Cycas arnhemica

Cycas arnhemica is a cycad of the savannas of Arnhem Land, in the north of Australia’s Northern Territory, where it forms locally very dense stands beneath the eucalypts around the Goyder River, along the north coast and on Groote Eylandt. Described by Ken Hill in 1994, this species of the genus Cycas was divided in 1996 into three subspecies, Cycas arnhemica subsp. muninga, subsp. natja and subsp. arnhemica, names now treated as synonyms. It is also one of the few cycads whose wild harvest has been studied experimentally.

Key facts about Cycas arnhemica

  • Accepted name: Cycas arnhemica K.D.Hill (1994), accepted by The World List of Cycads (version 2026.08.15) and by the Australian Plant Census (according to the Flora of Australia); POWO could not be consulted directly
  • Former names and synonyms: Cycas arnhemica subsp. arnhemica, Cycas arnhemica subsp. muninga Chirgwin & K.D.Hill and Cycas arnhemica subsp. natja K.D.Hill (1996); the Groote Eylandt plants were once called Cycas sp. “Groote”; placed under Cycas angulata by de Laubenfels and Adema (1998)
  • Family: Cycadaceae, order Cycadales
  • Common names: no English name attested; Aboriginal names behind the epithets muninga and natja (see Common names)
  • Natural range: Australia, Northern Territory: central Arnhem Land (Goyder River), the north coast (lower Blyth River, Elcho Island) and Groote Eylandt
  • IUCN status: Least Concern (LC), assessment by J. D. Bösenberg published in 2022; LC according to GBIF
  • 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: light understorey of savannas of Eucalyptus tetrodonta and Eucalyptus miniata, on deep white to yellow sands over laterite; old coastal dunes on Groote Eylandt
  • Habit and adult size: trunk to 4 m, rarely 7 m, 12 to 20 cm across; plants of Groote Eylandt and the north coast lower (1.5 m, rarely 2.5 m)
  • In the UK, US and Australia: photographed at the George Brown Darwin Botanic Gardens (2016); declared by the Australian National Botanic Gardens in Canberra in BGCI PlantSearch; no record in the UK or the US
  • Toxicity: no data specific to the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas arnhemica

Cycas arnhemica is recognised by its flat, short-stalked leaves with dark green, keeled leaflets with recurved margins, and by the dark brown felt that persists on the leaf bases and trunk, which the other Arnhem Land cycads lack. According to Hill (1994, 1996) and the Flora of Australia:

  • Trunk: up to 4 m, rarely 7 m, 12 to 20 cm across.
  • Leaves: 65 to 110 cm long (up to 160 cm according to the Flora of Australia), flat (rows of leaflets at 150 to 180°), with 120 to 270 leaflets, usually ending in a spine; petiole 9 to 36 cm, unarmed or spiny along at most half its length.
  • Median leaflets: 5 to 19 cm by 3 to 7.5 mm, inserted at 45 to 85°, hairless or loosely white to grey-brown hairy beneath, mid to dark green, keeled, with recurved or rolled margins.
  • Young growth: dense white or orange-brown down; cataphylls (the scales protecting the growing point) short (3 to 6 cm), soft and fleshy.
  • Male cones: narrowly ovoid, 18 to 36 cm long and 6.5 to 12 cm across; terminal spine of the microsporophylls fine, drawn out and upright.
  • Megasporophylls (the fertile leaves of female plants): 15 to 24 cm long, with grey and orange down, carrying 1 to 6 ovules; sterile blade 40 to 70 mm, regularly toothed (10 to 18 teeth of 2 to 5 mm), terminal spine 7 to 25 mm.
  • Seeds: flattened-ovoid, green then orange, without bloom, 28 to 37 mm by 26 to 32 mm.

The three known populations differ: the Goyder River plants have longer, broader (5 to 7.5 mm) and more widely spaced leaflets, angled towards the leaf tip; those of Groote Eylandt and the north coast have shorter, narrower, more crowded leaflets set almost at right angles to the rachis, and the Groote Eylandt plants have larger male cones and seeds than those of the north coast (Hill 1996).

