Posted on 3 December 2014

by Craig Marshall

Summer is the best time for thinking about firewood and firewood is something that takes time. The big advantage of wood as a fuel is that it is carbon neutral: burning it does produce CO₂ but it is not fossil carbon and firewood is typically only a few decades old at most. How you burn it does matter: an open fireplace is very inefficient and you will need a lot more (and produce a lot more smoke) than in some kind of efficient wood burner. Using wood typically generates heat in other ways too: some of these are discussed below.

Firewood is available in three main ways: bought from a merchant, cut from existing trees, and from a woodlot grown specially for fuel. Each has their advantages and costs and all require some work. Even bought firewood needs to be stacked (and it may need splitting) and you’ll need space to store it.

Ready cut firewood is easily available but can be quite expensive and you may find it is not quite ready to burn. The main options are either pine or eucalyptus (gum). Pine is relatively light wood that burns readily and hot, but doesn’t tend to last long. Gum is denser and burns for much longer and is usually more expensive. Native species such as manuka (usually kanuka in the south) show up from time to time and are very dense long burning firewood best used in combination with pine. Do find out where this sort of wood comes from before buying it. Kanuka, for example, can come from land clearance and it also may come from dead fall in regenerating native bush. It has also been planted in woodlots, so the source may be difficult to determine.. Most native species may now be cut only with specific permission and are not often seen as firewood any more.

If you have the right equipment and aptitude you might want to cut your own firewood.Cutting firewood is hard work and needs a certain number of tools although these may be hired as required. A good chainsaw makes cutting much easier but you need to know what you are doing. Chainsaws do cost something to run by way of fuel, chains and sharpening, along with the necessary safety gear. If you are not experienced take care: felling an old man macrocarpa is not for the faint-hearted and falling trees are very dangerous. You might be able to get access to felled trees and cut them up yourself. There is much potential firewood in the Blueskin Bay region and you may just need to ask a friendly landowner to get some. However, take great care if you are not experienced as even cutting felled trees has its risks.

A third option is the managed woodlot. This takes considerable planning and may seem like a big undertaking but it is a set of reasonably small steps that contribute to a large whole. If a woodlot seems like a good idea to you, start thinking about where you might do it and what kinds of trees you will use. A rule of thumb is that takes about 25 five to eight year old trees to fuel a typical enclosed wood-burner for a winter. Trees should be planted at between 2m and 4 m spacings depending on the soil and climate. You’ll need to figure out the details for your proposed site and there are many places you can find useful advice. Southern Woods (http://www.southernwoods.co.nz/ and look for information sheets) provide comprehensive advice and a wide range of species at good prices. A typical woodlot will contain 200 to 300 trees depending on how quickly they grow. At relatively close spacing this corresponds to an area of about 800 m² to 3200 m² for wider spaced and less promising sites. Quite a lot depends on how fertile your land is, whether it is well watered and how much sun it will get.

When choosing land for your woodlot, consider not only how well things might grow, but also how easy it is to get on to it. Remember that you will need to get at the trees to cut them down and to remove the firewood, and you’ll also need to do something with the slash from the harvest. It is easier to drag firewood down a steep slope than to try and haul it up. Vehicle access should be considered unless you plan to wheelbarrow your firewood to a collection point – something I don’t recommend.

One of the big questions is what kind of tree to plant. Most fuel woodlots are based on eucalypts or wattles, but alders, poplars and manuka or kanuka are also possible. There is a wide range of eucalypts that are suitable for firewood and many of them coppice after cutting. This means they regrow from the stump and the second harvest is usually quicker than the first as the existing root system leads to faster growth. Fast growing gums include E. nitens, E. delegatensis and  E. ovata that tolerate frosts, but there are many others that coppice and have other properties. Among these are flowers that attract bees and birds at various times of the year and which can be quite spectacular in their own right. Other trees also coppice: hazels, chestnuts and elms for example. These have a long history of use in the northern hemisphere, but are comparatively slow growing and you plant for succeeding generations.

Consider your site carefully before choosing what to plant. You can get a sense of how fertile the site is by what is growing there now. Gorse is not much fun to get rid of, but it does provide a rich soil (and old gorse makes good, if prickly, firewood). Dig some test holes to find out how deep the top soil is, how many rocks are going to make planting difficult, and what the underlying soil is like. You’ll also get an idea of how many grass grubs are present. These are common in the poor pastures typical of the hills in the Blueskin Bay area, but probably won’t be too much of a problem to fuel trees.

How wet is the site? Patches of buttercups suggest it is damp,  and rushes indicate it is wet. Is it exposed to wind or in a frost hollow? Is it shaded or sunny? All of these things will have an effect on the choices you make and growth of the trees

 There are frost-tolerant eucalypts that cope with sandy dry soils and others that thrive in swamps. Alders will grow almost anywhere (especially Alnus cordata) which can be used to remediate polluted sites and will fix nitrogen and improve soil fertility. Acacias don’t come in quite the same range of choices, but grow quickly and are pretty tough. Consider the eventual height of the trees, but keep in mind that if you cut these after only seven years, they won’t reach potential heights of 30 m or more. If you don’t get around to harvesting your trees, neighbours might not be happy to have 45 m eucalypts in their view – but by then it might not be your problem. Do consider your neighbours though: if your planned woodlot spoils their view or shades their house, expect some friction. It is worth thinking about fire too: a plantation very close to buildings might be a potential fire hazard, so isolating your woodlot is worth doing if practicable.

