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 used Turface and Oil-Dri for years before starting to use pumice and akadama. Some have had good results with Turface and deciduous trees—I had fairly good results with deciduous while using Turface years ago, too—but I found much less encouraging results with conifers, pines in particular. The upshot is that Turface has a narrower range of compatibility with plant species than with other soil mixes, and has some complications with maintenance.

Once I started using the volcanic soils that the Japanese prefer, I discovered much greater predictability of results, and root structures, penetrability of water, and ability to adjust water holding capacity of the soil with a much broader range of tree and shrub genera. That was a game changer. And I could do things with trees that I had not been able to do before, because I had a better root system.

You can keep a tree alive in Turface or Oil-Dri, that has been well proven. But we want to do a lot more than that in bonsai.


Turface, which ranks as one of our worst soil components

My experience with Oil-Dri and Profile, two other popular soil components, is that they have similar properties as Turface.

There are three 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, secondly it has a deadly hydrophobic property, on the surface, when dry, and thirdly the particle size is small and flattish.

How many of you have just watered a tree planted in 100% 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
  • Size of the particles, when sifted of the fines, are limited to rather small ones, and they are flattish, resulting in layers that repel the penetration of water.

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 (particularly 100%), 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, and for decades used many different types before trying the volcanic mixes.

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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  1. Lucia says:

    Thanks for speaking up for the roots Michael! Someone’s gotta do it 🙂
    Just because something has been a habit doesn’t mean it’s good!

  2. Turface is great for a pitcher’s mound and the baselines on a ball field which is what it was developed for. Warren Hill also made a comment on that Turface retain salts which could lead to soil toxicity.

    I quit using Turface 15 years ago. Great post

    Coincidentally –

    Yesterday I did a contact job for the City to do weeding on their ‘Green Roof’ the entire roof at City Hall is pumice and black lava rock with a fine mixture of compost. I would say a 80% pumice and black lava to 20% fine compost. Pulling weeds was tough roots everywhere!! Existing plants were Sedums, strawberries and wildflowers.

    Again a great post

    • crataegus says:

      Propagators and those growing young stock pay attention to Anton’s post—80% pumice and then 20% composted bark or something like that is one of the most effective soils for strong roots and early tree development.

      Later in bonsai training, once it’s in a bonsai pot, this is not the best soil, in my opinion, as fertilizer and water levels are more difficult to control. We end up with shoots that are stronger than we want them on old trees, for instance. But for many purposes, especially young plants, this mix is a good place to begin.

      • Roger Marr says:

        Good analysis of different substrates at link below. Scientific, but with good commentary.‎

      • Bruce Winter says:

        Michael…this is what I got when I clicked the link:

        HTTP error 404 The page you are looking for might have been removed, had its name changed or is temporarily unavailable

        Please try again later or contact FAO.

      • Roger Marr says:

        Try typing in the website in your browser. I am not sure why it won’t open by clicking the link.

        Or… it is by M. Raviv, R. Wallach, A. Silber and A. Bar-tal, 2002. “Substrates and their Analysis”

        I hope this helps.

  3. Mr Ison says:

    I see,sports fans will be disappointed.

  4. Dave says:

    I get my Akadama from Boon and various places here in California, but I here so many people say they cant get it where they live. What would you recommend as a viable option to someone who has no access to Akadama?

    • crataegus says:

      Very good question. If I had only one soil component to use for bonsai it would be 100% pumice. If you have akadama, add some. You don’t need lava (scoria), but you can add some if you like. But if you have neither of those you’ll see very good fine root growth in pumice which will last for a long time in the interior of the root mass without the decomposition that you see in the organic soils. In truth there is no good substitute for akadama, but you can use all pumice if it’s not available. If you don’t have pumice, try horticultural perlite, and sift to a middle size—3/8″ approx. for most purposes.

      My sense of soil particles in order of their importance is this:
      1. Pumice
      2. Akadama
      3. Lava

      • I used to use zeolite horse stall deodorizer when I had a dog to help reduce the smell of his urine in certain areas of my yard. It would release the ammonia when it rained. As a natural volcanic rock that holds water for quite some time, It came in a powder then a sandy granule and now I have found it in a 3-5mm size and wonder if it might be worth using in my bonsai soil. What is your thoughts? Even as a topsoil?

      • crataegus says:

        Zeolite is a possibility. I’ve never used it, but I hear it’s similar to pumice.

  5. Jonas says:

    Thank you, thank you, thank you! Well said.


  6. Sage Smith says:

    I can attest to the power of pumice thanks to Michael’s suggestion just over a year ago. It’s all about healthy roots. Hands down, the best investment I’ve ever made for my trees. Thanks again brother.

  7. Mike Fritz says:

    I use skoria, pigeon grit, fine orchid bark chips and it seems to work here in Arizona.

  8. Neil says:

    Thank you. I guess I got lucky cause I am so old school I only use real dirt and mixes there of…never heard of the stuff but if
    I do now-I know not to use
    from out on Cedar creek

  9. NO MORE TURFACE ! All my trees are ‘rooting’ for pumice 😉

  10. Bruce Winter says:

    Yeah but…the color is so akadama-ish. And akadama in the rainforest is death. I used to top dress with turface for a show. Now I just try to have enough moss to cover the pumice/milled sphagnum I’ve used for ever. Or at least a layer of dyed fine sphagnum.
    I’ve never understood adding black lava to pumice.
    Thanks for another great post!

  11. Bernard says:

    My standard soil mix is pumice, lava, and acadama. Since acadama is currently unavailable, can you suggest an alternative? I was going to try fir bark, but upon further reading, it seems to deplete nitrogen when decomposing.

    • crataegus says:

      Just use more pumice. Available substitutes for akadama are much worse than pumice.

    • Daniel Dolan says:


      While I agree completely with Michael’s observations here, please see Brent Walston’s comments on fir bark to alleviate your concerns about nitrogen depletion. He is most helpful and replies in detail to most Bonsai questions.



  12. cherylas2009 says:

    well said Mike! Never used turface, don’t plan on using turface, and repot trees in good mix almost as soon as I get them.

  13. backcountrydan says:

    I also have first hand experience with turface, oild dri and pumice. All I can say is I’m never going back from pumice. Unfortunately many of my trees are in my pre-pumice mixes, and will have to be changed out over time.