Hybrids

Ken Hill (1996) reports natural hybrid populations between Cycas arnhemica and Cycas orientis in the Northern Territory. North-east of the Goyder River, towards Badalngarrmirri Creek, plants have paler, glossier leaves and a slenderer habit, which he interprets as a gradual transition towards Cycas orientis. No garden hybrid is documented.

Possible confusion

  • Cycas maconochiei, its closest relative, also from the Northern Territory: cataphylls and crown covered in thick orange wool, absent in Cycas arnhemica;
  • Cycas orientis, from eastern Arnhem Land: mid-green leaves with a longer petiole, flat leaflets without recurved margins, and hard, pungent cataphylls;
  • Cycas calcicola and Cycas arenicola: leaflets covered beneath with a dense, persistent brown felt;
  • Cycas armstrongii, also from the Northern Territory: leaflet midrib as prominent above as below, flat margins, pungent cataphylls.

Taxonomy

Cycas arnhemica is accepted by The World List of Cycads; POWO could not be consulted directly. Ken Hill described it in 1994 in Telopea (volume 5, pages 693 to 696), together with Cycas orientis and Cycas canalis, explaining that these names were already circulating among horticulturists and that conservation authorities needed valid names to issue permits. He then mentioned an undescribed related species from Groote Eylandt and the north coast of Arnhem Land.

In his 1996 revision he finally placed these plants under Cycas arnhemica as two new subspecies, subsp. muninga (Groote Eylandt, described with Sharon Chirgwin) and subsp. natja (north coast), the Goyder population becoming subsp. arnhemica. He placed the species in series Calcicolosae, with Cycas calcicola, Cycas arenicola and Cycas maconochiei. The Flora of Australia (1998) followed this treatment.

These subspecies are now treated as mere synonyms of the species by the Australian Plant Census (according to the November 2025 update of the Flora of Australia) and by The World List of Cycads. None of the sources consulted says which study prompted this change. De Laubenfels and Adema (Blumea, 1998), for their part, had placed the species under Cycas angulata, a view that has not been followed.

Etymology and history

The epithet arnhemica refers to the species growing roughly in the centre of Arnhem Land (original description). The former subspecies names come from Aboriginal languages: muninga transcribes the name of the plant in the language of the people of Groote Eylandt, and natja its name in the language of the Aboriginal people of the north coast, which Hill spells “Bureia” (Hill 1996).

The type was collected on 16 June 1977 by John Maconochie at the Goyder River crossing; the holotype is in Sydney (NSW), with an isotype in Darwin (DNA). Ken Hill and Leonie Stanberg studied the species in the field in August and September 1991.

Common names

No English common name is attested. The only documented names are Aboriginal: the Groote Eylandt plant has a name transcribed “muninga”, the north-coast plant a name transcribed “natja” (Hill 1996). The sources consulted do not give their spelling in the languages concerned.

In the wild

Cycas arnhemica is an understorey shrub of the Eucalyptus tetrodonta and Eucalyptus miniata savannas of Arnhem Land. Around the Goyder River it is locally abundant on deep white to yellow sands over laterite. On the north coast it is known from the lower Blyth River and Elcho Island; on Groote Eylandt it grows mainly on old dunes near the coast.

A study carried out in central Arnhem Land by Anthony Griffiths and colleagues (Australian Journal of Botany, 2005) measured an average density of 1,630 stems per hectare, from 550 to 2,250 depending on the site. Seedlings were scarce, and entirely absent from plots burnt twice during the two years of monitoring. Ken Hill had already noted in 1994 that overly frequent fires hold back the species’ reproduction.

Conservation status and regulation

Cycas arnhemica is listed as Least Concern (LC) by the IUCN in the assessment by John Donald Bösenberg published in 2022, and the IUCN data relayed by GBIF confirm the LC category (consulted on 21 October 2026); in 2010 the species and its three subspecies had been assessed separately. In 1994 Ken Hill considered it abundant and fairly widespread, and therefore not threatened, while noting that it was not protected and that almost all its populations lie on Aboriginal land. The Red List itself could not be consulted directly.

