Bonfires - by Edward Eastwood
Part 1. Whether and where to have them
Part 2. How to ignite them and keep them going
Part 3. What to do when you have finished your bonfire
Part 1. Whether and where to have them
Bonfires are fun. Most people enjoy them. We certainly use them in our Pinetum but they are not to be treated lightly. There are some undoubted ‘downsides’ to their use, and they also constitute certain risks to both habitats and humans. Let me start by considering some of the ‘no no’ aspects of bonfires.
In a garden, and that applies to our Pinetum too, they are commonly used to get rid of waste material after a session of pruning, weeding, leaf and twig collection etc. One must remember though that tidiness is no part of the natural world. Untidiness makes for all sorts of ecological niches for a stunning variety of different organisms; places for them to hide and to find shelter and food. All gardens, if possible, should have wild areas. We are certainly going to keep some ourselves. For instance we are leaving wild strips between our various compartments both to delimit them, making the Pinetum into a series of ‘rooms’, as the Victorians/Edwardians did, and to make for a better balance of nature.
So, no over zealous tidying, but what does one do with the collected material? It can be composted or burnt. Both processes are as bad as each other in that they produce the greenhouse gas carbon dioxide. Burning produces its share quicker than composting, but by putting the ash back on the plants they then receive the nutritive benefits quicker. Composting, by contrast, produces more methane which is about 20 times worse as a greenhouse gas. Also one must not forget that incompletely rotted compost returned to flower beds may even impoverish the soil, at least for a while, because the micro-organisms that continue the rotting process will take nutrients from the soil for themselves. Finally in favour of composting, it obviously improves soil structure better than mere ash and does provide food for many soil invertebrates. Such creatures called saprophytes cannot eat the pure chemicals in ash.
Are there any other specific factors that have helped us decide about bonfires within the Pinetum? Yes there are. One of them concerns the heat beneath a bonfire which kills the roots of the surrounding trees. Tree roots are not always restricted underground to the area represented by their overhanging foliage. We found the roots of one of our Giant Redwoods at a radial distance from its trunk that represented a root coverage of nigh on an acre! Our solution to this is to have only a limited number of bonfires and to site them in the middle of large clearings. In one instance, we chose a site where vandals had had a whopper of their own anyway. It does mean that we all moan about how far we have to carry material to be burnt. Of course one would have to drag compost similar distances unless there was a compost heap round every corner.
A further reason for limiting the number of our bonfire sites is the nature of various parasitic fungi. Rhizina undulata, the Tea Break fungus, which we fortunately don’t appear to have in our Pinetum, is a good example. It is so called because woodsmen used to light small fires repeatedly to heat up water for a 'cuppa'. Bonfire ash triggers the spores of the Tea Break fungus, also called the Cow Pat fungus after the shape of the resulting fruiting body, and the fungus then spreads underground to its preferred tree hosts - conifers!
Some management teams use a flatbed trailer on which to have their bonfires. The folk at Kew Gardens, for example, occasionally use this technique. It obviously makes for easier removal of the ash afterwards, and avoids the spread of harmful fungi besides reducing the heating effect on life in the soil.
We have another ecological concern, namely, that we are not really interested in using either compost or bonfire ash on our trees. (The only exceptions to this are the ashes of humans and their pets -- cremated elsewhere, you understand).
Fertilising trees certainly makes them grow better but it also encourages their parasites disproportionately well, enabling them to get the upper hand. Over-fertilizing of many young trees also makes for a ‘whippy’ growth of their leading shoots. Staking then becomes a long-term necessity. Our Pinetum is correctly described as Botanic. That is to say, we leave the trees ‘to do their own thing’. We do not use any fertilisers or pesticide. We get a more informed view that way, of how well or otherwise the conifers are adapted to our circumstances. The first formal arboretum, which was in France, was a tree-trial site, which we are trying to imitate, and not a mere fanciful collection, as so many are these days.
