Western white gum

Scientific name

Eucalyptus argophloia. Family name: Myrtaceae.

Local names

Queensland western white gum, Chinchilla white gum, scrub gum, lapunyah.

Description and natural occurrence

Western white gum is a medium to tall (40 m) tree, attaining up to 1 m diameter. Naturally occurring trees have good form with stems clear of branches for at least half the tree height. It is a smooth ('gum') barked species, often with a stocking of decorticated bark to one metre from ground level.

Western white gum has a limited natural occurrence, restricted to 600 km2 near Chinchilla in southern Queensland. It is potentially suitable for windbreaks and as a plantation timber species in the 650 to 900 mm mean annual rainfall zone of Queensland.

Plantation grown timber

Early research results suggest that future supplies of plantation-grown western white gum will be available from central inland Queensland, the Burnett, Moreton and Downs regions on suitable soils and where the mean annual rainfall exceeds 600 mm. This species is classified as 'vulnerable' (Queensland Nature Conservation Act 1992) so harvesting or clearing of naturally occurring trees is restricted.

Wood appearance

Colour. The heartwood is orange-brown to deep red-brown with distinctly paler sapwood.

Grain. Fine to medium textured; grain variable from straight to interlocking; lacking in figure except around knots.

Wood properties

Air dry density. Natural-grown, mature: 1055 kg/m3; plantation-grown: 1005 kg/m3 (32-year-old), 860 kg/m3 (10-year-old).

Basic density. Natural-grown, mature: 855 kg/m3; plantation-grown: 840 kg/m3 (32-year-old), 725 kg/m3 (10-year-old).

Strength groups. Natural-grown, mature: unseasoned (S2), seasoned (SD3); full rotation plantation-grown timber: unseasoned (S3) (brackets indicate provisional value).

Stress grades. Natural-grown, mature wood: F11, F14, F17, F22 (unseasoned); F14, F17, F22, F27 (seasoned); full rotation plantation-grown timbers: F8, F11, F14, F17, when visually stress graded in accordance with AS 2082:2000, Timber - hardwood - visually stress-graded for stuctural purposes.

Joint groups. JD1 seasoned.

Shrinkage to 12% MC. Natural-grown, mature wood: tangential 4.9%, radial 2.8%; plantation-grown timber: tangential 3.7%, radial 2.5% (32-year-old); tangential 3.8%, radial 2.1%. (10-year-old).

Unit shrinkage. Natural-grown, mature wood tangential 0.4%, radial 0.3%; plantation-grown timber: tangential 0.33%, radial 0.29% (32-year-old), tangential 0.23%, radial 0.19% (10-year-old).

Durability. Anecdotal evidence supports a durability classification in the highest category (class 1 on a four class scale) for natural-grown, mature western white gum. Accelerated durability biosassay trials on plantation-grown material also place this species into durability class 1. Based on this work, western white gum is highly resistant to decay in ground contact or in persistently damp or poorly ventilated situations.

Lyctine susceptibility. Untreated sapwood is susceptible to lyctid borer attack.

Termite resistance. Not resistant.

Preservation. No available information for treating western white gum.

Seasoning. Western white gum can be air-dried or dried with a combined air- plus kiln-drying process. As with most high-density eucalypts, some checking will occur through heart material and in association with knots. A combined air- and kiln- drying experiment sucessfully dried green (40% moisture content) 25 mm boards (32-year-old plantation-grown). Total drying time, including an equalisation phase, was less than 20 days and resulted in very little degrade.

Hardness. Mature, natural-grown and plantation-grown wood is rated very hard (rated 1 on a 6 class scale), and thinnings material (10-year-old) is rated hard (2 on the same scale) in relation to resistance to indentation and ease of working with hand tools. Janka hardness has been determined for both 10-year-old and 33-year-old, seasoned material providing values of 10.6 kN and 14.4 kN respectively.

Machining. Straight-grained material machines well and a fine finish can be achieved. Where interlocking grain is present, some chipping out will occur.

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

Gluing. As with most high-density hardwoods with high extractives contents, machining and surface preparation must be undertaken immediately prior to gluing.

Finishing. Readily accepts stains, paints and polish.

Uses

Engineering applications. Poles, piles, railway sleepers, wharf and bridge construction.

Construction. General house framing, flooring, decking, lining, cladding, fencing, landscaping and retaining walls.

Decorative. Furniture and cabinetry, turning.

Identification features

General characteristics

Sapwood. Whitish and distinct from heartwood, forming approximately 20% of the cross-sectional area in full-rotation aged material and 35% of the cross-sectional area of 10-year-old thinnings material.

Heartwood. Orange-brown to deep reddish-brown.

Texture. Fine to medium textured; grain variable from straight to interlocking; lacking in figure except around knots.

Wood structure

Vessels. Small, solitary with tyloses.

Parenchyma. Thin layer surrounding vessels.

Rays. Fine, not visible to the naked eye.

Other features

Burning splinter test. Charcoal.

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 22 May 2012