What should be in your bonsai soil?

WHAT SHOULD BE IN YOUR

BONSAI SOIL?

Bio-Activity and Bonsai Growing Media.

Having been immersed in my own little world of growing bonsai for so long now I have picked up a few things. Some of those things could be described as newfangled, revolutionary or even cutting edge. However the modernization of many bonsai cultivation techniques is long overdue. The existing tome of ‘wisdom’ is so firmly rooted in ancient history that any new idea, no matter how simple, can be construed by some folk as incendiary. When you spend your time entirely immersed in something, as I have, it’s inevitable that you learn a few things. The more things you learn the more you see and the more you see the more you begin to realize what is…..

1.wrong with what we currently do and….

2.what we SHOULD be able to achieve.

The word KAIZEN is a Japanese word that, in it’s simplest form

means ‘continual gradual improvement’. The primary connotation

being that the way we are currently working is the worst solution. By

applying a modicum of common sense and expending a little effort

we can make considerable advancement in our technique and the

results it produces. As an example, starting a car engine with a crank

handle was all very well but it did offer a few disadvantages. For it’s

time it made sense but only a Luddite would choose it over a modern

starter motor. Keeping warm around an open fire, burning in the

middle of your living room, was the norm way back before some

bright spark invented the chimney and the anti-smoking movement

came into existence. Change is the only constant in life unless you

practice bonsai where the norm is to not change anything. ‘If it ain’t

broke’, the oft’ repeated mantra of the unindustrious, bone idle and

somnolent seems to apply here. However in my experience it IS

‘broke’. I just cannot comprehend why anyone would want to spend

years doing something like bonsai and be perfectly content with

skuzzy half-arsed results, especially when there are dummies like

me out there who are prepared to share all we know for free. There

really in no need to reinvent the wheel we just need to put a tyre on

it!

As I said at the beginning, putting together a new idea is a process with a circuitous path. I tend to get a feeling that something is going on upstairs, often long before I see anything. It’s not unlike getting a teenager out of bed, even though you know there is life up there you have absolutely no evidence to support the notion. I have always found that once I become aware my old grey matter is cooking something up it’s not normally very long before it hits the table. This event can be triggered by the strangest of events. Two things happened recently that caused an avalanche of information my mind had been cogitating for a long time. The first was a discussion with a customer about fruit flies and the other was a gift of wild mushrooms from one of our delivery drivers. Later I was having a discussion about soil selection and, not unlike a Monty Python sketch a fully formed conception dropped at my feet. In order to flesh out some of the details I decided to write it down as best I can so here goes……..

Conventional wisdom states that bonsai trees should be planted in sterile soil. The reason being that using sterile soil will prevent the ingress of pest and disease (P&D). Not an unreasonable idea. The notion, as so many other things in bonsai cultivation, has come from mainstream horticulture. A sterile growing medium has a few uses in horticulture such as seed germination, striking of cuttings and a few other technically demanding activities. However the practicalities of sterilizing large volumes of growing media make use of such a product an expensive proposition. Modern composting can sterilize soil as bacterial activity can generate high temperatures. The primary benefit however is the destruction of weed seeds. Garden centre’s do not want to spend lots of time weeding pots. However if you were paying attention you noticed that it was the bacterial action within composted material that generates heat, therefore the soil is not entirely sterile.

The growing media we use in bonsai cultivation however is not, as a rule, soil. We use a variety of natural and manufactured aggregates and organic products like chipped bark etc’. Many of these are easily sterilized or are sterile as a part of the manufacturing process. So to a degree it would be possible for us to use a sterile medium. However unless you use sterilized water and keep the plant in a sterile environment the soil will be contaminated as soon as it comes into contact with the atmosphere and water. So, the notion of sterilized soil is…..

Very hard to achieve and….

Virtually impossible to maintain.

In light of the above it’s easy to see that a perfectly

sterile soil is almost impossible to achieve and

absolutely impossible to maintain long term.

However I have to ask the question, is a sterile soil

really necessary? Are there any significant benefits

to using such a medium? What are the potential

down sides? Are there any benefits to NOT using a

sterile soil mix?