We use our surplus compost, once it has rotted, and our bonfire ash to put on our hedges, especially those recently planted. If only they would hurry up, and grow even faster to give us a secure boundary!
Why have compost heaps at all, you may well ask? Sometimes the material is too wet to burn. Leaves and grass cutting dampen down bonfires and make them smoke. Among the conifers, firs are particularly susceptible to smoke. In many pineta it was only the Algerian Fir, the Japanese Nikko Fir and the Grand Fir that survived that smoky period of the 1950s and 60s. When in the early 90s we began exploring our own Pinetum, sure enough, only these three species were left.
We regard our compost heaps, as we do the odd stacks of logs around the place, as wildlife reserves. Newts, slow worms and grass snakes are known to live in ours. I shall continue next time by considering hedgehogs and bonfires.
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In a garden, and that applies to our Pinetum too, they are commonly used to get rid of waste material after a session of pruning, weeding, leaf and twig collection etc. One must remember though that tidiness is no part of the natural world. Untidiness makes for all sorts of ecological niches for a stunning variety of different organisms; places for them to hide and to find shelter and food. All gardens, if possible, should have wild areas. We are certainly going to keep some ourselves. For instance we are leaving wild strips between our various compartments both to delimit them, making the Pinetum into a series of ‘rooms’, as the Victorians/Edwardians did, and to make for a better balance of nature.
So, no over zealous tidying, but what does one do with the collected material? It can be composted or burnt. Both processes are as bad as each other in that they produce the greenhouse gas carbon dioxide. Burning produces its share quicker than composting, but by putting the ash back on the plants they then receive the nutritive benefits quicker. Composting, by contrast, produces more methane which is about 20 times worse as a greenhouse gas. Also one must not forget that incompletely rotted compost returned to flower beds may even impoverish the soil, at least for a while, because the micro-organisms that continue the rotting process will take nutrients from the soil for themselves. Finally in favour of composting, it obviously improves soil structure better than mere ash and does provide food for many soil invertebrates. Such creatures called saprophytes cannot eat the pure chemicals in ash.
Are there any other specific factors that have helped us decide about bonfires within the Pinetum? Yes there are. One of them concerns the heat beneath a bonfire which kills the roots of the surrounding trees. Tree roots are not always restricted underground to the area represented by their overhanging foliage. We found the roots of one of our Giant Redwoods at a radial distance from its trunk that represented a root coverage of nigh on an acre! Our solution to this is to have only a limited number of bonfires and to site them in the middle of large clearings. In one instance, we chose a site where vandals had had a whopper of their own anyway. It does mean that we all moan about how far we have to carry material to be burnt. Of course one would have to drag compost similar distances unless there was a compost heap round every corner.
A further reason for limiting the number of our bonfire sites is the nature of various parasitic fungi. Rhizina undulata, the Tea Break fungus, which we fortunately don’t appear to have in our Pinetum, is a good example. It is so called because woodsmen used to light small fires repeatedly to heat up water for a 'cuppa'. Bonfire ash triggers the spores of the Tea Break fungus, also called the Cow Pat fungus after the shape of the resulting fruiting body, and the fungus then spreads underground to its preferred tree hosts - conifers!
Some management teams use a flatbed trailer on which to have their bonfires. The folk at Kew Gardens, for example, occasionally use this technique. It obviously makes for easier removal of the ash afterwards, and avoids the spread of harmful fungi besides reducing the heating effect on life in the soil.
We have another ecological concern, namely, that we are not really interested in using either compost or bonfire ash on our trees. (The only exceptions to this are the ashes of humans and their pets -- cremated elsewhere, you understand).
