The Sustainable Firewood Woodlot.

As the nights begin to cool many people start to focus on firewood, but for those of us living off the land and reliant on our wood burners this year’s wood should be in the shed and ready to burn. Leaving it till the cold sets in could leave us with smoky fires which struggle to warm the house or a hefty heating bill. Better still we aim to have at least two years’ worth of wood cut, with at least one years’ worth dry stored. The just in case factor. 

What trees are good firewood trees? 

Honestly, whatever you already have growing… 

The existing trees on your property are your first resource. I’m not saying go and cut them down, there are other, better, ways to get firewood. Look at pruning them, lifting branches, thinning if planted to close. If they are able to be coppiced learn how to do that and you will have renewable, sustainable firewood* But learn what your trees are and how best to manage them. Buying a property with trees is an amazing resource and removing trees should only be done if they are a risk or negatively impacting their surrounding environment. 

We believe that if you are going to plant trees, they should have many uses, multipurpose. The main uses would be edible crop producers, fodder and forage for livestock, timber or woodcraft sources.  

Fruit and nut trees can cover all three of these uses and are great firewood. Planting a large orchard and nut grove or including them in hedgerows, will eventually yield a decent supply of wood just from the pruning’s. 

Coppicing trees such as Alders, Birches, Hazels, Sweet Chestnuts, Poplars etc.* these provide a, usually, fast-growing renewable and sustainable resource for timber, nuts and fruits in some cases and livestock food as well as firewood.  

Fodder trees are well worth looking into if you have livestock, they are a great resource in times of drought but also provide diversity and added nutrition for your animals. If planted in areas where they are protected but next to or in paddocks, they can also provide shelter and shade. Two factors which are unfortunately often not provided for on many farms. An excellent small tree for fodder is Tree Lucerne (tagasaste) it is a high protein feed, drought hardy, fast growing and good firewood. Many of the fodder trees also fit in the fruit and nut category and can be coppiced. Mulberry is another high protein feed and if you can beat the birds has very tasty berries. It is also apparently, one of the top heat producing woods. 

Many people think gums when asked for firewood trees and they have their uses, but are not really for us. Having experienced the effects of root rot on a massive gum from our neighbours property, which took out our fence line but thankfully fell away from the house. They are also heavy feeders, sucking nutrient out of the surrounding soil, which can be mitigated by planting a nitrogen fixer/mineral accumulator such as Acacia. They are fast growers, but if not dealt with at a decent size they can get oversized and felling becomes an issue. As they age, they can also start dropping limbs which is a hazard for you and your livestock. We have a large gum at the end of our paddock which is now in this scary stage, with many broken limbs on the ground beneath it. If you are keen to grow the larger trees Acacia would be family to look at, they support the soil around them via their nitrogen fixer/mineral accumulator properties, are fast growing and make great firewood which is hot burning and easy to split. We especially like the Black wattle and Tasmanian Blackwood. But there are also Oaks, deciduous Beech and Maples, which can also be coppiced and are good firewood 

Finally, we will look at native trees, Manuka and Kanuka are great fast growing pioneer trees, they can be used with other small trees like Tree lucerne (not native), Mahoe, Kowhai and Pittosporums, to fill in the gaps while larger slower growing trees like NZ Beech and Totara are establishing, then felled for firewood etc. when no longer needed. Personally, we would not grow the slower natives for firewood, as it does not really fit into the sustainable woodland concept as they are generally not able to be coppiced. Only small number of native trees can be coppiced Mahoe, Pittosporums and Pohutukawa are among them. 

Harvesting and Drying your Firewood. 

‘Cut at low sap’ is some traditional advice, this would mean cutting your firewood in winter to early spring depending on the tree, while they are dormant. There are several reasons for this: 1. Traditional woodlots were also often Coppice Woodlands*. The trees were coppiced in winter for various timber uses and regrowth from the stumps occurred in spring.  

2. Tree sap ‘runs’ when they are actively growing, however there are differing views on how that effects the moisture content of the tree. One view is that apparently over summer they can contain up to 50% or half their weight in water. While they are dormant the sap supposedly flows to the roots, lowering the moisture content of the tree. The opposing view put out by forestry industry is that there is no real difference in seasonal moisture content and that trees in fact hold a relatively constant moisture content all year round. It is believed that cutting down a tree in sap run can actually speed up seasoning/drying time, due to the tree effectively ‘bleeding out’. 

3. Deciduous trees lose their leaves over low sap/dormancy and this can lower the weight of the tree and make clean up easier. However, if you are making full use of the tree, Ramial wood mulch can be made from the branches under 7 cm diameter, with or without the leaves. In full leaf there will obviously be a higher green matter content to the mulch and the fresher the branches the more nutrient available for the soil. 

4. Firewood can be hard and heavy work, cutting, moving and stacking firewood over the cooler months, which are often quieter farm wise, can be easier than doing it in the heat of summer. You have a higher appreciation of the results when you enter the warmth of the house after hours in the cold. 

