Among Australia’s toughest native trees, Ironbarks are instantly recognised by their deeply furrowed, dark bark and their ability to withstand drought, heat and bushfire. Valued both as landscape trees and for their exceptionally durable timber, more than 40 species of Eucalyptus are commonly grouped under the name Ironbark.
Unlike many other eucalypts, Ironbark trees do not shed their bark each year. Instead, the bark gradually builds up over time, forming a thick, hard protective layer. As this outer bark becomes impregnated with sap, it develops the rugged appearance and remarkable durability that gave Ironbarks their name.
This distinctive bark acts as natural insulation, helping protect the tree from intense heat and fire. Even after severe bushfires, dormant buds beneath the bark often survive and quickly reshoot, allowing the tree to recover.
Ironbarks vary considerably between species. Some have broader foliage, others narrower leaves, and bark colours range from dark grey and black through to reddish and silver tones. They are generally grouped into Red, Grey and Silver Ironbarks, with many species prized not only for their ornamental value but also for producing some of Australia’s hardest and longest-lasting timbers.
Uses For Ironbark Timber
Valued for the timber Ironbark trees are found over a wide area of Australia. They are harvested and the wood used for use as decking, raised garden beds and retaining walls.
The timber from these trees is very dense making it more difficult to work with than others, it is also more resistant to termites and borers than other timbers and are also more fire resistant than many other timbers. .
The great thing about all of these species is the durability, in-ground they are rated as ‘Class 1’ which indicated a life expectancy over 25 years. They are also regarded as being termite resistant. Ironbark along with Redgum are regarded as two of Australia’s most durable and long lasting timbers.
Ironbark Species
It is a little difficult to define the Ironbark tree as Ironbark refers to a number of different species. These include the red Iron barks, grey and silver. Some of the more widely grown species are listed below.
Ironbark timbers used for flooring and decking are the species usually grouped into these two main colour ranges. All are regarded as very hard and durable, with some variation in hardness between species. Some colour variation occurs within each species, but most suppliers blend boards to provide a visually consistent result.
Grey Iron Bark
- Eucalyptus paniculata – Grey Ironbark found along the NSW coast.
- Eucalyptus siderophloia also a grey ironbark is found from souther NSW through Queensland, again along the coast.
- Eucalyptus drepanophylla
- Eucalyptus fibrosa (sometimes marketed with red ironbarks, but can present in more neutral tones)
Red iron Bark
- Eucalyptus tricarpa, – From Gippsland in Victoria to the south coast of NSW, commonly called mugga ironbark,
- Eucalyptus sideroxylon. – Red Ironbark or Mugga Ironbark. Red flowers. – This one has a classic name, from the Greek sideros, meaning iron, and xylon, meaning wood. Found from southern Queensland through NSW into Victoria and isolated areas in South Australia.
- Eucalyptus sideroxylon rosea – Pink Ironbark
- Eucalyptus crebra – Narrow-leaved red ironbark and it is found along the coast from Cape York to Sydney.
Silver Iron Bark
- Eucalyptus melanophloia is mainly found from mid NSW through Queensland also know as the silver leaf ed Iron Bark
- Eucalyptus shirleyi is a smaller growing species found at altitudes and in poor soils, a mallee type. Found in Queensland
Other Species
- Eucalyptus jensenii, with its near black bark is from the Northern Territory and is commonly known as Wandi ironbark
Over 40 species of Eucalyptus are classed as Iron Bark.
Timber colour will vary from species to species as well as from where in the tree the wood is cut. Heartwood can differ in colour from other wood. Some trial Ironbark plantations are now being planted with perhaps this becoming a sustainable building material in the near future.
The importance or Ironbark species in gardening and horticulture can not be underestimated. It is one of the best timbers for raised garden beds and also one of the best for retaining walls. It outlasts most others by many years.
Ironbark trees being long lived and relatively problem free are also being used in street plantings where they suit wider streets and work well planted in avenues. One example is in Maffra where they are being used in Powerscourt Street near the Secondary College.