The study by Griffiths and colleagues (2005) tested the effect of harvesting plants from the wild, removing 10 to 32% of stems depending on the plot. Two years later, no clear effect appeared on survival, seedling numbers or the growth of the remaining plants. The authors conclude that a harvest limited to young stems, returning to the same site only every 15 to 40 years, would have a minimal impact on this abundant species, but urge caution for Cycas with smaller populations.

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

In short: no institution has published growing advice for Cycas arnhemica. 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 (deep, free-draining sands, tropical savanna with a long dry season and frequent fires) points to a plant for full sun or light shade, in a sandy soil. 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 arnhemica, 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 arnhemica.

In cultivation in the UK, US and Australia

In short: rare in collections, and recorded only in Australia. 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 Australian National Botanic Gardens, in Canberra, declare the species in BGCI PlantSearch, without saying whether it grows outdoors or under glass. It 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: no record in BGCI PlantSearch or in the online catalogues of Montgomery Botanical Center and Fairchild Tropical Botanic Garden.
  • 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.

Propagation

Like all Cycas, Cycas arnhemica 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, not collected in the wild.

Pests and diseases

No pest or disease specific to the species is documented. In the wild, Griffiths and colleagues studied the effect of fire and of disturbance by introduced feral animals on plant survival. In cultivation, scale insects, including Aulacaspis yasumatsui, can attack any 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 arnhemica. 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 listing in Canberra, a frost-prone climate, says nothing about hardiness, since the garden does not state whether the plant is under glass. Treat it as frost-tender; no USDA zone can be given without a documented trial.

Toxicity and precautions

No toxicity analysis specific to Cycas arnhemica 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

None of the sources consulted describes a use specific to this species. In northern Australia, Aboriginal people ate the seeds of several Cycas after detoxifying them by leaching in water or by ageing (review by Asmussen 2011); the existence of Aboriginal names for this plant, on Groote Eylandt and on the north coast, shows that it was well known to local people.

Frequently asked questions

Where does Cycas arnhemica grow?

In the north of Australia’s Northern Territory: in central Arnhem Land around the Goyder River, on the north coast (Blyth River, Elcho Island) and on Groote Eylandt.

Do the subspecies muninga and natja still exist?

Not as accepted taxa. Described in 1996, they are now treated as synonyms of the species by the Australian Plant Census and The World List of Cycads.

How can it be told from Cycas maconochiei?

By the absence of the thick orange wool that covers the crown and cataphylls of Cycas maconochiei.

Does wild harvesting threaten the species?

Not under the conditions tested. A 2005 study found no clear effect after two years, provided only young stems were taken and harvests were widely spaced in time.

Does fire help it?

Not when too frequent. Seedlings were absent from plots burnt twice in two years, and Ken Hill noted that overly frequent fires hold back its reproduction.

Can it be grown outdoors in the UK?

No, almost certainly not. No cold data exist; it is a plant of tropical savanna, best kept in a heated glasshouse.

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. (1994). Three new species of Cycas (Cycadaceae) from the Northern Territory, Australia. Telopea 5(4): 693–701. doi:10.7751/telopea19944995 [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.]
  • Griffiths, A.D., Schult, H.J. & Gorman, J. (2005). Wild harvest of Cycas arnhemica (Cycadaceae): impact on survival, recruitment and growth in Arnhem Land, northern Australia. Australian Journal of Botany 53: 771–779. doi:10.1071/BT04123 [Abstract consulted.]
  • Asmussen, B. (2011). “There is likewise a nut…” A comparative ethnobotany of Aboriginal processing methods and consumption of Australian Bowenia, Cycas, Lepidozamia and Macrozamia species. Technical Reports of the Australian Museum, Online 23(10): 147–163. doi:10.3853/j.1835-4211.23.2011.1575 [First page consulted.]
  • Bösenberg, J.D. (2022). Cycas arnhemica. The IUCN Red List of Threatened Species: e.T42031A67335549. doi:10.2305/IUCN.UK.2022-1.RLTS.T42031A67335549.en [Current assessment; reference checked on Crossref and The World List of Cycads, LC 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 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.]