I recently received an email from someone who was very concerned about the size of the leaves on his bonsai trees. The concern was that a change of fertilizer may have become an issue. In thinking about my reply it became obvious there was a little misunderstanding on the part of the gentleman but his question is not a new one, I have heard it many times before. Over the years I have heard a lot of silliness expounded as wisdom in relation to foliage size in bonsai and I figured now was as good a time as any to set the record straight. This may seem needlessly basic to some but stick with it. Here are a few basic ground rules.

  • 1. Bonsai are just regular plant varieties kept small by pruning.
  • 2. Bonsai must be supremely healthy in order to survive.
  • 3. Bonsai are NOT kept small by living in a small pot.
  • 4. Bonsai cannot be perfectly manicured and shaped all the time.
  • 5. Fertiliser will not determine the growth pattern of a bonsai tree.
  • 6. Foliage size is not determined by nutrient availability.

1. A lot of ignorant folk think bonsai are special types of tree. A friend of mine who sells bonsai out of his florists shop recently had an argument with a guy over a pyracantha. The ignorant fellow insisted it couldn’t be bonsai because it was a ‘motorway tree’. He was implying that as the variety is used for amenity purposes it was obviously NOT bonsai because bonsai are little trees. You really can’t blame the guy, it’s our own silly fault for shrouding our hobby in mystery and making it a lot more esoteric than it needs to be. Even seasoned hobbyists are missing some of the basics, I know I have to deal with the problem every day. Maybe there are a few folk out there who have benefited from this, in fact scrub that, A LOT OF FOLK HAVE BENEFITED FROM MAKING BONSAI A GREAT DEAL MORE COMPLICATED THAN IT IS.  Couple that to the fact that almost all the books available have been published by mainstream businesses only interested in shifting books (thus all beginners books) and written by authors on a tight brief only interested in increasing their own demand as teachers and you have the perfect ‘sh** storm’ of poor information and ignorant but hungry consumers. That’s how so much nonsense has become engrained in our hobby and much like the smell of kiddy sick in your car it’s hard to shift 😉

Bonsai are just regular plants that, returned to open ground, very quickly revert to their natural form. Selecting the plants with good character is half the battle. Choosing a raffia palm as a bonsai subject is just stupid, the leaves can be eighty feet long and ten feet wide. A chinese elm is better, it has small leaves and fine twigging, it’s also naturally not a monster. Keeping a giant sequoia as bonsai is always going to be tough. It’s pretty obvious a naturally large tree in a small pot is going to present a few issues long term. Now I am the last one to say these things are not possible, I have seen some remarkable things over the years but for most folk it’s much simpler to cross the road using a pedestrian crossing rather than stretch a tight-rope across the tops of the buildings and use that. For a start let’s just concentrate on crossing the street.

2. There is a wide spread belief that bonsai are kept small by some cruel means and that they are in some way ‘stunted‘. The dictionary defines stunted as…

To prevent from growing or developing properly. Synonyms: inhibit, impede, hamper, hinder, restrict, retard, slow, curb, arrest, check, stop.