Fertilising trees certainly makes them grow better but it also encourages their parasites disproportionately well, enabling them to get the upper hand. Over-fertilizing of many young trees also makes for a ‘whippy’ growth of their leading shoots. Staking then becomes a long-term necessity. Our Pinetum is correctly described as Botanic. That is to say, we leave the trees ‘to do their own thing’. We do not use any fertilisers or pesticide. We get a more informed view that way, of how well or otherwise the conifers are adapted to our circumstances. The first formal arboretum, which was in France, was a tree-trial site, which we are trying to imitate, and not a mere fanciful collection, as so many are these days.
We use our surplus compost, once it has rotted, and our bonfire ash to put on our hedges, especially those recently planted. If only they would hurry up, and grow even faster to give us a secure boundary!
Why have compost heaps at all, you may well ask? Sometimes the material is too wet to burn. Leaves and grass cutting dampen down bonfires and make them smoke. Among the conifers, firs are particularly susceptible to smoke. In many pineta it was only the Algerian Fir, the Japanese Nikko Fir and the Grand Fir that survived that smoky period of the 1950s and 60s. When in the early 90s we began exploring our own Pinetum, sure enough, only these three species were left.
We regard our compost heaps, as we do the odd stacks of logs around the place, as wildlife reserves. Newts, slow worms and grass snakes are known to live in ours. I shall continue next time by considering hedgehogs and bonfires.
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There must be as many ways of lighting a bonfire and keeping it stoked, as there are ways of “killing a cat”! There isn’t really one right way of doing it, but needless to say there are many matters to consider before getting started: so let’s discuss some of them here.
Once a bonfire has been decided upon, there is the immediate question as whether or not to collect the material for it before beginning. If one has plenty of space for a fire, as we do in the Pinetum, then it is probably a good idea to allow a pile to accumulate before lighting it, but if the fire is to be in a confined space, then take care. Bonfires are often difficult to start but sometimes they are not, and too big a pile of collected material may go up with an alarming ‘whoosh’ causing neighbouring damage and perhaps injury.
Let’s suppose for a moment that the material is to be collected in advance. As soon as it starts to accumulate, a variety of wild life will see it as an opportunity to move in: hedgehogs, grass snakes, mice, bumble bees, pet tortoises etc. Who comes will depend on who is around and the time of year but one must be careful in fetching a match to the pile. Trespassing vandals too, in our circumstance, will see the pile as a good site for their Guy Fawkes partying or as a useful job lot for stealing. The longer that piles are left, the more assuredly that wild life and trespassers will get to know of their existence.
One of the commonest mistakes in collecting material in advance is the practice of piling it up exactly where you intend to have the fire. The pile then has to be moved aside so that you can get your kindling underneath and then moved back again as the fire gets going. ‘DOUBLE LIFTING’! One often sees folk try to solve this problem by starting the fire beyond the edge of the pile so, over time, increasing the amount of burnt ground, OR - and this is much worse - delving into the edge of the pile to start the fire believing that they can slowly move the rest of the material across before it is too hot to get anywhere close enough. Then, as they escape from the heat, the whole pile is ablaze in no time. The heat of a fire alone and not just the flames can damage nearby log piles or trees.
The opposite common problem with pre-collected heaps is that they can become wet, soggy, tangled and even congealed with rain.
So what would I recommend? By all means bring the material to the site in advance and, if there is room, leave it around the site a short distance from the intended burn. Leave branches staked radially with their thick ends pointing inwards. It is very difficult to extricate branches to stoke a bonfire if they are stacked higgledy-piggledy. Also, if the piles are less compacted by being spread around, they will dry out quickly after rain.
In many instances, a bonfire will be partly pre-collected and then further collected once alight. This saves another ‘double lift’ because the material to be burnt can be thrown on directly.
Now to actually light the fire; and again there are as many methods as arsonists. I am not a purist taking on the one match challenge but by all means try this if you would derive satisfaction. One must remember that fires can be started by shards of broken bottles, by carelessly discarded cigarette butts and by lightning. We lost one of our special rare gift trees from Edinburgh by lightning which struck a larch, came down the outside of the trunk and jumped to the wire netting around the nearby sapling! The larch survived, the sapling is no more.
