PLANT OF THE WEEK

Dr. T. Ombrello - UCC Biology Department

CYCADS

Common name:           Cycads  

Scientific name:         Cycas species. and Zamia species

Explanation of scientific name:

Cycas - from Greek for palm tree

Zamia - from Latin zamia, loss, from the "sterile appearance" of the pollen cones

Cycad is the common name for the approximately 100 species that make up the plant division Cycadophyta.  They superficially resemble palm trees in their leaf and stem form, and some species were incorrectly identified as palms when first discovered.  The common names for some cycads, for example the Sago Palm (Cycas revoluta), reflect how palm-like they appear.

The Cycads are a relatively obscure group of plants closely related to pines, spruces, and other conifers since they are all considered gymnosperms.  Despite the palm-like foliage, Cycads have no flowers or fruits, and their naked seeds develop within cones just like the conifers.  A very old group, they were around to see the dinosaurs first appear and later become extinct.  Cycad fossils have been dated to 125 million years ago, and Cycad-like relatives go back 275 million years.  Once wide spread and an important part of Earth’s flora, today they are minor components of the vegetation of tropical regions in Central and South America, Australia, Japan, Africa, and Madagascar.  The only native Cycads in North America are found in southern Florida.

Never really found in significant numbers, the Cycads are sometimes referred to as “living-fossils”, with many botanists predicting the group to be well on its way to extinction in nature.  Some species already exist solely under cultivation.  One species, Cycas taiwaniana, is so rare that it was thought to be extinct for 80 years until a few remaining plants were rediscovered in 1975 by a scientific expedition to a remote region of Taiwan.

All of the Cycads have the same basic appearance, but their sizes vary.  Some species reach heights in excess of 60 feet with leaves 10 feet long, while other species never get much taller than 1 foot.  The leaves may look like a palm’s, but they open in an uncoiling fashion just like the “fiddleheads” of a fern.  Although they live in tropical regions, Cycads require a well-drained soil.  They can withstand drought, since the thick leaves lose little water.  When the leaves die, their stiff leaf bases persist.  Clasping the stem, they provide a thick, armor-like covering.

Cycads all develop a large taproot, with many branching secondary roots near to or on the soil surface.  The exposed roots develop spherical nodules that contain blue-green algae (Cyanobacteria) such as Anabaena, which “fix” nitrogen from the air into nitrates.  They Cycads utilize the nitrates to supplement what they can absorb from the soil, and the algae have the nodules as a protected environment in which to live.  This is a good example of mutualism, where both participants benefit from their intimate relationship.

Cycad stems are thick, but are not made of true wood.  They are fibrous, with much stored starch.  Often the stem and taproot are of equal diameter, making it difficult to determine where one ends and the other begins.  Cycad stems can be very slow growing in nature.  One individual with a 6-foot tall trunk lived 1000 years.  They grow much faster under cultivation.

All Cycads are dioecious, meaning that each member of a species will produce either male or female cones, but not both.  Male cones are small, but the female cones can reach several feet in length.  The large brightly colored seeds produced by the females have a fleshy outer covering that attracts birds and rodents.  In the process of consuming the flesh, these animals disperse the seeds.

Cycads have economic importance in today’s world only as ornamentals in frost-free regions throughout the world.  Their slow growth, drought, insect, and disease resistance make them virtually maintenance free components of a landscape.

Historically, however, the Cycads have been used as a food source.  This was especially true in what is today Florida, where the Seminole Indians extracted a starch from the roots and stems of the native Cycad (Zamia floridana) and prepared “sofkee”, a pudding that was a staple of every Seminole meal.  Later it was used as a substitute for scarce wheat flour and the Indians came to refer to the Cycad as the White Bread Plant.  Non-native settlers around Miami established the area’s earliest industry based on this starch (referred to as arrowroot cornstarch or, locally, as coontie) that persisted up until the 1920s.  Preparing the arrowroot cornstarch involved peeling, grating, and grinding the Cycad stems and roots into a flour.  The flour then had to be washed to remove the cycasin, a water-soluble toxin.  Unfortunately, this last step was overlooked by Confederate soldiers stationed in Florida during the Civil War, and the result was many fatalities.

The height of the coontie industry came with World War I.  It was discovered that coontie flour mixed with beef broth was the only food a gassed soldier could keep in his stomach for some time after exposure.  The United States Army created a tremendous demand for the material.  With the end of World War I, and the declining availability of Zamia floridana as a result of over-harvesting and the destruction of habitat by encroaching civilization, the coontie flour industry collapsed by 1930.

So today the Cycads, inhabitants on Earth for hundreds of millions of years, persist as rare members of the tropical flora.  Their continued existence probably depends on our cultivation of them in our landscape plantings.