Your Soil Mixes

Soil Mixes.

Throughout my bonsai life I have always been struggling with trying to find the best and correct soil mix to use. I had hoped to find a mix that would suit all of my bonsai. I can now tell you that I have learnt that there is only one way to decide on the best soil mix. Use whatever is available at the time that you are (re)potting.

You can find all sorts of formula that will tell you how much of this and how much of that to use. It will tell you names and descriptions that you have know Idea about. So leaving all that aside, there are some fundamental things to remember.

Perhaps the most important thing you need to decide is how much water you want your soil mix to retain. What I mean is this:

a. If you use a very friable mix then there will be a lot spaces within your mix surrounding the particles. This allows the water to drain through very quickly. If you happen to be slow in watering your bonsai, for one or even two days, then it will very quickly dry out. And this is the end for your bonsai.

b. If you use a mix that is less friable then the water is slower to drain through and the mix is slower to dry out. Your bonsai then has a chance to survive if you are slow in watering for a day or two. BUT if your soil mix is too saturated for too long then rot can set in and destroy the roots. When rotting actually begins is something you will have to learn for yourselves because it will be dependent on where your trees are located and how often you water them.

c. I can hear you ask, how does this friable business work? It has all to do with the amount of ‘fines’ that are within the soil mix. The ‘fines’ are the very small particles that ‘clog’ up those fine spaces between the particles. You could say that the ‘fines’ are the tap of the soil mix. They control the flow of water just like a tap over the kitchen.

d. If you want your bonsai to grow quickly then use a well fertilised and very friable mix. Make sure of course that you have a very good watering regime and that you intend to repot the bonsai each year.

e. If you want your bonsai to stay in the pot for a couple of years or longer, then have a less friable mix. The water will take longer to soak in, but the end result will be that your bonsai is still alive.

Now what ingredients to use?

You can use a ‘simple’ commercial potting mix. A mix that is free of too many added ingredients. Read the labels before you buy. They could well be the cheapest soil mixes. This is quite easy to purchase and you will find that your bonsai can grow quite happily in this mix.

For me, I have been reading about bonsai mixes for so that I feel that I must follow the dictates of everyone else in bonsai. For right or wrong I have developed this mix for me. I usually work in thirds.

I start with a third of a simple commercial potting mix. This mix does not have too many added ingredients. But remember that I have a few bonsai and I have sufficient ‘old’ soil from previous repottings. This material I microwave for 50 minutes to kill weeds etc and I use as a basis for my commercial mix.

The next third is ‘pea metal’. It is a small stone chip that you could find on a footpath after the council has re-sealed it. This gives the mix some draining abilities and provides some bulk to the mix.

The remaining third is compost from my household bin. It has been sieved to remove the larger pieces and in the future I am going to microwave this to remove any chances of any weeds that might have survived the composting experience.

Is my soil mix friable? From starting off with having a very friable mix I am now getting to a mix that is less friable. Do I sieve out the fines? No I don’t. BUT I am always looking to see that the soil mix is not going to end up as a thick congealed mass that will allow the roots to rot.

Fertilising is a personal thing and you can include some in your mix or can leave it out and apply it during the life of the bonsai. I am sure fertilisers and their application etc is the subject of another article.

Happy mixing.

Bevanbevan.