Imagine the time before the evolution of flowering plants, the time of the dinosaurs, 200 million years ago. The air is damp and smells of moist earth. The raucous cries of strange creatures reverberate through the jungle, and all around you are strange plants. What kind of plants? Jurassic plants -- Cycads.
Cycads, (pronounced si'kads), formed an extensive portion of the flora of that time, and no doubt the herbivorous dinosaurs grazed contentedly on the abundance. However, the dinosaurs disappeared, and so did most of the cycads -- except for a few incredibly resilient species that still cling tenaciously to existence today. Now they are referred to as living fossils, for they have remained virtually unchanged, and give us a glimpse into a long-distant past.
Family Tree. Cycads are among the rarest plants on Earth, comprising approximately 300 species in only 11 genera:
Bowenia, Ceratozamia, Chigua, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, Stangeria and Zamia
Description. Cycads are commonly mistaken for ferns or palms but are actually conifers, bearing conspicuous cones.
They display a remarkable diversity:
- Leaf size ranges from 8 inches in the diminutive Zamia pygmaea, to 23 feet in the gigantic Encephalartos laurentianus.
- Leaflet colour varies from yellow-green, lime green, dark green, purple-green, to silver and even blue.
- There are cycads with arborescent (tree-like) trunks, and cycads with subterranean trunks.
Longevity and growth rate also varies by species; Zamias can mature and reach coning age in only three to five years, while other, larger species such as the Dioons can take decades to cone and may live to be 1,000 years old.
Uniqueness. There are many aspects of the Cycad family that are quite remarkable. One trait that is nearly unique within living seed-bearing plants is that they produce motile sperm cells called spermatozoids that must travel from the male plant to a separate female plant to effect fertilization. The seed cones can weigh as much as 50 pounds. Cycas have a specialized tertiary root system called coralloid roots (because they look like coral formations) which host symbiotic blue-green algae that fix nitrogen from the air. This algae produces a neurotoxin which is found in the leaves or seeds of most cycads. Species with subterranean trunks have contractile stems and roots that pull the trunks underground to protect them from forest fires.
All these factors have earned cycads a special place in the hearts and minds of serious plant collectors. Plant hunters have scoured the globe for rare and exotic species, and installed them in botanical gardens and conservatories for over 100 years. Many rare species are extremely valuable, which has led to incidents of cycad theft and a black market on the plants.
Conservation status. Although they once covered the entire globe (fossil remains have been found in the Queen Charlotte Islands, Alaska, Nova Scotia and the Antarctic) today their range is limited to between the Tropic of Cancer and the Tropic of Capricorn. Even these populations are dwindling, however, as they are plundered by poachers and habitat is destroyed. Today many cycad species are in danger of extinction and there is a concerted world-wide effort to conserve and protect these fascinating plants. Cycad collections in botanical gardens are treasured as a genetic resource and are being hand-propagated to relieve pressure on wild populations while also making the plants available to collectors.
Antique botanical print of Zamia roezlii from L'Illustration Horticole (1873)