Why Plant Trees? / Making Money from Farm Forestry / Timber Products /
Wood Growth & Structure / Wood Properties
Why Farm Forestry
Why Plant Trees
Markets for products & services
Designing a Farm Forest

Wood properties

Timber’s properties vary enormously between species and as a result of tree age, stem form, soil types, climate, latitude, and forest management. Within the tree, wood properties also vary across the growth rings, with distance from the pith, and with height up the tree. Wood properties are also affected by:
• the presence and nature of knots
• pockets of resin or gum
• decay or insect attack
• the pith
• sloping grain
• other anomalies.

Properties of interest to timber users include durability, colour, density, interesting grain patterns and workability. Some users may also be interested in wood’s acoustic properties, electrical conductivity, allergic reactions, thermal resistance, and surface hardness.


Natural durability is an important wood characteristic. In almost all species, the sapwood is highly susceptible to fungal and insect attack. The heartwood of many species is durable in ground, above ground, or even under seawater. In some species the heartwood is particularly resistant to certain agents such as termites or fungi. For example, the high silica content of the native Turpentine—Syncarpia glomulifera—deters marine organisms.

In Australia, timber species are rated from Class 1 (highly durable) to Class 4 (non-durable). Recent research suggests that durability is affected by the tree’s age and the source of the timber. Timber’s ability to absorb and retain preservative also varies. This makes some species of low natural durability—for example, Radiata Pine—ideal for preservation treatment while many of the more durable eucalypts cannot be easily impregnated.


Wood’s colour comes from complex organic compounds deposited in the heartwood’s cells rather than from its basic structural components. This is evident from the change in wood colour that results during the transformation of sapwood to heartwood. The result is a wide range of wood colours including reds, blacks, yellows and even purple.

Natural grain, texture and figure

Timber’s display of natural grain, texture and figure is unique. Texture—either fine or coarse—is determined by the size of the cells. Grain may be straight, spiral, sloping, interlocked, curly, wavy or rippled.


Timber’s strength and structural performance are indicated by its stress-grading. The strength of timber for structural use is described using an F rating that ranges from F4 to F34. Based on an Australian standard, it provides an indication of the wood’s bending, tension, shear, elasticity and compressive strength.

In Australia, kiln dried plantation pine is usually rated between F5 and F11 depending on the wood’s age and the presence of knots or other defects. Green Eucalypt timber is often graded at around F11, but may increase to more than F17 when dried. The highest F ratings (such as F27) are achieved by very dense, defect-free dried hardwood timber, such as Red Ironbark.

Back to top

Farm Forest Line © 2009 | Disclaimer