This brings me to the gift of mushrooms I received. As a kid our house backed onto a huge school playing field. Every year I spent the latter half of the summer holidays tramping around the field collecting vast quantities of mushrooms that grew there. However it’s been thirty five or more years since I last did that. The gift sparked my interest and so the next time I took the dog out to the woods I gathered up a bag full of different ‘shrooms’. My friendly delivery driver helped me identify more than a few but that left me with a large number we couldn’t figure out. So, as I do, I headed to the interweband that helped me with a few more and also led me to a good old fashioned book. In the introduction I learned a VERY great deal about fungi and their fruiting bodies, mushrooms. Mushrooms and toadstools are exactly the same thing, a generic term that applies to the fruiting bodies of fungi. The appearance of such things in a bonsai pot is enough to cause an instant coronary in many bonsai growers and cause them to run, sweating, to the shed to break out the Armillatox.

Many bonsai growers are aware of the fungi that lives in the soil with pines, often referred to as mycelium. We know this is a sign that things are good but why? Also should we be seeing this with other plant varieties? Just to be clear an hypha (plural hyphae) is a long, branching filamentous structure of a fungus. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Hypha develop into a fine web like net through the material from which the organism gains it’s nutrition whether that be rotten wood or the root system of your bonsai tree. Most of these organisms are not visible other than with the use of a microscope. A single gram of garden soil can contain a million fungi. The type of fungi associated with pinus species is coarser and more abundant than some others and so we can see it. In order to produce a fruiting body (mushroom) two mycelia of the same species band together in the equivalent of a sexual stage. Then, given the right conditions of nutrition, humidity, temperature and light a fruiting body is formed. Then, given sufficient water, a mushroom is produced. Some fungi are parasitic and can cause the demise of their hosts. However here we are referring to what is commonly called Mycorrhiza, those fungi that are able to live with plants, creating a relationship that is beneficial to both (from myco meaning fungal and rhiza meaning root).

Fungi are the third kingdom (Linnaeus), just as important as animals and plants. Fungi are a very large classification of organisms which have similarities to plants but they lack chlorophyll and are unable to build up carbon compounds essential to life. Instead they draw their sustenance ready-made from living or dead plants or animals in exactly the same way as we animals do. As work on the ecology of fungi progresses we are beginning to realize that the world of plants is incredibly dependent upon fungi in every sense of the word. Fungi break down leaf litter and dead wood and ensure the surface of the world has a fertile layer of soil. However it is through the intimate relationships between fungi and the roots of trees and plants that the most important contribution of fungi is made.

Trees and woodland live in a symbiotic relationship with a vast number of fungi and were it not for the help given to the plants through these relationships many woodland areas would simply cease to exist. If fact, without the third force of the fungal world, life as we know it would not be possible, either for plants or the animal kingdom that is entirely dependant upon them. Virtually all plants develop mycorrhizarelationships. It is thought that only about 5-10% of plants function without some fungal help. It has been calculated that there are over seven THOUSAND species of fungi that form mycorrhiza relationships with a similar number of plant species. Within this symbiosis the fungi receives carbon from the plant and in exchange passes phosphorus, nitrogen, zinc, and a greatly improved water supply back to it’s friend. The supplies are passed through the mycorrhiza tips to the plants roots. It has been calculated that in the region of eight million tips are needed to form one small mushroom.

N.A.S.A (North American Space Agency) have been investigating the effects of fungal symbiosis for about fifty years. It carried out a long term, controlled experiment by planting a pair of young pines, both 1 meter tall, in very poor soil: one with a sterilized root system, was planted in sterilized soil. The second was infected with one of the Amanita species of fungi and planted in unsterilized soil. Both plants were observed and kept under controlled conditions for some 15 years. When the experiment was concluded, the sterile specimen had grown to just over 1.5 meters in height: by contrast the infected specimen had grown to 8 meters in height with a trunk more than 35cm in circumference. This graphically demonstrates the value of fungal symbiosis. Some time ago we took three large serissa bonsai and bare rooted them all. One was planted in sterile akadama. The other two were planted in our No1 and No3 Bonsai soils that are extremely bio-active. After a full growing season the one in straight akadama had begun to discolor and shed fine ramification and lower branches. The leaves were also smaller, softer and paler in colour. I think we might be onto something here….

