In Japanese, yamadori means “mountain tree”. In this country, the term has taken on a slightly different meaning which is a tree that has been collected from the wild. A new term has begun to appear in more recent times, namely “urban yamadori” which means a tree dug up from a garden, like the example below. When it was first dug in 1995 and later trained, the nebari or root flare was very ugly and one sided, so a few years ago it was air-layered to give a more balanced root spread. This has worked well and the tree bears smallish leaves year after year.
The first thing to remember is that you must not dig up trees from anywhere unless you have the landowner’s permission. If you do not, this is theft and carries a criminal charge with it. The other thing that you must now be aware of and one of the reasons why we as a society have not done any collecting trips for a few years, is the number of different tree diseases which are spreading across the country. As a society we have decided that we do not want to risk bringing back any diseases to our collections, but there is also the other issue of not assisting the diseases to spread to new areas. Being a group member of the prestigious Royal Horticultural Society (RHS) via our insurance, we get monthly magazines which keep us updated on the various phytopthera raging through our countryside.
Once you have permission to dig somewhere, please don’t go collecting everything in sight. Be selective. It is better to focus your attention on something that truly has potential, rather than on something that you collected because you felt you had to have something. If you know the landowner, or perhaps you have spotted something in your garden, there is always the potential to prune something back which has a decent base, but nothing else to work with. A tree will grow better in the ground in which it started than being dug up and put in alien soil (your garden) or in a pot. Return the following year, and if it has developed enough dig it up at this point. This obviously will only work if you know the tree will definitely be there the following year, and won’t have been spotted by some other budding bonsai grower, or worse still cleared for one reason or another!
How do you decide if the tree has potential? Well the advice we were given is that if you have a good base to the trunk and nice root system (nebari) then you are definitely closer to a potential good bonsai tree than if it has not. After all, the top can be cut back and regrown, but there is very little that can be done to make a boring trunk interesting and an ugly root system into something more pleasing. Basically by digging up something which has a suitable existing trunk, you are not only acquiring something which has grown showing its history, but you have saved time, because ground growing is the quickest way to improve the trunk thickness and acquire some maturity to the tree.
How can you maximise the chances of the tree surviving? Well, digging up as large a root ball as possible helps as well as keeping as much soil with the root ball, this helps the roots to stay moist until you get it home, but also reduces the shock to tree as it is already used to growing in that type of soil. Putting the root ball into a large plastic bag or sack and tying it around tightly to stop the soil being shaken off the roots and will help to stop it drying out before you get the tree home. If you have space, plant the tree into your garden. Put some new compost into the hole to start its transition to bonsai Leave it there for a good year it allows new roots to develop, as invariably some large roots will have been cut or broken in order to physically lift it. If you cannot put it into your garden, give it as large a container as possible. This then acts as its own mini garden. The person giving the talk advises a very gritty compost if it is in a container. If after at least a year your tree appears to be thriving, then you can begin to consider training it as a bonsai, and getting it into a training pot. Don’t go straight to a bonsai pot, reduce the root ball size gradually. Even then it will not be a ‘bonsai’ in the accepted sense, but a potential bonsai. It will not become a bonsai until the branches have been reduced and you have decent ramification.