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Northern cypress

Scientific name

Callitris intratropica syn. C. columellaris var intratropica. Family name: Cupressaceae

Other names

Cypress pine; blue cypress; northern Christmas tree; laguni (Waguni people); karntirrikani (Tiwi people)

Description

  • Small to medium conifer.
  • Slow growing, 20–30m high.
  • Foliage is blue-green to dark green.

Occurrence

  • Occurs across northern Australia in habitats with free draining (sandy) soils.
  • Almost 3000 hectares of plantations were established in the Northern Territory mainland and several surrounding islands during the 1960s and 1970s.

Appearance

Colour

  • Heartwood is pale yellow to streaky gold and brown.
  • Sapwood is whitish pale yellow.
  • As with other cypress timbers, knots are a feature.

Grain

  • Generally fine and even, occasionally interlocked, producing an attractive figure (pattern).

Uses

  • Construction: used as sawn timber in general house framing, internal and external flooring, linings, joinery and fencing.
  • Decorative: internal furniture, outdoor furniture, turnery.
  • Others: beehives, oyster stakes, essential oil (Australian blue cypress, blue cypress oil).

Properties

  • Density: 675kgm3 at 12% moisture content; about 1.5m3 of seasoned sawn timber per tonne.
  • Strength groups: S4 unseasoned, SD5 seasoned.
  • Stress grades: F4, F5, F7 (seasoned and unseasoned) when visually stress-graded according to AS 2858—2008: Timber—Softwood—Visually graded for structural purposes.
  • Joint groups: J3 unseasoned, JD3 seasoned.
  • Shrinkage to 12% MC: 2.8% (tangential), 2.1% (radial).
  • Unit shrinkage: 0.22% (tangential), 0.18% (radial); low shrinkage, very stable timber.
  • Durability above-ground: Class 1 (provisionally)—life expectancy over 40 years.
  • Durability in-ground: Class 1—life expectancy 15–25 years; heartwood highly resistant to decay when fully exposed to the weather and/or used in the ground.
  • Lyctine susceptibility: not susceptible.
  • Termite resistance: resistant to subterranean termites.
  • Preservation: negligible penetration of heartwood and sapwood using current commercial processes.
  • Seasoning: satisfactorily dries using conventional air and kiln seasoning.
  • Hardness: firm to indent and work with hand tools.
  • Machining: machines well.
  • Fixing: pre-drill before hand-nailing seasoned timber to prevent splitting.
  • Gluing: rough the surface to enhance the strength of the bond.
  • Finishing: readily accepts paint, stain and polish.

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, 2008, AS 2082—2008: Timber—Softwood— Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.