Help! Great nursery plant in heavy clay soil.
I found a very nice-looking boxwood at the nursery I want to train as bonsai. It was in a five-gallon nursery pot, so is a pretty big specimen. It has a very thick trunk and lots of exposed nebari.
The problem is, it must have been field-grown (probably locally, here in the NW) as it is in very dense, heavy clay (I can't even use the word "soil").
Although it may be impossible, I am wondering how to remove enough of the clay, while saving enough of the roots to plant into a much more porous bonsai mix.
Today I took off a whole lot of the outer clay and managed to cut a really strong taproot. I just can't seem to be able to remove any more of the clay though. My intent was to put into a training pot and reduce the root mass even more next year--finally putting it into a bonsai pot.
How can I break up this clay, though? Is it impossible?