Cycas pruinosa

Cycas pruinosa is a cycad of the rocky hills of the eastern and southern Kimberley, in Western Australia, which also occurs in the Spirit Hills, just across the border in the Northern Territory. This species of the genus Cycas was described in 1978 by the Australian botanist John Maconochie, who named it after the greyish-white bloom on its seeds. It is characterised by narrow leaflets with strongly rolled margins, long, spindle-shaped male cones and long, deeply toothed megasporophylls; depending on the population, its leaves are blue or green. The IUCN lists it as Least Concern.

Key facts about Cycas pruinosa

  • Accepted name: Cycas pruinosa Maconochie (1978), accepted by The World List of Cycads (version 2026.08.15) and by GBIF; the World Checklist of Vascular Plants (WCVP), on which POWO is based, also accepts it (consulted through GBIF on 31 October 2026)
  • Former names and synonyms: none
  • Family: Cycadaceae, order Cycadales
  • Common names: none attested, in English or in any other language
  • Natural range: Australia, eastern and southern Kimberley (Western Australia) and Spirit Hills (Bullo River station, Northern Territory)
  • IUCN status: Least Concern (LC), assessment by J.D. Bösenberg published in Red List version 2022-1; LC according to GBIF
  • CITES and other protection: CITES Appendix II (seeds exempt under annotation #4); Annex B in the European Union; no federal or state listing according to the Flora of Australia
  • Documented hardiness: no measured value (see Cold hardiness)
  • Light and soil: in the wild, hillsides and the foot of cliffs, on skeletal, sandy soils over siliceous rocks (metasandstones to granites), once on terra rossa over limestone
  • Habit and adult size: trunk to 1.5 m, rarely 2.5 m, 15 to 30 cm across; leaves 60 to 125 cm long
  • In the UK, US and Australia: Montgomery Botanical Center (Florida) holds two accessions; Kings Park and Botanic Garden (Perth) declares it; 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 pruinosa

Cycas pruinosa is recognised by its narrow, hairless leaflets with strongly recurved margins, its long, slender male cones and its long megasporophylls with an elongated, deeply toothed sterile tip (Hill 1996). Its seeds are covered with a greyish-white bloom. The description below follows Hill (1996), who completed Maconochie’s original description (1978).

  • Trunk: up to 1.5 m tall, rarely 2.5 m, 15 to 25 cm in diameter, rarely 30 cm.
  • Leaves: 60 to 125 cm long, keeled in a V (opposite leaflets set at 45 to 90° on the rachis), with 130 to 320 leaflets, usually ending in a pair of leaflets; petiole 8 to 23 cm long, hairless or with white down, spiny over half to all of its length.
  • Median leaflets: 11 to 17 cm long and 2.5 to 4 mm wide, hairless, usually glaucous, with strongly recurved margins, 5 to 9 mm apart.
  • Young growth: thick grey-white down; the cataphylls (the scale leaves that protect the growing point), up to 7 cm long, carry a pale orange-brown down.
  • Male cones: spindle-shaped, pale brown, 35 to 45 cm long and 5 to 7 cm in diameter; each microsporophyll ends in a slender, sharply upturned spine 6 to 25 mm long.
  • Megasporophylls (the fertile leaves of female plants): 25 to 45 cm long, with grey and pale orange-brown down, bearing 2 to 6 ovules; the sterile tip, 9.5 to 19 cm long, is narrowly triangular and deeply and regularly toothed (14 to 24 teeth 5 to 20 mm long), with an apical spine 10 to 45 mm long.
  • Seeds: flattened-ovoid, green turning yellow and strongly bloomed, 32 to 36 mm long and 28 to 32 mm in diameter, with a fleshy coat 2 to 3 mm thick.

Leaf colour varies: the glaucous wax may be present or absent, making the plants blue or green. According to Hill (1996), the character seems to be genetic, since some populations are entirely blue (Lake Argyle, Bedford Downs), others entirely green (Deception Range) and others mixed (Cycad Hill). A similar variation occurs in Cycas furfuracea, where green plants are much rarer.

Hybrids

No hybrid is documented for this species.

Possible confusion

Maconochie (1978) described it at the same time as Cycas calcicola, from the Northern Territory, which differs in the down that persists in the grooves on the underside of its leaflets, in leaves that are flat or arched in section and in shorter megasporophylls (up to 15 cm). Cycas arenicola, from Arnhem Land, also has narrow leaflets with recurved margins and a narrow male cone, but its leaflets remain downy and its cones are much shorter (about 25 cm). In the Kimberley, Cycas furfuracea, of the same series, has broader leaflets, often covered in white down, on strongly keeled leaves (Hill 1996).

