Cycads (Cycadales): order, families and genera

Cycads (order Cycadales) look like palms or tree ferns, but they are neither: they are gymnosperms, seed plants with naked seeds and no flowers or fruit, like conifers and the ginkgo. Their lineage goes back to the Permian, more than 280 million years ago, which is why they are often called “living fossils”. Today the order has ten genera and about 380 species, spread across the tropical and subtropical regions of the Americas, Africa, Asia and Australia. Among these ornamental plants, the best known is Cycas revoluta, the Japanese sago palm of gardens and conservatories; many other species are rare, protected and keenly sought by collectors. Some, adapted to long dry seasons, sit comfortably alongside succulents in a collection.

Key facts about Cycadales

  • Group: gymnosperms; reproduction by cones (strobili), without flowers
  • Families: Cycadaceae (the genus Cycas alone) and Zamiaceae (the other nine genera), as accepted by POWO; some authors still separate a family Stangeriaceae
  • Diversity: 10 genera; 382 species plus 14 subspecies or varieties, i.e. 396 accepted names, according to The World List of Cycads (August 2026 version)
  • Natural range: tropical and subtropical America (from the south-eastern United States to Bolivia and Brazil), sub-Saharan Africa, Madagascar, South and East Asia, Australia and the Pacific islands
  • CITES: every species is listed; Appendix I covers all Ceratozamia and Encephalartos, plus Microcycas calocoma, Stangeria eriopus, Cycas beddomei and Zamia restrepoi; all the others are in Appendix II
  • Conservation: about two-thirds of the species assessed by the IUCN fall into a threatened category, making cycads the most threatened plant group assessed so far
  • In the UK, the US and Australia: grown almost entirely under glass in Britain, apart from a few plants in exceptionally mild gardens (Ventnor, Tresco); grown outdoors in South Florida, coastal Southern California and Australian gardens such as Melbourne (see In cultivation in the UK, US and Australia)
  • Toxicity: all parts are poisonous, the seeds above all (see Toxicity and precautions)

What a cycad is: the main characteristics

A cycad is a trunk topped by a crown of large leaves. The trunk, also called a stem or caudex, is usually single and cylindrical. In some species it branches, or stays underground so that only the leaves show above the soil. It is clad in the bases of old leaves and can store water and starch.

The leaves are pinnate: divided into leaflets arranged on either side of a central axis, stiff and often leathery. There are two notable exceptions. Bowenia has bipinnate leaves, divided twice, and a few species of Cycas, such as Cycas debaoensis, have leaflets that are themselves divided. New leaves appear in flushes, often all at once, and unfurl over a few weeks.

Besides their ordinary roots, cycads form coralloid roots. These small, branched, coral-like roots grow up towards the soil surface and house cyanobacteria (Nostoc and related genera) that fix nitrogen from the air. This partnership helps cycads live on poor soils.

All cycads are dioecious: each plant is either male or female. Males bear pollen cones; females carry their ovules on modified leaves called megasporophylls. In the Zamiaceae these megasporophylls are packed into a compact cone. In Cycas they form a loose crown at the top of the trunk, with no true cone. The large seeds have a fleshy coat, often red, orange or yellow.

Taxonomy and classification

The classification of gymnosperms published by Christenhusz and colleagues in 2011, and followed by Plants of the World Online (POWO), recognises two families in the order Cycadales:

  • Cycadaceae, containing only the genus Cycas;
  • Zamiaceae, containing the other nine genera: Bowenia, Ceratozamia, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, Stangeria and Zamia.

Older classifications, still common in books and nursery catalogues, kept a third family, Stangeriaceae, for Stangeria and sometimes Bowenia. This change of rank does not alter any genus or species name.

The South American genus Chigua, still found in older literature, has been sunk into Zamia: its two species are now united under the name Zamia restrepoi, with Chigua bernalii treated as a synonym by The World List of Cycads.

The number of species keeps rising, because new ones are described every year, especially in Mexico, Central America, China and South-East Asia. Figures therefore vary with the source and its date. This site follows POWO for accepted names and, for species counts by genus, also cites The World List of Cycads, the reference checklist maintained under the IUCN Cycad Specialist Group.

Molecular studies add a nuance to the “living fossil” label. The lineage is very old, and the general appearance of cycads has changed little since the Mesozoic, the age of the dinosaurs. Yet most of today’s species are young: they arose in a burst of diversification within the last ten to twelve million years (Nagalingum et al., 2011).

