Yellow walnut

• Well-shaped, medium-sized tree
• Grows 25–30m high.
• Stem is 1.0–1.5m diameter.
• Trunk is sometimes crooked or irregular and slightly buttressed for 2–5m from the ground line.
• Bark can be up to 25mm thick, brown and partly rough with small pustules.
• When cut, the middle layer of bark is reddish brown and has an odour like sugar cane.

• Occurs in North Queensland rainforests around the:
  • Johnstone and Russell Rivers
  • Evelyn and Daintree Rivers
  • Bellenden-Kerr Range
  • Atherton Tableland.
• Timber has very limited commercial availability.

Colour

• Heartwood is pale to bright lemon yellow.
• Sapwood is generally paler but sometimes difficult to distinguish from the heartwood, especially since it can occupy up to 50% of the stem radius.

Grain

• Moderately course, straight grained with little or no figure (pattern).

• Decorative: plywood, furniture, joinery, turnery, carving, panelling.
• Other: sawn timber in general house framing, flooring, linings, mouldings and joinery.

• Density: 640kg/m³ at 12% moisture content; about 1.6m³ of seasoned sawn timber per tonne.
• Strength groups: S4 unseasoned, SD5 seasoned.
• Stress grades: F7, F8, F11, F14 (unseasoned); F8, F11, F14, F17 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
• Joint groups: J3 unseasoned, JD3 seasoned.
• Shrinkage to 12% MC: 3.8% (tangential), 2.1% (radial).
• Unit shrinkage: 0.27% (tangential), 0.17% (radial)—these values apply to timber reconditioned after seasoning.
• Durability above-ground: Class 4 (life expectancy 0–7 years).
• Durability in-ground: Class 4 (life expectancy 0–5 years).
• Lyctine susceptibility: untreated sapwood susceptible to lyctid borer attack.
• Termite resistance: not resistant.
• Preservation: sapwood readily impregnates with preservative, but penetration of heartwood is unsatisfactory using available commercial processes.
• Seasoning: dries satisfactorily using conventional air and kiln seasoning.
• Hardness: firm (rated 4 on a 6-class scale) to indent and work with hand tools.
• Machining: abrasive to machine cutters and tools due to silica in the wood.
• Fixing: no difficulty using standard fittings and fastenings.
• Gluing: bonds satisfactorily using standard procedures.
• Finishing: readily accepts stain, polish and paint.

General characteristics

• Sapwood: pale yellow to nearly white.
• Heartwood: pale to bright lemon yellow, often with dark streaks towards the heart.
• Texture: moderately course and uniform, grain is generally straight.

Wood structure

• Growth rings: absent.
• Vessels: solitary or in radial groups of 2–5 cells with occasional clusters; medium and evenly distributed; obvious vessel lines on dressed longitudinal surfaces.
• Parenchyma (soft tissue): numerous, irregularly spaced, apotracheal bands—prominent as they are lighter than the background.
• Rays: fine and distinct but less prominent than parenchyma.

Other features

• Burning splinter test: wood burns with some smoke to a charcoal tip and grey ash filament.
• Figure: dressed back-sawn surfaces may occasionally show figure (pattern) due to earlywood/latewood cells forming rings.

• 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.