I like these gas blowlamps with their press button ignition. One must remember however to remove the lamp if left in place, once the fire is well and truly lit. Why do I mention such an obvious point? I wonder why!
It is obviously easier to light the fire in dry and slightly windy conditions. The actual nucleus of the kindling should be positioned up wind of the bonfire site as otherwise the wind will extend the site during the burn.
One hesitates to mention that a variety of fungi make good kindling. In the interests of conservation they should only be used in a Ray Mears type of situation.
The first heap of kindling, six to twelve Inches high, must be as dry as possible and it is fairly immaterial as to the orientation of the components. Some folk like to build the kindling between two small ‘loglettes’ to improve the airflow. Others like to make a wigwam of their kindling. That’s all grand but as additional twigs and branches are added they should all be lying in the same direction. This ensures a good ‘heart’ to the fire. One must avoid the fire developing a hollow heart which actually goes out under the overlying material.
To get the fire going it may well be necessary to cut up material with secateurs or loppers but once the fire is burning well, stop doing that and put the branches on the fire complete. You will save yourself unnecessary work.
We need to add a note or two here about the safety aspects of throwing material on a bonfire. For one thing, don’t throw yourself on the fire! This is not as silly as it sounds. It is easy to lose one’s footing by misjudging the lack of recoil, tripping over ground hazards or entangling your contribution to the fire with that of someone else contributing at the same moment. We have met all these, fortunately without incident. Bonfire sites are on slopes need extra caution. Take care too not to over throw material, so as to compromise workers on the other side.
Don’t operate on the down-wind side of a burning heap and warn others away too. Heat, smoke and flying embers are dangerous and could damage one’s health. Take care of your hair, and avoid operating in fluffy fleece jackets and hats. Brushwood, thrown on an open fire, sends up showers of burning ash. Keep out of range and think of others whether they are merely watching or about to pile on material themselves. Large accumulations of some materials, for example laurel, can be associated with poisonous fumes. Heat and various volatiles have been known to damage the coatings on spectacle lenses. Finally avoid damaging neighbouring trees and starting fires in the undergrowth.
Bonfires are wild things. Provided you are safely in control though, the only extra you will need is a fork of some kind with which occasionally to push in stray burning embers and on which to lean, enjoying the mystique of fire as it returns the complexity of life to the entropy of ash.
Return to the top of the page
Once a bonfire has been decided upon, there is the immediate question as whether or not to collect the material for it before beginning. If one has plenty of space for a fire, as we do in the Pinetum, then it is probably a good idea to allow a pile to accumulate before lighting it, but if the fire is to be in a confined space, then take care. Bonfires are often difficult to start but sometimes they are not, and too big a pile of collected material may go up with an alarming ‘whoosh’ causing neighbouring damage and perhaps injury.
Let’s suppose for a moment that the material is to be collected in advance. As soon as it starts to accumulate, a variety of wild life will see it as an opportunity to move in: hedgehogs, grass snakes, mice, bumble bees, pet tortoises etc. Who comes will depend on who is around and the time of year but one must be careful in fetching a match to the pile. Trespassing vandals too, in our circumstance, will see the pile as a good site for their Guy Fawkes partying or as a useful job lot for stealing. The longer that piles are left, the more assuredly that wild life and trespassers will get to know of their existence.
One of the commonest mistakes in collecting material in advance is the practice of piling it up exactly where you intend to have the fire. The pile then has to be moved aside so that you can get your kindling underneath and then moved back again as the fire gets going. ‘DOUBLE LIFTING’! One often sees folk try to solve this problem by starting the fire beyond the edge of the pile so, over time, increasing the amount of burnt ground, OR - and this is much worse - delving into the edge of the pile to start the fire believing that they can slowly move the rest of the material across before it is too hot to get anywhere close enough. Then, as they escape from the heat, the whole pile is ablaze in no time. The heat of a fire alone and not just the flames can damage nearby log piles or trees.