  14. Marty Klein says:

    Thank you so much for your detailed, candid posts. You have changed my whole juniper routine for the better – I hope. It is all so confusing though. I was blessed that my first bonsai class many years ago was with John Naka. When talking about junipers, John’s mantra was “pinch,pinch,pinch.” It became a joke between us. When I would see him I would say “I pinched 100 times today”. He would say “No I said 200 times”. Regarding soils, I remember when Warren Hill would go around denouncing Turface because it “hold salts”. I am an old engineer but I do not pretend to be knowledgeable about soil chemistry. It seemed to me that any porous material would “hold salts”. Whey doesn’t pumice hold salts? Okay, I am going to stop using Turface for a while, but I remain confused. Many of the “masters” that I know do use it. I once bought some bonsai soil from the amazing Suthin and it was mostly Turface. Our local nurseries still use it. My best roots actually come when some of my bonsai start life in Metro-Mix with coir and other materials that people denounce. So much still to learn.

    • crataegus says:

      It is difficult to get pumice on the east coast, but I would encourage people over there to go in together and ship it in bulk. Ask nurseries to carry it. I can’t speak for other’s experience. If I lived on the east coast and did not have exposure to pumice I would not know about it either. But having seen both sides of the country, and seeing what they use in Japan, I think pumice is more important than akadama.

      Having said all that, perlite is an ok soil component if you can put something heavy on it so it does not float away.

    • crataegus says:

      Yes, some organics like coir and bark can produce good roots, but seemingly only over the shorter term. We want roots that if need be can be left in contact with their soil particles sometimes for decades. In the interior of the soil mass in Japan sometimes things are not touched for a very long time, if things are happy there. And they only seem to remain happy if in a volcanic mix. The exterior is changed, the interior is only worked on periodically and never as severely as in the west because there is no need to.

      There is a lot to learn, but we’ve been trying to reinvent the wheel over here in places where it’s not wise to do so. Much of horticultural soil science assumes replacement in several years time. In bonsai, this is simply not the case. Sometimes in the interior of the mass we want it to remain there for much longer. And that’s the whole problem with western assumptions of repotting: Changing out the soil mix. With organics you have to because they break down into something that gets worse and worse over time.

      As for pumice retaining salts, I’m just reporting what I see. I am not a soil scientist either and I don’t feel I need to be, because the roots speak volumes. We can think our way around things but in truth a lot of bonsai technique is counter-intuitive and in comparing things we should use what works best, and in my growing certainty from what I see, there are very good reasons why the Japanese prefer volcanic soils. Without them, if they are not available, I’d have a high percentage of perlite in my mix because it works very well and that too makes sense—exploded sand is very much like what a volcano does when it makes pumice. Perlite is the technological answer to a natural process. The main fault with it is it breaks down easily under agitation. Again, I think it’s wise to import pumice to areas where it’s not yet carried. Our pumice here in the United States, from the Cascades mountains, is I think superior to what they use in Japan which is heavier and does not have the same gas exchange.

  15. Katy McReynolds says:

    Turface is not an ideal soil component, however, what is a realistic substitution here on the Eastern Seaboard? I use pine bark fines, haydite and screened and rinsed turface as my components. Sometimes I use permatill or granite in lieu of the Turface.. I have had great success growing healthy root systems with this mix. Proper watering, compensating for Turface’s known drawbacks, I have not experienced the problems you describe. I am willing to concede that I must water more deeply and more frequently, so there is no doubt more labor and waste associated with using Turface. We experience brutally humid and hot summers and often very dry, mostly mild winters here in Southeastern Virginia, Zone 8A. What component would you recommend, that is not pumice.

    • crataegus says:

      You can learn to use almost anything, but that does not mean it’s ideal. Pumice provides the widest range of healthy growing conditions in a pot I’ve ever seen—you can over water it, under-water it, and it creates great fine root growth second only to pumice mixed with about 50% akadama. If you want more water holding capacity add some perlite, sifted. Or perhaps a small amount of shredded spagnum (orchid moss, NOT peat). But to your point, there is no good substitution for akadama on the east coast, but more importantly, there is very little that is good drainage, either. if you have hot summers, don’t use granite as it’s a heat and a cold sink. roots will cook. you need insulation. try sifted perlite. I used it in arizona and it worked great. just weight it down on top with something heavier—I know that’s not ideal, but give it a try.

      • Katy McReynolds says:

        Thank you for your informative and prompt reply and thank you to everyone else who also passed on helpful advice. I will start the transition during Spring repotting season.

    • crataegus says:

      The main problem with the horticultural perlite is that it’s very soft and if you chopstick in your soil then it will break down. Be careful with it—and if you can, encourage a local nursery to carry pumice. I have seen it bagged here on the west coast, so it does exist in a transportable form. Not sure why it does not show up in the Midwest or East coast—maybe not enough people have asked for it.

  16. Connie says:

    Hi Michael,
    Now that i want Pumice, where can i find it? I live in the midwest, can i find it locally or can i order it from somewwhere online? Great thoughtful post. Connie

    • crataegus says:

      I have seen pumice bagged here on the west coast, so it does exist in a transportable form. Not sure why it does not show up in the Midwest or East coast—maybe not enough people have asked for it. Might inquire at a local nursery.

      • Daniel Dolan says:

        To All:

        I live in Chicago…..nurseries and garden suppliers here do not carry pumice. I have this modest recommendation. At present there are 28 listings for horticultural pumice in 4 or more sizes and as many different quantities on Ebay. I have purchased from 3 vendors and while they vary, all are suitable to terrific. Go to Ebay and use keywords “pumice soil” or else you will spend a lot of time reviewing personal hygiene products.

        Best regards,


  17. Joseph McCoy says:

    I’ve only found Turface to be hydrophobic when it is bone-dry new out of the bag, and then only when it is used as the primary ingredient. Once it absorbs water and is hydrated, it is like any other clay-based soil component, but doesn’t break down to mush. I guess it depends on your watering/growing conditions, but I’ve never had a problem with it as an additive/absorbant.

    • crataegus says:

      Hydration is a problem with Turface, Oil-Dri and Profile; they all have strange water holding properties and can become oddly water repellant on top on a hot, dry summer’s day, impeding water penetration. So it works both ways and is a very dangerous situation.

