bonsaiTALK Community - View Single Post - Repotting Cork Bark Pine

Many older bonsai specimens were grown or developed with field soil (earth or clay) as a component of the mixture. This can be particularly difficult situation, because portions of the mix will drain freely, but the older soil, next to the trunk will not drain well and could result in crown rot. In any case the compacted soil will not promote good root growth in those areas and it's best removed.

Develop a realistic plan for this. It's not a good idea to completely strip a pine of its soil (although this exact procedure is required by law for importation in many areas). Instead, plan to remove the field soil over a number of transplantings. Work off the outermost in the first transplanting and be sure to drive a chopstick through the clay or earth masses closest to the trunk so you can work some free draining bonsai soil into those troublesome spots.

If the tree is healthy, you can be more aggressive, but if not, you just want to remove what soil you can without damaging any of the succulent roots.