Symbiotic fungal relationships can make the difference between life and death to plants and trees, particularly those planted in less than ideal conditions. Also bear in mind that if the plants fail the fungi go with them, neither will survive alone. Forest clearance can change the fungi present in soil with the result that fungi disappear. Therefore, attempting to replant forest regions may not always be successful. That’s one reason why, when ancient woodland is destroyed, it can never be reinstated. In the ancient past areas like Scotland were predominantly covered in beautiful woodland but following deforestation it is impossible to restore the habitat. We need to be aware that the fungi present in ancient woodland systems have built up over thousands of years and destroying the habitat by clear-felling will damage the whole delicate ecological balance. When you consider what our bonsai have to go through is it any wonder so many trees are left struggling? I speculate that once we learn more and take heed of these facts we can dramatically improve the growth, health and development of our bonsai trees.

So, to summarize the above. We know that plants are the basis of all life on earth because they take water, oxygen and sunlight and create carbohydrates that are used as an energy source by other life forms that can’t perform this clever trick we call photosynthesis. Fungi cannot produce their own energy source and so get what they need from plants, However unlike humans they are not greedy or inconsiderate because they give back in equal measure. In relation to the soil in which it grows a plants root system is very coarse and not overly efficient at gathering the water and nutrient it requires. Fungi however are infinitesimally small and are spectacularly efficient at getting the best from the soil. However, perhaps surprisingly to some, there is no ‘goodness’ in the soil, just raw materials. In order to make use of those materials you need a chemical factory to turn them into something useful. Fungi have just such a facility. They don’t own it, they didn’t build it but they do work hard to keep it working day and night for their own survival and much like a modern chemical facility it’s called a plant. Fortunately for us there is also enough left over for us too, at least there is until we destroy the whole system. This relationship between a plant and a fungi is called a symbiosis and both benefit enormously from it. As we can see fungi are vital to all life on earth so what in the world would cause someone to think that bonsai, or any other cultivated plant, should be kept in a sterile soil?

At this point it’s important to consider another level of activity within a healthy soil we could refer to as soil fauna. Soil is a word used very loosely but it refers to “the upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles”. So, a complex mix of elements are required to create something we can call soil, it’s not just a growing medium but a whole eco’ system. I hate using the word soil to refer to horticultural growing media because it has become such an ambiguous term. As we have seen, one large element of a balanced and healthy soil is the fungi that live within it. However in order to create soil in the first place, and to maintain it’s health long term, we need large volumes of organic material which ultimately becomes ‘humus’, another ambiguous and mis-understood term. Organic material from plants and animals falls to the soil surface known as the soil-litter interface. Here the activity of soil organisms break down the material. For sake of simplicity consider these levels of activity like a sieve. Larger organisms break down waste that is progressively passed to smaller organisms and so on until we reach single celled organisms we call bacteria. Once they have finished with the material we have humus. This atomically binds to aggregate particles within the soil turning it the familiar dark colour and providing a negatively charged coating that attracts and holds chemicals needed for plant growth. These are what the fungi pick up and pass to their host plant and so the circle is complete.

Soil fauna consist of earthworms, nematodes,

protozoa, bacteria and different arthropods, not

forgetting fungi too. Without these life within soil is

extremely difficult for plants. So, not all creepy

crawlies and fungi are bad for our bonsai, in fact

most are very good. If we can keep our trees strong

and in a healthy natural condition they will be

resistant to the advances of their natural enemies.

Hopefully I have set this out clearly enough that it’s

plain to see, breaking the chain of events will cause

us dramatic problems. Evidently we may need to

adjust some of our techniques if we are to take

advantage of this situation.

When I studied horticulture we covered a wide range of subjects and different disciplines. When it came to pot culture of plants it was made plain that this was one of the more complex and difficult areas of horticulture to master. Now bear in mind that in commercial horticulture the primary reason to grow plants in pots is so they can be easily transported for localized use or sale. A small plant in a pot is a very nice little package. However most of those plants are destined to be either short lived as would be the case with vegetable or fruit bearing plants like tomatoes, or planted out into open ground as with most garden plants. Very few commercially produced potted plants are expected to remain in their pots for decades as is the case with bonsai. So, we have taken one of the more difficult aspects of horticulture, pot growing, and done that with very large, very old plants and put them into entirely unsuitable small, and worse still, shallow pots. These are often grown by folk who have very little background in horticulture and also fancy themselves of an ‘artistic’ bent. It’s a bit like giving a small kid a box of matches and a box of fireworks. Given a little time it can all go horribly wrong. So what can we do to take advantage of a natural phenomenon that is right beneath our feet?