The name has also been misapplied in print and in the trade. De Laubenfels and Adema (1998) note that a photograph labelled Cycas pruinosa in Krempin’s Palms and Cycads around the World (1990, p. 226) in fact shows Cycas cairnsiana, and that photographs published under this name by Jones (1993, pp. 102–103) belong to another species. On the French forum Fous de palmiers, a collector reported in December 2009 and February 2010 that a seller was offering plain Cycas siamensis, a common South-East Asian species, under the name Cycas pruinosa. A young blue plant sold under this name is therefore worth checking.

Taxonomy

Cycas pruinosa is a name accepted by The World List of Cycads and by GBIF; the World Checklist of Vascular Plants (WCVP), on which POWO is based, also accepts it (consulted through GBIF on 31 October 2026). John R. Maconochie described it in 1978 in the Journal of the Adelaide Botanic Gardens (1(3): 177–178, fig. 2), from a female plant collected by D. Symon in June 1975 in Ternonis Gorge, in the Durack Ranges. He compared it with Cycas revoluta and Cycas cairnsiana, which also have leaflets with rolled margins.

Hill (1996) placed it in subsection Endemicae of section Cycas, in series Furfuraceosae, defined by lower leaflets that diminish gradually until they are reduced to spines and by large, non-pungent teeth on the megasporophylls. The series also includes Cycas furfuracea and Cycas basaltica, both from the Kimberley. De Laubenfels and Adema (1998), who sank many Australian species into synonymy, kept Cycas pruinosa as a species, so the name has not changed since 1978.

Etymology and history

The epithet comes from the Latin pruinosus, “covered with a waxy bloom”. Maconochie (1978) related it to the bloomed surface of the seeds; The World List of Cycads, after Haynes (2022), relates it to the glaucous, whitish-blue leaves. Both organs are bloomed in many plants.

The holotype is kept at the Northern Territory Herbarium in Darwin (DNA), with isotypes in Brisbane (BRI), Canberra (CANB), Kew (K), Leiden (L), Sydney (NSW) and Perth (PERTH) (Hill 1996). The earliest collection Hill cites dates from July 1952 (R.A. Perry, The Grotto, Carr Boyd Range, near Kununurra). No history of its introduction into cultivation is documented, but seed has circulated among European collectors: an offer from a specialist seed merchant is mentioned on the Fous de palmiers forum in August 2013, and seedlings were reported in Italy the same year.

Common names

No common name is attested for this species, in English, French or any Aboriginal language. The British nursery Trebrown knows of none.

In the wild

Cycas pruinosa is a widespread but scattered species of the eastern and southern Kimberley, in Western Australia (Carr Boyd Range, Lake Argyle, Bedford Downs, Deception Range, Elgee Jump Up), also present in the Spirit Hills on Bullo River station, in the Northern Territory. It grows mainly on skeletal sandy soils over siliceous rocks, from metasandstones to granites; one population, in the Napier Range near Tunnel Creek, grows instead on terra rossa over limestone (Hill 1996; Flora of Australia). Maconochie (1978) described it on hillsides and at the foot of steep cliffs.

The region has a tropical monsoon climate, with a long dry season. Pollination and phenology are not documented.

Conservation status and regulation

The IUCN lists Cycas pruinosa as Least Concern (LC), in the assessment by J.D. Bösenberg published in version 2022-1 of the Red List, which follows an earlier assessment by K.D. Hill (2010); the Red List data relayed by GBIF confirm the LC category (consulted on 24 October 2026). Hill (1996) did not consider it to be at risk. The online Flora of Australia gives no federal or state conservation listing for it.

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

In short: grown by a few collectors, but published reports are rare and mostly describe how difficult young plants are. Heat, sun, a very mineral substrate and caution with water in cool weather are the recurring points.

Outdoor and in-ground cultivation

Outdoors, it can only be considered in a tropical climate with a marked dry season, close to that of its habitat. Its natural sites, rocky hillsides and skeletal sandy soils, point to full sun and perfect drainage; this is a deduction from the wild, not a tested recommendation. No outdoor trial has been published in a Mediterranean, subtropical 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, Simon Lavaud, a French nurseryman specialising in cycads (Cycadales.eu), does not name Cycas pruinosa, but ranks the cycads of the Northern Territory (except Cycas angulata) and Cycas furfuracea, its neighbour in the Kimberley, among the species that are “very difficult” in a temperate climate.

