Eucalypts
Eucalypts have a number of applications. The Blue Gum group is suitable for tongue and groove flooring, in-sequence parquet, overlay, joinery stairs, doors, furniture, paneling, decking, outdoor furniture, and sliced veneer. The Stringybark group is suitable for flooring, joinery, decking, cross arms (mainly E. microcorys), and sliced veneer. The Ash group is suitable for furniture, joinery, and sliced veneer.
Sustainability of supply
New Zealand has 28575 hectares planted in eucalypts, with a median age less than 10 years. Approximately 7.5% is of millable age.
Eucalypts are exceptionally fast-growing, with timber grown in New Zealand to 30 years age similar to much older material from Australia.
Most of the harvestable timber available at present is located in the Central North Island, although small quantities are also becoming available in Northland and Auckland regions.
Significant plantings of young Eucalypt trees have been made in the past 5 years in the Otago and Southland regions, and also the Central North Island.
The eucalypt species have common names in Australia but are known by their botanical names in New Zealand.
This avoids confusion over the type of eucalypt being referred to, due to the extremely large variety of eucalypt species.
Confusion can remain, however, when imported timber classifications are used when marketing timber from Australia.
It is therefore recommended to request the botanical name of the species from any timber supplier, or else to request information regarding the mechanical properties and durability class of the timber being sold.
The eucalypt species grown in New Zealand are grouped as follows for simplicity because of their similarities:
The Eastern Blue Gum group: E saligna and E. botryoides
The Stringybark group: E. muelleriana, E. globoidea, E. eugenoides, E. microcorys, E. pilularis.
The Ash group: E. delegatensis, E. fastigata, E. regnans, E. obliqua.
Summary fact sheet for Eucalypts - Printable PDF
2007 Sawn Output of New Zealand Grown Eucalypts - Excel document
Quick Facts
Botanical name: Eucalyptus spp
Other common names:
Eucalypts
Strength
Eucalypt timber has good strength properties.
Durability
The heartwood of all the blue gum and stringybark species are durable in ground contact, lasting 15 to 25 years in ground contact and up to 40 years out of ground contact, giving an equivalent durability of H3.2. The ash group species are only moderately durable, lasting 5 to 15 years in ground contact giving an equivalent durability of H3.1.
Finishes
The dry timber finishes well, and takes all types of stains and paints. The higher density species may be difficult to glue, e.g. E. muelleriana.
Working properties
Difficulties with eucalypts relate mainly to the sawing of logs, where growth stresses may be a problem, and with drying, as some species are collapse-prone.
Appearance
The heartwood of the blue gums, E. saligna and E. botryoides is dark pink to reddish brown with a paler sapwood. The heartwood of the stringybark group species is yellowish-brown with a pink tinge, and the sapwood paler. The heartwood of E. fastigata is predominantly pale brown with occasional purplish flecks. E. obliqua looks very like European oak. The heartwood of E. regnans and E. delegatensis is pale pink or light brown that is sometimes difficult to differentiate from the pale sapwood. It has a moderate-coarse texture and straight grain.
Description
Eucalypt timber has several appealing characteristics. It is strong, dense, offers attractive colour choices, and the timber of some species has natural durability.
These wood properties differ between species, although species with similar attributes are often treated as one product line.
New Zealand-grown timber is less dense than Australian-grown timber, but has similar properties to mature Australian stands, although being considerably younger when cut (usually around age 30).
The Blue Gums
The heartwood of E. Saligna and E. Botryoides is dark pink to reddish brown with a paler sapwood. The wood has a fairly coarse, even texture with an interlocked grain. Gum veins are common.
The Stringybarks
The heartwood of the stringybark group species is yellowish-brown with a pink tinge, and the sapwood paler. The wood has a fine-medium and even texture, and the grain is often interlocked.
Stringybarks are characterised by high density, good durability, excellent sawing characteristics, and high strength.
Stringybarks have been used for a wide range of suitable end uses, included non-submerged wharf decking, cross-arms, sports arena and dance hall flooring, in-ground posts, durable half rounds for landscaping, as well as high quality furniture.
E nitens, though a blue gum, also has these excellent high strength and hardness properties of the group.
The Ash group
The Ash timbers were planted primarily as a replacement for tawa as a pulping timber, with the lower sawlogs available for solid wood utilisation.
The heartwood of E. fastigata is predominantly pale brown with occasional purplish flecks. It has a medium and even texture, and grain can range from interlocked to straight.
The heartwood of E. regnans is pale pink or light brown that is sometimes difficult to differentiate from the pale sapwood.
It has a moderate-coarse texture and straight grain. The Ash group has best appearance when quartersawn, with a ribbon-like mahogany-type appearance.
