A supply of timber on your farm can be invaluable, both as a source of firewood, and as a future source of income if you grow trees for fine timbers.
Maxine Fraser, who also provided information on planning and planting an orchard, established a timber lot with her late husband Tony on their 80-acre property at Te Pahu, in the Waikato. Her long experience in permaculture and involvement with the Tree Crops Association and the New Zealand Farm Forestry Association provides the background for the valuable advice she offers on establishing a woodlot on your property.
What kind of woodlot?
The first consideration is whether you want purely firewood or whether you want a timber lot. Maxine's advice is that a dedicated "firewood lot" is probably unnecessary. In her experience, and that of many other owners of lifestyle blocks, you get so much wood from other sources (regular pruning and occasional felling of orchard, ornamental and shade trees) that your firewood needs are met without needing specific firewood trees. Therefore it is probably more sensible to plant one or several timber lots, which will provide adequate firewood during the necessary pruning processes and will also yield a valuable crop, albeit thirty or forty years in the future.
What do you need to check out before you plant a timber lot on your property? The considerations are not as complex as for planting an orchard: north facing and sloping sites are not as critical. In many cases, the practicalities of harvesting are more significant than the need to optimise growing conditions.
The main thing to do is put your trees somewhere accessible – eventually you will need to either prune or fell them and you must be able to get machinery and vehicles to the site. Right at the back of your near-vertical property is not a good place! Ensure that your trees are either near the road, or near your internal farm roads. You also need to think ahead to be sure that your trees, which will grow large, are a safe distance from buildings and will not shade existing buildings or orchard and garden areas.
It is also worth noting that you don't have to plant all your timber trees in one place. Small pockets can be very effectively used. Maxine cites the work of James Sholto Douglas, whose book "Forest Farming" laid out the then-radical proposition of having "mosaics" of timber trees interspersed with native tree blocks and grazing. This approach can be quite demanding, because the grazing areas must be fenced off from most of the trees, but it does provide very sheltered conditions for the animals and can greatly enhance biodiversity.
What to plant?
Pine trees can be included in a timber lot, just as they would in a firewood plantation, because they do yield good timber, especially if allowed to grow long enough (about 80 years) to develop proper hardwood. Normally, they are grown for the minimum 20 to 25 years, and therefore need tanalising treatment. However, Maxine also recommends "fine timber" trees such as Acacia melanoxylon (Tasmanian or Australian Blackwood), which takes about 35 years to reach maturity. It produces beautiful timber which is used for furniture and instrument-making (see here). Many eucalypts can also be grown for timber, and some are ground durable, meaning they can be used for fence posts along with other applications. However, they tend to be "soil robbers," dragging large amounts of nutrients and water out of the soil. If you have an unwanted wet spot on the farm, try planting a eucalypt on it to dry it up.
Maxine also recommends the Cupressus (cypress) species. Most of us know about Cupressus macrocarpa (our well-known macrocarpa hedge), which yields a very pleasing timber and can be grown right on the coast. But you can also try Cupressus lusitanica, especially in the warmer areas and away from the coast. There is little difference in the nature of the timber, but while macrocarpa tends to have a somewhat fluted cross-section, C. lusitanica has a more evenly round trunk, which can lead to less wastage during milling.
Californian coastal redwoods (Sequoia sempervirens) are also gaining in popularity as timber trees in certain areas of New Zealand, and may have export potential, but they are slower to mature and need up to 60 years to develop to millable size.
For a useful series of case studies involving a wide variety of plantings in New Zealand, see the Farm Forestry Association's website at this location. If your interests include producing an edible crop as well as wood, the Tree Crops Association's resources site is full of helpful information, particularly in the 'crops' subsection.
A final consideration is having a mix of wood that provides good burning properties, since you will almost certainly use some of it for home heating purposes. For a general explanation of heat units as related to firewood, see here. Maxine recommends having a variety of woods with a mix of high and low heat units. Trees providing high heat output include Robinia, which comes literally with fish-hooks – it is covered in enormous thorns and tends to sucker, so Maxine suggests steering clear of it. Less intimidating varieties include acacias and tagasaste (tree lucerne), which are both legumes and therefore fix nitrogen. Tagasaste also provides good fodder for stock and attracts bees and kereru, serving several useful functions at once. Low heat units are provided by trees like pine and willow, so a mix of many varieties spread around the farm in accessible positions is highly desirable.