      What I’ve seen between different soil particles is that Turface does not create a good root system, and pumice, lava, and perlite are far better for fine root growth and allow more uniform water penetration. We can argue about it all day and for what reasons, but the fact is it is not as good as other particles. Yes, you can find a way to use nearly anything. I’m just saying Turface has the narrowest parameters of healthy root growth of anything I’ve seen. Even under the best of husbandry trees grown in Turface have fewer fine roots than other soils. I don’t see a reason for using it when there are better options.

      Without access to pumice I would suggest perlite. Horticultural perlite is best, and can be sifted to many different sizes.

  18. Zach says:

    Thanks for the great post; any thoughts on the type of Akadama; i.e. the two line, high fired type vs the soft type? The high fired type seems to have a similar consistency to turface

    • Chris says:

      Not sure if someone already mentioned this, you can easily obtain pumice at feed stores on the east coast. There is a product called dry stall which is 100% pumice. The company is based in CA and you can find it at agway stores. $16.99 a bag and each bag yields about 75% in usable bonsai soil. Boo ya!!

    • crataegus says:

      Too hard akakama is not the greatest either… a bit of breakdown is a good thing over time, it holds the rootball together. Medium hardness is the best.

  19. Steven Koenig says:

    Michael have you ever heard of Dry-stall? It is a pumice like material used for stabilizing the ground in horse stalls. I live here in the Midwest now but when I lived in SC I could get this at Southern States (there is one near here in IN). Just thought I’d share.

    • crataegus says:

      Yes, Dry-stall is pumice. It is useful for bonsai soil, not bad, but the sizes are a bit small. So for smaller pots this product is ok. The other thing is that it seems crushed, and therefore it has less pore space than the pumice taken up buy shovelful in the Cascades which is rounder. But Dry-stall is usable.

  20. Sam Ogranaja says:

    I’ve been using Turface for a while because folks in my club said it was great to use. But I’m watering at least 5 times more than they are. It gets SUPER dry on top. I have no proof of this but I feel it doesn’t dry uniformly. Weirdly enough the trees in 100% organic that I haven’t repotted yet seem to do better than the stuff in Turface. I’m one of the only members in my club that gets full sun; if it’s up it’s covering my yard. Some folks don’t realize that sun exposure makes a huge difference in what you grow and how well they can take that sun. One of my maples in Akadama, and Lava mixture took full sun quite well until late August when it finally started showing stress.

    I cannot locate Pumice for the life of me. Nurseries here locally say “Pumice? Isn’t that for scrubbing your feet?” I know I can get Perlite though. I should give that a try.

    Michael, are you suggesting mixing Perlite with something else? Is this a water retention component or more for air?

    This rant reminds me a little of Tony Furtado’s – Angry Monk. You should Spotify it, I think you’ll like it 🙂

    • crataegus says:

      As for perlite, I’d only use it if you’ve no other recourse in locating pumice. I’ve seen it bagged here in west coast nurseries, so it must be shippable. I’d start there. Find enough people interested and soon you’ll have a supply. For a while you might be the only people asking so it might take some cajoling.

      Perlite does both, water retention and air. Remarkable stuff, really, only problem is, it’s very light and very soft. Handle with care.

  21. Steve Moore says:

    Like Marty, I’m withholding judgment at present. I’ve rarely found Turface to be hydrophobic unless it’s been allowed to dry bone-dry; but then the same can be said of organics like composted bark. Also, Jack Wikle (Tecumseh, MI,) has been using Turface for decades; when I asked him about this ongoing controversy, he responded, “What I can say is that I’ve never had any problems with it.” Given his experience and expertise … when giants contend, the small are left perplexed!

    Pumice is no more easily available for me than for Sam O., and the perlite available here is so soft it crushes to powder if you look at it cross-eyed. I started using at least 50% scoria a couple of years ago, just to try it out; so far I’ve been happy with it.

    We need to remember, of course, that for each of us, soil recipe, watering habits, and climate all interact.

    • crataegus says:

      I can totally understand skepticism. Healthy even, I’d say.
      As for Jack, we have to remember that Jack is a wizard who could grow a broomstick in pea gravel and make it sprout. I’m not surprised he could use Turface successfully. But this is really to the point—I think we can USE just about anything, but I’m trying to make some other observations that are very broadband in nature. For one, we have a lot of communication and travel these days which has changed our notion of what is available out there, and we’re able to see how different soils work. Much of this information is relatively new. Pumice was not a common bonsai soil medium even on the west coast until relatively recently.

      I don’t think—In fact I know—most of us do not have the horticultural skills of Jack Wikle and the question is not ‘is it possible’ but ‘what is best for the widest range of people, lifestyles, and backyards’—and from what I’ve seen in different soils in different circumstances, which is given the volume of trees i’ve worked on and root masses I’ve poked around in, Turface produces the least roots of anything but beach sand. I HAVE seen some good root systems in it. But not nearly enough of them to convince me that most people could grow a good root system in it.

      Please consider me a reporter. I’m reporting what I see. I do hope that after reading this Turface will be a little less stable on its pedestal than it’s been, and I hope that people should do their own investigations.

  22. Bruce Winter says:

    Seems like any nursery should be able to order pumice from their supplier. Also, there’s a hydroponic substrate called grostone, basically, manufactured pumice i.e. glass. Light, reusable and not expensive. I use it interchangably with pumice as it’s the same thing. Seems to be available all over, even in rainy old Hilo 😉
    Check out the

  23. Marty Klein says:

    Thank you Michael. I am so grateful that you have started this discussion. What you are saying makes a lot of sense. I had a long career making sonar equipment. I would read what the theory and the books said (back then I knew what an equation was) but then I would go out and find out what really works. I spent a lot of time rolling around on ships. But eventually I produced some gratifying results. I have always wondered what happened in the inner root ball of those ancient bonsai. I am not sure what you mean “if things are happy there.” I would think that “happy” means the interior roots are still healthy and are providing the functions of roots – water and nutrient uptake etc. If this is the case then the volcanic mix is fine. Thanks for the note about Perlite. I have been using Perlite for many years but I usually do not mention it in public because it makes eyes roll. People think it is unattractive but they do not realize that some darker cover layer on the surface hides the white particles. I have also been using an Espoma product called “Soil Perfector”. It has a nice dark color and it seems similar to pumice. Sadly I am just finishing putting my trees away for a long winter’s night so all of this discussion is something to dream about for next year. As John Naka says “Spring is tomorrow.” Happy Thanksgiving.

