Bonsai Soil
Bonsai For Beginners

For those of you that have been asking for wire I now have some in stock

Coming Events

Model X June 3rd 4th and 5th
The Bonsai Society have a display at this event each year it is held at the West Wave centre Alderman drive Henderson 9am to 5pm Saturday and Sunday 9am to 4pm Monday Adults $5.00 Children free

Auckland Bonsai Convention
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Auckland Bonsai Society
Meetings: 2nd Thursday of each month, 7:30pm Greyfriars Church Hall, Cnr Windmill & Mount Eden Roads, Mount Eden, Auckland

Bonsai Soil

I managed to get along to the last Bonsai Society meeting here in Auckland and was pleased to see a lot of new faces as well as the few that seem to hold the club together. Another thing I noticed is some experimentation with new soil mixes. I have just recently started to experiment with different combinations myself.

So here it is my opinion on soil. I say mine because there are as many opinions on soil as there are bonsai enthusiasts. There is not magic formula and to be honest a bonsai will grow in anything as long as it provides the basic requirements for oxygen support, moisture and nutrition.

If we discuss these basic requirements you will better understand how to formulate your own mix and vary it for plants specific requirements.

During the late 20th century when bonsai first came to Europe and America trees failed to thrive. This started the perception that there must be some magical properties to bonsai, which still persists even today. Later when knowledge of plant husbandry developed and the requirements of plant growth were better understood the myth was somewhat dispelled. Part of the understanding was in the soil requirements.

Soil is important for any potted plant. A lot of plants have evolved to grow in a specific environment such as carnivorous plants, orchids and cactus. All these plants require a specific soil mix. Because bonsai is such an intensive form of horticulture some attention has to be given to the growing medium and while there is no specific bonsai mix, providing optimum growing conditions for our plants must be considered.

There are several advantages to a good bonsai mix

  • Increased oxygen to the roots
  • Improved drainage
  • Ease of transplant ( will comb out of small roots)
  • Greater surface area
  • Increased number of branches
  • Constant soil temperature
  • Correct PH
  • ideal conditions for ion exchange
  • Development of helpful bacteria
  • Esthetics
  • Ease of nutrient application
  • Eliminates root rot
  • Increased vigor each year

The five main considerations when making up a soil mix are particle size, texture, soil composition, microorganisms and esthetics.

Particle Size

This I think is one of the most important factors in Bonsai. Roots actually grow on the surface of soil particles. They seek out pockets of water that are adjacent to air. Where one of these components are missing there is no root tip growth. If the particles in your soil are too small the tension in the water will create a capillary effect and the water will cling to the soil particles. This will eliminate oxygen from your mix. When your soil dries out your plant will briefly be able to access the oxygen it requires but not the water. While the plant can survive for a time in this environment it will eventually weaken and die. So what is the right size? Any particle that will fit through a fly screen with a mesh of 3/32 of an inch is too small and should be removed from your mix. Any particle that will not fit through a mesh about 1/8 of an inch is too big and should also be left out. If your soil particles are correct there is no need to graduate particle size down through the pot. In fact it is now thought that large gravel on the base of the pot will cause water to travel from the large particles to the small causing a dry zone in the bottom of the pot. Good mix throughout the pot is the key.


A strange phenomenon is that branch structure tends to emulate root structure. So the more fibrous your plant roots the better your trees ramification. A rough particle is going to provide far more surface area than a smooth particle of the same size. With a smooth surface the roots can slide between the particles with little resistance. A rough particle will cause the roots to divide to pass by. They will also irritate the root surface causing it to produce root hairs which help feed your tree.

Soil Composition

Different trees have different soil requirements an Azalea will require a more acidic soil than a Juniper would. All soil is basically made up of two components organic and inorganic. Organic comes from living things such as bark, sawdust, leaf mould, animal manure or compost. Inorganic comes from things that have never been alive such as stone chips, sand, vermiculite, scoria etc. The organic materials provide the nutritional value while the inorganic provide the minerals. A combination of these two materials is essential to any soil mix. Different plants will require different combinations of these two elements try to simulate your particular plants natural environment as best as possible. Fine tuning of PH and food requirements can be carried out with top dressing applications.


Most potting mix comes in a sterile state; it has either been heat or chemically treated to eliminate weeds and soil borne organisms. This is great no body wants a pot full of weeds or a root rot from their soil but it also eliminates the good guys. Probably the most recognized soil borne fungus is on the pines. It is a fungus that grows on the roots that has a symbiotic relationship with the pine. It is called Mycorrhizae the pine provides a home for the fungus and it in turn helps the tree absorb nutrients and moisture from the soil. Once it is established in your trees it can be transferred when repotting from tree to tree. Some organic fertilizers need the soil to be alive with microorganisms to help break it down into a useable form for your plant.


Goes without saying, you grow your trees not only for the horticultural challenge but for the pure beauty of your creation. Why spoil it with an intrusive coloured soil or a soil surface with particles out of proportion to your tree.

Sorry a lot of print in this newsletter I guess we could have just put a good soil mix is 50 percent organic to 50 percent inorganic with the correct particle size of course.

Or for you beginners who just want an easy solution use four parts good potting mix to one part small stone such as sap 7 scoria. This mix will get you started and be fine for most plants.

I have added a section with a photo demonstration on how to create a bonsai Juniper from Nursery stock. If you would like to take a look click on the link below or copy this URL into your browser

juniper from stock