Abstract. Cycads have survived on this earth for over 250 million years. One reason for this is because they can grow where the faster growing angiosperms can not survive. They can thrive in sandy soils with no nutrients. Some live on top of solid rock. Cycads even have a specialized root system, called coralloid roots, that in essence produce nitrogen for the plant to use. For many reasons cycads are perfect for xeriscaping projects, and growing in our sandy soils here in Florida. Most of us are familiar with sagos, cardboard plants, and coonties, commonly used in landscapes. But what about the other 250 species? Uncommon cycads growing in Florida nurseries are an important resource that has been untapped by landscapers throughout our state, mainly because people are not familiar with them. I will discuss five uncommon, but available cycads that are best suited for the Florida landscape.
Cycads are the oldest living, seed-bearing plants left on earth. The first fossil cycads date back 250 million years. During the age of the dinosaurs, cycads were the most prominent plant group. Around 75 million years ago the flowering plants evolved, and ended up to be the most prevalent plant group today. The few hundred species of cycads that exist today are a small fraction of the species that used to exist. The cycads that are left are the ones that can survive where the faster growing flowering plants cannot. These habitats are usually deserts and other sandy areas, on top of stone outcroppings, and forest areas too dark for flowering plants to grow well.
Cycads have structural mechanisms that have helped them to survive all these years. Most have some sort of spines on the leaflets, and cataphylls on the stems to ward off any animals that may want to eat them. Cycads have a specialized, secondary root system called coralloid roots that grow up to the surface instead of down like most roots. A blue green algae grows on top of these roots and helps with a nitrogen fixing process that, in essence, produces nitrogen for the plant to live on. This is why a cycad can grow on solid rock without any nutrients. The stems of cycads are also very hardy. Cycad stems have a starch content of around 65%. If something happens to the foliage or a part of the stem is damaged, the plant will live off the starch until new leaves or new growing apexes are produced. In certain habitats, seasonal fires are a way of life. The stems get burned, and the next year new foliage emerges. Cycad stems can even be propagated by cutting them up into small pieces and planting them separately.
The ground that landscapers have to work with here in Florida is usually sand, in most areas, and coral rock, in some of the southern parts of our state. It is hard to get many of our plants to grow in these areas. Use of native plants and xeriscaping is increasingly the way of the future for landscapers. Cycads are perfect for these types of landscapes and soil conditions. Native Zamias are already being used by municipalities and road departments all over the state in great numbers. Are there any other cycads that can be used in these cases? There are many cycad species growing in Florida nurseries that would be perfect for these xeriscape projects as well as in our everyday landscapes. The main reason that people don't use these unusual cycads in the landscape is that they are not familiar with them. Lack of supply of these cycads has also been a determining factor. In the last five years there has been a lot of interest generated by new books on the subject of cycads and by the many cycad societies that have been formed all over our state. Supply of unusual cycads in wholesale nurseries all over Florida has probably tripled in the last five years.
There are several unusual cycad species that can be grown quite successfully here in Florida, but a good supply of these plants for the landscape trade might be several years coming. I am going to discuss five species that will work well in our landscapes, and either already have a widespread availability or will have in the next few years. These plants will be discussed in the order of the most available to the least available at this time.
|Dioon edule is probably top on the list for cold hardiness of all the cycads that grow well in Florida. After the freeze of 1989 my king sagos were totally defoliated. My Dioon edule plants did not even get tip burn at 17°F. I know of people who have tested this plant down to 10°F. In habitat, these plants grow in sandy areas, and sometimes on rocks over looking the Gulf of Mexico, also showing their great salt tolerance. In fact, they will grow well in almost any kind of soil that drains well. Barring any insect or pathogen damage, these plants will live for 1500 years with no real care at all (the plant to the right is at least 200 years old). Dioon edule has the general appearance of the king sago, with lighter green foliage. These plants are available all over the state by wholesale nurseries that carry other more well-known cycads.|
|Cycas taitungensis, commonly known as the Prince Sago or Emperor Sago, is starting to be widely used in areas where a larger, but cold hardy cycad is needed. The leaf spread of the King Sago will normally be around six feet wide, whereas the spread on this species will be around eleven feet. The foliage has been found to be slightly less frost tolerant compared to the king, but the stems are known to be more cold hardy. People have been growing these plants as a test in Atlanta and in central Alabama. These plants are also very salt tolerant. Cycas taitungensis is probably the fastest growing cycad on earth. If grown in full sun and fertilized heavily, these plants can push up to six leaf flushes per year. With the right growing conditions, these plants can grow from a sprouted seed to a plant with a two-foot tall stem in less than five years. Availability is very good on this species, with more than 100,000 plants being produced each year in Florida.|
|Encephalartos ferox is a species from South Africa that is getting to be the most sought after and unusual cycad in south Florida. This species has leaflets that resemble the leaves of a Rotunda Holly plant, making it very showy. The best attribute this species has is the bright red cones that are produced on the mature plants. A female cone can be fifteen inches tall and ten inches wide. A larger plant can produce as many as five female cones at one time. With the dark green foliage, these red cones can really stand out in the landscape. I like to use these plants with Aztec Grass to add to the contrast of color and texture. Encephalartos ferox prefers to grow in a semi-shady area to look the best. The plant can tolerate temperatures down to 18°F, but is not very frost tolerant. If grown in the shade, it would be protected from these frosts. This species will attain a spread of nine feet in only eight years of proper growing. Supply of this plant is not meeting the demand yet, but there are a dozen nurseries in Florida propagating these plants from seed.|
|Ceratozamia kuesteriana is a cycad from Mexico that is just now coming into the scene. The foliage is very frost tolerant and the stems have proved to be cold hardy down to 17°F. This is a subterranean species, so if the stem is planted below ground level, it would tolerate a lot lower temperatures. This is one of only a few species of cycads that are totally unarmed, or in other words there are no spines on these plants. This species would make a good accent plant near walkways where most people would not want to use other cycads. Ceratozamia kuesteriana has what cycad collectors call brown emergent leaves. The new soft leaves come out brown and then harden up to a light green. This color change can be very attractive in the landscape where contrast is needed. A single headed plant will attain a spread of five feet, but multiple heads can be produced to increase the spread to around seven feet in time. This is another plant that would prefer to be in a somewhat shady location to look it's best. Several years ago two or three thousand plants were imported into Florida and there are currently quite a few people with breeding colonies. Somewhere around 10,000 seeds are produced each year in Florida, but this will have to increase if demand for this species becomes more popular in the future.|
|Ceratozamia hildae, commonly known as the bamboo cycad, has got to be the most exciting new species of cycad to enter Florida. This plant grows more in a shape similar to bamboo instead of having a fountain form like most cycads. The foliage and the stem are very cold hardy, and have been tested in Louisiana with very good results during the 1989 freeze. Except for bamboo, there are not too many cold hardy plants that have this upright habit. These plants can be used in smaller areas where sagos would be out of the question. The leaves on this species will attain a height of around seven feet, and the leaflets are arranged in clusters that resemble a bow tie in appearance. Ceratozamia hildae is a fairly fast growing species and can become mature in only four to five years. This plant looks it's best in partial shade but can be grown in more sun and in deep shade. This is a plant that we will have to look for in the future. Around 6,000 seeds are produced each year in Florida, but in five years this figure will increase to 50,000. When more people realize how beautiful and versatile these plants are, there will be a great demand for public and private use.|