A couple years back I wrote a post which became one of most viewed posts I’ve ever written. It was about Turface and similar soil ingredients like Oil-Dri and Profile, and my skepticism about their qualities as a bonsai soil ingredient, following 30 years of experience with many different soil types. The post was meant to call into question the belief that Turface is the best soil ingredient. I don’t believe it is, having witnessed its performance for years, but that doesn’t mean you can’t grow a tree in it, or that it may be one of the few options in your area due to availability issues.
In rough strokes, there have been three main evolutions in our soil usage in North America. Earliest was the potting soil/sharp sand period, decades ago. Then came the Turface era, which was definitely an improvement on the earlier mixes. Then came the volcanic mixes preferred by the Japanese, the pumice, lava, and akadama soils, one of which, akadama, needs to be imported.
While the debate hinges on what works better, it is compounded by issues of availability and price. On the east coast akadama is very expensive, needing to travel farther from its source in Japan. Pumice is rarely available in the east, and is only spottily available in the middle states.
Certainly if you hate the very idea of importing soil components, like akadama—an understandable position, I don’t like it either—try pumice if you can find it. It’s from our mountains here in the western US, and locally is dirt cheap, 17 cents a gallon in some places, and works well as a base soil ingredient to which other things may be added (such as akadama and lava if you have a bonsai, or composted bark/steer if you have young stock.) Naturally, trucking pumice east is going to be expensive.
If you prefer to use Turface, definitely sift out the small stuff. You may find that deciduous trees are happier in it than pines, as it tends to hold a lot of moisture and the particles are not very large. Also, you may need to water very frequently in order to prevent the hydrophobic qualities of the fired clay product that happens on its surface on dry, windy days. These comments are for 100% Turface; adding other things may mitigate these issues.
I think we’re looking for a base ingredient that can be used all over North America (apologies to those readers in other continents/islands, although there may be a similar discussion worth having in your area.) I think pumice is a much better base ingredient than Turface, with much more dependable horticultural properties. If that is impossible to find in your area, I have no argument.
Some have had success using Turface. You will be able to find people who have had good luck with it, their trees are strong and healthy with good root systems. And then there are a lot people who can’t seem to replicate those successes.
At the end of the day, it’s really amazing how many different types of soils one can use to grow plants in. I’ve seen people use something close to concrete, a clayey thing that was terrifying to behold, and have a margin of success with it. In some places in China they use essentially pond muck. We can learn to use almost anything. But I really don’t think that’s the question, or at least, it’s not a question I’m interested in. I’m curious what is the best thing I can recommend to the broadest range of people wanting to grow bonsai, the broadest set of abilities and goals, and in answering that, I repeatedly come back to the volcanic soils the Japanese have used for a long time, and continue to use.
If volcanic soils are unavailable, keep experimenting, keep exploring, but don’t settle for Turface (and Oil-dri.) It’s not impossible to grow a tree in it, that’s not the point, it’s just not ideal.
Incidentally, James Hooper has just had a delivery on the east coast of some of our western pumice, and offered to have his name and number put here for anyone seeking it: 617-823-7154
(Finally, a disclaimer: It won’t matter much what soil we use if we’re using questionable horticultural practices like barerooting old trees each time we repot. Please don’t do this. Without leaving a solid mass of soil on the roots we won’t manage to create the dense, stable, dependable root systems that we should see in our pots each time we take them out. This disclaimer could go on for pages on multiple subjects. But soil choice is a primary decision.)
Further reading…or pre-reading, actually, as this was the first post on Turface: