Posts Tagged ‘pumice’

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:


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Life Without Turface…

…is full of sweet birdsong and rainbows.

I feel the need to comment on Turface, which is still, unfortunately, a common bonsai soil component. I say unfortunate as this is one of the worst soil components you could ever use. I used Turface and Oil-Dri for years before starting to use pumice and akadama. That was a game changer. I could do things with trees that I had not been able to do before, because I had a better root system. Sure, you can keep a tree alive in Turface or Oil-Dri. But we want to do a lot more than that in bonsai.


Turface, which ranks as one of our worst soil components

I will not go into the soil science of ion exchange or things of that nature. Given the evidence from the trenches, it hardly matters. My experience witnessing root development in many types of soils has confirmed that Turface ranks dead last. Oil-Dri and Profile are equally bad.

There are two obvious faults of Turface. The first is that it produces some of the most anaemic, thready root systems that can be had for any money, and secondly it has a deadly hydrophobic property when dry. How many of you have just watered a tree planted in Turface, scratched the surface of the soil and found it to be bone dry underneath? For the ‘No’ answerers, I hope you never have the pleasure. This dangerous property will result in dead zones in your soil, creating a situation where the majority of the roots will grow in the worst places in the pot, which are along the sides and the bottom. The main problems of Turface may be summed up this way:

  • Hydrophobic properties lead to unpredictability in water penetration
  • Turface either stays too dry or too wet, and so it is not able to create a middle moisture level that enhances root growth

These problems are severe, with this conclusion:

  • Root growth in Turface is erratic at best, without the benefits of predictability seen in volcanic soils

Given that the foundation of the tree is the roots, and that bonsai training is by nature stressful to the tree, having a marginalized root system is to be avoided at all costs. You don’t have to use akadama. But at least don’t use Turface, and you won’t experience random, poorly ramified root structures that cannot support bonsai training. There are many things that can work, but I will say that, aside from akadama, pumice is a near-perfect particle for fine root growth.

I know many of us use Turface out of habit or availability, and can understand skepticism of this post. Maybe you’ve not seen what I’ve seen. I do get around and see a lot of soils. But at the end of the day, roots are not something to be taken lightly, for having an excellent root system is so much more important than owning fancy, expensive bonsai tools, expensive fertilizer, expensive pots, or even expensive trees. Buying cheap or easily available soils simply because they are cheap and easily available will make all of that magnificence entirely moot. In bonsai, a finely ramified, healthy root system is everything.


Pumice, one of our best soil components

If you have some Turface, don’t ‘use it up’ by adding a small proportion to your mix. Give it away. Pay someone to find a use for it. Or put it in a box, label it with an unknown address, and offer it to the post office. It’s safer there, wherever it ends up, than in your bonsai pots.


Pine roots after five years in Oil-Dri. This is the kind of root system I see in Turface, Oil-Dri and Profile. You can certainly grow a tree in it, it will likely stay alive, but bonsai training assumes the effort at creating ramification in the shoots, and with a root system like this you’re hamstrung from the start.


Pine roots after 3 years in pumice. This is typical of the solid mass of fine roots that we find when growing in pumice (or some of the lighter in weight lava/scoria). With this kind of root system you can do a lot of work to the top and expect a great response in budding.

Postscript: Not long ago I resisted teaching or writing in an emphatic manner, to avoid upsetting people or to avoid arguments. But much like the concerns offered in my post Never Pinch Junipers!, I see so many weakened bonsai as a result of using Turface, Oil-Dri, and Profile that I have to speak. My main loyalty is to the trees. This is one area where cutting corners is really not the best way to go. Spend money on soil. If things like pumice, scoria, and akadama are not readily available, get it shipped and split the cost with friends. It’s not the lightest thing on the planet, but then thankfully it’s not lead, either.

For a follow-up post, try this one from Jan. 2016:


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