    • crataegus says:

      Thanks Marty, all of you have instigated a great discussion. You have read my obscure reply correctly, by being ‘happy’ in the interior of a root mass i mean ‘continuing to produce healthy new roots’. I’m writing a book now that has a chapter detailing some of this soil and repotting stuff more clearly, which is a challenge because it’s not really very logical, and is only beginning to make sense to me.
      John was a gift to all of us-

  24. Mark Erdmann says:

    Michael, can you comment on Haydite? According to the manufacturer it is expanded shale “ceramic, lightweight aggregate prepared by expanding select minerals in a rotary kiln at temperatures over 2200°F”. Do you or others have experience with this compared with Turface or Pumice?

    • crataegus says:

      Haydite is another particle that does not seem to produce very respectable roots. A root will grow through it, but roots do not hang out and create very fine root structures as it does in pumice or skoria or akadama. So we see thready root systems in these types of ceramic products. It is possible to keep a tree alive in it, but creating a ramified top will only come from a ramified bottom, and getting there by bonsai technique applied to the top only will stress the tree out on the bottom.

  25. walton brainerd says:

    Good advice! What is your experience with zeolite?

  26. Daniel Dolan says:


    Being a fair-minded person your comments are always balanced. Unerringly, you tend toward the positive, your only shortcoming.

    Add this most recent post to the archive of things …..”Not to Do,” which includes your Juniper Pinching article and only a few others. I know you despair of most Bonsai books but this could be your next one…..”Don’t Do This.”

    I have struggled with this product as a novice for 5 years as all the experts in my area preached its merits…..the same folks who had me pinching Shimpaku to death.

    Look forward to your next lesson.

    Best regards,


    • crataegus says:

      Well…actually I’m writing a book that might be on the list of those to throw into a book burning, as anyone saying ‘don’t do this’ is asking for a whopping from someone. It covers what we’re talking about here in more depth, among other weird and wild things. Sadly I’m too busy to get at it every day. Or even every other day.
      Thanks for the encouragement to be a gadfly…

  27. Chris O. says:

    The dry stall product is not available everywhere…for instance, I haven’t located a single supplier in the Rochester NY area. My experience with turface is that, if anything, it tends to stay too wet. Particle size is also on the small size. But I know quite a few people who use it successfully. Are other materials superior or easier to use? Probably…but if you can’t get them, turface can work. There’s plenty of evidence of that!

    • Chris says:

      Contact your local Agway. Even if they don’t have it in stock they carry it at their warehouses. I live in CT and they get it delivered from their warehouse within three days.

      • Chris O. says:

        Chris…I will look into that. I did contact a couple of the local agway dealers a while back and was told it was something they could not or would not order. I have resorted to having pumice shipped in from the west coast for testing…but that’s not really cost effective on a larger scale unless I can find a bunch of people to split costs.

        How is the particle size? I think someone here posted that it’s kind of on the small size (similar to turface) but I don’t have time right now to read through all the comments to find that.

    • crataegus says:

      Yes, dry stall is an option but from what I’ve seen the particle size is very small. Usable perhaps for the top of soil or very small trees. But another problem is it seems crushed, and does not have the pore space between particles. I recommend trying to find horticultural pumice which will be siftable, and you will need to layer it in the pot.

      Yes, I agree, Turface does stay too wet and it is on the small size, too.

  28. Ryan NIchols says:

    Hey Michael,
    Sounds like folks around the country could benefit from my soils seminar that I gave at the GSBF convention earlier this month! I’m sure you would have gotta real kick out of it!

  29. Mark Erdmann says:

    Thank you so much for this post! I finally realize what was wrong with two of my plants last summer! I repotted a Jade plant and a Crepe myrtle using Haydite, crushed granite, and pine bark chips. The Jade was losing leaves and didn’t grow all year, and the Crepe myrtle leafed out but didn’t increase in size at all, the leaves were pale, and it didn’t flower. I thought it was because of the cool wet summer we had, but these were the only plants that did really poorly, and the only ones that were potted with Haydite (expanded shale)

    • Chris says:

      I think the particle size is fine. One bag yielded about 75% usable soil. Each bag is 40lbs. My idea of usable is a particle size that does not pass through a window screen. I primarily grow American larch so I make a soil mix that retains a lot of moisture.

  30. nickalpin says:

    For anyone having trouble finding pumice, try finding a local dealer selling Dry Stall. This is pumice sold as horse bedding, so any feed or farm stores may carry it. Here in Florida, Southern States carries it, according to their site.

    Although I won’t remove Turface from my mix – it’s a component in the standard Florida mix – I’ve begun to use expanded shale and will also incorporate pumice.

  31. endsurg says:

    Thanks, Michael. Great post. Ryan Neil has been a big proponent of pumice and, as has been said, difficult to find on the East Coast. So Karen Harkaway and I bought a pallet of 50 bags and split it. No shortage anymore. I do have a few questions. You seem to imply that potting in 100% pumice would be acceptable. Is that correct? Also, the pumice particle size in these bags is very varied and Ryan feels that consistency in the size of the particle is important for good root growth so sifting out to 1/4 mm particle is important. Do you agree? This is a lot of sifting and I lose half of the bag. Do you think this is critical and I just have to bite the bullet and sift? Also, Colin Lewis is a big advocate of enhancing the mix with 20% live sphagnum moss from a bog. What’s your feeling on that?


    • crataegus says:

      As to your question, it is possible to pot a tree in pure pumice. I do it all the time. It is one of the prime techniques for getting a weak pine strong again in Japan, for instance—they nest the old rootbal in pure pumice. You can get crazy root growth and a very strong tree.
      It is one of the only particles that is a water retaining drainage material, and does not hold too much water, like Turface. As far as I’ve been able to tell, it’s fairly unique. (There are some iron-bearing skoria particles that are very light and are essentially pumice. The heavier ones I avoid.)

