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Cypresses

Cypresses are best used where its appearance and durability are put to advantage, for example, in panelling, exterior cladding and boat building.

Sustainability of supply

lusitanica_90Plantations have increased from about 4,000 ha in 1986 to about 8,000 ha at the end of 2007 (Ministry of Agriculture and Forestry National Exotic Forest Description, 2007).  Plantations have a median age of less than 10 years. From these, about 20,000 m³ of timber per year is harvested.

The most widely planted species are macrocarpa, lawsoniana and lusitanica, in that order. In addition to planted stands, cypresses have been planted for hedges and shelterbelts, particularly on farms in the 1920s and 1930s.

Planted trees can succumb to the cypress canker disease and some may not reach maturity. Demand for the timber currently exceeds supply. In a few cases, the various cypress timbers have been marketed with, or as, macrocarpa, particularly lusitanica.

Lawson cypress has been marketed separately, and, because of its lighter colouring, Leyland cypress is now recognised and marketed as a distinct cypress timber.

 Summary fact sheet for Cypresses (.pdf)

Quick Facts

Botanical name: Cupressus lusitanica, Chamaecyparis lawsoniana, Cupressocyparis leylandii

Other common names: Lusitanica, Lawson cypress, Leyland cypress

Strength: Lawson cypress is the strongest of the cypresses, and has significant stiffness properties. Lusitanica is less susceptible to collapse and internal checks than macrocarpa, and has greater dimensional stability. Lawson cypress is not known for collapse or internal checking issues when dried. In New Zealand, Lawson cypress has been used for house framing, roof trusses, weatherboards, roof shingles, interior panelling, furniture and joinery.

Durability: Cypress heartwood gives some protection for above-ground purposes, but the sapwood is non-durable.The timber cannot be pressure treated with copper, chromium and arsenic (CCA), but can be boron treated to Hazard Classes H3.1 and H1.2. When used as framing, boron-treated Hazard Class H1.2 cypress can be used wherever H1.2 treated radiata pine framing is acceptable. Untreated timber can be used for interior framing and finishing, and non-skillion roof trusses.

Finishes: There are no known problems of incompatibility with any type of adhesive. Wipe-on stains tend to give a streaky appearance. Clear finishes enhance the natural lustre and work well when the timber is given an initial oil coating.

Working properties: Cypresses are easily worked with hand or machine tools, and take an excellent finish, provided cutters are kept sharp and free from extractives.

Appearance: Cypresses have a yellow-brown coloured heartwood and paler sapwood, with a fine, even texture. The timber has a natural lustre that makes it a good substitute for kauri, particularly lusitanica.

Description

Lusitanica

Lusitanica grows well in warm regions, and is available in the North Island and upper South Island.

In most aspects, lusitanica has the same properties as macrocarpa, but is likely to produce greater volumes of timber because it is less prone to fluting of the trunk, and has smaller knots.

It is also slightly lighter in colouring and has a wider sapwood band than macrocarpa.

When freshly cut, it has a fragrant spicy odour. The heartwood is a yellow-brown colour, slightly darker than lawsoniana but not quite as dark as macrocarpa.

Lusitanica is a low-to-medium density softwood, with a fine, even texture and pronounced growth rings.

Lusitanica, like macrocarpa, is moderately durable in the ground, but is slightly less durable than macrocarpa.

Because it looks like kauri, and has good machining properties, lusitanica has been used in New Zealand for furniture manufacture.

Lawson cypress

Lawson cypress is also known in North America as white cedar.

The name, cedar, relates to the spicy smell of the wood, a feature common to the cypress species.

Lawson cypress is the most fragrant of the species grown in New Zealand.

It has been planted for shelterbelt timber and in plantation blocks, and is a hardy species.

The heartwood is pale yellow to pale brown in colour, and barely distinguishable from the sapwood when dry.

Leyland cypress

Leyland cypress is used to describe a group of trees that are all sterile hybrids.

There are no naturally occurring Leyland cypresses, and all are propagated by rooted cuttings because the resulting trees are infertile. Leyland cypress is knotty.

The heartwood is dark yellow in colour, fading to the pale yellow of lawsoniana.

Performance

Durability

The heartwood of the cypresses is rated as Class 3 durability, which is equivalent to Hazard Class H3.1.

The heartwood gives some protection for above-ground purposes, but the sapwood is non-durable.

The timber cannot be pressure treated with copper, chromium and arsenic (CCA), but can be boron treated to Hazard Classes H3.1 and H1.2.

Cypresses are therefore suitable for exterior exposed, but not in-ground, applications.

Lawsoniana is recommended for exterior uses like weatherboards but only if it is cut from trees 80 years or older in which the sapwood is 50 to 75 mm deep.

Strength values refer to 20 x 20 mm clearwood specimens but are not available for C. Ovensii.

Mechanical properties

Please note these comparative measures of strength are “laboratory” values using standardised short lengths of clear timber. These will not be the same strength properties as structural lengths of timber. For the properties of structural length timber please see the tables under the structural design section.

 LusitanicaLawson Leyland
Density at 12% moisture content (MC)460 kg/m3 480 kg/m3

495 kg/m3
Modulus of elasticity 6.5 GPa121 GPa6.9 GPa
Bending strength69.6 MPa97.7 MPa85.6 MPa
Compression strength38 MPa37.3 MPa38 MPa
Side hardness2.6 kN2.5 kN 1.9 kN
Tangential shrinkage – green to 12% MC2.6%3.6%3.2%
Radial shrinkage – green to 12% MC1.4%2.2%1.4%

Lawson cypress is the strongest of the cypresses, and has significant stiffness properties.

Lusitanica is less susceptible to collapse and internal checks than macrocarpa, and has greater dimensional stability. Lawson cypress is not known for collapse or internal checking issues when dried.

In New Zealand, Lawson cypress has been used for house framing, roof trusses, weatherboards, roof shingles, interior panelling, furniture and joinery.

Only then will there be a reasonable chance of the tree containing a high percentage of heartwood.

Leyland cypress is slightly more durable than macrocarpa, and lusitanica is slightly less durable than macrocarpa.

When used as framing, boron-treated Hazard Class H1.2 cypress can be used wherever H1.2 treated radiata pine framing is acceptable.

Untreated timber can be used for interior framing and finishing, and non-skillion roof trusses.

Machining

Cypresses are easily worked with hand or machine tools, and take an excellent finish provided cutters are kept sharp and free from extractives.

Lawsoniana works well with hand and machine tools, and it takes an excellent finish.

Lusitanica has a natural lustre that makes it a good substitute for kauri. The timber is best used where its appearance and durability are put to advantage, for example, in panelling, exterior cladding and boat building.

The timber can be used for furniture, but is softer than many other furniture timbers. In connection with boat building, it should be noted that the cypresses are not good steam-bending timbers.

Considerations

There are no known problems of incompatibility with any types of adhesive. Wipe-on stains tend to give a streaky appearance.

Clear finishes enhance the natural lustre but yellowing occurs inover time, however, this can be minimised by giving the timber an initial oil coating.

Availability
Go to the NZ Farm Forestry Association Marketplace for availability of Cypresses