Grey gum

Scientific name

Eucalyptus propinqua var. propinqua, E. punctata. Family: Myrtaceae

Local names

Grey iron gum (both species), small fruited grey gum E. propinqua var. propinqua

Description and natural occurrence

The grey gums can grow to 40 m in height and 1 m diameter. On better sites form is generally good with a straight bole extending for half or two-thirds the tree's height.

The bark decorticates in large irregular patches exposing a cream to bright orange surface, which after a time weathers to grey or grey-brown.

Varieties of grey gum occur along the east coast of Australia from Wyong, New South Wales, to Maryborough and inland to the Carnarvon Ranges and Blackdown Tablelands in Queensland.

Wood appearance

Colour. Heartwood is red to red-brown, sapwood is distinctly paler.

Grain. Grain usually interlocked, with coarse but even texture. Occasionally marked by grub holes.

Wood properties

Density. 1055 kg/m3 at 12% moisture content; approximately 1.0 m3 of seasoned sawn timber per tonne.

Strength groups. S1 unseasoned; (SD2) seasoned.

Stress grades. F14, F17, F22, F27 (unseasoned), F17, F22, F27, F34 (seasoned), when visually stress graded in accordance with AS 2082-1979, Visually stress-graded hardwood for structural purposes.

Joint groups. J1 unseasoned; JD1 seasoned.

Shrinkage to 12% MC. 7.0% (tangential); 4.5% (radial).

Unit shrinkage. Not available.

Durability above-ground. Class 1 - life expectancy over 40 years.

Durability in-ground. Class 1 - life expectancy over 25 years.

Lyctine susceptibility. Sapwood not susceptible to lyctid borer attack.

Termite resistance. Resistant.

Preservation. Sapwood readily accepts preservative.

Seasoning. Slow to dry, but little degrade occurs.

Hardness. Very hard (rated 1 on a 6 class scale) in relation to indentation and ease of working with hand tools.

Machining. Machines well, however, some care needed with interlocked grain.

Fixing. No difficulties have been experienced with the use of standard fittings and fastenings.

Gluing. As with most high-density species, machining and surface preparation should be done immediately before gluing.

Finishing. Will readily accept paint, stain and polish.

Uses

Engineering. Railway sleepers, landscaping sleepers, cross-arms, poles, piles, mining timbers.

Construction. Framing, flooring, retaining walls.

Others. Boat building, butcher's blocks.

Identification features

General characteristics

Sapwood. Pale, reddish-brown distinguishable from heartwood.

Heartwood. Reddish-brown to red.

Texture. Medium to coarse, interlocked grain.

Wood structure

Vessels. Small, solitary, uniform distribution. Vessel lines prominent in some specimens of darker colour. Tyloses abundant.

Parenchyma. Not visible with lens.

Rays. Fine.

Other features

Burning splinter test. A match size splinter burns to charcoal leaving no ash.

Further reading

Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, 'Forest trees of Australia', 5th edn, CSIRO Publishing, Collingwood Australia.

Bootle, K 2005, 'Wood in Australia: types, properties and uses', 2nd edn, McGraw-Hill, Sydney.

Hopewell, G (ed.) 2006, 'Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland, Class 1 and Class 10 buildings', books 1 and 2, Department of Primary Industries and Fisheries, Brisbane.

Ilic, J 1991, 'CSIRO atlas of hardwoods', Crawford House Press, Bathurst, Australia.

Standards Australia, 2000, 'AS 2082-2000: Timber - hardwood - visually stress-graded for structural purposes', Standards Australia.

Last updated 04 August 2010