There are of course other factors for timing of firewood cutting. Pruning done at any time is potential firewood or wood mulch and can be specific to what season suits each particular tree. Fruit trees are good example of this with stone fruit usually pruned in summer to avoid disease. Weather being another factor, in very wet climates the drier months might be the only time to get firewood done. But the general time frame would be cut wood in the winter or early spring, dry over summer and into the shed by March ready for those cooler nights. 

So, the trees are down or the branches are pruned, what now? 

The wood needs to be cut and split into sizes suitable for your woodstove, often we will just ring it into the right length and leave it in piles until we are ready to shift it. It is thought that by leaving the wood in the elements the rain will wash out the sap which keeps it green and speed up seasoning. However, most trees are best split fresh as they can harden over time and if you are hand splitting with an axe it is easier to split the wood fresh. We then stack the cut wood on pallets to keep the wood off the ground and allow airflow underneath. A tidy outer wall layer is stacked with attention put into stabilising or ‘locking in’ the corners with crossover pieces. It’s a bit like building a 3D jigsaw, most of the wood is either flat, triangular, half round or round and can be fitted together to make a stable structure. The gap in the centre is filled with the odd pieces, short bits and knobbly bits etc. These are put in randomly but the space needs to be filled as you stack the walls and be relatively close packed to support the walls. Air will still flow through as there will be many small gaps in the stack. Once the stack reaches about 1.2 metres we level it off and place several sheets of old corrugated iron on top, weighed down with some heavy chunks of wood.  

Why go to all this trouble you might ask?   Firstly, firewood is an extremely important resource for us, it not only heats our home, but all our hot water via wetback and we use our woodstove for cooking, we do have a gas stove but the gas is an outside expense and the wood is a homegrown sustainable resource. Secondly, the structure that is created is very stable and can be built in the paddock where the livestock are, the cow might occasionally try to knock it around a bit but the structure stays standing. The size of the stack, which is the width of a pallet and usually 3 or 4 metres long, means we can stack for drying a large quantity of wood, approximately 2 cord, in a relatively compact space. Most firewood stacking advice that I have seen says to single width stack, while this works, for us it would take up too much area, not be as stable in the paddock and be difficult to put a corrugated iron ‘roof’ on. 

The corrugated iron provides a heat sink which warms and dries the air inside the pile, while keeping the majority of rain off. Yet the outside of the stack is still exposed to the elements especially wind and sun. We find the stacked wood is ready to be transferred to shed storage in about 3 to 4 months, it will be bone dry and excellent burning. Bone dry wood burns hotter, longer and, when the fire is shut down, turns to charcoal which creates a low burn to last through the night. Once shed stored it should stay dry, but it pays to check the roof for leaks and have a shed that is North or North West facing for maximum sun and that allows air flow. A simple cheap design is a corrugated iron roof on four poles/posts 2m or taller. Cover the floor with pallets to let the air flow under and keep the wood off the damp cold ground. Hurricane netting can be used around the outside ‘walls’ to hold the wood in but still allow air flow and if necessary, a wall can be built on the prevailing rain side or to the south, as long as the sun side is left open. Any wood on the outer edges that gets rain wet will soon dry on a sunny day as long as it was seasoned/dried before going in the shed. The 1000l pod cages (without the plastic tank) or the big wooden produce bins can be used, but make sure to cover the top with corrugated iron or something to keep the top rain out. 

Burning wet or unseasoned firewood firstly produces less heat and secondly can cause creosote buildup in your flue, especially with softwoods, which can cause chimney fires. A good example of this is when we first moved into our property in the winter. The note from the previous owner said we would need to clean the flue every month to keep the fire burning well and that the drier wood was in the rear of the middle bay, which involved climbing over wood to get to it… We thought what the hell, well used to wood fires, it should only be cleaned once a year and why would I want to climb over wood to get the firewood. But once the stack of wood by the back door was gone, we realised the issue. The whole three farm shed bays of firewood, which was pine, had been wet stacked. It was moldy and damp. This was causing excessive smoking and clogging of the flue, and we wondered about the health impacts of burning moldy wood. Luckily after a few days of wet weather it cleared for a couple of weeks and we pulled out the front of one stack to open more wood up to the sunshine and air. Each time we went to get firewood it had to be checked for dryer pieces, while still not bone dry it was a lot dryer than before. As the wood dried out the smoking and flue issues eased as well. Our primary wood shed is about 100 metres from the house, this is not ideal and we will build one closer. It is a good idea to have at least a weeks’ worth of wood close to the house in the event of bad weather. Trudging across a paddock in the rain with a wheelbarrow load of firewood is not cool for you or the wood. 

There are many views on firewood and systems to manage it, but this suits us and provides us with loads of well-seasoned firewood throughout the year. By planning a sustainable woodland or large multipurpose orchard and nut grove, we can provide ourselves not only with firewood but food, livestock food, garden mulch and stakes, fencing materials, timber and a beautiful landscape. 

*https://fodderfarm.co.nz/2021/04/18/coppiced-woodlands/