      So, yes, you can use entirely pumice. Bear two things in mind— it should be layered in the pot from large to small on the top, and putting orchid moss/sphagnum moss on top is necessary to prevent too rapid drying of the top in the summer. (this is, incidentally, typical technique in Japan for mixes with pumice and akadama). And secondly, you may be watering a bit more than you’re used to.

      I’m glad to hear Ryan is promoting pumice as well. I think we’ve been seeing the same things. And yes, consistency in the particle size is essential—if you do any chopsticking at all, to settle the soil around the roots, particles of different size will stratify exactly opposite what you want for drainage/drying: big on top, small on the bottom. So, yes, definitely sift your pumice to several sizes. The big stuff can be useful on the bottom for your pines and whatnot, the 1/2″ size, and the smaller stuff of about 1/8″ on the top. But sphagnum mixed with perhaps the top layer is not a bad idea. I shred the sphagnum over a big screen and apply it last. So I don’t mix it in as Colin does but I can see the possibility.

  32. paul3636 says:

    I don’t understand why “Diatomaceous earth” (Napa 8844 oil dry) would be as harmful as turface.

    • crataegus says:

      Frankly I don’t either, I just see very similarly haphazard root development in Turface, Oil-dri, and Profile media.

      • Soj says:

        Turface, Oil-dri, and Profile are all calcined clay products.

        NAPA 8822 (not 8844) is calcined DE.

        I have no idea how it compares to calcinced clay, other than that I have been told its water release and gas exchange are supposedly better than Turface. Personally I think the particle size leaves something to be desired – too small. Mostly seems to be around 1/8″ with maybe 10% at 1/4″-ish. And its mostly chip-shaped, eg more or less flat.

        Dry-stall is more round but seems heavy for the particle size, which is also on the small size – pretty uniformly in the 1/8″ to 3/32″ area.

        I have used the NAPA 8822 in a “gritty-like” mix recently (1:1:1 calcined DE, Dry Stall (crushed pumice), and bark) and I have not liked the results. Similar to the gritty mix, it dries out fast on top – hence does not stay evenly moist throughout – and it is heavy. Perhaps not quite as heavy as if I had used gravel in the mix – but still too heavy.

        And my M. koenigii starts are not happy in it. I may have to repot them, which in and of itself could be damaging. Sort of a devil and the deep blue sea situation.

      • crataegus says:

        Dry stall is two small for most uses. It’s rather crushed, which is not the best form for soil particles. All soils of this type however need moss on top or it will dry too fast, and unevenness in moisture will result.

      • Soj says:

        Correction: The particle size of the NAPA 8822 (calcined DE) is actually mostly just over 1/16″, with about 10% up to 1/8th” ish.

        It is very small. All in all it doesn’t seem to suit my purposes very well.

  33. ken s (ohio) says:

    I use a combo of pumice, Hydrocks (a roofing product), haydite, poultry grit, and decomposed orchid bark (1/4″ particles). this seems to work for most species, with some all-purpose sand added for trees requiring more soil moisture. I have found that turface breaks down into mud, no matter how much you sift/ wash it, & I haven’t used it for 4 or 5 years. After 20+ years of growing bonsai, I still kill one occasionally , but usually by overworking the tree, not by over / under watering.

    • Zack Clayton says:

      I use turface and have had no problems with it, but I use coffee for my organic mix so go figure. I have better luck rooting cuttings in the turface fines than in sand. My experience is that turface will absorb a lot of water in the pore structure and allow excess to drain from between the particles. keeping high humidity around the root hairs. That said I have started switching over to the Hydrocks that Ken mentions. It is a main component for green roofs in this area. Failing to find pumice it might be better to check out suppliers of “green roof” soil medium rather than going for other material. I find haydite to have the claimed drawbacks of turface, without the moisture retention that I have observed.

      • Soj says:

        I don’t get it – Hydrocks is also calcined clay. How is it any different than turface?

      • crataegus says:

        Hydrocks may work, the space between the particles is probably bigger. That’s the main problem with Turface, even the larger stuff is too small, and then the shape is very bad, it layers because it’s sort of flat. You don’t want flat particles in your soil mix. Same goes for Haydite.

  34. Ben says:

    Thanks for this post. I tried Turface MVP but for me it was too small except for all but the smallest mame and shohin sized material. I’ve seen a professional use it for growing plants like Julian Adams with good results, he uses it with some bark mixed in for the majority of the stock he sells. For trees in pots though why take the chance. Just spend a little more money for a good bag of akadama it’s a small cost for the health of your trees in the grand scheme of things.

  35. Chris says:

    Great post! Thank you! That confirmed some doubts I had since I began using turface 2 years ago. Being up north in Quebec, I’m one of the east coast folks who don’t have access to pumice, and akadama is very expensive. We don’t have very hot summers here, temperatures rarely go higher than 83°F. I’ve seen your earlier comments on granite being a ”hot or cold sink”. What would you think of a 33% decomposed granite, 33% perlite and 33% pine bark soil? Would the granite still get too hot in those proportions?

    • crataegus says:

      I think some decomposed granite might be ok, but I’d use more pumice. Try 10% granite and 20% bark and the rest pumice if you can find it. Bark is not the worst additive to a mix, although I’m doing some writing about organics in bonsai mixes that end up over the long term being problematic.

  36. Bruce Winter says:

    Thanks, Michael for this spot-on post. 57 replies? WOW!
    Pumice and sphagnum works for me, and as you say…”the roots grow like crazy.”

  37. crataegus says:

    To attach a general commentary onto my post—Firstly, I’m gratified at the level of sociability in the responses. I know that talking about soils is nearly as iffy as insulting someone’s pet, so I thank everyone for the level of this discussion.

    There is no right or wrong. Please consider me a reporter. I see a lot of bonsai handled in different ways and this includes bonsai soil types, and I’m just reporting on what I see. Sometimes I don’t understand what I’m seeing—I’m not a soil scientist. But that does not preclude observation of root systems in a wide range of soil types in different yards under the vastly differing care of all of us who are uniquely suited to our lifestyles and assumptions. Turface can and has worked for some bonsai practitioners, and some get good ramified root systems with it. What I see, though, is that it does not work for everyone as well, and that points to a narrower bandwidth of usability and healthy soil environment for Turface than for Pumice. In my experience Pumice is a far easier soil component to get good results with than Turface.

