Western white gum

Scientific name

Eucalyptus argophloia. Family name: Myrtaceae

Other names

Queensland western white gum; Chinchilla white gum; scrub gum; lapunyah

Description

  • Medium to tall tree, growing to 40m high.
  • Stem grows to 1m diameter.
  • Naturally occurring trees have good form with stems clear of branches for at least half the tree height.
  • Smooth ('gum') bark, often with a stocking  of removed bark to 1m from ground level.

Occurrence

  • Limited natural occurrence, restricted to 600km2 near Chinchilla in southern Queensland.
  • Potentially suitable for windbreaks and as a plantation timber in the 650–900mm mean annual rainfall zone of Queensland.
  • Early research suggests that future supplies of plantation-grown timber will be available from central inland Queensland, the Burnett, Moreton and Downs regions on suitable soils and where the mean annual rainfall exceeds 600mm.
  • Classified as 'vulnerable' (Queensland Nature Conservation Act 1992) which restricts harvesting or clearing of naturally occurring trees.

Appearance

Colour

  • Heartwood is orange-brown to deep red-brown.
  • Sapwood is distinctly paler.

Grain

  • Fine to medium texture.
  • Grain varies from straight to interlocking.

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.

Properties

  • Air dry density: natural-grown—1055kg/m3 (mature); plantation-grown—1005kg/m3 (32-year-old), 860kg/m3 (10-year-old).
  • Basic density: natural-grown—855 kg/m3 (mature); plantation-grown—840kg/m3 (32-year-old), 725kg/m3 (10-year-old).
  • Strength groups: natural-grown, mature—unseasoned (S2), seasoned (SD3); full rotation plantation-grown—unseasoned (S3) (brackets indicate provisional value).
  • Stress grades: natural-grown, mature—F11, F14, F17, F22 (unseasoned); F14, F17, F22, F27 (seasoned); full rotation plantation-grown—F8, F11, F14, F17, when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: JD1 seasoned.
  • Shrinkage to 12% MC: natural-grown, mature—4.9% (tangential), 2.8% (radial); plantation-grown, 32-year-old—3.7% (tangential), 2.5% (radial); 10-year-old—3.8% (tangential), 2.1% (radial).
  • Unit shrinkage: natural-grown, mature—0.4% (tangential), 0.3% (radial); plantation-grown timber, 32-year-old—-0.33% (tangential), 0.29% (radial); 10-year-old—0.23% (tangential), 0.19% (radial).
  • Durability: natural-grown, mature—anecdotal evidence supports a rating in the highest category (Class 1 on a 4-class scale); plantation-grown—accelerated durability bioassay trials also rate as 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 information is available for treating.
  • Seasoning: air-dry or dry with a combined air-plus kiln-drying process. As with most high-density eucalypts, some checking will occur through heartwood and associated with knots. A combined air- and kiln-drying experiment successfully dried green (40% moisture content) 25mm 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 (1 on a 6-class scale), and thinnings material (10-year-old) is rated hard (2 on the same scale) to indent and work with hand tools. Janka hardness (seasoned)—10-year-old is 10.6kN, 33-year-old is 14.4kN.
  • Machining: straight-grain machines well and achieves a fine finish; some chipping out will occur with interlocking grain.
  • Fixing: no difficulties using standard fasteners and fittings.
  • Gluing: as with most high-density hardwoods with high extractives content, machine and prepare surface immediately before gluing.
  • Finishing: readily accepts stains, paints and polish.

Identification features

General characteristics

  • Sapwood: whitish and distinct from heartwood; forms about 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 texture; grain varies from straight to interlocking; lacks figure (pattern) except around knots.

Wood structure

  • Vessels: small, solitary with tyloses.
  • Parenchyma (soft tissue): thin layer surrounding vessels.
  • Rays: fine, not visible to the naked eye.

Other features

  • Burning splinter test: charcoal.

Research and resources

  • Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, Forest trees of Australia, 5th ed., CSIRO Publishing, Collingwood, Australia.
  • Bootle, K 2005, Wood in Australia: Types, properties and uses, 2nd ed., McGraw-Hill, Sydney.
  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • Queensland Government, DAF 2018, Construction timbers in Queensland: Properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.