Red siris

Scientific name

Paraserianthes toona. Family: Leguminosae

Other names

Mackay cedar; acacia cedar

Description

  • Medium-sized tree grows to 30m high.
  • Stem to 1m diameter and not prominently buttressed.
  • Bark is grey or brown, scaly in parts.
  • Bark may show irregular depressions where bark scales have fallen off.
  • Bark is pink when freshly cut.

Occurrence

  • Distributed mainly in North Queensland coastal rainforests between Mackay and the Endeavour River.
  • Timber availability is very limited.

Appearance

Colour

  • Dark red with yellow streaks causing a striated pattern on the longitudinal surface.
  • Sapwood is white and up to 50mm wide.

Grain

  • Coarse, large pored with pronounced vessel lines.
  • Occasional curly grain.

Uses

  • Construction: sawn timber for general house framing, flooring, linings, mouldings and joinery.
  • Decorative: furniture, turnery, joinery.

Properties

  • Density: 720kg/m3 at 12% moisture content; about 1.4m3 of seasoned sawn timber per tonne.
  • Strength group: (S5) unseasoned, (SD6) seasoned (brackets indicate provisional value).
  • Stress grades: F5, F7, F8, F11, (unseasoned); F7, F8, F11, F14 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: JD3 seasoned.
  • Shrinkage to 12% MC: 4.5% (tangential), 2.0% (radial).
  • Unit shrinkage: not available.
  • Durability above-ground: Class 3 (life expectancy 7–15 years).
  • Durability in-ground: Class 3 (life expectancy 5–15 years).
  • Lyctine susceptibility: untreated sapwood is susceptible to lyctid borer attack.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily impregnates with preservative, but penetration of heartwood is negligible using available commercial processes.
  • Seasoning: satisfactorily dries using conventional air and kiln seasoning.
  • Hardness: moderately hard (rated 3 on a 6-class scale) to indent and work with hand tools.
  • Machining: machines, and turns well, to a smooth surface.
  • Fixing: no difficulty using standard fittings and fastenings.
  • Gluing: satisfactorily bonds using standard procedures.
  • Finishing: readily accepts paint, stain and polish.

Identification features

General characteristics

  • Sapwood: creamy yellow, distinct from heartwood.
  • Heartwood: red to red-brown, often with yellow or lighter coloured streaks.
  • Texture: coarse, grain usually straight, but occasionally interlocked.

Wood structure

  • Growth rings: absent.
  • Vessels: medium to large, uniformly distributed, solitary, but also in radial chains with an infrequent cluster; obvious vessel lines on longitudinal surfaces; frequent dark red deposits in the vessels.
  • Parenchyma (soft tissue)plentiful, aliform and confluent; lighter-coloured sheaths of soft tissue around the vessels are distinct on all surfaces.
  • Rays: fine, invisible without a lens; ripple marks occasionally present.

Other features

  • Burning splinter test: match-size splinter burns to a partial dark grey or black ash filament.
  • Figure (pattern): parenchyma around the vessels, combined with the coloured streaks, give this timber an attractive figure.

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.