Cycad

Scientific

Cycadophyta is one of the four major divisions of living seed-bearing plants (the others being Pinophyta = conifers, Ginkgophyta = [[ginkgo]], and Magnoliophyta = flowering plants). Cycads’ approximately 300 living species across ~10 genera are distributed across tropical and subtropical regions of every continent except Europe and Antarctica.

The lineage is ancient — cycad fossils appear in the Permian period (~280 million years ago). Cycads, conifers, and ferns together dominated the Mesozoic landscape alongside the dinosaurs; flowering plants emerged ~150 million years ago and gradually displaced cycads from ecological dominance.

The superficial similarity to palms (the trunk-and-frond growth form) and ferns (the spreading compound leaves) is convergent rather than evolutionary — cycads, palms ([[date-palm]], [[oil-palm]]), and ferns ([[fern]]) are each in completely different lineages.

Cycads reproduce via cones (like conifers and ginkgo) rather than flowers and fruit. Most species are dioecious — separate male and female plants — with the male cones producing pollen and the female cones bearing the seeds.

Modern conservation crisis

Cycads are the most-endangered plant group by IUCN assessment. Approximately 60–70% of all cycad species are threatened with extinction. Factors:

• Habitat loss — many cycads have narrow geographic ranges that have been heavily impacted by agricultural conversion and development
• Illegal collecting — the rare-cycad market is one of the most-active illegal plant trades globally; some specimens have sold for tens of thousands of dollars; many wild populations have been targeted by poachers
• Slow regeneration — most cycads take decades to reach reproductive maturity; harvested wild plants are not quickly replaced
• Climate change — narrow-range species are particularly vulnerable

CITES (the Convention on International Trade in Endangered Species) lists most cycad species in Appendix I or II — among the highest levels of international trade protection.

Cultural

The most-cultivated cycad — the “sago palm” Cycas revoluta — is a common houseplant across temperate climates. Despite the name, the species is not a palm and true sago starch is made from an unrelated palm tree (Metroxylon sagu). The “sago palm” cycad does have starchy seeds and a starchy trunk pith — both edible only after extensive processing to remove the cycasin toxins that occur naturally throughout the genus.

The plant is also extremely toxic to dogs and cats — sago palm ingestion is one of the most-serious houseplant-poisoning emergencies in veterinary practice. Even small ingestions can cause acute liver failure.

The Seminole and other Indigenous peoples of Florida traditionally processed the native Florida cycad (Zamia integrifolia, coontie) as a starchy food source — the processing technique to remove the cycasin toxins required leaching, fermentation, and extensive washing.

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

• Shares approach with: [[ginkgo]] · [[date-palm]] · [[oil-palm]] · [[fern]]
• Member of: [[plants]]

Sources

• Wikipedia — Cycad
• IUCN Red List cycad assessments

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A plant entry in the 0mn1.one [[directory]].