There are some pretty negative connotations there. However it does not take a genius to realise that we want bonsai to live a long time. It takes many years to develop a tree and that is accomplished by growth. Because of the time involved, bonsai are expensive and so a tree that is stunted by having it’s growth restricted or inhibited in any way will, ultimately, result is a dead tree and a complete waster of time. If a bonsai tree is unhealthy for any reason in time it will die, all life forms have a limited amount of stored energy and once that is depleted it’s all over. The NUMBER 1 rule in bonsai is tree health before ANY other consideration.
3. Bonsai pots arrest growth. It is impossible to develop anything other than secondary branch structure in a bonsai pot. Trying to develop a trunk in any way will take more than a life time in a bonsai pot. All commercially produced bonsai are made from field grown trunks. So a bonsai pot will stop much happening, however that is not how bonsai are kept small. We use those lovely small pots simply because they look good. However for the well being and ultimate health and survival of bonsai we need a strong and dynamic root system that, as it happens, needs to be small. Allow me a motoring analogy. I recently bought Catherine a little Mini Cooper S (not the classic one). That’s the smallest engine car I have had since I was in my teens. It’s little and surprisingly quick and a perfect little runabout with it’s 1.6 engine. I also bought a 1967 Ford Pickup with a loud and proud 5 litre engine. Unlike the Mini it’s useless for town work, it’s wider than all the roads around here, has no power steering (or anything else) and knocking out over 300 bhp makes it a little thirsty. However throw a ton in the back and it’ll make no difference to the truck at all. Throw a ton in the Mini and that’ll be the end of it. As they say ‘horses for courses’. Bonsai are the same. Raw material needs a big lazy root system with a lot of power and massive energy reserves. Bonsai trees in pots need a high performance root system that does everything very efficiently. Very few folk seem to know what a ‘bonsai’ root system is, what it looks like or how to develop one. So again, bonsai pots are for looking good not keeping trees small.
4. Take a look at any bonsai book or magazine and you will be presented with endless pictures of perfectly manicured bonsai trees. After all most books are sold on the pictures. Go to any bonsai show and you will see row upon row of immaculately turned out bonsai trees. For the unaware it is easy to get the idea that our trees should all look just like that, perfect and beautiful all the time. Now if you live in a place where the climate is ideal that may, to a greater or lesser degree be possible but if you live in Blighty it’s simply not. In fact it’s entirely impossible to keep all of our trees beautifully manicured at all times and certainly not desirable. In order to continually develop and maintain a bonsai tree it’s important to keep it’s energy levels high, we tend to call that vigour. Much like a bank, if you always take out what you put in you never have anything for a rainy day. As a general rule a perfectly manicured bonsai will, in the UK, not make all the energy it needs. Therefore over a period of years the tree looses vigour, development slows and keeping the tree at it’s best becomes extremely difficult. Consider a plant as a little solar generating machine. The ONLY place a plant gets energy is from the sun. A plant does not draw energy from the soil. Leaves are little solar panels and if we do not have sufficient the tree will slow down. This may be imperceptible for years but one day you will see the result. A lost branch, twig die back, poor roots, poor disease resistance, yellowing foliage, the results are varied but inevitable. If you live where the sun is bright and the growing days are long this is less likely but here it happens a lot. The only answer is to allow your tree to grow unchecked for a period of time each year, sometimes for a year or two in succession. More leaves mean more energy and more energy means more buds and more leaves and more energy. Large leaves also produce a lot more energy than small ones.
5. Fertiliser does not have the ability to determine the growth pattern of a tree. A tree takes water and chemicals from the soil and uses them to build tissue and support biological processes. The energy required for this comes from the sun via photosynthesis in the leaves. A plant uses these raw materials to build and maintain cells. If the plant has ideal nutrient supply it will be in perfect equilibrium and the growth pattern will be ideal for what the plant needs and only limited by it’s root mass and external factors such as light availability. If our plant is in this ideal situation adding more fertiliser will do nothing. You can ask you barman to put a quart in a pint pot but all you will get is a pint, the rest will be in the sink. Applying excess amounts of ANY nutrient element will not have any effect, at least not until the concentration becomes critical at which point things can go bad. Now if the tree has a nutrient deficiency adding that element will have a noticeable effect but only to the point of reaching the trees requirements. It’s also ridiculous to assume we can add a product to force the tree to do something like produce flowers. Now if a lack of flower production is caused by a nutrient deficiency then it can happen but if the tree is not producing the right hormones (auxins) to instigate flower and fruit you can pour stuff on it all day long and nothing will change. In order to encourage flowering a change of care regimen is often required as in the case of hawthorns that refuse to flower.
6. If a tree has large leaves it is not because you have over fertilised, it is because the tree NEEDS big leaves and you have provided the ideal conditions for the tree to do what it needs. Mess with this at your peril. If a tree of a given size needs ten square inches of leaf to make it’s energy and it only has one bud you are going to get a big leaf. However if the tree has ten buds you will get 10x much smaller leaves and that’s the entire crux of developing all bonsai with leaves and needles.
There are two ways to get what we need in bonsai, we can force the tree to ‘have’ to do something or we can encourage it to ‘want’ to. Much like teenagers the latter is the better option. You can get small leaves or needles by withholding water and, or nutrients but this causes stress and leaves us on the negative side of the vigour equation. That’s VERY poor technique and I will NEVER recommend such procedures.
Let me quote an example. About eight years ago I bought a massive and stunning yamadori scots pine. The needles were less than an inch long but the foliage was on straggly thin and floppy twigs like string that on average were a couple of feet from where I needed them. I started to improve the vigour of the plant with careful cultivation. The following year the needles doubled in length and a few back buds appeared in late summer. By the end of the following year the needles were four inches long and I had more buds than I would ever need. Gradually over time I was able to shorten the branches as new growth worked it’s way up the branches, always being careful not to tip the balance by removing too much. Today I have twice the foliage mass I need to style the tree, all the foliage is piled up directly on top of the tree, I have back buds on 1/2″ thick branches and the needles are less than an inch long even though I feed the tree extremely well. At no point did anything happen to stress the tree or reduce it’s energy generating abilities.
THAT is how we get the foliage and development we want whilst giving the tree what it needs. THAT is what bonsai IS. It’s got nothing to do with any high faluting notions of art or oriental culture. The art is in managing the life processes of the tree in order to help it thrive and mature and that is where the beauty comes from. We are not trying to grow something that looks like a little tree we ARE growing a little tree and the only way to do that is to cultivate the plant in exactly the way a tree grows in nature. Once we get our arms around the process all the pushing and pulling stops and we are able to simply allow the plant to become bonsai, an old mature tree in miniature. And what a journey that is!