Etymology and history

The order takes its name from the genus Cycas, published by Linnaeus in 1753. According to the explanation most often given, Linnaeus took it from the Greek kykas, itself thought to be a copyist’s error for koïkas, the name of a palm in Theophrastus: cycads would thus owe their name to their resemblance to palms. The name Zamia, also published by Linnaeus, is traced in the same way to a misreading of a Latin word used by Pliny for pine cones.

Cycads were abundant and diverse during the Jurassic and Cretaceous. Their present range, fragmented across several continents, is what remains of a once much wider distribution.

Common names

In English the whole order is simply called cycads. Cycas revoluta is sold as the sago palm, and the Royal Horticultural Society lists it as the Japanese sago palm. These names are misleading: the true sago palm is a palm (Metroxylon sagu), and no cycad belongs to the palm family. The genus pages give the common names attested for each genus.

Distribution and ecology

Cycads live in the tropics and on their margins:

  • in the Americas: Zamia, Ceratozamia, Dioon and Microcycas, from the south-eastern United States to Bolivia and Brazil, with a centre of diversity in Mexico;
  • in Africa: Encephalartos, throughout sub-Saharan Africa, and Stangeria, in South Africa and southern Mozambique;
  • in Australia: Macrozamia, Lepidozamia and Bowenia, all three endemic, plus many species of Cycas;
  • from Madagascar and East Africa to Japan and the Pacific islands: Cycas, the only Old World genus outside Africa and Australia.

Their habitats are very varied: tropical rainforest, savanna, high-altitude grassland, limestone cliffs and coastal dunes. Many species endure marked dry seasons, and some grow on very poor soils thanks to their coralloid roots.

In most of the species studied, pollination is not carried out by the wind but by insects, mainly small weevils and thrips. These insects live and feed inside the cones. At pollination time the cones run a daily cycle of heat and scent that first draws the insects in, then drives them out, laden with pollen, towards the female cones.

Horticultural and cultural importance

Cycas revoluta, native to southern Japan, is the most widely grown cycad in the world: a house plant, a patio plant and, in mild regions, a garden plant. Botanic gardens and collectors also grow many species of Encephalartos, Dioon, Zamia and Macrozamia, prized for foliage that may be blue-grey, rigid or finely cut.

In several parts of the world, cycad trunks and seeds have been used as a source of starch, after lengthy processing to remove the toxins. Inadequate preparation can cause serious poisoning.

In cultivation in the UK, US and Australia

Short answer: in Britain cycads are glasshouse plants with very few exceptions, while South Florida, coastal Southern California and Australian gardens such as Melbourne grow large collections outdoors. The examples below come from the gardens’ own catalogues and publications, each with its date. A species listed in the BGCI PlantSearch database (the shared database to which botanic gardens report their holdings) shows that a garden has declared it at some point, not that a living plant is there today.

United Kingdom

  • Royal Botanic Gardens, Kew: a specimen of Encephalartos altensteinii brought from South Africa and planted in 1775 is recognised by Guinness World Records as the oldest pot plant in the world and is displayed in the Palm House; a 2025 study of the Missouri Botanical Garden collection describes it as the living type specimen of the species, growing at Kew since 1775.
  • Royal Botanic Garden Edinburgh: a 2010 study published in the garden’s journal Sibbaldia counted 35 species in the living collection, from every genus except Microcycas. The public glasshouses are now closed for restoration (the Edinburgh Biomes project), and some 40,000 plants have been moved out since spring 2021.
  • Ventnor Botanic Garden (Isle of Wight): the garden describes its microclimate as about 5 °C (9 °F) warmer than the rest of the UK. A male Cycas revoluta growing outdoors produced a cone in 2013 according to the garden’s Google Arts & Culture story (2012 in other accounts), and in summer 2019 a larger male cone and a female cone appeared together, which the garden presents as the first cones produced outdoors in the UK.
  • Tresco Abbey Garden (Isles of Scilly): an open-air garden that describes its climate as mild and practically frost-free; its July 2026 garden diary shows tall plants captioned Encephalartos natalensis in full sun.

The Royal Horticultural Society rates Cycas revoluta H3, “hardy in coastal and relatively mild parts of the UK” (−5 to 1 °C; 23 to 33.8 °F), and advises growing it under glass, or in the open ground only in frost-free areas. Tresco also declares Macrozamia communis in BGCI PlantSearch. Apart from these examples, no cycad growing in the open ground in Britain is documented in a verifiable source.