The opposite common problem with pre-collected heaps is that they can become wet, soggy, tangled and even congealed with rain.
So what would I recommend? By all means bring the material to the site in advance and, if there is room, leave it around the site a short distance from the intended burn. Leave branches staked radially with their thick ends pointing inwards. It is very difficult to extricate branches to stoke a bonfire if they are stacked higgledy-piggledy. Also, if the piles are less compacted by being spread around, they will dry out quickly after rain.
In many instances, a bonfire will be partly pre-collected and then further collected once alight. This saves another ‘double lift’ because the material to be burnt can be thrown on directly.
Now to actually light the fire; and again there are as many methods as arsonists. I am not a purist taking on the one match challenge but by all means try this if you would derive satisfaction. One must remember that fires can be started by shards of broken bottles, by carelessly discarded cigarette butts and by lightning. We lost one of our special rare gift trees from Edinburgh by lightning which struck a larch, came down the outside of the trunk and jumped to the wire netting around the nearby sapling! The larch survived, the sapling is no more.
I like these gas blowlamps with their press button ignition. One must remember however to remove the lamp if left in place, once the fire is well and truly lit. Why do I mention such an obvious point? I wonder why!
It is obviously easier to light the fire in dry and slightly windy conditions. The actual nucleus of the kindling should be positioned up wind of the bonfire site as otherwise the wind will extend the site during the burn.
One hesitates to mention that a variety of fungi make good kindling. In the interests of conservation they should only be used in a Ray Mears type of situation.
The first heap of kindling, six to twelve Inches high, must be as dry as possible and it is fairly immaterial as to the orientation of the components. Some folk like to build the kindling between two small ‘loglettes’ to improve the airflow. Others like to make a wigwam of their kindling. That’s all grand but as additional twigs and branches are added they should all be lying in the same direction. This ensures a good ‘heart’ to the fire. One must avoid the fire developing a hollow heart which actually goes out under the overlying material.
To get the fire going it may well be necessary to cut up material with secateurs or loppers but once the fire is burning well, stop doing that and put the branches on the fire complete. You will save yourself unnecessary work.
We need to add a note or two here about the safety aspects of throwing material on a bonfire. For one thing, don’t throw yourself on the fire! This is not as silly as it sounds. It is easy to lose one’s footing by misjudging the lack of recoil, tripping over ground hazards or entangling your contribution to the fire with that of someone else contributing at the same moment. We have met all these, fortunately without incident. Bonfire sites are on slopes need extra caution. Take care too not to over throw material, so as to compromise workers on the other side.
Don’t operate on the down-wind side of a burning heap and warn others away too. Heat, smoke and flying embers are dangerous and could damage one’s health. Take care of your hair, and avoid operating in fluffy fleece jackets and hats. Brushwood, thrown on an open fire, sends up showers of burning ash. Keep out of range and think of others whether they are merely watching or about to pile on material themselves. Large accumulations of some materials, for example laurel, can be associated with poisonous fumes. Heat and various volatiles have been known to damage the coatings on spectacle lenses. Finally avoid damaging neighbouring trees and starting fires in the undergrowth.
Bonfires are wild things. Provided you are safely in control though, the only extra you will need is a fork of some kind with which occasionally to push in stray burning embers and on which to lean, enjoying the mystique of fire as it returns the complexity of life to the entropy of ash.
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This is the third of my contributions on the subject of bonfires. The first considered whether and where to have them, the second discussed how to ignite them and keep them going.
We come now to the end of the story. Our bonfire is dying down and it’s nearly time to go home. Is it safe to walk away? Well, when we began our restoration of the Pinetum, the answer was “Certainly not”. There was so much leaf litter, so many fallen tree trunks and pieces of lesser-sized rotting timber lying around, most of it highly inflammable resinous material, that we had to be careful that our bonfires did not spread. This was true whilst our bonfires raged but it was all the more important at the end of the day, in our absence, when only the dying embers of a fire remained. It is much safer now at our designated bonfire sites but in those early days we never left a fire without at least soaking it and the ground around with water.
