Trees of the genus Cycas are primitive gymnosperms that superficially resemble palm trees. However, they are quite distinct from true palms, and form an entirely different lineage.
Description and Identification
Cycas trees – like most other members of the class Cycadopsida – feature a ring of pinnately compound (feather-like) leaves attached to the top of the trunk. You can further recognize members of the genus by noting the prominent mid-ribs of the leaflets and lack of any obvious secondary veins.
Like all other cycads, trees of the genus Cycas are dioecious, with distinct male and female plants. In both cases, the cones lie at the top of the trunk and emerge from the center of the leaf ring.
While some members of the genus feature round, subterranean trunks and are essentially shrub-like, others have tapering, tree-like trunks that grow aboveground. Most cycads feature relatively shallow root systems and grow very slowly. The majority of species remain rather small, with the largest specimens reaching perhaps 35 to 40 feet in height.
Relatives and Relationships
Between 90 and 115 species comprise the genus Cycas (the only genus in the family Cycadaceae), making it one of the largest lineages in the class Cycadopsida. Commonly known as the cycads, the ancestor of this group of species is thought to be the sister lineage to the other families in the class.
Cycads are ancient species that were found across most of the world by the beginning of the Triassic period. In fact, the entire Mesozoic era (which spanned from approximately 225 million years ago to 65 million years ago), is often called the “Age of the Cycads,” because of the plants’ dominance in these ecosystems. According to the University of California, Museum of Paleontology, cycads represented one-fifth of the world’s flora during much of the Triassic and Jurassic periods.
Habitats and Geography
Cycas trees are confined to the Old World. They are found from Japan, west to Africa and Madagascar, and south as far as northern Australia. As a group, the trees inhabit a variety of landscapes; some forms grow in tropical rainforests, while others grow along rocky escarpments.
Some species, for example, Cycas circinalis are well adapted to living along shorelines. The seeds of these trees are buoyant and capable of lasting extended periods of time floating through the ocean, until they eventually wash up in a habitable location.
Culture and Uses
One of the most commonly cultivated species is the so-called sago palm (Cycas revoluta). It prefers full sun, but some people succeed in growing them indoors. Because they remain relatively small, they are often planted in restricted spaces. If provided with a suitably large vessel, sago palms often thrive when grown in a container.
Several indigenous cultures throughout the range of these plants collect and eat the trees’ seeds as a food source, and some harvest starch – called sago — from the stems. However, neurotoxins are found throughout many different portions of the plants; if consumed, the poisons can cause serious disease or death. Accordingly, most people who eat the seeds or sago attempt to leach out the toxins with copious amounts of water.