cycad

Cycads are seed plants of division Cycadophyta, order Cycadales. They are gymnosperms characterized by stout trunks or subterranean bases and a crown of large, pinnate leaves. Although they resemble palms, cycads are not true palms and belong to an ancient lineage that predates many modern plant groups.

Most cycads are dioecious, with separate male and female plants. Male individuals produce pollen cones; female plants bear fleshy, often colorful seeds. A distinctive feature is their coralloid roots, which host symbiotic cyanobacteria that fix atmospheric nitrogen, helping the plant grow in sometimes nutrient-poor soils.

Geographically, cycads are native to tropical and subtropical regions of Africa, Asia, Australia, and the Americas. They inhabit a variety of environments, from forest clearings to rocky slopes. They are slow-growing and long-lived, and many species have restricted ranges, making them particularly vulnerable to habitat loss and over-collection.

Cycads are among the most ancient seed plants, with fossil records extending to the Permian period. They are often described as living fossils. Because of habitat destruction and exploitation, numerous cycad species are endangered or threatened. Conservation efforts include habitat protection and cultivation in botanical gardens and private collections.

In cultivation, cycads are valued as ornamental plants for their sculptural form and evergreen fronds. Handling seeds and tissues should be done with care, as some parts contain toxins such as cycasin; ingestion can be hazardous, and skin contact may cause irritation.