated glass.

United Kingdom, United States and Australia

No cold reading and no dated growing report were found, either on forums or from botanic gardens. The only plants located in cultivation grow in tropical Darwin. Treat it as frost-tender; no USDA zone can be given without a documented trial.

Toxicity and precautions

No toxicity analysis specific to Cycas arenicola 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 specific to this species is documented. Aboriginal people of northern Australia detoxified and ate the seeds of several Cycas, but none of the sources consulted mentions Cycas arenicola.

Frequently asked questions

What does arenicola mean?

“Sand dweller”: the plant grows on the sandy screes of the sandstone ranges of Arnhem Land.

Where does it grow?

Only in the north of Australia’s Northern Territory, on the upper East Alligator and Liverpool rivers.

How can it be recognised?

By the dense brown felt that remains beneath the adult leaflets, its flat leaves and its narrow male cone. In Australia only Cycas calcicola shares this felt, with far more numerous and finer leaflets.

Is it endangered?

Probably not. The IUCN data relayed by GBIF give Least Concern after the 2023 reassessment, but the Flora of Australia gives Near Threatened; like all Cycas, it is covered by CITES.

Can it be grown outdoors in the UK?

No, almost certainly not. No cold data exist; it is a tropical plant, and the Northern Territory Cycas are reputed to be among the hardest to grow in Europe.

Is it in cultivation?

Rarely. Plants grow at the George Brown Darwin Botanic Gardens, and a few American gardens declare it; no growing report from Europe was found.

Is it poisonous?

It must be assumed so. No toxicity analysis specific to the species exists, but the Cycas studied contain dangerous toxins, especially in the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Hill, K.D. (1993). Cycas arenicola (Cycadaceae), a new species from the Northern Territory of Australia. Telopea 5(2): 419–422. doi:10.7751/telopea19934985 [Original description; 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; 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).]
  • 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; not consulted directly, cited after The World List of Cycads and the Flora of Australia.]
  • Hill, K.D. (2010). Cycas arenicola. The IUCN Red List of Threatened Species: e.T41969A10613296. doi:10.2305/IUCN.UK.2010-3.RLTS.T41969A10613296.en [Previous assessment; reference checked on Crossref, Red List page not consulted (access blocked).]
  • Ottley, H. & Liddle, D. (2023). Cycas arenicola. The IUCN Red List of Threatened Species 2023: e.T41969A67335169. doi:10.2305/IUCN.UK.2023-1.RLTS.T41969A67335169.en [Current assessment; reference checked on Crossref, LC category relayed by GBIF; 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 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.]