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Tuesday, January 26, 2010
Cycads in gardens
Cycads have a long history in gardens in several parts of Asia. Chinese and Japanese cultures value them highly as symbols (as indeed every feature of the oriental garden is symbolic of more than meets the eye). Cycads in China are symbols of longevity, as evidenced by the widely used vernacular name of Feng Wei Cao (Phoenix tail grass) or Feng Wei Jaio (Phoenix tail palm), an allusion to the mythical phoenix, a legendary creature said to be reborn eternally from the flames of its funeral pyre. Taoist temples traditionally feature 4? plants - a white Camellia, a red Camellia, a ?Ginkgo and a cycad. Cycas revoluta is the favoured species and most frequently seen, although local cycads also have been used in many places. A plant of C. taiwaniana said to be 800 years old (and looking weather-beaten enough to really be that old) is now regarded as a national treasure in the Fen An Shi temple in Pu Meng in eastern Guangxi province. The species C. szechuanensis was described from plants cultivated in the Emei Shan temple in Sichuan province. This plant - a female - has been widely propagated from offsets, and passed around temples and gardens in several parts of southern China. All known plants are consequently female.
Cycads in Japanese gardens are often equally old, and examples said to be more than 1000 years old are known. One such is the -- Tree of Ryukyu Islands (a plant of Cycas revoluta), a national treasure now featured on a postage stamp.
Modern practice in Asia often echoes the old. Almost any large institution will feature a matching pair of large plants of Cycas revoluta flanking the main entrance doorway. The dwarf species of southern China and northern Vietnam are immensely popular as Bonsai plants in their native regions, but (perhaps fortunately for their conservation) little-known outside these regions. Many city-dwellers in these regions have only small courtyards or balconies, and these dwarf species are ideal in such situations. Private Asian gardens are frequently composed of collections of potted often Bonsai-style plants, and small cycads are again ideal and popular. Other cycads will be found planted in gardens in their native regions, but usually as the poor mans cycad when plants of C. revoluta cannot be afforded.
European gardens have not such long history of tradition and symbolism, and trends in garden design have fluttered through the ages to the fickle whims of fashion. Favoured plants have similarly fallen in and out of style. Europeans were not acquainted with the cycads until the waves of colonial expansion of the 18th Century brought floods of novelties from all corners of the world. Among so much novelty, the cycads never really stood out, and have attracted the interests of only a few collectors over the years. Interests have varied from country to country, but cycads are seldom seen as major garden features or landscape subjects. This is unfortunate, since cycads can and do make outstanding gardens and landscape plants in the right situations.
Cycads in landscapes
Cycads can take several places or be used in several ways in a landscape. A striking approach is to follow the Asian styles, with large paired plants in containers or feature beds flanking entrances such as driveways, gates, doorways. A single large cycad also makes an excellent feature plant in a landscape emulating a tropical or desert setting, substituting for a palm where a large crown is desired without the tall trunk.
For sheer majesty, it is difficult to surpass one of the larger Encephalartos species with 2-3 m of trunk. It is also difficult to obtain such plants, and most gardeners must settle for something else. Many fine large fast-growing cycads are available, and will soon reach a spectacular size with correct culture.
The blue cycads are also spectacular in landscapes. These are also difficult to obtain as large plants, and difficult to maintain in the blue colour in more humid climates. The blue species offer the additional challenge of being slower and generally more difficult to grow, and will always be at a premium for this reason.
Smaller cycads can be mass planted to give a ground cover with an interesting and different texture, although this works better on a large scale.
Cycads can also have a place in a small garden landscape where space is limited and consequently plant size is limited. Many cycads can create striking and exotic flavours in such landscapes, depending more on climate than any other factor.
A well-placed container-grown cycad in carefully chosen container can greatly enhance the small-garden setting. There are a number of miniature cycads now known that can be used in such a way.
Much has been written about cultivation, and readers are referred in particular to Jones, Encephalartos and Onelist. Amid the multitudes of advice and inclination to make the simple into something complicated, clearly a few uncomplicated common factors emerge. There are really only two options when growing your cycads: in the ground, or in containers. Cycads adapt well to either, and require certain basic conditions, not necessarily the same in either situation or for all species:
Light and temperature are also important environmental conditions that must be considered although often cannot be changed. Climate is particularly a limiting factor in outdoors and in-ground plantings, largely restricting cycad use to subtropical and tropical regions.
There is an enormous volume of literature on container-growing of plants, and endless combinations of growing media mixes. Cycads will actually grow well in almost any medium provided that it is well-drained. Remarkable results are being achieved with the modern soil-less nursery formulations.
Cycads are heavy feeders, and respond well to a good nutrient supply. Most growers find that a fertiliser with an even NPK balance and supplemented trace elements included in the potting medium provide a good start. Plants are kept moving with regular dressings of a balanced slow-release formulation such as Osmocote.
Although perfect drainage is essential and many cycads can withstand severe drought, best growth is always achieved with a uniform and ready supply of water during the growing season. Some species from highly seasonal climates become more or less dormant for a part of the year, and can suffer if kept too damp during this time; others will grow and require ample moisture throughout the year. A useful rule of thumb to follow through the seasons is colder = drier.
