River sheoak is the tallest of the Casuarinas, growing to about 35 metres and is thought to resemble a conifer due to its long, weeping, wiry branchlets. It is usually dioecious, meaning individual trees are either male or female, and the pollen released from male flowers is wind borne.
The tree produces a rose-brown heartwood (with slightly paler sapwood) and has clearly defined ‘rays’ running through the timber which enhance its value in appearance-grade products.
Indigenous Australians have long used river sheoak for making boomerangs, shields and spear-throwers. They also found that a gum that can be scraped from under the bark makes an effective sealant for canoes and various compounds can be extracted for medicinal purposes.
A highly versatile species, river sheoak can withstand drought conditions and handle periodic flooding. It has a wide distribution being found on both sides of the Great Dividing Range in New South Wales and Queensland, from Bega on the south coast of New South Wales to the northern tip of Queensland, and extending from the coast across the tablelands to the Gulf of Carpentaria and beyond to Daly River, south of Darwin.
River sheoaks provide a range of environmental benefits to the landscape. They have an extensive root system that binds the soil together, helping to prevent erosion of stream banks, and they improve soil fertility by fixing nitrogen. For these reasons river sheoak was a protected species in New South Wales.
Commercial farm trees have the potential to offer a range of benefits to farmers and land managers by increasing Australia’s long-term timber supply while contributing social, economic and environmental benefits to regional areas.
Trees are often planted to provide windbreaks and shelterbelts for crops and livestock, to manage the watertable or to protect topsoil from erosion. However, many landholders, using existing infrastructure and integrating tree management practices into existing farm operations, may be able to earn an alternative income from planting farm trees that earn a commercial return. The risk inherent in all commercial tree operations is the long period between establishment and harvest which can range from 30-50 years.
The commercial production of river sheoak will depend on resolving a number of processing issues, which see the timber warp in some milling situations.
Facts and figures
- River sheoak is known around the world as a multipurpose tree, utilised for its environmental benefits and timber production
- It is fast growing, long-lived and hardy
- While showing good plantation potential, river sheoak is not considered a commercial industry in Australia
- The timber is suitable for furniture, flooring and construction
River sheoak is not considered a commercial species in Australia and so there is no information on commercial production status.
The timber of river sheoak is suitable for furniture, flooring and construction uses, however, it is not considered a commercial species.
It has some potential for commercialisation, through its reputation as a reliable species and as a provider of environmental benefits to landholders through erosion control (particularly next to streams) and used as permeable windbreaks.
As its name implies, river sheoak grows along rivers and on adjacent river flats. It occurs on both sides of the Great Dividing Range in New South Wales and Queensland, from Bega on the south coast of New South Wales to the northern tip of Queensland, and extending from the coast across the tablelands to the Gulf of Carpentaria and beyond to Daly River, south of Darwin.
River sheoak will grow on most soil types but prefers clay, and sandy and silty loams. It will tolerate infertile, moderately saline and acidic soil conditions.
River sheoak requires rainfall between 500–1500mm per annum. Because they grow near streams and rivers, a rainfall figure does not provide an exact indication of the moisture used by river sheoaks. If planning to grow river sheoaks in rainfall areas down to 375mm per annum, supplementary water (irrigation or manual watering) will be necessary.
The river sheoak is distributed widely throughout eastern Australia where the mean average temperature ranges from 12-29°C. Some elevated regions in New South Wales record up to 50 frosts per year and temperatures fall as low as –8°C, while the mean maximums range from 30-38°C.
There are no varieties of river sheoak that have been identified as suitable for commercial production. Seeds and seedlings may be available from specialist nurseries. Contact your local Department of Primary Industries or Forestry to determine if there is any improved seed for your region.
There are several other Casuarinas that could be farmed for timber. Swamp sheoak (C. obesa) is an increasingly popular species for farm forestry in Western Australia and rock sheoak (Allocasuarina huegeliana) produces good timber. In the tropics, forest oak (Allocasuarina torulosa) is a good species for plantations. The eastern swamp sheoak (Casuarina glauca) is potentially another option for the eastern states.
Planting and crop management
When selecting the site, accessibility to the trees for maintenance and harvesting is an important consideration. Being on flat, accessible land, with good access roads and room to manoeuvre heavy equipment will make management easier and keep costs down over time.
Propagation can be from seed or seedlings directly sowed into soil that has been prepared by spraying for weeds, ripping and mounding. Emerging and planted seedlings need to be protected from grazing animals by fencing or tree guards.
River sheoak seed can be sown directly into prepared ground in very warm and moist conditions. For successful germination (which occurs in about three weeks), a temperature of around 30°C with adequate light and moisture will be needed.
Recommended establishment density is 830 trees per hectare. High initial stocking density encourages competition for light, forcing the trees to grow straight and tall with little room for branching. However, growth will stagnate if the trees are not strategically thinned over time. The first thinning will enable malformed or small trees with poor vigour to be removed.