    Pumice is somewhat unique in its water holding abilities. I see, comparatively, a very modest amount of water retention in pumice. But it is enough that it is both a water holding and a drainage particle—a lot like Turface. However it seems the roots like the amount of internal absorption of pumice, and the release of that which results in high gas exchange in the soil, which might be more than other types of soils. I can’t claim to know this is a correct observation. But it is a drier soil than most, which means more air in the root mass. But unlike many drainage materials like granite or sand, it has a fine pore space in the interior of the pumice particle, it’s not simply supporting a film of water on the outside, like sand does. This sounds a lot like Turface, doesn’t it? Only, pumice seems to have a very different relationship with the roots that grow through it. Some of that is the larger size that pumice can be sifted to, which translates to better pore space, but again, it’s more than that. It is obvious to me, since I’ve seen many roots in both substrates, that there is a significantly different climate inside a pumice root ball and a Turface root ball. Having said that, you might find better luck with deciduous in Turface because it holds so much more water, and less luck with conifers such as pines.

    This leads me to answer publicly a few private emails that asked what I use as a soil mix, which I failed to offer in this post. There is ultimately only so much that we can cover. Firstly, all of this is contingent on how you use it. There is no silver bullet. There would be many ways to use pumice or things you could add to it. But, if you don’t sift your pumice, and you chopstick to settle soil particles around roots, you will leave large particles on top of your pots and the small will go to the bottom—which is exactly opposite what you want—and you might not get good results. The top will dry out very fast. So sift your pumice and put the small on top and big on the bottom. All of this soil talk presupposes considerate, skilled root work, some of which is really hard to pass on by words. Hence my preference for in-person education. Developing a tree in 2-3 years as I show in my ‘Portfolio’ page is certainly possible, but only by setting up the root system to succeed.

    Some asked if I use 100% pumice. The answer is yes, I have. I don’t usually, most of my mixes contain 30-50% akadama. What I see in 100% pumice is much greater vigor of the trees, and sometimes more watering needed because of the nature of pumice which is drier and because it’s a more strongly growing plant that needs more water. 100% pumice is the soil of choice if you have a weak pine, for instance, and wish to get it stronger. In Japan we’d take a weak tree and gently nest the original soil mass in a box of pure pumice. It is also the soil of choice for recently collected trees, which are unable to use a lot of water and so it encourages the roots to grow out. So can you use it in a bonsai pot at 100%? Of course.

    If you use soils of this nature, keep your soil particles uniform. Sift to sizes and use them appropriately, and apply some grated sphagnum (orchid moss, not peat) over the top layer. There is a post here somewhere, a year ago I think, on growing moss on bonsai. Might take a look at that, too.
    This comment has gone on long enough…thanks for reading!

    • Chris O. says:

      Michael, I’m curious about something you said in this message: “In Japan we’d take a weak tree and gently nest the original soil mass in a box of pure pumice.” If you do this, doesn’t most of the new root growth wind up in the pumice…which would mean you still have the problematic root system at the core? I can see how this would restore vigor to the tree overall but it doesn’t seem like it would solve the issue with the root system…as I would think you’ll have to eventually discard much of the newer roots in the pumice and re-invigorate the core.

      Or maybe it’s a multiple step process? Step 1: place old root mass in pumice and get tree vigorous, Step 2: Reduce root mass and gradually replace bad soil/root system taking advantage of the increased vigor?

      Curious because I have a couple of pines that are a bit weak and I need to deal with them next year. Thanks!

      • crataegus says:

        You’re spot on. Good instincts. We have two situations here. One is a weak tree with a root problem, the other is a weak tree without one. A tree with a root problem sometimes needs to be addressed often by removing some of the soil or roots. In other situations we just let it recover on its own. But often, to address the second issue of a weak tree without a root problem, we simply need to create conditions where the tree can get so strong that it solves its own problems. For instance, a tree that suffered from a very severe summer, that weakened it. Or a disease that is really tenacious and the chemicals we throw at it need help— a very strong tree metabolism. How do we get that? Get it out of a bonsai pot and put it in a box of screened pumice. Later you can often put this tree right back in the same bonsai pot without really addressing the original soil mass. There were no problems there.

  38. Graham says:

    Many thanks Micheal for creating a sound discussion on this topic,
    We’ve just found a supplier up here and many of us are using it in our mixes.
    I’ll be very interested in reading about your thoughts/experiences on “organics in bonsai mixes that end up over the long term being problematic”,
    Cheers Graham

  39. Mark Erdmann says:

    Michael, here’s another attempt to locate something locally available in Ohio, have you heard of Growstone? Apparently made from recycled glass, highly porous, comes in 3/8″ particle size. It’s my last ditch effort to find something I don’t have to pay shipping for.

    • crataegus says:

      I have never tried that. Good luck and let us know-

    • Bruce says:

      Mark…please see my Nov 26 post refering to grostone. I’ve mentioned it on 2 forums with no interest. Odd, since pumice is volcanic glass and grostone is the same material and process except manmade. The “Super Aerator” size is quite suited for our needs. It’s found in hydroponic supply outlets and quite popular I’m told.
      Hope this helps.

      • Soj says:

        I’ve recently obtained and evaluated the Growstone in the smaller size (3/32″ to 3/8″). From my observations, this is a great substitute for perlite but a lousy substitute for natural pumice. It’s porosity is great, it is very lightweight. But its moisture retention is little short of abysmal.

        I am using it as a substitute for perlite in more “conventional” potting mixes, but I think you should stick with natural pumice rather than the Growstone for other uses.

      • crataegus says:

        Bruce, can you forward me a link to your post? Not sure where to find it.

      • Bruce Winter says:

        Not sure who to send this to, you? Mark asked me but how do I send to him?