Obviously our primary consideration is to select a soil or growing medium that is going to be beneficial to supporting a dynamic and biologically diverse rhizosphere. This is a spectacularly complex job requiring a lot of knowledge, understanding and experience. I have laid out the basics in my article on Choosing Soil for Bonsai. We have also developed an all encompassing range of soil products you can use right out of the bag to save you all the head ache and heart ache of costly experimentation with your prized bonsai. It never ceases to amaze me why folk in bonsai, some of whom have very expensive trees, insist on finding the cheapest growing media they can, it’s just such a false economy putting your thousand pound tree into cat litter because it’s a pound cheaper than something that can produce VASTLY superior results. It’ like putting cheap tyres on your 200mph super car, sooner or later it’s going to go horribly wrong. Lesson No1 DON’T BE CHEAP! It makes you look bad and your trees will end up looking worse.

Good bonsai soil will have a high degree of bio-activity built into it. It will also have the ability to hold nutrients, maintain drainage, hold moisture, prevent capillary action, have the mechanical strength to survive for long periods and provide increasing space for a developing root system without causing compression. It will also need an almost infinite structure of micro pores in which to provide a moisture reservoir and a foot hold for all those lovely fungi and bacteria. Also don’t forget that after a few years it will need to come apart and release roots without damage when you come to re-pot your bonsai. Sorry to say there is not a single product you can buy out there for peanuts that will do all of these things. Even many traditional products used for bonsai fall seriously short, products like John Innes mixes, horticultural grit and even Akadama only give very poor results at best and can cause the demise of plants in less than extreme circumstances. After 25 years of cultivating tens of thousands of trees I can honestly say that the most suitable medium available in the UK toady is our own soil mixes. These are constantly being improved and refined to give the very best overall performance possible cultivating the widest range of bonsai in UK conditions. Maybe in time there will be a breakthrough and we will all go over to using something else but for now that’s not even on the horizon, if it were I would have trees growing in it.

Having decided upon our suitable growing medium it’s important to consider how we get our bonsai into it. I have covered bonsai re-potting technique extensively in Graham’s Guide to Repotting Bonsai Trees. The best growing media in the world will be of little benefit if 80% of your plants rootball is an impenetrable brick of compacted old akadama or similar. A bonsai lives in a very small amount of soil and it’s important that ALL of it is available for root development, moisture and nutrient supply and the provision of air to the developing roots. I will deal with the subject of compacted root systems in a forthcoming article but for now the idea of a new inch of soil around the outside is not acceptable. When re-potting bonsai ensure the rootball is dry before you start, dry soil comes away much easier than when it’s soggy and wet. NEVER wash the roots of a tree because this will carry away the seeds of a beneficial community of bio-active colonies that are vital to the re-establishment and long term health of the plant. If you decide to use a product likeRootgrow bear in mind it will be wasted if you are using pure aggregate products like cat litter, akadama, kiryu and their ilk. These types of product simply don’t have the mechanisms in place to support the fungi that such valuable products contain. Finally, after re-potting only give the soil a very slight watering. Pouring water through the soil until it runs clear out of the bottom of the pot may seem on the face of it to promote drainage but if you are using that all important bio-diverse soil medium what do you think is being washed out of the pot? After re-potting bonsai ensure the soil is just damp throughout and try to keep it that way until full growth resumes. Cold wet soil discourages bio-activity and severely retards the healing and subsequent development of new root mass. Also if there is a lot of water held in the soil there will be less oxygen available which, at this stage of the re-potting process, is more important than a copious water supply.

In order to maintain a bio-active bonsai soil mix and healthy rhizosphere long term a few simple points need to be observed. The most important factor being only ever use organic fertilizers. Chemical fertilizers are too aggressive for bonsai, they work great for fast growing plants like tomatoes or bedding plants but should be avoided for bonsai use in my opinion and experience. I already mentioned the fauna required for the development of a healthy root zone and many of these live on what is called the soil-litter interface, the surface of the soil. In a bonsai context this is the top half inch of soil including the area from about half way through and moss covering down into that top layer of growing media. These incredibly diverse array of organisms produce a valuable service in breaking down organic material, including fertilizers, so that they can be accessed by bacteria that in turn release nutrients that plants can access. If you take an inorganic fertiliser such as Tomorite, an oft recommended product for bonsai, and mix it for use. Then swill your hand around in it for a few seconds you will likely be surprised just how much it stings your cuticles and will hurt like an S.O.B if you have any tiny little cuts. Imagine pouring that into your bonsai pot, all the life in there will be covered until next time you water. Keep chemical fertilizers out of bonsai all together they don’t bring anything to the table that’s not available from a good quality organic product like Green Dream Original. I will be covering the subject of fertilizers in a future article but at this juncture it’s worth pointing out a few things in relation to the use of organic products.