On one occasion we returned to a bonfire site next morning to discover that the rotten interior of a large log, albeit five foot away, must have started smoldering unnoticed in the intense heat of the previous day. This had then travelled along inside the 24-foot rotten trunk, to re-emerge at the other end starting a new fire in the undergrowth; a new fire with flames at a total of 29 feet away! On another occasion some trespassers had had a small campfire which began to spread. One of our Friends, out walking, called the fire brigade (many thanks), and the firemen had to dowse and dig over a roughly circular patch, about 25 paces across, before successfully putting out the fire. One must watch fires where there is undergrowth or, more especially, accumulated leaf litter. There are, by the way, six fire beaters in the hut and when we have finally installed our ram pump with its storage tank there will be an additional supply of water for the fire brigade. Large fire engines cannot get up the hill beside the Pinetum and so have sometimes had to pump their water to a smaller vehicle that can get up and it, in turn, pumps this water along the top contour to where it is needed.
All this ‘leaf litter’, as it is collectively called, may pose risks but it makes excellent tinder with which to start a fire. I suppose, because we have never had any difficulties starting our bonfires, I did not say much about tinder in my first article.
Many of us will have heard of The Ice Man, Ötzi, Europe's oldest (5000 years) natural human mummy found in September 1991 preserved in the snow and ice on the border between Austria and Italy. One of the interesting points about this character is that he was carrying tinder in the form of pieces of the bracket fungus Fomes fomentarius (commonly known as the tinder fungus, hoof fungus, tinder conk, tinder polypore or now of course, ice man fungus). Fragments of the mineral pyrites were found on his tinder fungus, so it is supposed that Ötzi struck pyrites with a flint to spark his tinder; an early example of a Ray Mears method of starting a fire.
Some of the worst natural fires occur in coniferous forests. The reason for this is that the leaf litter and larger twig and branch material decomposes only slowly in this rather acidic environment and thus accumulates, to constitute a good base to keep fires burning. The rising air above an initial fire causes oxygen to be drawn in in ever increasing up draughts. Eventually, as the heat intensifies and the flames reach the topmost branches, there is an explosion hurling burning material considerable distances thus progressing the fire in leaps and bounds. Fire wardens say of such an event that the fire has ‘crowned’ and to approach it at all closely is very dangerous.
Fires in grasslands, on the other hand, have soon burnt what little ground material there is and thus move on before doing much damage to the topmost tree branches. There is no lingering ground fire to maintain huge infernos.
Many conifers, and indeed hardwoods too, have adaptations to minimise the damage caused by fires. Their bark for example is often thick as a kind of thermal insulation and if the tree has a scaly bark, then should the bark begin to burn, its scaly flakes are spat away like little bits of sizzling bacon. Further, many conifers that grow in fire risk areas also deliberately lose their lower branches at an early stage so denying a fire the ladder by which it may reach the crown.
What can you do with the ash once the fire has burnt through? To start with there are several nutrients in bonfire ash. Calcium is the most abundant at approx 20%. So, wood ash is useful for increasing soil pH, making it more alkaline. One would not want to use it therefore on acid loving trees, as in our Pinetum. Nor is it helpful on acid loving plants and shrubs like azaleas, most rhododendrons, gardenias, and blueberries. Wood ash however is a fine ‘soil sweetener’ or liming material. Its use is recommended at 34-68 grams per square metre. Considering the other nutrients in wood ash, one finds it to be a “low grade” fertilizer with a N-P-K ratio (Nitrogen - Phosphorus - Potassium) of about 0-1-3. Potassium (K), is especially needed by carrots, cabbages, celery, corn, tomatoes and potatoes, but beware in the last case as excess potassium can encourage scab in potatoes.
