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Saturday, September 17, 2016

Bonsai Soil DIY

Bonsai soil mixes.

Bonsai Soil DIY

Bonsai soil is for conditioning the tree following grow out. If you are trying to grow out a tree you use a standard nursery soil in a nursery container.  If the tree is grown out, then read on.

This is our first foray into the actual bonsai placement.  The soil for bonsai seems to be much like the preferred soil for all of our acid loving bonsai plants.  This is pretty convenient.

Soil Mixes

Grow Out Soil Mix

Keep in mind that the specific plant needs may require a different grow out soil mix.  This would include acidic soil mixes.
  • 6 parts topsoil
  • 3 parts compost
  • 1 part potting soil

Bonsai Soil Mix

In our area, the air is very dry.  The shallow bonsai pots are where the trees live.  We are combining two circumstances that are in opposition to each other and yet try to maintain the bonsai tree.  To achieve the best health for our arid climate bonsai, these are the mixes predominantly used in our area:
  • 1 part decomposed granite + 1 part general purpose potting soil mix. (conifers)
  • 1 part decomposed granite  + 1 part chicken / poultry grit + 2 parts general purpose potting soil mix.
  • 4 parts chicken grit + 4 parts forest mulch + 1 part peat moss.  
  • 4 parts chicken grit + 1 part forest mulch + 4 parts peat moss (acid loving plants) 

Calculating Amounts Of Soil

Diameter measures across
the widest part of the circle

Due to our arid climate, it is acceptable to have a bonsai pot that is 2 - 3 times as deep as the bonsai trunk diameter.  For example, a new-ish bonsai tree with a trunk 1 inch across, or 1 inch in diameter then the bonsai pot can be three inches deep at most.  Unless, of course we are working with a cascading bonsai, then the depth of the planter can be much deeper due to aesthetics.

After calculating the depth, we also need to look at the length and width of the bonsai pot.  The pot should be about 66% of the height or width of the tree, whichever is larger.  The width of the bonsai pot should be just inside the width of the bonsai tree.  The shape matches the masculinity or femininity of the bonsai and the straight lines or curvatures.

Once we have the length, width and depth of the pot determined, we use simple math to determine the cubic yards of soil needed.  As an example, a 24 x 12 x 3 inch pot is first converted to feet. 24/12 x 12/12 x 3/12 = 2 x 1 x .25.  The feet are multiplied 2 x 1=2; 2*.25 = .5. Multiply the result by 72 (cubic feet in a yard).  This is 36 cubic feet.  Divide this by 27, and we have the final result of 1.33 cubic feet of soil needed for this container.

This is where the calculations get sketchy, because the soil mix can have different weights to fill the same amount of space.  For this,it is probably best to mix and guestimate for approximate needs and have some on hand for re-potting.

Taiju Esaka 1st Place Bonsai

Exceptions To The Rules

And then there are times where the rules must be broken, when conventional pot size rules are overturned based on the goal of bonsai - to create a beautiful, moving artistic experience.

"I have chosen this tree to express the arrival of spring. The soft lines of the tree go well with those of the pot. With both pots I was careful not to repeat shapes." ~ Taiju Esaka

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