United States

  • Montgomery Botanical Center (Coral Gables, Florida): its online catalogue held 225 accepted species and 1,802 accession numbers in October 2026, and the garden has an outdoor Cycad Walk.
  • Fairchild Tropical Botanic Garden (Coral Gables, Florida): more than 700 accessioned cycads according to the garden, and 119 accepted species in its online Garden Explorer (October 2026).
  • Ganna Walska Lotusland (Montecito, California): a cycad garden built in 1977–1979 on raised beds grouped by genus. The summer 2026 newsletter reports the end of a multi-year renovation against Armillaria root rot, with improved drainage.
  • University of California Botanical Garden, Berkeley: according to a 2015 Plant Collections Network profile, the San Francisco Bay climate is “ideal for many Encephalartos” but “marginal” for Dioon and Ceratozamia, while Microcycas, Bowenia, Stangeria, Cycas multipinnata and Cycas micholitzii need the glasshouse there.
  • Missouri Botanical Garden (St. Louis): 49 taxa from nine of the ten genera in 2025, mostly in the Climatron glasshouse. Two Dioon edule received from the Mexican commission at the 1904 World’s Fair and planted in the Climatron in 1966 are still alive.

Australia

  • Royal Botanic Garden Sydney: 143 accepted species in its Garden Explorer (updated 1 October 2026), each plant with its bed number; the sister garden at Mount Annan grows 29 Australian species.
  • Royal Botanic Gardens Victoria: the living collection census lists about 450 cycads of 54 accepted species. At Melbourne Gardens almost all grow in outdoor beds, including four Encephalartos woodii in three beds; only a cycad house and a tropical house are glasshouses.
  • Australian National Botanic Gardens (Canberra): in 2004 the gardens planted 17 large cycads and palms rescued from road clearing in Queensland, including Macrozamia moorei and Cycas media.

The genus pages give, genus by genus, the species recorded in these gardens and the growers’ reports that could be checked.

Growing cycads: general advice

Cycads grow very slowly, often producing a single flush of leaves a year. Their general needs are:

  • full sun or partial shade, depending on the species;
  • a very free-draining growing medium;
  • moderate watering: they tolerate a dry season, but prolonged waterlogging rots the trunk and roots.

They are propagated from seed or from basal offsets, both slow methods.

In cool-temperate climates such as most of the UK, nearly all species are grown in a glasshouse, a conservatory or a bright room. Where winters are mild and the soil drains well, some can be planted out: Cycas revoluta first, then, according to growers, certain species of Dioon, Encephalartos and Macrozamia. Gardens in south-eastern France, such as the Jardin zoologique tropical at La Londe-les-Maures (Var), report their own outdoor results on the genus pages; this Mediterranean experience may help readers in comparable climates, such as coastal California or southern Australia, but it is French experience and gives no exact temperature equivalent for any other place. Cold tolerance varies greatly from one species to another; each species page gives the values known and their source.

Regulation and conservation

Cycads are among the most threatened living things on the planet. According to IUCN assessments, about two-thirds of the species fall into a threatened category, and in 2020 four taxa were considered Extinct in the Wild. The best-known case is Encephalartos woodii: only male plants are known, all propagated in cultivation from a single individual found in South Africa. The main threats are:

  • habitat destruction;
  • illegal collection of wild plants for private collections;
  • growth so slow that populations recover poorly.

All cycads are listed in the appendices of CITES, the convention that governs international trade in endangered species. Species in Appendix I may be traded internationally for commercial purposes only if they are artificially propagated and accompanied by the required documents. They are all species of Ceratozamia and Encephalartos, together with Microcycas calocoma, Stangeria eriopus, Cycas beddomei and Zamia restrepoi. The other species, in Appendix II, move with permits; for them, seeds, pollen and in vitro cultures are exempt from CITES controls (annotation #4).

The United Kingdom, the United States and Australia each apply CITES through their own national legislation and permit systems; in Britain, the government publishes guidance on when a CITES permit is needed. For readers in the European Union, CITES is implemented by Council Regulation (EC) No 338/97: species in CITES Appendix I are normally listed in Annex A of the Regulation, and those in Appendix II in Annex B. Before buying, importing or selling a rare cycad, check its status and the documents required with the national CITES authority. This general information does not replace the official texts.

Toxicity and precautions

All parts of a cycad are poisonous, the seeds above all. They contain cycasin, a glycoside that the body converts into methylazoxymethanol (MAM), which damages the liver and the nervous system. Poisoning can be serious, even fatal, in animals and in people. Dogs are the most frequent victims, because they readily chew the seeds of Cycas revoluta. Keep these plants out of reach of children and pets. If any part is swallowed, contact a poison centre, a doctor or a vet without delay.

The cycad genera

Species numbers follow The World List of Cycads (August 2026 version); subspecies and varieties are counted separately.

Family Cycadaceae

  • Cycas: 118 species (and 6 infraspecific taxa), from Madagascar and East Africa to Japan, Australia and the Pacific; the only genus without a compact female cone.

