Bonsai soil is one of the most critical aspects of growing bonsai. A good soil mix will allow you to get away
with some mistakes. A bad soil mix will quickly kill your trees.
One of the first things to make clear is that bonsai soil is not dirt. But there is a joke that bonsai soil becomes
dirt when you drop it on the floor. Dirt around your house varies widely from area to area but I know of no location
where the native soil would be good for bonsai in pots. In fact, when planting nursery material in the ground, I
backfill the holes with my bonsai mix because it get the garden plants off to a better start.
If you have one or two trees, the bonsai mixes available from many garden stores are adequate. Note that I did
not say potting mix. Do not try to use the Miracle Grow or other potting mixes available in garden shops and big-box
stores. Theywill lead to the quick demise of most bonsai. Read further for details about what constitutes a good
If you have a number of bonsai, you will want to start making your own mix. And if you have tens of bonsai,
you will probably be at the point where you will want to start specializing your mix.
My mix is a moderately coarse mix that provides good drainage and aeration while holding some moisture for
longer periods. I prepare it in 20-25 gallon lots using 5 gallon buckets. It is a long-lasting potting mix that withstands
the three or four years between repottings for some of my bigger, older trees. I have chosen this mix because I still
work and travel and it is suited to our area. What this implies is that it can be over-watered while maintaining the
health of the plants. It is not unusual for us to get a week of rain. Or when I travel, I use an automatic watering
system because my wife is totally unreliable with my bonsai and she often travels with me. My system slightly
overwaters my trees and will run on rainy days. Thus good drainage is essential.
My basic mix starts off with three components: porous inorganic, non-porous inorganic and organic. All
should be sifted to remove fines. The organic should be double sifted to remove both large pieces and fines. I mix
them in a 2:1:1 ratio by pouring the back and forth between 5 gallon buckets.
Porous inorganic: I prefer to use Turface MVP. It is a large-particle, light-tan, porous calcined
(medium fired) clay that holds water internally as well as between points of particle contact. Its
primary use is in the infields of baseball diamonds so that the field can be played on soon after a
rain. It is widely available from farm stores and some grass seed stores for Little League
diamonds or dirt volley ball courts.
Akadama is a pumice material available from
Japan and is used for bonsai such as pine, juniper,
cedars and other acid loving plants. Kanuma is another
pumice material that professionals use primarily for
azaleas, but I find it too soft and too quick to
deteriorate in my environment, so I stick with Turface
or akadama. Akadama and kanuma are available online
or from higher-end bonsai vendors.
Nonabsorbant inorganic – It is good to have some sharp-edged inorganic
material in the mix. My mainstay is Gran-i-grit brand
turkey grit which is 5/16” - 7/16” crushed granite, easily
available from farm stores. It is light gray to white and is
quite good for the soil. The downside is that t does not visually match the Turface and can be
considered a bit unsightly.
A better but harder to get alternative is Haydite which is a calcined (high-fired) shale. It has an
appreciable iron content so it is red-brown to black and is esthetically pleasing in a bonsai mix. It is
also often used to top-dress a plant when being put on display. It is often available form bonsai
vendors or from the manufacturer:
Hydraulic Press Brick Company.
5505 W 74th St, Indianapolis, IN 46268
Phone: 317-290-1140 * FAX: 317-290-1071
Organic: For the organic component, I use pine bark fines or pine bark soil conditioner. It is available from
Timberline and it or related products can generally be located at Lowes or Home Depot. This should not be confused
with pine bark mulch which is much larger pieces. Other materials that individuals have used are cocoa shells (if you
live within striking distance of Hershey, PA), or fine orchid soil.
Having established the basic mix, there are many variations or
specializations that should be considered. If being used for a pine or
juniper, I cut back the organic. As mentioned above, for azaleas, I replace
the Turface with akadama. For flowering trees, add up to a cup of bone
meal to a 5 gallon bucket of mix to promote blossoms and fruit. For
better water retention add more Turface while reducing the crushed
granite. For better drainage, aeration, and less water retention, you can
use one part Turface rather than two
As mentioned above, all of the materials should be screen to
remove fines which will block drainage and reduce aeration. This time-
consuming process is generally done by hand. One BBS member with a
large collection who required a lot of bonsai mix, built a screening
machine that was shaken by a Sawsall and deposited the various sized
materials into different piles by using graded screens down an incline.
The graded screen are visible in the photograph.
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educational purposes. If large portions are copied, we would appreciate attribution. We welcome links to this site.