Cycas ferruginea

Cycas ferruginea is a cycad of the limestone cliffs of western Guangxi, in southern China, and of northern Vietnam, where it grows in rock crevices on steep, often bare limestone faces. This member of the genus Cycas takes its name from the dense, deep rust-red down that covers its young leaves and growing parts. Described in 1994 from a single plant grown at Guilin, it was later found in the wild on both sides of the Chinese–Vietnamese border. The IUCN lists it as Near Threatened, and it is a first-class protected plant in China. It remains rare in cultivation, where plants sold under its name are not always what the label says.

Key facts about Cycas ferruginea

  • Accepted name: Cycas ferruginea F.N.Wei (1994), accepted by The World List of Cycads (version 2026.08.15); 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: no synonym; cited in error as Cycas miquelii in a Chinese book of 1996 (Hill 2008)
  • Family: Cycadaceae, order Cycadales; section Stangerioides (Hill 2008)
  • Common names: no English name attested; in Chinese 锈毛苏铁 (xiu mao su tie, “rust-haired cycad”) (see Common names)
  • Natural range: China (western Guangxi) and northern Vietnam (Lạng Sơn and Thái Nguyên provinces)
  • IUCN status: Near Threatened (NT), reassessment by J. D. Bösenberg published in 2023, after the 2010 assessment (criteria B1ab(iii,v))
  • CITES and other protection: CITES Appendix II; Annex B in the European Union; first-class protected plant in China, like all Chinese Cycas
  • Documented hardiness: no data; a British nursery rates it USDA zone 9b (commercial rating, see Cold hardiness)
  • Light and soil: in the wild, crevices in bare limestone, exposed to half-shaded, at 200 to 500 m
  • Habit and adult size: trunk often underground or short, up to 1.2 m; leaves 1.3 to 2.1 m long
  • In the UK, US and Australia: Montgomery Botanical Center (accession of 1998); listed by five other American gardens and Cairns Botanic Gardens in BGCI PlantSearch; no British record
  • Toxicity: no data for the species; treat it as poisonous, like all Cycas (see Toxicity and precautions)

How to recognise Cycas ferruginea

The most striking feature is the down: young leaves, petioles and growing parts are covered in a dense, deep rust-red tomentum, which partly persists on older leaves. According to Ken Hill (2008), this dark tomentum at once separates it from Cycas sexseminifera, as do its longer leaves, its longer leaflets, often curved and with recurved margins, and the larger blade of its megasporophylls. Hill’s description gives the following.

  • Trunk: tree-like or without an aerial trunk, up to 1.2 m tall and 12 to 18 cm in diameter; crown of 10 to 25 leaves.
  • Leaves: deep green or grey-green, highly glossy to semi-glossy, 130 to 210 cm long, flat or barely keeled, with 120 to 200 leaflets; white, orange or brown down, shed or persisting beneath; petiole 35 to 80 cm, hairless or downy, spiny along 30 to 100 % of its length.
  • Median leaflets: simple, often curved, 190 to 380 mm long and 8 to 13 mm wide, narrowed to 2.5–4 mm at the base, with recurved margins and a sharp, pungent tip; midrib raised above.
  • Cataphylls: narrowly triangular, pungent, hairy, 90 to 120 mm long.
  • Male cones: spindle-shaped, orange, 25 to 45 cm long and 4 to 6 cm across; microsporophylls soft.
  • Megasporophylls: 11 to 19 cm, with brown tomentum, bearing 2 to 6 hairless ovules; blade round, 70 to 110 mm by 50 to 80 mm, deeply comb-like, with 28 to 42 soft lateral spines 18 to 40 mm long and a distinct terminal spine 15 to 50 mm long.
  • Seeds: ovoid, 19 to 24 mm by 15 to 21 mm; yellow sarcotesta, not waxy, without a fibrous layer; warty sclerotesta.