Since a woodlot is intended to produce a staggered harvest, it makes sense to plant 25 to 30 plants a year. This gives you the chance to experiment with species for your site. You could plant five species in each of the first few years to see what does well (and what does not). You might get a lower overall yield this way, but you reduce the risk of planting something that doesn’t do. You’ll also be able to assess how many trees you are likely to need depending on how fast they grow.

Doing a row a year spreads the work as planting even a single row of trees is a lot of effort. My experience is that preparing the holes over the early winter and leaving them to ‘age’ until the spring works well. I clear the grass from the row by mowing and use a post-hole digger to make a planting hole about 400 mm deep (depending on rocks) and return the spoil to the hole. This gives the new planting a chance to establish itself in loose soil. Each small tree can be easily put into the soft earth in the spring along with a fertiliser tablet and pressed down. Cerebos Greggs sell coffee and spice sacks very cheaply and these make excellent mulch for a couple of years. I cut a cross in the centre of a couple of sacks and put them over the plant. If the site is windy or you plan to mow around the trees, make some simple wire stakes to hold each corner of the sack and prevent it lifting or catching in the mower. Keep in mind that many eucalypts are shallow rooted and will establish better if they don’t have to compete with grasses and weeds.

You might also consider protecting new planting from rabbits and hares. You can buy cheap plastic sleeves which can be stretched over three bamboo sticks to provide protection. Eucalypts seem to be relatively uninteresting to rabbits but they will nibble on alders and some acacias. Hares have a nasty habit of pruning anything: the air may well turn blue when you discover your new plantings reduced to small segments lying on the ground. Tree protection may save both the tree and your blood pressure.

Most woodlot trees grow quickly but will benefit from weed and grass control for a couple of years in addition to the sack mulch. Options here include spraying with Roundup (for everything) or Gallant (for grass) or you can keep mowing around the trees (or sacks) every month or so over the summer. Organic weedkillers are available (fatty acid solutions for example) but I’ve not found them to be very effective. After a couple of years the trees will start to suppress the grass themselves but they may still benefit from clearing by spraying or by mowing once or twice a year.

Once established, a woodlot takes relatively little looking after. You may wish to prune the lower branches and reduce multi stemmed trees to just one trunk. Consider replacing any dead trees fairly early: if it is the odd tree it might be just bad luck, but if several of a species turn up their toes, try something else there.

Harvesting is a matter of choice. If you cut the trees while their trunks are small, you probably won’t have to split your firewood, but your yield will be less. If you plan to coppice, cut in late winter or early spring and leave at least a metre or so of trunk to allow for regrowth. Trees can be felled and left to lie with their branches and leaves attached to assist in drying out.This makes them harder to saw so an alternative is to cut them wet and let the firewood dry in a stack. Cutting produces a lot of slash in the form of small branches not suitable for firewood (although you might to use some for kindling) along with all the leaves. I typically chip the slash and use it as garden mulch (after composting). Big chippers can be hired and they will eat small trees. Smaller chippers work well too providing you are patient, keep the chipper blades sharp, and are not too optimistic about what you feed it.

Felling trees in a woodlot is typically much safer than trying to cut down large and unbalanced trees, but it is a potentially dangerous business all the same and you need the appropriate skills. Even a small trees can kill you or break a leg, and chain saws are not for the faint-hearted. Learn how to do this or find someone who will do it for you

Once cut, the single most important thing about firewood is drying it. Pine can take up to a year to dry and gum (and kanuka) much longer. Cut and split wood dries much faster than whole logs, and storing the wood out of the rain but where the wind and sun can get to it makes drying quicker. Cut it to a length that suits whatever you are going to burn it in. Wood split to fit through a 125 mm ring typically  dries faster and burns cleaner than large chunks.

What about the overall economics of this? Cutting your own firewood involves sweat equity: it depends on how you value your time as to whether it is worth doing. If you like working outside and enjoy getting dirty, and have access to some land then the equation might favour a woodlot. On the same basis, cutting established trees might also be worth it too. If none of this appeals to you, buy your firewood. Keep in mind that Consumer suggests that 4 m³ (about a season’s burning) cost between $320 for pine and $480 for gum. A row of 25 trees is typically about $90 to $100 and will probably yield about the same amount of wood after five to eight years, and you will have to factor in your time and the costs of planting and harvesting.

Overall, a woodlot is a sustainable and satisfying way of heating your house (and keeping you fit) while ensuring you have a sustainable heating fuel close to hand. If you have more space, you might consider selling firewood although I imagine it would be hard to make a living from firewood alone.

Finally, eucalyptus and acacia plantations are surprisingly attractive to birds. If you plant trees that flower and provide nectar you will most likely see a significant increase in the bird and insect life and most of us think this is a Good Thing.