- Category: General Information
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.
Pests and diseases
- Scale insects: Numerous species have been recorded on cycads, some causing varying degrees of damage. Of particular note is the recent introduction of a cycad-specific scale insect into the USA from Thailand in recent years, causing great damage to some species of ornamental cycads. Most scale can be controlled on these species 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. It is Imperative that you Import only from CITES Accredited Cycad Suppliers, we are also an NIASA Accredited (Nursery Industry Accreditation Scheme Australia) ensuring that our Nursery is up to and exeeding nursery guidelines and regulations.
- 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. 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 man y 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
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 available. 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.
Encephalartos ferox female and male cone
See below an excellent Report by Mark Brundrett on The Benefits of Mycorrhiza in growing Cycads and other plants. Please go to the Website Link of CSIRO Forestry and Forest Products.
Written and Illustrated by Mark Brundrett CSIRO Forestry and Forest Products
What are Mycorrhizas?
|Mycorrhizas are highly evolved, mutualistic associations between soil fungi and plant roots. The partners in this association are members of the fungus kingdom (Basidiomycetes, Ascomycetes and Zygomycetes) and most vascular plants (Harley & Smith 1983, Kendrick 1992, Brundrett 1991). In the mycorrhizal literature, the term symbiosis is often used to describe these highly interdependent mutualistic relationships where the host plant receives mineral nutrients while the fungus obtains photosynthetically derived carbon compounds (Harley & Smith 1983). Mycorrhizal associations involve 3-way interactions between host plants, mutualistic fungi and soil factors. Roles of mycorrhizal associations are explained further in Section 5.|
|Araucariaceae||Agathis, Araucaria, Wollemia||tree||VAM||beaded roots (Baylis et al. 1963, McGee et al. 1999)|
|Wollemia||tree||ECM||most roots with VAM (McGee et al. 1999)|
|Cupressaceae||Callitris||tree||VAM||(Reddell & Milnes 1992)|
|Podocarpaceae||Podocarpus||shrub||VAM||beaded roots (Baylis et al. 1963)|
|Zamiaceae||Macrozamia||cycad||VAM||(Brundrett & Abbott 1991) coralloid N2 fixing roots (Lamont 1982)|