The sources do not agree on everything. The Flora of China (Chen and Stevenson 1999) describes a trunk usually underground, at most 60 cm above the soil, with a swollen base, 25 to 40 leaves 1 to 2 m long, leaflets 13 to 18 cm long with strongly rolled margins, a megasporophyll blade of 3.5 to 5.5 cm by 3 to 5 cm (the dimensions Hill gives for Cycas sexseminifera), a smooth sclerotesta and seeds 2 to 2.8 cm long, yellowish when fresh and brown when dry. Wei’s short original description (1994) gives leaves up to 1.95 m by about 50 cm, a petiole of 50 to 70 cm with short spines on both sides, rarely unarmed, 56 to 80 leaflets on each side, thick and leathery, 15 to 25 cm by about 1 cm with strongly inrolled margins, and megasporophylls densely covered in rusty velvet on both faces; it describes neither the trunk, nor the cones, nor the seeds.

Hybrids

No horticultural hybrid has been described. In the wild, Hill (2008) reports plants grown in the villages of Vo Nhai and Yen Son, in Thái Nguyên Province, Vietnam, that are intermediate between Cycas dolichophylla and Cycas ferruginea, which he interprets as hybrids: in that region Cycas ferruginea is abundant on exposed limestone faces, and Cycas dolichophylla in the neighbouring forests on deep soils.

Possible confusion

Confusion mainly involves other cycads of limestone rocks and, in the trade, woolly forms of common species:

  • Cycas sexseminifera, from the same habitat: paler tomentum, shorter leaves and leaflets, a much smaller megasporophyll blade (35 to 55 mm by 30 to 50 mm, against 70 to 110 mm by 50 to 80 mm) and smaller proportions overall (Hill 2008).
  • Cycas tropophylla, the cycad of Ha Long Bay, also a limestone rock dweller: Hill notes the same habitat preference.
  • Cycas siamensis: on the French forum Fous de palmiers, a grower reported in 2009 that a seller offered as Cycas ferruginea plants that were only Cycas siamensis or other common species, and in 2010, in another thread, a participant attributed a woolly-leaved plant thought to be Cycas ferruginea to a form of Cycas siamensis from Kanchanaburi Province, Thailand.

A study of the chloroplast genome (Yang et al. 2022) places Cycas ferruginea close to Cycas debaoensis, Cycas bifida and Cycas szechuanensis: species of very different appearance, but of the same southern Chinese lineage.

Taxonomy

Cycas ferruginea is a name accepted by The World List of Cycads; the World Checklist of Vascular Plants (WCVP), on which POWO is based, also accepts it (consulted through GBIF on 31 October 2026). Wei Fanan described it in 1994 in the journal Guihaia (14(4): 300, figure 1). The holotype is a female specimen collected on 31 August 1994 (F.N. Wei 2220) from a plant grown at Guilin Botanical Garden, thought to come from Longzhou County, in south-western Guangxi; it is held at the herbarium of the Guangxi Institute of Botany (IBK). The World List of Cycads gives the collector number as 1986, a gathering made at the same place on 22 June 1994, but the original description designates number 2220 as the holotype, and Hill (2008) does the same.

The species belongs to section Stangerioides, the group of Cycas of southern China and northern Indochina with small, soft male cones, hairless ovules, a sarcotesta without a fibrous layer and a warty sclerotesta (Hill 2008). According to Hill, a Chinese book of 1996 (Wang) cited it in error under the name Cycas miquelii.

Etymology and history

The epithet ferruginea comes from Latin and means “rust-coloured”, after the abundant dark red tomentum of the young shoots, which partly persists on older leaves (Hill 2008). Wei described the species from a single plant grown at Guilin, whose wild origin was then unknown. According to Hill, surveys in Vietnam in 1997 found large populations of a cycad matching the type plant in Lạng Sơn Province, and wild plants were later discovered in Tiandong County, in western Guangxi. In 1998 the type plant was still growing at the Guilin Institute of Botany. That same year Montgomery Botanical Center, in Florida, received the accession it still holds, judging by its number.

Common names

No English common name is attested: the British nursery Trebrown states “None known”. In Chinese the species is called 锈毛苏铁 (xiu mao su tie), literally “rust-haired cycad” (Flora of China; Xi et al. 2022). No Vietnamese name is documented.

In the wild

Cycas ferruginea has a restricted range. In China, a 2022 review (Xi et al.) records it in Guangxi in the counties of Dahua, Longzhou, Mashan, Pingguo, Tiandong, Tianyang and Yizhou; in Vietnam it is known from the provinces of Lạng Sơn (Hữu Liên Nature Reserve) and Thái Nguyên.

