Australian hardwoods, why so different?

Tough trees evolved from a tough environment

A land of frequent fire

Eucalypt tree sprouting new growth after a fire.

The majority of Australian ecosystems have adapted to frequent fire. Fossil pollen records show the Eucalypts became dominant approximately 40,000 years ago assumably due to increased fire frequency judging by increase in carbon in the same fossil layers.


Fire causes gum veins and other marks in the timber.

A dry country

Maud Correa at unsplash

Australia is the driest continent in the world. Low rainfalls mean the trees grow slower and harder and denser. In semi arid areas the growth rings are often caused by rain events rather than the seasons.

In high rainfall areas (such as rainforest) we do find 'regular' density trees but most of these are now protected due to the high levels of harvesting with first settlement as these 'normal' timbers were far easiter to process and use than the denser 'hardwoods'.

A land of voracious insects

Scribbly Bark -Marianne Horak vis CSIRO website

Everything fights for survival, including the insects.  Trees produce chemicals (called extractives) to deter insects and to preserve the timber from decay. These extractives can give beautiful rich colours.  These extractives also affect glue adhesion and drying and stability during use.

Borer holes of various sizes and scribble marks are often found in timber to the extent where Australia has specific grading requirements for the timbers.

The mechanical difference

More Elastic

Australian Hardwoods VS Traditional Timbers

Common NameLatin nameADD Density*
Hardness (Janka)
Modulus of elasticity (Gpa)Modulus of rupture (MPa)
BlackbuttEucalyptus adrewsii9009.119144
Brush BoxLophostemon confertus9008.515123
JarrahEucalyptus marginata8208.513112
Forest Red GumEuc. teritacornis10501214120
IronbarkEucalyptus paniculata11201417135
Red Mahogany Euc. resinifera 9501216140
Rose gumEuc. grandis6207.517122
Spotted GumCorymbia maculata9501123150
Sydney Blue GumEucalyptus saligna8509.018140
AVERAGE 90610.2 16.9132
Radiata pinePinus radiata5003.31081
Red CedarToona australis6402.39.465
Oak (European)Quercus spp.6905.51095
Queensland MapleFlindersia brayleyana5804.71077
Silky OakGrevillea robusta6203.71092
European BeechFagus sylvatica6906.413118
AVERAGE 6204.3 10.4 88
Australian Hardwoods are146% heavier236% harder162% more elastic150% stronger (rupture)