photo of female cone
Cycads are one of the most interesting and most imperiled of all plant species on earth. Found in tropical and subtropical regions-there are 11 genera with roughly 300 species left.
Thought of by many as living fossils, the ancient relatives of these
primitive conifers have been found as far back as 280 million years. Today's remaining representation of cycads seems to have diversified from a common ancestor about 12 million years ago; during this time, one of the most radical processes of diversification of genetics ever discovered in plant evolution, took place. It is postulated that climatic events were the main cause of this massive speciation incident. The fact that such a primitive group of plants could account for such speedy diversity, as a process of evolution, just adds to the intrigue of this group of plants.
Cycads are known as gymnosperms; this group of plants doesn't produce flowers-they produce cones like pine trees, cedars and cypress. With all cycad species, every individual plant is either a male or a female.
Being dioecious (separate male and female plants) can be a huge disadvantage when populations become low; if there is just one individual left, the plant is already extinct.
However, having two different plants to supply the genetic make-up often ensures more genetic diversity. Without this added genetic material, it might not have been possible for cycads to have adapted to past climate changes, so quickly and diversely.
Cycads can be found scattered around the world from tropical to subtropical regions; some species tolerate frosts but you won't find cycads living in snowy environments.
Most Cycads come from arid regions and are succulent in nature. Still some come from high rainfall areas and must not dry out, completely, if they are to survive. Cycads are fairly squat, short plants with the largest specimens reaching only about 60 feet with the addition of several centuries-Dioon spinulosum and Encephalartos laurentianus are examples of such giants. Many plants like our native coontie cycad, never grow an above ground trunk. For the most part, cycads look like primitive palm trees, though they have no close relation to any palm or flowering tree.
photo male cone
In general, there is no sexual dimorphism in the growth habit of a cycad-the only way to distinguish the gender of a plant is by looking at the cones. Discerning which sex is fairly easy; male cones tend to be longer and thinner than the larger female cones of the same species. Male cones will have pollen while female cones will develop and drop seeds, viable or not.
Cycad seeds tend to be large and poisonous, so long distance seed dispersal is rare. As such, large and tight colonies tend to form in habitat; this can make populations extremely vulnerable to local disturbances. Many cycad cones will emit heat when they are ready to attract pollinators. Beetles are most often the pollinators. Seeing beetles rummage through a receptive cone, speaks to a relationship made, long before bees ever existed.
South Florida is a great environment to grow most cycads. These interesting plants can be grown for conservation purposes, or purely on tastes. Cultivation wise, cycads are mostly simple to grow and their water requirements are often less than most other landscape options. Cycads have specialized roots found near or above the surface of the soil, called coralloid roots. Different from the branch roots found lower in the soil, these coralloid roots house organisms within, that are part of a mutualistic symbiosis for both organisms. As such, many cycads can grow well in poorer soils, other plants may struggle with-much in the same way legumes do. Many cycads can take full sun while many cannot.
Often, the original habitat is a good indicator of the exposure it will take and like-the same research should yield water requirements.
With the proper placement and choice of plant, cycad landscaping can be rewarding, responsible and resource practical. These are all things that make Cycads appealing for the private home. In a Botanical Garden, it is more of a duty to grow cycads.
Educating the public about these denizens of prehistoric times, and their modern struggle to exist, is how this particular group of plants can be saved.