  40. John B. Wall says:

    Now this is a post that generates discussion! hahaha….I can see the many benefits of pumice and I believe it to be a fine soil component. I however use a product very similar to turface called Marbets Mule Mix, made in Columbia TN. It is high fired Mississippi clay particles ….wont break down, sharp granules. It is a form of Turface. I have used this product as my main soil component now for over a decade with excellent results. It is not hydrophobic even when very dry and seems to retain water well and keep soil temps resonable even in the very hot TN summers. This product was used on the world series pitching mound a couple of world series ago!! I really think the secret is your fert. regimen….with weak organic low nitrogen fertilizer….you will most likely have weak spindly roots in this mix. However with a stonger nitrogen content chem. fertilizer, you will have excellent root ramification with this product. As i said I have used this product for over a decade with excellent results. No salt buildups…no problems. I have many western yamadori trees that thrive in this mix….from ponderosas to Colorado Spruce, to Rocky mountain junipers. Even some old grandpappys well over 400, 500 yrs old. Great respect to you as an artist Mike, your one of the best in the country, but it would take an act of congress to make me change my mix….bc it works that well. Super fast draining inorganic mix+ lots of water, fertilizer and strong TN sun= excellent growth.

  41. Michael, Great Article, I Enjoyed reading Your Book and look forward to the
    New one. I always enjoy Your Posts, Styling Work and most of all the Pots I’ve purchased from You over the years. This Soil Media is a very Controversial subject, but someone has to do it. I’m a little surprised that Water Retention Values and Annual Rainfalls didn’t come into play?

    • crataegus says:

      Since living in Upstate NY, Arizona, and now rainy western Oregon I have a firm belief that it matters little what’s going on outside the pot. Ideal environment inside the pot remains the same. If you’re in a hot area, pay attention to the top inch of your soil, and use a more water retentive soil, smaller soil particles, and put shredded sphagnum on top. One of the benefits of pumice is that it’s very insulating. I’d use it particularly in hot and cold climates. I’m not in one of those, but it would be my go-to particle if I was.

  42. vonsgardens says:

    Thank you Michael.

  43. Bill says:

    There are three ‘types’ of water in soils: Hygroscopic (bound to the soil particle), gravitational (occupying large pores in soil, will drain away), and capillary (moves against gravity due to surface tension in small pores).

    * Gravitational water is available to the plant for a time, until it drains away.

    * Capillary water is available to the plant for the longest period of time.

    * Hygroscopic water is never available to the plant – it’s held to the soil particle too tightly for the plant to use it.

    Turface was developed to dry – remove water – from infields. It was not developed to grow plants in. Turface has a very small pore size(< 1 micron) and therefore has a low water release rate due to the high water tension of the small pores.

    Turface has 3 times as much hygroscopic water by weight and 5 times as much by volume than pumice. Water in Turface is significantly less available to plants than water in pumice. (Primary source citation available.)

    I agree that one can grow a tree in about anything, dependent on one's own behaviors regarding water, fertilizer, etc.

    I strongly disagree that all media are equivalent. Some are better than / easier to grow in than others. And telling new growers that media composition doesn't matter is bound to lead to frustration and confusion.

  44. Bruce says:

    Thank you professor, that pretty much nails it.
    Turface will never again darken my doors, er, pots, again.

  45. Steve Moore says:

    Jack Wikle prepared some comments of his own for the Ann Arbor bonsai society; not in a spirit of hitting back, but of rounding out the picture. Since he doesn’t have a blog, and I think his thoughts *and* yours should reach a wide audience, I tried to bring them together in my own latest blog post. I trust you won’t mind the link; this is relevant to your post.

  46. drew51 says:

    Jack Wilde is very experienced, but really presents no evidence to support his view other than anecdotal. Let’s look at a study using turface and you can draw your own conclusions of how good the substance is for root growth.

  47. Chuck Muia says:

    Would you please give me the formula using pumice or do I just use pumice?

    • crataegus says:

      The most important thing is to screen it. It can be used straight, but usually only for recently collected trees or weak conifers. The screened sizes will be determined by how big your tree is, and your purpose. 3/8″ to 1/4″ size is about right for most things, though.

      My main mix for anything in a bonsai pot is 50% pumice, 50% akadama, I sometimes use less akadama but I would use more if it was affordable. I see very strong root growth in this mix, almost too strong in some cases for more refined trees, as the pumice promotes that.

      For stock plants growing really hard you could try 100% pumice. I’ve also used 80% pumice, 15% composted bark, 5% steer for the really heavy feeders. This again is only for stock plants, as there is no control over the growth in such a mix, plants will just push hard. And now we’re talking about our soil ideals in two different directions—in a bonsai pot, and before it gets in one, and those are two very different things.

  48. drew51 says:

    Bill you say “primary source citation available” Could we see it?

  49. crataegus says:

    I wanted to share this communication from Jack Wikle. We’ve been in touch for quite some time about soils and I know many of you know him well and that he’s been an authority on this subject for decades. With his permission, here are a couple of paragraphs from a recent email exchange. Jack writes:

    ‘I do recognize that akadama soil has unique properties which make it superior as a container-growing medium and I don’t question that pumice is probably our best substitute for akadama. Of course this leaves Turface somewhere lower on the desirability ladder. Yet Turface is both widely available and economical. And, with a little amending Turface has worked pretty well for some people.

    The big question remains, what is going on that would explain pronounced differences in the experiences people are having with Turface as a container-growing medium. Through a friend, I’ve recently gotten access to articles reporting university-level technical research. So, I am looking forward to some exploring in that arena to see what I can learn. In the meantime, you have inspired me to do more in trying to upgrade my own Turface-based soil mixes.’

    • Chicago Stonepro says:

      Could the the pH of the Turface be part of the problem? I have a bag that comes in at about 4.0. It improves slightly with screening and thorough rinsing. My tap water runs about 8.0.

      I called the company, to find out the reserve acidity, to help me guage buffering. I wanted to treat the Turface before using it in a growing medium, didn’t want to waste time, nor overshoot my pH target. The tech checked into it and called me back – they didn’t have that info. I had to do some calculations, and give it my best guess.

      What they were able to tell me, was the wide pH range ( 4.0 to just above 8.0 ) was the result of different clay deposits – depended on the quarry, or mix of quarries, represented in the bag you got. When I asked if it was due to the amount of aluminum in the clay, he said that was exactly the case.

      I could definitely see how folks could be experiencing differing results from what looks like the same product, if in fact, it isn’t. There’s always going to be the human factor – no two people will screen and wash their aggregate the same way – but beyond that, calcined clay aggregate is at its core, a natural product. Its chemistry is just going to vary, and it seems to me, caution for our plants would dictate at least checking the average pH, of a bag of calcined clay/Turface, before building a growing medium with it.