It is a rock-dwelling plant of limestone. Hill (2008) describes it on bare limestone faces and steep cliffs, with no visible soil around the roots, like Cycas sexseminifera and Cycas tropophylla. The Flora of China places it in half-shaded rock crevices in broad-leaved forest on limestone hills, between 200 and 500 m, with pollination in March and April and seeds ripening from August to October.

Conservation status and regulation

Cycas ferruginea is listed as Near Threatened (NT) by the IUCN, the current category relayed by GBIF (consulted on 21 October 2026). The first assessment, by Osborne, Hill, Nguyen and Phan, published in 2010, used the criteria B1ab(iii,v), which The World List of Cycads still shows; a reassessment by J. D. Bösenberg was published in Red List version 2023-1, and the category remained NT. In China all species of Cycas are first-class plants on the national list of protected wild plants (Xi et al. 2022), which Yang et al. (2022) confirm for this species.

Like every species in the genus except Cycas beddomei, it is listed in CITES Appendix II, where the family Cycadaceae has been included since 4 February 1977, with annotation #4 (version in force since 5 March 2026): seeds, pollen and seedlings or tissue cultures obtained in vitro in sterile containers are exempt, while international trade in live plants needs an export permit. The United Kingdom, the United States and Australia 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+ confirms this status, with China and Vietnam as range states (consulted on 21 October 2026). This general information does not replace the official texts: check the rules in force before buying or exchanging plants, and ask for proof that a plant was raised in cultivation.

Growing Cycas ferruginea

In short: no growing recommendation specific to the species has been published, and it remains rare in collections; its cliff habitat suggests a very free-draining mineral mix, good light and no stagnant water.

Outdoor and in-ground cultivation

Its natural habitat, bare limestone faces with no soil and no standing water under a subtropical monsoon climate, suggests a very free-draining mineral mix, possibly with limestone, good light and watering that never leaves the soil soggy: this is a deduction from the habitat, not a growing result. Montgomery Botanical Center grows its collection outdoors at Coral Gables, in southern Florida, but publishes no notes on this species. On the Fous de palmiers forum, a grower listed it in 2013 among the Chinese cycads that are “very hard to obtain”.

Container cultivation

In the United Kingdom and other temperate regions it is a plant for a frost-free glasshouse or conservatory. No container report has been published; given its rock-crevice habitat, a shallow-rooted plant in a gritty mix and a pot that drains fast is the logical approach, again a deduction rather than a tested method.

In cultivation in the UK, US and Australia

In short: represented in a few American collections, rare elsewhere. 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.

  • United States: the online catalogue of Montgomery Botanical Center (Coral Gables, Florida) lists one accession, 981843, from 1998 judging by its number. BGCI PlantSearch adds the Missouri Botanical Garden (where cycads are grown under glass), Naples Botanical Garden (Florida), The New York Botanical Garden, the conservatory of the University of Minnesota and Atlanta Botanical Garden.
  • Australia: Cairns Botanic Gardens list it in BGCI PlantSearch; it does not appear in the catalogue of the Royal Botanic Garden Sydney.
  • United Kingdom: no British garden lists the species in BGCI PlantSearch or in the online catalogues consulted.

No dated report from a private grower in the United Kingdom, the United States or Australia has been published.

Propagation

The plant is dioecious: a male and a female plant are needed for seed. No germination data specific to the species have been published. Seeds are exempt from CITES under annotation #4; given the rarity of the species and its protection in China, look only for seed or plants of legal origin raised in cultivation, and beware of the labelling errors reported in the trade (see Possible confusion).

Pests and diseases

No pest or disease specific to the species is documented. Cycad scales, including the Asian cycad scale, Aulacaspis yasumatsui, can attack all cultivated species, and rot of the roots and trunk is the main risk in an over-wet mix.

Cold hardiness

There are no cold-tolerance data for Cycas ferruginea. It grows at 200 to 500 m under a subtropical monsoon climate, and no source says what frost it can stand. The British nursery Trebrown rates it USDA zone 9b, that is average annual minima of −3.9 to −1.1 °C (25 to 30 °F); this is a commercial rating, not backed by growing observations. No dated cold report is documented on growers’ forums or in botanic gardens, and the Jardin zoologique tropical at La Londe-les-Maures, in the south of France, has published nothing on the species. In the UK, keep it frost-free under glass.

