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Miro

Miro timber has traditionally been used in New Zealand for house building purposes.

During early European settlement it found use as load-bearing beams. Figured miro is useful in cabinet making and ornamental turning. It is used increasingly as a matai flooring substitute. The tree has useful berries, gum and bark which Maori use in traditional herbal remedies (rongoa).

Description

miro_90Miro is similar in colour and grain to rimu, and was therefore often marketed in the past as or with rimu timber, particularly for flooring.

The heartwood is a lighter biscuit colour with dark reddish to black streaks, with a light beige colour sapwood.

The heartwood cross-section section is irregular, allowing beautifully figured sawn timber. Miro, with matai, are referred to as the New Zealand ‘plum’ trees due to their large red berries.

Miro is similar in appearance to matai, but has a darker heartwood, and larger proportion of sapwood.

The bark is dark grey to black with a rough irregular surface. The bark sheds in flakes, like matai, but reveals a purple inner bark. The grain is moderately straight with a fine and even texture.

Miro is one of the most widely distributed natives, growing throughout the podocarp forests of New Zealand, in lowland forest zones to 1000m, from Northland to Stewart Island. It is very abundant in the central plateau. The tree grows to a height of 15-25 m with a trunk diameter of 30-90cm.

Botanical name: Prumnopitys ferruginea

Other common names: Miro

Strength: Miro is slightly stronger than rimu and is hard and elastic.

Durability: Neither the heartwood not sapwood is durable. A stake in the ground would last 5-10 years.

Finishes: Not applicable.

Working properties: Excellent machining properties.

Appearance: The heartwood is a lighter biscuit colour with dark reddish to black streaks, with a light beige colour sapwood.

Properties

Though often bracketed with rimu in the past, it is inferior for decorative purposes and not as easily worked. Miro is slightly stronger than rimu and is hard and elastic.

Miro has average density of 625kg/m³ at 12% moisture content, with a modulus of rupture of 94 MPa and modulus of elasticity of 10.1 GPa.

The heartwood has excellent machining properties; however the timber is more prone to distortion than rimu, with tangential shrinkage of 5.9 % and radial shrinkage of 2.5% when dried from green to 12% moisture content.

Neither the heartwood not sapwood is durable. A stake in the ground would last 5-10 years. The timber is therefore unsuitable for applications where it would be exposed to weathering or ground contact.

As an indoor finishing timber, however, it is excellent, with good machining properties, coats easily, and the timber lends itself to being steam bent. The dry heartwood is, however, prone to splitting, and should be pre-bored for nailing.

Availability
Limited supplies of Miro may be available. Refer to the New Zealand Farm Forestry Association website for information regarding local timber suppliers.