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Black bean

Scientific name

Castanospermum australe. Family: Leguminosae

Other names

Moreton bay bean; Moreton bay chestnut; beantree

Description

  • Tall tree to 40m high.
  • Stem diameter to 1.2m.
  • Trunk is not obviously buttressed.
  • Very dense crown consists of abundant dark-green glossy foliage.
  • Large pendant bean-like fruit are clearly visible in the crown.
  • Bark is slightly rough with very small pustules, and from grey to brown.

Occurrence

  • Scattered throughout rainforest regions from Lismore, New South Wales to Iron Range, Cape York Peninsula.
  • New Caledonia.
  • Vanuatu.

Appearance

Colour

  • Heartwood ranges from dark brown to chocolate shades, deepening to almost black; sometimes streaked with lighter bands.
  • Sapwood is white to yellow.

Grain

  • Porous and coarse.
  • Striated vessel lines are prominent on longitudinal surfaces, due to chalky, grey soft tissue (parenchyma) surrounding the vessels.

Uses

Engineering

  • Used, in the past, as sawn and round timber in bridge construction and as mining timbers.

Construction

  • Limited use, historically, for general house framing, and common use for flooring, lining, mouldings and joinery: rarely now used for these purposes.

Decorative

  • Plywood, furniture, shop and office fixtures.
  • Joinery, turnery, carving, inlay work.
  • Walking sticks, umbrella sticks.

Others

  • Gunstocks, knife handles.
  • Vehicle and carriage building.
  • Was popular for timber split fence posts during early settlement in the Atherton Tableland’s rainforests.

Properties

  • Density: 755kg/m3 at 12% moisture content; approximately 1.3m3 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, JD2 seasoned.
  • Shrinkage to 12% MC: 5.8% (tangential), 1.8% (radial).
  • Unit shrinkage: 0.40% (tangential), 0.16% (radial)—these values apply to timber reconditioned after seasoning.
  • Durability above-ground: Class 1 (life expectancy more than 40 years).
  • Durability in-ground: Class 1 (life expectancy more than 25 years).
  • Lyctine susceptibility: untreated sapwood susceptible to lyctine borer attack.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily impregnates with preservatives but penetration of heartwood is negligible using available commercial processes.
  • Seasoning: be careful when seasoning, as this species shrinks irregularly and is prone to collapse.
  • 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 finish; dry dust can irritate your nose and throat.
  • Fixing: no difficulty using standard fittings and fastenings.
  • Gluing: satisfactorily bonds using standard procedures.
  • Finishing: staining isn’t normally necessary; polishes well but the coarse texture may need prior filling.

Identification features

General characteristics

  • Sapwood: white to yellow, distinct from heartwood.
  • Heartwood: dark brown to chocolate, sometimes with fine white streaks from vessel contents or more diffuse streaks due to soft tissue surrounding vessels.
  • Texture: coarse, with some figure (pattern).

Wood structure

  • Growth rings: absent.
  • Vessels: medium to large, in radial rows but with some solitary; chalky, white deposits in some vessels.
  • Parenchyma (soft tissue): abundant, aliform (resembling wings) with some confluent (merging).
  • Rays: visible without a lens.

Other features

  • Burning splinter test: match-size splinter produces a full-white to buff-coloured ash.
  • Figure: Prominent figure (pattern) caused mainly by the parenchyma associated with vessels.

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 edn, 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.