The only dated European reports come from Italy and are useful to growers in comparable climates. A grower in Ravenna (Emilia-Romagna, Italy) reports on the Tropicamente forum, in October 2013, that the species loves heat and sun and prefers to be frost-free; in February 2014, four of his five seeds had germinated, one of them with a partly rotten root; by February 2015 he had a single surviving plant and concluded that “Australian cycads are difficult”. These were seedlings raised in pots under shelter. The Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published no observation on Cycas pruinosa.

In cultivation in the UK, US and Australia

In short: very rare in collections.

  • United States: the online catalogue of Montgomery Botanical Center (Coral Gables, Florida) lists two accessions, 20140736 (2014) and 20150052 (2015).
  • Australia: Kings Park and Botanic Garden in Perth declares the species in the BGCI PlantSearch database (consulted on 24 October 2026). A member of the French forum Fous de palmiers photographed plants labelled as this species at the George Brown Darwin Botanic Gardens in 2016; the identification is the forum’s.
  • United Kingdom: no garden declares it in BGCI, and no other record is documented.

Outside these countries, BGCI also lists the Mazhar Botanic Garden in Egypt. 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 an English-speaking grower has been published.

Propagation

Like all Cycas, Cycas pruinosa is dioecious: a male and a female plant are needed for fertile seed. Sowing is the only documented method; the Italian report quoted above records a good germination rate (four seeds out of five) but heavy losses afterwards. Seeds are exempt from CITES under annotation #4.

Pests and diseases

No pest specific to the species is documented. The problem reported in cultivation is root rot in young plants. Scale insects, including Aulacaspis yasumatsui, can attack any Cycas.

Cold hardiness

No cold-tolerance value has been published for Cycas pruinosa. Its range in the Kimberley has no regular frost, and the only European grower who has written about it judges that it prefers to be frost-free.

Mediterranean and European experience

No cultivation result has been published in Europe in the open ground, and no dated frost episode concerns the species. The only European reports, from Ravenna, concern seedlings grown in pots under shelter.

United Kingdom, United States and Australia

No cold reading and no dated growing report are documented, 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

No toxicity analysis specific to Cycas pruinosa has been published. 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 is documented for this species.

Frequently asked questions

What does pruinosa mean?

“Covered with a waxy bloom” in Latin: its seeds, and often its leaves, carry a greyish-white wax.

Is Cycas pruinosa always blue?

No. Depending on the population, plants are blue, green or mixed; the character seems to be genetic.

Where does Cycas pruinosa grow?

In the eastern and southern Kimberley (Western Australia) and in the Spirit Hills (Northern Territory), on rocky slopes and poor, sandy soils.

How can it be told from Cycas calcicola?

By its leaflets and cones. Cycas calcicola has down in the grooves beneath the leaflets, flat or arched leaves and much shorter megasporophylls.

Is a Cycas pruinosa bought from a garden centre genuine?

Not necessarily. Cycas siamensis has been sold under this name, and the name has been misapplied in books; buy from a specialist supplier who guarantees the origin.

Can it be grown outdoors in the UK?

No. No cold data exist, its native climate is hot all year, and the European reports concern pot-grown seedlings under shelter.

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

  • Maconochie, J.R. (1978). Two new species of Cycas from Northern Australia. Journal of the Adelaide Botanic Gardens 1(3): 175–178. [Original description.]
  • Hill, K.D. (1996). A taxonomic revision of the genus Cycas (Cycadaceae) in Australia. Telopea 7(1): 1–64. doi:10.7751/telopea19963040 [Full description (pp. 60–62), type and isotypes, series Furfuraceosae, colour variation, habitat, status.]
  • 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).]
  • Bösenberg, J.D. (2022). Cycas pruinosa. The IUCN Red List of Threatened Species: e.T41993A69155381. doi:10.2305/IUCN.UK.2022-1.RLTS.T41993A69155381.en [Current assessment; reference checked on The World List of Cycads and Crossref, LC category relayed by GBIF.]
  • de Laubenfels, D.J. & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43(2): 351–400. [Cycas pruinosa kept as a species (pp. 387–388), misapplied photographs in Krempin (1990) and Jones (1993).]
  • 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.]
  • 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.]