The most important aspect of growing bonsai is the horticultural requirements that the different species require. A Japanese maple requires a completely different environment than a juniper. And even within the same genus the cultural requirements can be vastly different. A Chinese juniper such as a shimpaku will need different growing conditions when compared to a California juniper or a procumbens nana.
The strength of any tree starts with the root system and improving the root system needs to be the first goal in turning a possible bonsai into a truly great bonsai. So how do we improve the root system so that we can supercharge the growth and start our tree on the road to a bonsai? The proper soil mix is the first item that we need to look at. What are the climatic conditions that our trees are subject to, how often are we watering, how hot does it get, what are the humidity levels, how about the prevailing winds, how fast will our trees dry out? Do we grow Shohin size trees or do we prefer to grow the larger trees, or do we have both?
 |
| Medium size soil mix |
 |
| Shohin size soil mix |
Bonsai masters in Japan prepare a soil mix specifically for each tree, and we need to be looking to the masters for instruction and try to follow their lead on horticultural practices when we can. Many of us use a premixed soil that we can purchase and this is a good starting point. Most premixed soil from Japan will come with 60% to 65% akadama, 30% to 35% pumice with 5% scoria (cinders) and 5% to 10% kiryu which is a course sand similar to decomposed granite. For pine and junipers the 60% akadama is good but with deciduous trees you might want to add to it and have a ratio of 65% to 70% akadama. Now the CEC (cationic exchange capacity) rate of this mix is very poor and we will need to add some items that will increase the ability of this soil mix to hold and disperse the nutrients rather than having them flush through the soil and onto our benches where it's not doing anybody any good. One of the best soil components that we can add is vermiculite. This has a very high CEC rate but is very light so will need to be added at the last minute and mixed in well, 5 percent is a good quantity to use and will improve root growth. I started using vermiculite about three years ago mainly because my teacher Kenji Miyata was complaining about how they quit using it in Japan because they had to transplant more often because the roots were filling the pot to quickly. I decided that was a problem that I could live with and I have noticed that I am getting better root growth when mixing in 5% vermiculite. There are other components that you can use. Certain Zeolites have a very high CEC rate but they are difficult to find in sizes that are economically suitable, or they are impossible to find in a lot of areas.
 |
| Mitsuya-san preparing a pot for repotting |
One problem that I see a lot of is people repotting their trees too often. Repotting is a major surgical act to perform on a tree and will often set the tree back and produce a slower growth rate for a season until the tree reestablishes a root system. However the opposite is also true if we postpone repotting until after the tree is root bound. That can have disastrous consequences also, so we need to know what to look for to determine when to repot. One thing that we can be doing is picking up the pot and looking at the drainage holes. Do you see roots growing through, is the soil above the drain holes full of roots, when you push down on the soil on the top of the pot is it hard or can you push you finger into the soil? Do you see roots growing out of the soil on top of the pot. These are all indicators that we need to be looking at.
 |
| Time to repot |
One of the things that Bonsai masters will say when they come to the US for conventions or shows is that we don't fertilize enough. If you use the soil mix above you will need to be using an organic fertilizer. There are more and more high quality organic fertilizers on the market at your local garden shop, many with added mycorrhiza and beneficial bacteria. In looking for a quality fertilizer consider the delivery mode, are you top dressing, are you using fertilizer baskets, how do you prevent the fertilizer from caking over and compromising that beautiful soil that you worked so hard to make so that you had good drainage and air exchange? I've used fertilizer baskets for the last ten years or so and find for myself that this is the best may for me to be able to control the application of the fertilizer without compromising my soil. You might have other means to do so. Some people use tea bags that they fill with their fertilizer. You can buy the empty tea bags online or at many oriental markets. I've tried this also and it works marvelously until the birds take off with them and you have empty tea bags all over your yard. In looking at fertilizers try to make sure that it is a balanced blend and that it contains the micro nutrients that all plant life needs to truly flourish. Here you will find a list of micro nutrients that your plants will need: Iron, Molybdenum, Boron, Manganese, Sodium, Zinc, Nickel, Chlorine, Cobalt, and Aluminium. Try to make sure that your fertilizer provides these elements or you can purchase trace element frits that you can add to you fertilizers.
 |
| Using tea bags for fertilizing |
The next thing that we need to consider is the climatic conditions that we are trying to grow our trees in. What we need to embrace is climate change, not for the whole world, but only for that part of our yard that we are trying to grow our bonsai in. Now where I live it will hit 100 degrees around the first to second week of May and never drop below 100 degrees until the end of September and sometimes into the first week or so of October. This last summer we had 20 days in a row where the highs for the day were 115 plus.
 |
| Tough bonsai weather |
Using shade cloth will protect your trees from the worst of the midday sun and by keeping your benches and surrounding areas wet you can increase the humidity levels and this will decrease the transpiration load on your trees and slow down leaf burn. By enclosing as much of our bonsai garden as we can it will also help protect the trees from the drying winds and for some of you hail storms. For those of you that live in an area where you can grow your trees out in the open without any shade or protection from the weather, we envy you.
 |
| Bonsai nursery with shade cloth and wind protection |
So lets be looking at our growing conditions from the roots up. We will never be able to complete our vision of what we want to achieve with our bonsai if we don't have healthy trees, and the very best growing conditions that we can provide will help us reach that goal.
