Language English Dioon spinulosum Photo: Gilles Murray Dioon edule Photo: Gilles Murray In Japan, the inner stem of Cycas revoluta is eaten Photo: Jardin botanique de Montréal (Gilles Murray) Cycas revoluta in fruit Photo: Jardin botanique de Montréal (Gilles Murray) Zamia kickxii is on the Red List of endangered species (IUCN) Photo: Jardin botanique de Montréal (Gilles Murray) Groupe tabDescriptionThese plants had their heyday back in the times of the dinosaurs, some 150 million years ago. Although they resemble palm trees, they are actually related to conifers, in that they produce cones where the sexual cells form. The plants are either male or female, so it takes one plant of each sex to produce viable seeds. This is a problem for the many cycads on the Red List of endangered species (IUCN). Their popularity with collectors and landscape gardeners, in particular, has caused their populations to decline. Cycads comprise three plant families and include the genera Cycas, Zamia, Encephalartos and Dioon, all of which can be seen in the Hacienda and Arid Regions Greenhouse. Where and whenArid Regions Greenhouse, Hacienda: year round. Based on articles by Céline Arseneault and by Denis Barabé published in Quatre-Temps magazine. Interesting factsEndangered species Learn and discoverCycas circinnalis Cycas circinnalis (Cycadaceae family) is a rare plant native to southern India, Sri Lanka, Java, Sumatra, Taiwan and the Philippines. Cycas plants have a single, aerial stem that can reach more than 10 metres tall. These plants grow about 1 cm a year. The male and female reproductive organs are borne on separate plants. The inner stem of Cycas circinalis is consumed in India and Sri Lanka. In Japan, the inner stem of Cycas revoluta is eaten. Until the end of World War II, Cycas circinnalis seeds were a food source for the Chamarro people of Guam and Rota, islands in the Mariana Islands chain in Micronesia. A number of researchers have found that eating Cycas circinnalis seeds appears to be related to an increased incidence of Parkinson’s Disease associated with progressive Alzheimer-type dementia amongst the Chamorro people. Before 1955, this disease was 50 to 100 times more common on Guam than in industrialized nations. There is a male Cycas circinnalis specimen in the Hacienda greenhouse. The male cone sits in the centre of a rosette of large pinnate leaves. Dioon edule and Dioon purpusii The name Dioon (Zamiaceae family) comes from the Greek word dis, or two, and oon, or eggs, referring to the pairs of seeds. Members of the Dioon genus have a crown of persistent, stiff leaves atop a trunk varying in length. The reproductive organs, in the centre of the plant, are contained in cones. Male and female cones are borne on separate plants. The seeds are the size of a walnut and have a high starch content. They are toxic, however, if eaten raw. Dioon purpusii is a rare plant native to Mexico. Visitors can admire some lovely specimens of this plant in the desert regions and Hacienda greenhouses. Encephalartos Encephalartos (family Zamiaceae) have a single underground or aerial stem, which in some cases can grow to 10 metres or more. Species with underground stems produce tuberous roots that are thought to be a climatic adaptation, since these plants do not have a stem capable of storing water. Encephalartos plants form aerial roots that contain a blue algae called Anabaena. This symbiotic association allows the plants to capture nitrogen directly from the air. The pinnate leaves are composed of a main rachis bearing several leaflets with parallel veins, the shape, edges and colour of which vary from one species to the next. These features help to identify the different species, in fact. In mature plants, the leaves appear to be arranged in a whorl, with the number of leaves per whorl varying from 4 to 50, depending on the species. Encephalartos reproduction and propagation Encephalartos are dioecious, meaning that the male and female reproductive organs are borne on two separate plants. Sexual maturity is attained only after 25 to 30 years of growth. The cones are made up of a large number of modified leaves (megasporophylls), arranged spirally around a central axis. Each megasporophyll has two ovules varying in size and colour depending on the species. The ovule integument is made up of three distinct parts: a fleshy outer layer, usually orange or yellow, a sclerified middle layer and a fleshy inner layer that dries and quickly takes on a paper-like texture. The male cones are smaller and more numerous than the female cones. There are hundreds of microsporangia, or pollen sacs containing pollen grains, on the abaxial (lower) surface of the microsporophylls. In the wild, plants have to be close enough together for pollination to occur. The large amount of pollen produced is an adaptation to anemophily, or wind pollination. Some botanists doubt that insects play a role in pollinating Encephalartos. They believe that, even if bees can be observed collecting pollen from male