Plantation Forestry TreesBackground
New Zealand is home to over 6 million hectares of protected native bush and nearly 1.8 million hectares of managed exotic plantation forestry. Nearly all our industrial usage comes from this exotic forest resource, unlike most other countries that are still cutting down native timber. 89% of New Zealand’s exotic forests are Radiata Pine with the rest a mix of Douglas fir, Acacia, Cypress and Eucalyptus. Forestry employs nearly 25,000 people throughout the country and accounts for nearly $4 billion in export earnings.
When thinking about forestry it is important to understand the timeframe for most of these crops. Most trees will need at least 30 years before maturity. During this time they will need inputs of labour, with very little potential for any return. Plantation forestry crops work well on a mixed style property. They suit marginal land such as hillsides and gullies, leaving the more productive flat land available for conventional farming or intensive crop options.
There are three main ways trees are grown in New Zealand today.
1. Partnerships between landowners and forestry companies with contract gangs
doing all of the work. This includes land clearing, planting and pruning,
thinning and final harvesting.
2. Landowners doing all the planting and management by yourself and then sell
the mature crops cutting rights to a forestry company.
3. Register the block under the forestry Registration Scheme which allows a
landowner to sell the land but retain cutting rights to the trees.
The rest of this fact sheet will concentrate on a few key points for each of the main types of plantation forestry crops that can be grown in Otago. Look at the contacts section at the end of the sheet to access more detailed information.
As the name suggests Pinus radiata comes from the family of pine trees. It is an excellent exotic plantation species that can usually be harvested after 28 years. The timber has a straight grain and relatively knot free. Pinus radiata is used for a range of industrial purposes including logs and chips, paper and paperboard, lumber for building and wood pulp. New Zealand has strong export markets for these products in Australia, Japan, Korea, USA and China.
Because of the volume produced, growing Pinus radiata is well under stood by forestry professionals. It does best where rainfall exceeds 650mm per year and it does not seem to like growing over 600m above sea level.
Douglas fir accounts for around 6% of New Zealand exotic forestry plantations. It likes to grow in cool moist sites making many parts of Otago ideal for this crop. The only potential problem is that the trees do not like frosts and these can be very damaging in the early part of a plantations life. The most ideal site appears to be near the bottom of a slope, with air movement to prevent the cold air settling and frosts forming.
Douglas fir is considered an excellent structural timber. Compared to Pinus radiata it is drier, stiffer, stronger and resistant to borers. Until recently it was able to be used for framing in a house, without the need for the expensive treatment given to Pinus radiata.
There are two main species of Cypress that are grown in New Zealand for their wood. These are Cupressus lusitanica and Cupressus macrocarpa. C. lusitanica is more suited to milder inland sites as it does not tolerate salt wind. C. macrocarpa on the other hand is a hardy species that suits cooler coastal sites. Both species prefer a well drained soil type with good levels of fertility to grow well. Regular rainfall will reduce moisture stress and keeps the trees growing all year long.
Cypress wood is valued for its fine grain, yellow-brown wood and even texture. Although it is classified as ‘softwood’ it is rated moderately durable. This means it is expected to last in the ground for between 10-15 years. It can also be used untreated in house framing, making it ideal for eco-style houses. Cypress is also used in the furniture making industry where un-pruned logs with interwoven knots, make for interesting and exotic looking products. Because of the relatively high prices paid for this wood, Cypress suit small plantations, far more than something such as a Pinus radiata. The key thing is to grow the right species on the right site.
Growing Eucalyptus trees as a plantation forestry crop can be a risky business if attempted without professional help. These trees are susceptible to smothering from weeds and correct pre-planting ground preparation is crucial.
Eucalypts can be grown for pulp with a harvest life of around 12 years, or they can be grown for other uses with the more traditional harvest life of between 30-40 years.
Although there are over 650 different Eucalypt species only a handful are suitable for cropping. Many are frost sensitive so it is essentail to get professional advice to match the correct species to the site.
Acacia melanoxylon or the Australian Blackwood is one of a number of Acacia’s being grown in New Zealand but this is the only one suitable for forestry. It is ideal for a range of high class uses in the furniture and cabinet industries as it is a dry and very stable wood.
Blackwoods grow best in a sheltered position on the sides and lower slopes of valleys. It requires a soil with good organic matter content and good drainage, as it does not like wet feet. Some plantings have a fast growing species such as Eucalypts around the outside of a Blackwood block to give them added protection. They need regular on-going 'form pruning', to ensure double leaders are removed, with the crop being mature after 35-40 years.
Taking good professional advice is absolutely crucial if you are thinking about growing plantation forestry crops. Look in the phone book for local contacts or write to the address below for more information.
New Zealand Farm Forestry Association
PO Box 1122
phone 04 472 0432 (Mon - Wed only)
Forest Research Institute
Private Bag 3020