Twig ash content 15% potash
Heartwood ash content <4% potash less in conifers than hardwoods
There is more potash in branches and twigs (sneddings) than in the trunk of a tree because that is where the tree stores and uses it.
Bracken ash has plenty 50% potash
Wood ash is also an excellent source of many trace elements that plants need to thrive.
We use our bonfire ash only on the Pinetum hedges and certainly not on the trees. Apart from the undesirable liming effect of ash, there is another reason to be careful. If one fertises a tree it grows better but so do the bugs that live on it, and it seems that the bugs grow better than the trees! See potatoes above.
The words ‘Potash’ and thus ‘Potassium’ are derived from the fact that ash was originally soaked in a pot before being used as a fertiliser or to extract this element. The word ‘potash is now a widely used term for any potassium compound, whatever its origin. It no longer solely means the potassium in wood ash to most people. It can mean potassium sulphate (K2SO4), potassium chloride (KCl), potassium nitrate (KNO3), potassium hydroxide (KOH), or potassium oxide (K2O). People cling to ‘potash’ (the ‘potassium in ash’) because it is the term used in the manufacture of fertilizers. And fertilizers are far and away the most important use of potassium rich compounds today.
Bonfire ash can also be used as a fungicide sprinkled on dahlia tubers when storing them over winter. The yellow powder, called ‘Flowers of Sulphur‘, was the substance of choice in the past but it is no longer legal as a fungicide. The ash from an indoor burner that has had some coal on it would be even better.
Let me conclude by commenting that wood ash also has a long history of being used in ceramic glazes, particularly in the Chinese, Japanese and Korean traditions, and now of course, it is used by many craft potters. It acts as a flux, reducing the melting point of glazes, and some ashes can add particular colours.
Edward Eastwood
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We come now to the end of the story. Our bonfire is dying down and it’s nearly time to go home. Is it safe to walk away? Well, when we began our restoration of the Pinetum, the answer was “Certainly not”. There was so much leaf litter, so many fallen tree trunks and pieces of lesser-sized rotting timber lying around, most of it highly inflammable resinous material, that we had to be careful that our bonfires did not spread. This was true whilst our bonfires raged but it was all the more important at the end of the day, in our absence, when only the dying embers of a fire remained. It is much safer now at our designated bonfire sites but in those early days we never left a fire without at least soaking it and the ground around with water.
On one occasion we returned to a bonfire site next morning to discover that the rotten interior of a large log, albeit five foot away, must have started smoldering unnoticed in the intense heat of the previous day. This had then travelled along inside the 24-foot rotten trunk, to re-emerge at the other end starting a new fire in the undergrowth; a new fire with flames at a total of 29 feet away! On another occasion some trespassers had had a small campfire which began to spread. One of our Friends, out walking, called the fire brigade (many thanks), and the firemen had to dowse and dig over a roughly circular patch, about 25 paces across, before successfully putting out the fire. One must watch fires where there is undergrowth or, more especially, accumulated leaf litter. There are, by the way, six fire beaters in the hut and when we have finally installed our ram pump with its storage tank there will be an additional supply of water for the fire brigade. Large fire engines cannot get up the hill beside the Pinetum and so have sometimes had to pump their water to a smaller vehicle that can get up and it, in turn, pumps this water along the top contour to where it is needed.
All this ‘leaf litter’, as it is collectively called, may pose risks but it makes excellent tinder with which to start a fire. I suppose, because we have never had any difficulties starting our bonfires, I did not say much about tinder in my first article.
Many of us will have heard of The Ice Man, Ötzi, Europe's oldest (5000 years) natural human mummy found in September 1991 preserved in the snow and ice on the border between Austria and Italy. One of the interesting points about this character is that he was carrying tinder in the form of pieces of the bracket fungus Fomes fomentarius (commonly known as the tinder fungus, hoof fungus, tinder conk, tinder polypore or now of course, ice man fungus). Fragments of the mineral pyrites were found on his tinder fungus, so it is supposed that Ötzi struck pyrites with a flint to spark his tinder; an early example of a Ray Mears method of starting a fire.