cones, they do not visit female cones. Other botanists think that a weevil from the Curculionidae family, a kind of beetle that lives on Encephalartos, is a pollinating agent. In horticulture, it is especially difficult to collect seeds because the male and female plants, if one has both, must produce cones at the same time. At pollination time, the ovule secretes a liquid, or pollen droplet, from the micropyle, to capture the pollen. Among Gymnosperms in general, and Cycads in particular, several months elapse between pollination (when the pollen is carried to the ovule) and actual fertilization (when the male and female gametes fuse). Afterward, Encephalartos development is fairly direct. In fact, there is no dormancy period in Cycads. As soon as fertilization is complete, the development process begins, and once the cone splits and releases its seeds, the well-developed embryo inside the seed feeds directly on the endosperm. If the protective inner layer is broken, the embryo could be damaged by moisture or fungal spores, or heat and dehydration. A waiting period of up to 6 months is recommended before planting, by which time the radicels will have begun piercing the envelope. After 6 or 7 months, the Encephalartos embryo is composed of two cotyledons separated by the plumular leaf and the radicel. Plantlets have less water storage than mature plants and are thus more sensitive to irregular watering. There are also a number of vegetative propagation methods. The first, obviously, is to separate the suckers that form at the base of the trunk, with their own roots. This must be done carefully, and fungicide applied to the parts injured by the incision. Young plants formed if the main trunk is damaged near the top may also be separated. Such ramifications are infrequent and are often confused with the plantlets that may form from the crown of the parent plant. This unstable situation can last only as long as the plant is not disturbed. Obviously, it can happen only with female plants. Stangeria Stangeria eriopus is related to the Zamiaceae but belongs to the Stangeriaceae. It is a rare plant native to South Africa, where it grows in coastal grasslands and inland forests. Four pinnate leaves grow from the tip of the underground stem. In forest forms, the stem may be up to 2 metres long. The male and female cones are borne on separate plants. Each stem produces a single cone. The Garden’s collections contain one male and one female plant. Zamia Zamia floridana (family Zamiaceae) was once fairly common throughout the Florida peninsula. Today it is a rare species, limited to pine groves, dry sites and coastal dunes. Most of its habitats have been destroyed, in part by the tourism industry. The male and female cones are borne on separate plants. Zamia floridana rhizomes contain a toxin that must be destroyed before their starch is extracted. Many soldiers are said to have died during the American Civil War (1861-65) from eating uncooked rhizomes. The toxin is also present in the leaves and seeds. It causes tremors in livestock. Once properly processed, the starch extracted from the rhizomes can be made into flour. This plant was a major food source for local inhabitants in the 19th century. Based on articles by Céline Arseneault and by Denis Barabé published in Quatre-Temps magazine. Botany and ecologyBotanical and ecological informationBotany Plants in three families with fairly similar features and evolutions are commonly grouped together and called cycads. Cycads differ from conifers in their shape. Conifers have a well-developed, highly ramified trunk, with many branches covered in small leaves reduced to needles (for pines) or scales (for thujas), and hence a preponderance of the trunk over the leaves. Cycads present the opposite phenomenon, with a preponderance of the leaves over the trunk. The trunk in cycads is ordinarily short, but may grow to 3 to 4 metres (Microcycas, Microzamia) and even 10 metres (Dioon). It is almost never ramified and bears a crown of very large fern- or palm-like leaves at its tip. For this reason, local populations ordinarily mistake cycads for palms and have given them such common names as Dolores palm, flour palm and sago palm. The other major differences between cycads and conifers are all related to their reproductive organs. All cycads are dioecious, like gingkos. This means that individual plants bear only male reproductive organs (male cones) or female reproductive organs (female cones). Amongst almost all conifers, the same tree bears both male and female cones: this makes conifers monoecious. Habitat In their natural habitat, cycads are found from sea level to altitudes in excess of 1,800 metres. Their extensive underground and surface root system allows them to survive summer droughts. Plants growing on rocks often have exposed roots that can spread for up to 12 metres in order to anchor them firmly. They also have other xerophytic adaptations allowing them survive dry spells, including, very thick, stiff leaves that reduce