Plant Fact Sheet

Cycadaceae
Cycads
Cycas Species

The family, Cycadaceae, was originally described in 1753 by Carolus Linneaus, and consists of about 30-40 species.  It is compromised on one genus:  Cycas, whose members occur naturally in Southeast Asia, Southern China, Malaysia, tropical Australia, and islands in the Western Pacific Ocean, with a disjunctive species from Africa and Madagascar.

Cycas revoluta, or the Sago Palm, which is native to islands off of Japan, is probably the most well known cycad, and is probably the most propagated cycad.

The lush fern and palm-like foliage and appearance draw attention to cycads for use in garden and landscape situations.

Cycads are gymnosperms. They make naked seeds that do not have a fleshy protective layer, and the seeds are borne in cones, similar to pine cones. Due to the fact that they are gymnosperms and that they closely share characteristics with their ancestral plants, cycads are often termed living fossils. Modern cycads represent only a fraction of their prehistoric ancestors, which reached a growth peak during the Jurassic and Early Cretaceous Periods, a time when cycads dominated the vegetation. Comparisons of fossil remains with living specimens show that cycads have changed very little in 200 million years.

Even though cycads have a long history of various uses by humans, they have no real economic importance. Australian Aborigines may have utilized cycas and macrozamia plants as long as 13,000 years ago. From the trunk of palms and also cycads, a starchy compound called sago is derived. Sago is also known as arrowroot, but it is usually used only in times of food shortage. It must be obtained by the proper method, because many parts of cycads are toxic to humans, especially the seeds.

Cycads have three root types: a primary system like a tap root system, coralloid roots, and adventitious roots. The adventitious roots emerge from offset plantlets and grow down though the air near the main trunk. It is in the noteworthy coralloid roots that a special symbiotic relationship occurs. Coralloid roots have a compact structure that resembles coral, they grow in close proximity to the trunk, and they grow upward through the soil, not downward. The cells of the coralloid roots harbor blue-green algae, or cyanobacteria, which are nitrogen-fixing microorganisms. In their symbiotic relationship with the cyanobacteria, the cycad provides a home for the algae, and the algae provide extra nutrients for growth. Coralloid roots are only known to occur in cycads and in turn cycads are the only known gymnosperms to form symbiotic relationships with nitrogen-fixing organisms.

In the Primitive Plant Garden at the Living Desert, many Sago Palms, or Cycas revoluta can be found. Other cycads, from the family Zamiaceae can also be seen including Zamias, Ceratozamias, and Dioons. In addition to the Cycads, another well-known living fossil is on display in this garden: the Dawn Redwood, or Metasequoia glyptostroboides.