There are over 700 Acacia species native to Australia, but only a handful of acacias were introduced to New Zealand during the 1860s, and have subsequently naturalised. Of these, Acacia melanoxylon (Blackwood) is the most widely recognised, and the most widely planted Acacia in New Zealand.
The highly decorative hardwood of blackwood outshines almost every other timber in the range of colours which it possesses.
It is classed with an elite group of woods for fine furniture, such as mahogany, teak and walnut.
The heartwood is a rich golden brown through which there may be streaks of reddish brown or almost black.
There is little sapwood (30 to 50mm) which is a pale cream-brown, contrasting strongly with the heartwood.
Grain is usually straight but sometimes wavy, producing a fiddleback figure.
Blackwood and paulownia are included in Ministry of Agriculture and Forestry (MAF) statistics which show a total planted area of 16,000ha in 2007 for hardwoods other than eucalypts and native species.
The median age of these stands is less than 15 years.
Silver Wattle has a rotation age of 25-40 years.
The sawn timber exhibits few growth stresses, and is of a similar appearance to Blackwood, having the same characteristic lustre and straight grain, only slightly paler.
The heartwood is a pale cream with darker red-brown markings.
The sapwood is pale cream. It has a fine textured and overlapping grain.
Acacia melanoxylon is the most widely planted Acacia spp. in New Zealand
The heartwood of blackwood is moderately durable (5 to 15 years in ground contact) and is very resistant to impregnation with preservatives, but the sapwood is perishable.
Blackwood is easier to convert into sawn timber and easier to dry than the ash type eucalypts.
It shrinks comparatively little. It is very easy to work, easy to nail and glue; and it steam bends well. It takes all kinds of stains and paints although its attractive figure begs the use of clear finishes. Blackwood has excellent woodworking properties, and is of fine texture
Blackwood density is very wide rangling, with past studies showing a range from 465 -670 kg/m³. Blackwood has a low shrinkage. Shrinkage from green to 12% moisture content is 3.6% and 1.8% tangentially and radially respectively.
Black wattle has very high basic density of 550- 590kg/m³, and is much lighter in appearance. The timber is less dimensionally stable than the other acacias, and should be used quartersawn to prevent cupping.
Silver Wattle a basic density of 600kg/m³. Silver Wattle splits easily along the grain, and plains and dresses well. The timber is dimensionally stable.
Blackwood is highly popular with cabinet-makers and makes excellent sliced veneer. It carves very well. The recommended uses are furniture, veneer, panelling and flooring although at present, available supply could preclude the latter two uses. It is one of only six species sought internationally for use in gun butts.
There is concern that the available resource is unlikely to sustain even the current level of supply until new plantings reach millable size around 2015-2020.
With pressure on the existing Rimu timber sources, blackwood is poised to provide a more than suitable substitute.
Both black and silver wattle are presently little used for timber, and have greater use in the pulp and paper industries. There is, however, great potential for these species to complement the growing interest in blackwood as a timber species.
Silver wattle is an excellent timber for furniture, turnery and panelling, and has also been used for tannin production, pulpwood and firewood.
Black wattle has excellent durability, and has been used for marine applications. It has a very attractive grain and high density, suitable for furniture production. The bark of black wattle is used in the production of tannins.
- Case Study
Blackwood is popular as an appearance timber and can be used to great effect in interior joinery.
Great Barrier Island House
This house was built from Blackwood timber grown in the area. View the full case study.
Go to the NZ Farm Forestry Association Marketplace for availability of Blackwood