Today ends my 2 year journey to test the viability of turface as a substitute for akadama growing medium for sample bonsai in my collection. It has been recommended in club meetings and by cost conscious bonsai artists over the past few years as the price of Japanese Akadama has increased. Over the past year I have lost a small pine completely and weakened some tropical trees and young plants. Today, however, I took the last tree in the experimental mix to check the results. Over the two year period I had noticed the struggling foliage on the juniper procumbins with concern. I had fertilized and watered like all the rest of the juniper but this one was not growing much at all. The mix was 70% turface, 10% pumice, 10% lava, 10% fur bark. The fur bark had completely decomposed. I hydrated my trees as usual before the re-potting process.
I found that the turface held a lot of water and the juniper was not draining well. The turface was breaking down into power holding even more water. What was most disturbing was the lack of root growth. Normally when potting a tree after two years I would be cutting off roots. Not in this case. There was evidence of negative root growth so I did not trim roots at all. The juniper is now re-potted in the standard 70% akadama, with mixture of pumice, lava, kiryu. I am looking forward to better root development and thus a better foliage mass.
So my end results are that turface, holds a lot of water, breaks down to powder quickly and fails to hold nutrients that feed the tree. It can discourage root development and weaken the plant. I have also been doing soil temperature testing an found the turface medium had a slower rate of heat retention from the akadama mixes and dissipated heat much faster. After having several species either fail or weaken I will never recommend turface as an akadama replacement. I have read this from many bonsai purists but wanted to test it for myself. Even though turface is an inexpensive medium alternative, akadama proves it offers much better nutrient holding because of its surface structure and inherent nutritional benefits. I would rather pay the extra for healthy plants.