Casuarinas are nitrogen-fixing trees, which helps their survival and rate of growth, particularly on low fertility soils. In plantations, the relationship between tree and nitrogen fixing bacteria can be established by inoculating the river sheoak with bacteria nodules.
Timely pruning of branches to promote good form should be undertaken over time, as required. The light branching of River sheoaks makes pruning fairly easy by a skilled operator with a chainsaw.
Weeds, pests, and diseases
Weed control in plantations is particularly important before planting and during the first few years of growth, when competition by weeds for sunlight, nutrients and moisture can reduce growth rates.
River sheoak is relatively pest and disease resistant. In native stands it can play host to insects and caterpillars, but no major damage has been observed.
Land is the main infrastructure requirement for commercial tree growing.
If planting trees on a small scale and integrating them into the agricultural enterprise as windbreaks and shelterbelts, then manual maintenance, including pruning and thinning, can usually be managed with a chainsaw and farm equipment.
If planting a commercial plantation of high value sawlogs, then tree farm-scale, tractor-based forestry equipment may be necessary, including logging winches and chains. Unless the plantation is large and consists of high value logs, it will not be economical to purchase specialised harvesting equipment or modify existing farm equipment to undertake harvest. Contractors with specialised equipment and machinery may also be considered.
Processing of river sheoak timber from a trial plantation has identified issues around drying and reconditioning, and solutions will need to be developed prior to establishing a viable river sheoak processing sector.
Once these issues are resolved, appropriate harvest methods can be determined. Unless the plantation is large and consists of high value logs, it will not be economical to purchase specialised harvesting equipment or modify existing farm equipment to undertake harvest. If the trees are large, pruned and well spaced, specialised equipment may not be required at all. A trained operator using a chainsaw, farm tractor, loader and log trailer may be able to undertake the job in a cost-competitive way.
Initial site selection for commercial trees will have an influence on harvest method—well-spaced trees near access roads will be easier and cheaper to harvest.
Although it has many marketable attributes, including the potential for appearance-grade end uses like furniture or flooring, river sheoak is not a commercial species in Australia.
If considering commercial tree production, it is important to examine current and/or future markets before choosing which species to grow. However, with commercial trees taking around 30 years to provide a return on investment (in most cases) it is difficult to accurately predict future market opportunities at establishment.
Another consideration is distance from markets which will affect the profitability of a commercial timber enterprise, generally speaking, when the plantation is more than 100km from the processing centre (or road conditions are difficult), transport costs transport costs are higher. The closer the planting is to the processing centre, the greater the return for any given product, particularly if providing a high volume of a lower value timber, such as pulpwood and woodchips.
Planting and managing for high quality sawlogs can counter some of the market uncertainty and absorb transport costs, as it is often easier to find markets for high value timber, even with longer transport distances involved. High value timber requires ongoing maintenance of trees, ensuring they are managed for the specifications particular to high value markets, essentially: good form, diameter and limited defects.
Consideration of local markets for the timber provides options should future markets change as described in the Risk/challenges section. Local markets could include the building or construction industry in the region, farm use as fence posts, or domestic use as firewood.
Uncertainty and risk are inherent in commercial tree operations due to the long period of time between establishment and harvest (around 30 years).
Some of the risks include:
- mills closing or relocating, leaving plantings at an uneconomical distance from processors
- timber preferences or ‘fashions’ changing, resulting in decreased markets as certain colours or grades of timber fall out of favour with designers and builders and consumers
- government policy changing, impacting on industry structure and profitability
- alternative products developing, resulting in a falling demand for timber.
River sheoak is highly suited as a plantation species, is currently free of significant pests and diseases and offers flexibility via a range of product and market options. However, river sheoak is not considered a commercial species at this time, although trials are underway in a number of states. Those trials are showing that when good genetic stock is used, river sheoak performs consistently in plantations and has the capacity to produce high value saw logs. However, some issues have been identified at the processing stage where logs have warped during milling. Refinements in drying and reconditioning will need to be developed before a commercial industry will be viable.
Alternative benefits from commercial tree plantings should be investigated to help reduce exposure to risks. It is recommended that a short-, medium- and long-term return or benefit be identified when considering planting commercial trees. For example, a short-term benefit could relate to carbon sequestration or watertable abatement. A medium-term benefit may be derived from the trees providing a windbreak or shelterbelt for crops and livestock, and a long-term benefit might be income from harvested timber.
To further manage risk, it is recommended that tree selection take into account the potential for local use for the timber. A timber versatile enough to be processed and used locally will limit some of the uncertainty around future markets if there are alternative opportunities to earn income. For example, local markets could include the local building and construction industry, farm uses such as fence posts, and domestic uses such as firewood.
If seeking to establish a commercial plantation (the definition differs by state, but is generally defined at around 30-40 hectares) liaison with the relevant state government agency will be necessary. Regulatory systems vary across states, with some requiring plantations to be authorised and others requiring plantations to meet legislative requirements and/or a management Code of Practice.