Ironbark

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The Ironbark variety of Eucalyptus species got its name because of its dark wood which is deeply furrowed due to accumulation of dead bark. This accumulation also creates fissures which dry out and become hard as rock with the buildup of the dark red sap from the tree. This tough outer layer of bark is resistant to fire and heat in moderate forest fires. However, if the fire is extreme, the bark still protects the dormant buds which lie beneath the surface and allows the tree to grow back quickly.

There are many varieties of trees of the Eucalyptus species called Iron Bark such as:

  • Broad-leaved Red Ironbark
  • Grey Ironbark
  • Lemon Ironbark
  • Narrow-leaved Red Ironbark
  • Silver-leaved Ironbark
  • Broad-leaved Red Ironbark

Eucalyptus Fibrosa or Broad-leaved Red Ironbark is found along the coastal areas of New South Wales and Queensland as well as along the slopes of New South Wales.

The Heartwood is dark red while the Sapwood is pale yellow. The texture of the wood is moderately course and even, while the grain is interlocked. The growth rings of the Broad-leaved Red Ironbark are quite indistinguishable.

The Sapwood is not susceptible to Lycid attack and the Heartwood is resistant to Termite infestation. The Natural Durability rating of Heartwood above ground and In-ground contact is rated as Class 1.

Timber Attributes of Ironbark:

  • Janka rating – Dry: Very Hard
  • Very hard to work with
  • Slow to dry
  • Surface checking can be minimized with extreme care

Grey Ironbark

Grey Ironbark is found in the coastal areas of New South Wales and Queensland. The color of the heartwood varies from pale brown to dark red with many shades between. The sapwood varies from brown to buttery brown and the grain is usually interlocked. The growth rings on Grey Ironbark are not easily discernible.

The Grey Ironbark is not susceptible to Lycid borer attack and termite infestation. However, The Marine Borer Resistance of Heartwood is certified as Class 3 while the Natural Durability Rating both above ground and In-Ground contact are rated Class 1.

Timber Attributes of Ironbark:

  • Janka rating – Dry: Very Hard
  • Very heavy wood
  • Cumbersome to nail or work with
  • Planes with difficulty

Narrow-leaved Red Ironbark

This tree grows along on the plains and western slopes of New South Wales as well as on the east coast from Sydney to Cairns.

The Heartwood is dark red and the Sapwood is pale yellow. The texture of Narrow-leaved Red Ironbark is medium and even. The grain is interlocked and the growth rings are not easily distinguished.

Unlike the Broad-leaved Red Ironbark, the Narrow-leaved Red Ironbark Heartwood is not termite resistant inside above ground. However, similar to its Broad-leaved twin, it is not susceptible to Lyctid or Marine Borer infestation. The Natural durability Rating of Heartwood Above Ground as well as In-Ground Contact is Class 1.

  • Janka rating – Dry: Very Hard
  • Very hard to work with
  • Slow to dry
  • This variety, however, has a greater resistance to surface checking

Ironbark applications include:

  • Decking
  • Flooring
  • Building framework
  • Furniture
  • Sleepers
  • Cladding
  • Heavy Engineering
  • Marine construction
  • Shipbuilding
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