Toxicity and precautions

No toxicity analysis specific to Cycas ferruginea is documented, 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) among plants poisonous to dogs, cats and horses. Unless shown 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 of this species is documented.

Frequently asked questions

What does ferruginea mean?

“Rust-coloured”, in Latin. The name refers to the dense, dark red tomentum that covers the young shoots of the plant.

Where does it grow?

On the limestone cliffs of western Guangxi, in China, and of Lạng Sơn and Thái Nguyên provinces, in northern Vietnam, between 200 and 500 m.

How can it be told from Cycas sexseminifera?

By its very dense rusty tomentum on young shoots, its longer leaves and leaflets and the much larger blade of its megasporophylls. The two species live in the same kind of habitat.

Is it endangered?

Partly. The IUCN lists it as Near Threatened (2010 assessment, category kept by the reassessment published in 2023), and China protects it in the first class, like all its Cycas.

Are plants sold under this name reliable?

Not always. On a French forum, plants sold under this name turned out to be Cycas siamensis, a Kanchanaburi form of which also has woolly leaves. Before buying, ask for the origin and compare the leaflets and megasporophylls.

Can it be grown outdoors?

Only in frost-free climates, as far as is known. No cold data or growing result exist; the only documented outdoor collection is in southern Florida, and elsewhere a pot kept frost-free in winter is the prudent choice.

Is it poisonous?

It must be assumed so. There is no analysis for the species, but all the Cycas studied contain serious toxins, especially in the seeds.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Wei, F.N. (1994). Cycas ferruginea F.N.Wei. Guihaia 14(4): 300, fig. 1. [Original description (Latin diagnosis, types, figure); consulted in October 2026.]
  • Chen, C.J. & Stevenson, D.W. (1999). Cycadaceae. In Wu, Z.Y. & Raven, P.H. (eds), Flora of China 4: 1–7. Science Press, Beijing; Missouri Botanical Garden Press, St Louis. [Description, habitat, phenology; online version.]
  • Hill, K.D., Nguyen, H.T. & Loc, P.K. (2004). The genus Cycas (Cycadaceae) in Vietnam. The Botanical Review 70(2): 134–193. [Treatment of the Vietnamese populations, p. 165; cited from The World List of Cycads.]
  • Hill, K.D. (2008). The genus Cycas (Cycadaceae) in China. Telopea 12(1): 71–118. doi:10.7751/telopea20085804 [Full description (pp. 107–108), key, history, range, hybrids with Cycas dolichophylla (pp. 87–88).]
  • Osborne, R., Hill, K.D., Nguyen, H.T. & Phan, K.L. (2010). Cycas ferruginea. The IUCN Red List of Threatened Species 2010: e.T42075A10619883. doi:10.2305/IUCN.UK.2010-3.RLTS.T42075A10619883.en [NT assessment; reference checked on Crossref.]
  • Bösenberg, J.D. (2023). Cycas ferruginea. The IUCN Red List of Threatened Species 2023: e.T42075A68901141. doi:10.2305/IUCN.UK.2023-1.RLTS.T42075A68901141.en [Current assessment, NT according to GBIF; reference checked on Crossref.]
  • Xi, H.-H., Wang, Y.-Q., Pan, Y.-Z., Xu, T., Zhan, Q.-Q., Liu, J., Feng, X.-Y. & Gong, X. (2022). Resources and protection of Cycas plants in China. Biodiversity Science 30(7): 21495. doi:10.17520/biods.2021495 [Review in Chinese with English abstract.]
  • Yang, X., Deng, T., Tang, W. & Wu, T. (2022). Characterization of the complete chloroplast genome of Cycas ferruginea, a vulnerable species. Mitochondrial DNA Part B 7(6): 1048–1049. doi:10.1080/23802359.2022.2082894 [Chloroplast genome, affinities with Cycas debaoensis, Cycas bifida and Cycas szechuanensis.]
  • 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 used 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.]