Organic fertilizers are made from nutrient rich ingredients. These require the activity of soil fauna to release them. This often results in a covering of mould and a few creepy crawlies all going about their important task. In the case of fertiliser pellets this can even result in the colonization by maggots for a short period of time. These are all wonderful pointers to the fact you selected a good quality product full of nutrients and that it’s working as it should. Products like Bio-Gold are treated with a strong pesticide to prevent all this taking place and is not, in my opinion, worthy of the title organic. Fertilizers should only be used when the temperature is constantly above 12° Celsius. Below that most root activity and cell division ceases and even if some activity takes place it will not be requiring nutritional supplementation. Our rule for spring is 12° for 12 days before we give the first feed. Always choose a product with a multiple nutrient source. Products like chicken manure (shit) are single source and are very poor fertilizers containing low levels of nutrients, often in a very narrow band and missing lots of vital micro elements. A great supplemental feed for your fast growing vegetable crops but not for bonsai. A good product like Green Dream will contain diverse sources of nutrient bearing compounds from bone meal to seaweed. So a little smell, a little fuzz and a few little animals taking advantage of the bounty is all a part of the bio-activity and diversity our bonsai trees so desperately need.

Just one last point to consider and that’s the use of ‘soil pesticides’. A very great deal of commercial activity is developed on the back of fear. Just take a look around you. We are sold products all the time that in reality do very little, if anything at all. Products to stop us looking older, to make us more popular, more energetic, fitter, healthier etc’. If you could produce a product that a nerdy, spotty teenager could spray on himself in order to attract beautiful girls do you really think it would be for sale for a couple of quid in supermarkets? I have yet to find a bonsai grower who does not turn sickly green at the sight of a vine weevil. But, let’s just think about it in the cold light of day. The hype around these little critters has come from nurseries that grow soft tissue plants. These types of plant are grown en-masse in huge commercial establishments raising tens of thousands of the same plants, normally in the cheapest nasty wet compost available, after all a lot of water means a bigger plant which means more bucks. If you had never laid eyes on a mature vine weevil and just relied on the reputation it has in bonsai circles you would imagine something the size of a lion with the hands of a huge mole and a wood chipper for a mouth. In reality it’s a crunchy little beetle that can neither fly or swim that matures from a little grub smaller than the average maggot. They love multi purpose compost and peat based substrates because they are easy to burrow into and support a lot of fleshy root growth upon which they feed. In practice you may find a weevil or two when re-potting but seeing as they don’t eat wood and only live on fleshy roots and are a few millimeterslong how much damage can they do? If you grow begonias and the like I would be careful but in bonsai cultivation over 25 Years I have never seen any damage inflicted by these guys sufficient even to mention. Also bear in mind that they are now firmly established in Britain’s carefully manicured lawns and grasslands and are here to stay. The best line of defense is to choose a good bonsai soil mix at the outset and they will soon meander off to find easier pickings. Using soil application pesticides really should be avoided unless you have a more serious and persistent infection of something like root aphid. If we can maintain a good healthy balanced rhizosphere harmful pests will either never appear or be kept in check by everything else that’s happening down there.

To sum up, I think that as kids we are taught to fear a lot of things in order to keep us safe. Mushrooms are bad, well some are but a great many are not and provide some good eating, but do take the time to learn which is which, ignorance can kill. We are also taught that bacteria is bad, the exception being those stupid little bio-pots of yogurt that, judging by the price, must contain some alien life from a distant planet. I was also led to believe that if it smells bad then it must be bad. My dog eats raw tripe every day and that smells pretty bad to me but he loves it and is the picture of health. French cheese can smell pretty bad too but they seem to like it. So not all bad things are bad for everything and some good things are bad for other things. We need to keep our ideas in context, think these things through, clear out the commercial nonsense and develop a way forward that works for, in this case, our bonsai trees. A healthy bonsai tree is a happy bonsai tree and a happy bonsai tree makes for a happy owner and now I am getting a bit confused and need to go buy some of that nerdy spray.

Graham Potter.

http://www.kaizenbonsai.com