evapotranspiration, and the ability to store nutrients in the stem and roots. In addition, mountain forms have narrower leaf blades and woolly cones that enable them to tolerate extremely cold conditions in exposed sites. A few mountain forest species, including some in genus Encephalartos, do not have these features because their micro-climate habitat offers them ample protection. Colour also varies with habitat, ranging from blue-green to bright pale green, depending on exposure to sunlight. This is because the amount of chlorophyll produced is affected by light intensity. Distribution Before the continents broke apart, some 150 million years ago, cycads’ ancestors were distributed around the globe, in large numbers. It appears that those cycad species, that did not disappear in the course of evolution, avoided stiff competition with other plants by adapting to the arid, rocky conditions in the tropics and sub-tropics, where environmental conditions have remained relatively stable for millions of years. This is a feature common to very early groups. Classification There are now 10 genera, in 3 families, with a total of 150 species. We use the Johnson (1959) family subdivision, with the following genera: Cycad, or Cycadaceae, family: Cycas: Japan, India, Thailand, Taiwan, Philippines, Okinawa, New Caledonia, New Guinea, Australia, Comoro Islands, Madagascar, west coast of Africa and Mozambique. Zamiaceae family: Bowenia: Australia Lepidozamia: Australia Macrozamia: Australia Microcycas: Cuba Dioon: Mexico Zamia: Florida (USA), Mexico, Colombia, Dominican Republic, Costa Rica, Puerto Rico, West Indies, Cayman Islands, Brazil, Bolivia and Chile Encephalartos: South Africa, Zimbabwe, Mozambique, Tanzania, Uganda, Ghana, Malawi, Kenya, Sudan and Nigeria Stangeriaceae family: Stangeria: South Africa Protection Most countries where cycads grow in the wild have adopted legislation protecting the habitat of these living fossils and regulating exports (Endangered Species legislation). The International Union for Conservation of Nature threatened plants committee has published a list of cycads (including species origin) as a way of identifying the collections at botanical gardens around the world. Based on articles by Céline Arseneault and by Denis Barabé published in Quatre-Temps magazine. Cultivation tipsGreen pagesCulture and growth Although Cycads sometimes grow in rainforests, where the fairly dense coverage filters the sun’s rays, they do not all make good houseplants. Their growing requirements are frequently similar to those of succulents. They require bright, sometimes indirect, sunlight. The most important factor is the potting medium used – it must be well drained and provide good aeration for the roots. Cycads have few insect pests. Those that do attack them affect mostly the leaves and stem and are limited to certain species or ones endemic to a particular region. A healthy plant has arched, but not drooping, fronds that are dark or light green depending on the species, and a stem, or trunk, that is firm to the touch. When grown in a greenhouse or indoors, as they must be in our climate, they must be protected from the roots of neighbouring plants, especially mid-sized trees, by placing them in their own containers. This also makes it easier to move them and to transplant them, which must be done only in late summer or early fall, when their annual growth slows down. It is important to ensure that the soil is sufficiently moist before transplanting them, and also to avoid removing any leaves or roots. Cycads are slow growers. The lifespan of the crown varies depending on the species and climate. The leaves can survive for one to three years, or even longer at times. Afterward, the leaflets drop off, the central vein dies back and eventually the leaf splits away at the base of the leaf stalk. At the same time, a phenomenon similar to that in deciduous trees in autumn happens – a special kind of protective tissue forms at the base of the live leaf so that a scar is formed before the wound actually occurs (the abscission zone). As the trunk grows, it is covered with these leaf scars, which form a sort of armour. This armour makes it possible to estimate a Cycad’s age. This method has some drawbacks and limitations, however, because it requires that specimens be observed over a period of several years. Young plants produce and lose the leaves in their first crown very quickly, falsifying the data. Mature plants that produce cones may or may not have a short resting period and irregular growth cycles. Cycads are surprisingly long-lived. The oldest plant in cultivation is at the Royal Botanic Gardens, Kew. The Encephalartos longifolius specimen was taken back to England by Francis Masson in 1772. It is still producing cones more than two hundred years later. Based on articles written by Céline Arseneault and by Denis Barabé published in Quatre-Temps magazine. Cycas Genus Cycas includes several species native to tropical and subtropical zones, mainly in Africa and Asia.