Blackwood

24.05.17

Blackwood (Acacia melanoxylon) is a member of the wattle family. It is a hardwood tree that occurs naturally across southern and eastern Australia and Tasmania; thriving in fresh water swamps and riverine areas and as a common understorey plant in wet eucalypt forests.

Overview

The current source of blackwood timber is from native forests on both public and private land. Future supplies are uncertain leading to interest amongst some private landholders in the potential for commercial plantations of blackwood for high quality timber. Internationally, blackwood has been grown to final harvest in plantations in South Africa, New Zealand and Chile.

The blackwood industry in Australia is relatively small, but one that supports furniture manufacturing and craft industries. It has an established favourable reputation as a furniture timber and is a high value species capable of filling a market niche created by declining availability of cabinet timbers from native forests.

While blackwood is well suited to cultivation and management in plantations, it is costly and labour intensive to grow commercially because of the 30–50 year period between planting and harvest, high establishment and maintenance costs, and generally, no income throughout the rotation. These characteristics make blackwood a daunting or prohibitive investment for many people. Fortunately, blackwood is a locally native species in many areas that provides a range of non-timber values and can be incorporated in many agroforestry plantings including shelterbelts, shade trees, riparian buffers and erosion control plantings. If the trees grow well they can be pruned with a view to keeping the options of a commercial harvest alive. Pruning will also reduce the fire hazard, increase pasture and native understorey production and improve the shade value for stock.

Facts and figures

  • Blackwood is a member of the wattle family
  • It is a hardwood tree that occurs naturally across southern and eastern Australia and Tasmania, growing well in swampy and riverine environments
  • The timber ranges in colour from a very pale honey, through to a dark brown with streaks of red tinge
  • Blackwood timber is used in furniture manufacturing, boat building, musical instruments and craft pursuits
  • Blackwood is harvested from native forests, with about 7000 cubic metres of sawlog-grade material produced annually
  • Blackwood has good potential for farm forestry in higher rainfall areas on sheltered sites but producing quality blackwood timber in plantations is costly and labour intensive

Production status

Tasmania is the largest producer of blackwood timber, with production of around 7,000 cubic metres of sawlog-grade material, derived from native forests, each year. While native forest production will most likely be the main source into the future, there have been plantings of around 1,000 hectares of blackwood in far north west and southern Tasmania.

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Map of current and potential growing regions

Uses

Blackwood is internationally regarded as one of the best furniture and cabinet timbers, as both a solid timber and for use in decorative veneers. Large pieces of blackwood are used in panels, veneer, furniture and boat building while smaller pieces are used for craft wood, carving, rifles (gunstocks) musical instruments and turning.

Blackwood is also valued as a reasonable quality firewood so the thinnings and harvesting waste can be used or sold as firewood. Blackwood can be an effective windbreak tree because of its branching habitat when planted in exposed sites, although the growth rate will be adversely affected in these conditions and the timber quality will be low.

Production Requirements

Growing regions

Although blackwood occurs naturally from the Atherton Tablelands in north Queensland, down the east coast of Australia to the southeast of South Australia, and in Tasmania, it is susceptible to longicorn beetle attack if subjected to drought stress so it is best to confine commercial plantings to sheltered, well-watered sites in the medium to high rainfall areas.

In Tasmania, blackwood occurs in freshwater swampy areas, on lower valley slopes and even exposed hilltops. Even though it grows in a range of environments, blackwood develops best in the lowland wet forests in the far north west of the state, which is the main location for blackwood harvest from native forests.

Soil type

Blackwood naturally occurs on a wide range of soils but the best growth will occur on well-drained, deep fertile sandy loams over clayey subsoils. Blackwood has a higher tolerance of saturated soil conditions if the water is moving and well oxygenated.

Climate

Blackwood is most common in cool humid areas, with warm summers and cool winters, and low frost intensity, reflecting the species’ susceptibility to frost.

Blackwood will grow in areas where the annual average rainfall exceeds 600mm per year, however best results are achieved on sites where the mean annual rainfall is greater than 1000mm per year.

Blackwood thrives in freshwater swampy and riverine conditions; it will tolerate flooding for part of the year although it does not do well if submerged in still water.

Varieties

The industry of blackwood timber is based on native harvest, therefore types or lines within the species have not been selected for varietal development.