Some of the worst natural fires occur in coniferous forests. The reason for this is that the leaf litter and larger twig and branch material decomposes only slowly in this rather acidic environment and thus accumulates, to constitute a good base to keep fires burning. The rising air above an initial fire causes oxygen to be drawn in in ever increasing up draughts. Eventually, as the heat intensifies and the flames reach the topmost branches, there is an explosion hurling burning material considerable distances thus progressing the fire in leaps and bounds. Fire wardens say of such an event that the fire has ‘crowned’ and to approach it at all closely is very dangerous.
Fires in grasslands, on the other hand, have soon burnt what little ground material there is and thus move on before doing much damage to the topmost tree branches. There is no lingering ground fire to maintain huge infernos.
Many conifers, and indeed hardwoods too, have adaptations to minimise the damage caused by fires. Their bark for example is often thick as a kind of thermal insulation and if the tree has a scaly bark, then should the bark begin to burn, its scaly flakes are spat away like little bits of sizzling bacon. Further, many conifers that grow in fire risk areas also deliberately lose their lower branches at an early stage so denying a fire the ladder by which it may reach the crown.
What can you do with the ash once the fire has burnt through? To start with there are several nutrients in bonfire ash. Calcium is the most abundant at approx 20%. So, wood ash is useful for increasing soil pH, making it more alkaline. One would not want to use it therefore on acid loving trees, as in our Pinetum. Nor is it helpful on acid loving plants and shrubs like azaleas, most rhododendrons, gardenias, and blueberries. Wood ash however is a fine ‘soil sweetener’ or liming material. Its use is recommended at 34-68 grams per square metre. Considering the other nutrients in wood ash, one finds it to be a “low grade” fertilizer with a N-P-K ratio (Nitrogen - Phosphorus - Potassium) of about 0-1-3. Potassium (K), is especially needed by carrots, cabbages, celery, corn, tomatoes and potatoes, but beware in the last case as excess potassium can encourage scab in potatoes.
Twig ash content 15% potash
Heartwood ash content <4% potash less in conifers than hardwoods
There is more potash in branches and twigs (sneddings) than in the trunk of a tree because that is where the tree stores and uses it.
Bracken ash has plenty 50% potash
Wood ash is also an excellent source of many trace elements that plants need to thrive.
We use our bonfire ash only on the Pinetum hedges and certainly not on the trees. Apart from the undesirable liming effect of ash, there is another reason to be careful. If one fertises a tree it grows better but so do the bugs that live on it, and it seems that the bugs grow better than the trees! See potatoes above.
The words ‘Potash’ and thus ‘Potassium’ are derived from the fact that ash was originally soaked in a pot before being used as a fertiliser or to extract this element. The word ‘potash is now a widely used term for any potassium compound, whatever its origin. It no longer solely means the potassium in wood ash to most people. It can mean potassium sulphate (K2SO4), potassium chloride (KCl), potassium nitrate (KNO3), potassium hydroxide (KOH), or potassium oxide (K2O). People cling to ‘potash’ (the ‘potassium in ash’) because it is the term used in the manufacture of fertilizers. And fertilizers are far and away the most important use of potassium rich compounds today.
Bonfire ash can also be used as a fungicide sprinkled on dahlia tubers when storing them over winter. The yellow powder, called ‘Flowers of Sulphur‘, was the substance of choice in the past but it is no longer legal as a fungicide. The ash from an indoor burner that has had some coal on it would be even better.
Let me conclude by commenting that wood ash also has a long history of being used in ceramic glazes, particularly in the Chinese, Japanese and Korean traditions, and now of course, it is used by many craft potters. It acts as a flux, reducing the melting point of glazes, and some ashes can add particular colours.
Edward Eastwood
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