Family Zamiaceae

  • Bowenia: 2 species from eastern Queensland (Australia), the only cycads with bipinnate leaves.
  • Ceratozamia: 45 species from Mexico, Guatemala, Belize and Honduras; the scales of their cones bear two small horns.
  • Dioon: 19 species from Mexico and Central America, very slow-growing and very long-lived.
  • Encephalartos: 65 species (and 6 infraspecific taxa) from sub-Saharan Africa, much sought after and often critically threatened.
  • Lepidozamia: 2 species from eastern Australia, among the cycads with the tallest trunks.
  • Macrozamia: 41 species, all endemic to Australia.
  • Microcycas: a single species, Microcycas calocoma, endemic to western Cuba.
  • Stangeria: a single species, Stangeria eriopus, from South Africa and southern Mozambique, with fern-like leaves; it was first described as a fern.
  • Zamia: 88 species (and 2 infraspecific taxa), the largest American genus, from the south-eastern United States to Bolivia and Brazil, including the Caribbean; type species: Zamia pumila.

Frequently asked questions

Is a sago palm a palm?

No. Cycads are gymnosperms, closer to conifers and the ginkgo than to palms, which are flowering plants. The resemblance is a convergence of form: a single trunk topped by a crown of large leaves.

Are cycads succulents?

Not in the strict sense. Their trunks store water and reserves, and many species withstand long dry seasons. That is why succulent collectors often grow them, with similar care: a free-draining mix and moderate watering.

How long does a cycad live?

A very long time, but precise ages are rarely documented. One well-dated example is the Encephalartos altensteinii in Kew’s Palm House, planted in 1775. Slow growth and great longevity explain both the value of large specimens and the difficulty of rebuilding wild populations.

Can cycads grow outdoors in the UK?

Only in the mildest places. The RHS rates Cycas revoluta H3 (−5 to 1 °C; 23 to 33.8 °F) and recommends planting out only in frost-free areas. Ventnor on the Isle of Wight grows it outdoors, with cones in 2012 or 2013 and again in 2019, and Tresco in the Isles of Scilly grows Encephalartos natalensis in the open. Elsewhere in Britain, a cool glasshouse or a bright room is the safe choice.

Where can I see cycads in the UK, the US or Australia?

In the large botanic gardens. In Britain, Kew is the best-known, with its 1775 Encephalartos altensteinii in the Palm House; Edinburgh’s glasshouses are closed for restoration. In the United States, Montgomery Botanical Center and Fairchild in Florida, Lotusland in California and the Missouri Botanical Garden’s Climatron hold major collections. In Australia, the Royal Botanic Garden Sydney and Royal Botanic Gardens Victoria in Melbourne display many species outdoors. Check opening arrangements before visiting.

Can I buy a cycad freely?

Yes for artificially propagated plants sold legally in garden centres, such as Cycas revoluta. For rare species, especially those in CITES Appendix I, import, sale and sometimes possession require documents: ask the seller for them and check the official rules in your country.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Christenhusz, M.J.M., Reveal, J.L., Farjon, A., Gardner, M.F., Mill, R.R. & Chase, M.W. (2011). A new classification and linear sequence of extant gymnosperms. Phytotaxa 19: 55–70. [Peer-reviewed; the two-family classification followed by POWO.]
  • Nagalingum, N.S., Marshall, C.R., Quental, T.B., Rai, H.S., Little, D.P. & Mathews, S. (2011). Recent synchronous radiation of a living fossil. Science 334: 796–799. [Peer-reviewed; recent diversification of living species.]
  • Calonje, M., Stevenson, D.W. & Osborne, R. The World List of Cycads, online edition, version of 15 August 2026 (consulted 1 October 2026). [Reference checklist.]
  • Marler, T.E. & Marler, P.N. (2015). An assessment of Red List data for the Cycadales. Tropical Conservation Science 8(4). [Peer-reviewed; proportion of threatened species.]
  • Clugston, J. (2010). Student project: data capture and taxonomic determination of Cycadales at the Royal Botanic Garden Edinburgh. Sibbaldia 8. https://journals.rbge.org.uk/rbgesib/article/download/134/124 [Garden journal; Edinburgh collection in 2010.]
  • Deloso, B.E., Colligan, A., Sucher, R. & Ramirez, V. (2025). Missouri Botanical Garden’s cycad collection: a journey through time. Plant Species Biology. doi:10.1111/1442-1984.12509. https://cycadlist.org/storage/references/open/14087e12-f586-4616-a8df-89c4ea575212.pdf [Peer-reviewed; Missouri collection, Kew’s Encephalartos altensteinii.]