Planting and crop management

Blackwood is an easy tree to grow and potentially a good use of land along river banks or in areas that become too waterlogged for other trees or crops. However, to grow blackwood for timber production well sheltered moist sites are required and the trees should be carefully pruned to control their form and branch size. In addition, when selecting a site to grow blackwood, easy access for maintenance and harvesting to maintain cost competiveness must be considered.

Planting density depends on design, site quality and more.Young seedlings may need to be fenced or guarded to restrict animals, such as wallabies, that may graze on the new plants. Shelter is important in the early years to improve tree form and can be achieved through close spacing (3x3m spacing) or by mixing with other faster growing species.

Blackwood usually needs form pruning in the first few years. This may involve the removal of any branch over 2.5cm in diameter and the removal of any obvious double leaders. Stem pruning to create a clear bole of at least 3m involves the removal of any branch on the trunk up to a point where the stem is 8cm in diameter. Both form and stem pruning should be performed every year until the desired pruned height is achieved.

Thinning should be undertaken to remove trees with poor vigour and to minimise the competition for light, nutrients and moisture. Finding the balance between giving blackwood space to reduce competition while encouraging straight growth in plantations is critical. Be aware that as an understorey species, blackwood is also susceptible to exposure and may suffer if the thinning is too rigorous. The final stocking rate will depend on the site but should generally be around 100 stems per hectare.

Blackwood initially grows slowly, but from about 10 years its diameter growth may actually increase as long as the competition between the trees is controlled by thinning. Harvesting of sawlogs would not be expected before 25 years. In lower rainfall areas the time to final harvest may be at least 50 years.

Research has been undertaken to identify the best management practices leading to maximum growth and optimised stem form to further develop the blackwood industry, but unlike other species of tree for plantation development there has been little genetic improvement.

Weeds, pests, and diseases

Weed control in plantations is particularly important before planting and during the early years of growth. Competition by weeds for sunlight, nutrients and moisture can reduce growth rates in young trees.

Blackwood is very susceptible to damage from wallabies, aphids and longicorn beetle. It is not affected by the rusts and galls that affect many other Acacia species and, as it is highly tolerant of Phytophthora cinnamomi, it can be used in wetter areas where this fungus is thought to be a problem.

Blackwood foliage is particularly palatable to many browsing animals (rabbits, wallabies, wombats and cattle), so young seedlings should be fenced or tree guards used.

Infrastructure Requirements

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.

Harvesting & Processing

Initial site selection for commercial trees will have an influence on harvest method — well-spaced trees near access roads will enable easier and cheaper harvesting.

Harvesting is generally undertaken in two ways. If timber production is the sole objective of the plantings, then clear felling is the logical method. However, if the trees form part of a shelterbelt, then harvesting of small volumes over a longer period of time is the more practical solution.

The timber is usually sold in two ways; either as ‘standing’ where a professional contractor pays a ‘stumpage rate’ to harvest and transport the logs, or ‘mill door price’ where logs are delivered to the timber mill having been harvested and transported privately or using contractors.

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.

Blackwood is a relatively easy tree to process. The timber is fairly stable and because air drying is recommended, it can be harvested and processed on farm, by a skilled operator, for sale or use by the grower.

Markets & Marketing

It is important to consider current and/or future markets before choosing which commercial tree 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.

Distance from markets will affect the profitability of a commercial timber enterprise, generally speaking, when the plantation is more than 100 kilometres from the processing centre (or road conditions are difficult), due to higher transport costs. 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.

Risks & Regulations

Risks/challenges

Producing quality blackwood timber in plantations is costly and labour intensive.

Uncertainty and risk are inherent in all 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.

Alternative benefits from commercial tree plantings should be investigated to help reduce exposure to these 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. Because blackwood can be dried easily and a skilled operator can harvest and process the timber on farm for sale or use, some risk may be mitigated.

Regulatory considerations

If seeking to establish a commercial plantation (the definition differs by state, but is generally defined at around 30 or 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.

Image Gallery

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Blackwood flowers (Source CSIRO)

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Blackwood vase by Guilio Marcolonglo, Melbourne

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Blackwood Regeneration in the Great Otway National Park (Source Oliver Strewe for ATSC)

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Blackwood pods (Source Maurice McDona)