Although often restricted to very specific sites in nature, cycads in cultivation will tolerate a wide range of soils. These however MUST be well drained. Best success appears to be in deep sandy soils, and many growers will build raised or terraced beds of imported sandy soil up to 1 m deep. A sloping site is a great asset in this case, allowing raising beds by terracing and not importing large amounts of soil.
As for container growing: mid-range NKP, trace elements, regular and fairly high supply.
As for container growing: constant regular supply during growing periods, drier otherwise.
Pests and diseases
There are many pests and diseases that are common to most cultivated plants, including cycads. There are also problems specific to cycads and even to particular genera of cycads.
Scale insects. Numerous species have been recorded on cycads, causing varying degrees of damage. Of particular note is the recent introduction of a cycad-specific scale insect from Thailand to Florida in recent years, causing great damage to some ornamental cycads. Most scale can be controlled with regular and frequent applications of a horticultural soluble oil such as white oil. This is of low toxicity and does not pose great environmental threats, but requires a long and rigorous program of regular and frequent application to really control some scale insects. Many growers resort to the more toxic systemic insecticides for control, and most of these are effective.
Weevils. The naturally Macrozamia-specific weevil Tranes internatus causes sporadic deaths in wild Macrozamia populations, the larvae eating out the entire caudex. This insect has been introduced into cycad collections in Australia, USA and South Africa, and has causes extreme damage most notably to Encephalartos species. Control can only be by a program of regular and heavy treatment with a systemic insecticide once these pests are in a collection. Best to keep them out by careful selection of plants and treatment of anything doubtful before it is introduced into a collection.
Chewing insects. larvae of many species of insects, especially moths butterflies and beetles can seriously damage cycad plants by attacking emerging fronds. This immediately renders the plants unattractive, and in the longer term depletes the plants growing reserves and causes gradual decline. Control can be by contact or systemic insecticide, or one of the bacterial preparations.
Seeds or offsets are the two alternative means of propagating cycads at present, although recent advances in tissue culture promise to provide plants from this source in the future. Offsets do not occur regularly or frequently in many species, leaving seeds as the best method generally. Although cycads have a reputation of being extremely slow-growing, this is not very well-founded. Many Zamia species are really very quick, reaching reproductive maturity in as little as 2 or 3 years. Some Ceratozamia and Asian Cycas species are almost as quick, maturing in 5 years. Even large Encephalartos and Dioon can reach coning in 10-12 years. Some species such as the Australian Macrozamia and Lepidozamia and some Cycas appear very slow, although probably all species can be brought to reproductive maturity in less than 15 years if conditions are ideal the whole time.
Seed germination techniques of different growers are many and varied. All have in common however that they counter the two major risks to germination in some way. The first risk is that cycad seeds have no dormancy and the embryo is biologically required to keep growing and developing. This means that if seeds dry out the embryo can be killed. The second is that the emerging radicle and embryo can be susceptible to damping off in early stages in unhygienic or excessively wet conditions.
Many growers pre-germinate seeds, usually in plastic containers or bags with a moist sterile medium such as peat, perlite or vermiculite at slightly elevated temperatures. Seeds are then planted out into community pots when the radicles emerge. Such pre-germination is not wholly necessary, and others have success planting seeds directly into a pot of germinating mix, which can be just a regular potting soil. Attention to moisture balance is probably a little more critical under such conditions.
Propagation from offsets is best if the offset is cleanly removed from the parent plant with a sharp implement, leaving the minimum wound possible. The wound should then be treated with a fungicide such as sulphur and dried for about a week before planting into a sterile medium. Experiments have shown that a larger wound gives more area for callus and root production and consequently faster growth, but this also opens the way for more infection, and the technique is probably best left to the specialists.
Indoor and balcony plants
Few cycads or indeed few plants of any kind will thrive in the low light and dry atmosphere of the indoors. Given some attention however Bowenia, Lepidozamia Stangeria and Zamia will thrive and look attractive. These all have the added advantage of lacking spines, prickles or spiny leaves. A critical factor in maintaining healthy indoor cycads is maintaining a moist but not wet potting substrate.
Balconies and patios can offer a quite different set of extreme conditions, often with baking sun and high exposure, and sometimes high winds. Some of the xeric cycads can do well in these conditions, again provided that an appropriate moisture balance is maintained. The dwarf Asian Cycas species occurring on limestone cliff faces are ideal here, but not yet readily avaiable. Xeric Zamia, Macrozamia and Encephalartos species are also well-suited, as is Cycas revoluta. The last can be readily maintained under Bonsai conditions at any size required.
Sources of plants and seedsSEEDS Seeds are recommended as the most environmentally acceptable way to propagate cycads, and also the best way to move cycads internationally in accordance with CITES. There are many sources of cycad plants and seeds around the world. Since a listing here may be viewed as an endorsement, we suggest your cycad society as an introduction. Many good suppliers are also now online, and a net search on "cycads" will lead you to them.
© 1998-2004 Royal Botanic Gardens Sydney
Written and maintained by Ken Hill
Friday, January 22, 2010
What I do really know is that this plant is very interesting and exotic species. So if you have any information of this plant and want to share with me on this blog, please send via email and give some information about your plant.