      Might not have been necessary, years ago, but given wide disparities in growers’ experiences, it seems prudent now.

      • Steve Moore says:

        Stonepro, I think your information sheds a lot of light on the question. Thanks!

        Presumably, the maker of Turface has multiple processing plants as well as drawing from multiple quarries; also presumably (but it seems a good bet to me) each processing plant gets its clay from the closest quarries to save transportation costs. Distributors, in turn, buy from the closest processing plant for the same reason, I would expect.

        So we can end up with significant differences between the Turface(R) sold in Oregon and the Turface(R) sold in the Great Lakes area.

      • I was told that oildry and turface soak up the oil in fertilizer and because oil and water do not mix, eventually the oil keeps the water away and these will no longer hold and release the water needed like akadama. I wonder if for some reason pumice does not do this and that is why it is superior? Just throwing that out there. This might be something to look into when looking into the research methodologies. Because of the designs of research studies factors such as longitudinal factors get factored out of the study.

      • crataegus says:

        I had not heard that about the oils in fertilizer.

        As for the whys of many of these questions, I can only guess and would prefer not to…I see the results, having used a wide spectrum of soil types over 30+ years, and volcanic soils win out. We do need someone with more of a scientific toolbox to run experiments with controls on these questions like yours. Thanks for the comment.

  50. Steve Moore says:

    Drew51, you said that Jack Wikle “…really presents no evidence to support his view other than anecdotal.” I suppose, unless you consider 40-plus years of experience to be backing for his view.

  51. drew51 says:

    So Jack’s experience counts but Michael’s does not? Whom am I to believe? Show me hard facts like formal studies..
    Anecdotal evidence from either does not confirm anything. I’m from the science world, and prefer to examine formal studies to form an opinion. I have 40 years of growing experience too, but didn’t present my opinion because it doesn’t really mean anything. I don’t grow bonsai, I grow cacti, but the mineral soils are similar so this is of great interest to me to find the best amendments.
    I don’t have a dog in this debate. I could care less whom is correct, I just want information that is actually useful, and confirmed to be true.
    Also Jack is open to changing his mind, as am I. One study is not enough.
    I look forward to any other info.

  52. Steve Moore says:

    No, I didn’t say Michael’s experience doesn’t count. It does. And obviously the situation is not very simple.

    Maybe I misunderstood, but you seemed to be dismissing the value of Jack’s experience out of hand. If I did misunderstand, I apologize.

  53. Henry says:

    For those folks in the East Coast. Look for aggregates as a substitute for pumice. It’s sometime refer as pumice aggregate. Aggregate is mainly used to paved roads. It’s light and has good moisture retention and porous. I have good luck with it and fairly inexpensive. The only downside is that sold by a truckload. Upside is you’ll have several years of supply.

  54. Bruce says:

    I can sure vouch for pumice and rapid root growth. I mix it with about 10-20% milled sphagnum and use it for stock plants and those futher along in pots. Any suggestions for slower root growth? It rains about 150″ per year here so drainage is crucial.

  55. I have been using a diatomaceous earth mixture with other grit and organic material mixes within and haven’t seemed to have problems yet. It’s very difficult to buy pumice unless I go to a bonsai nursery in which the price is jacked up just as high as akadama. And even if I buy online, the cost of shipping nowadays makes it just as bad if not more than just going to the bonsai nursery. I’m not nearly as experienced as most of you but I would think a lot has to do with the mining/firing of the product vs just saying across the board every similar product to Turface is bad. The first thing I did before I started using the diatomaceous earth I do, is researched the company that makes it and researched their process. I also researched the sciences behind it and then did my own tests with it before using it.

    • Steve Moore says:

      eschmidtpabonsai, I think you’re onto something: “… I would think a lot has to do with the mining/firing of the product …”

      • Thanks steve. I know when dealing with clay, its properties are greatly affected by how its mined and fired. And I need to correct my previous comment……. the clay I use is a calcined montmorillonite clay instead of diatomaceous earth clay. They
        carry slightly different properties which may be why the kind I use works better than turface.

  56. Brian says:

    Wish I read this sooner I just grabbed 2 50lbs bags of turface mvp. Is that the same as regular turface?

    • crataegus says:

      Not sure, but if you use turface just be sure you screen it. You’ll likely have better results with deciduous than conifers with turface, but still, i think other soils are better.

    • Steve Moore says:

      Brian, Turface MVP is one of the largest in average size that I know of. I agree with Michael on screening it. I don’t use anything under 2 mm for anything except cuttings and bald cypress; nothing under 1 mm at all.

  57. Juris says:

    Great article. What about cat litter?


    • crataegus says:

      Cat litter seems to create a similar root system as turface, long and stringy. They grow straight through, as if looking for something better. And it holds too much water for the most part.

      • Brian says:

        Well I just add lava and pumice to help out as I’m on a budget so I don’t have a lot to spend on pumic n such for so many trees

    • treebeard20 says:

      Juris, cat litter looks similar, but is fired at a lower temperature and (I think) is made of a different clay, with different properties. Upshot: breaks down quickly to an anaerobic mush. (Real Turface (R) keeps its structure for 20+ years.)

  58. Soj says:

    Update on Growstone:

    I’ve had my curry leaf trees in Growstone mixes and a few still in the gritty-like mix described in a 2014 posting above. I repotted about half of the latter into Growstone mix over the course of 2014-2016. I still had half a dozen in the gritty like mix.

    This past winter I was very ill and none of my plants – indoors at the time – got watered for 2 or 3 months. Not a drop. I swear.

    Everything in the Growstone mixes survived with no worse than a bit of leaf browning. Half the gritty-like mix plants died. My jasmine was in a crushed pumice/peat/bark mixture and it NEARLY died but ultimately survived – that round of neglect.

    I again hit a health bump and my plants, now outside in the hot arid High Sierra Desert climate, in June/July/August – did not get watered for 2 to 3 weeks at a time.

    ALL the remaining gritty-like mix plants died. I also lost the jasmine. But everything in the Growstone mixes not only survived, they thrived, showing new plant growth throughout.

    Now I’m not sure what to think of all this, given my previous impression that water retention in the Growstone was (according to me) “abyssmal”. And frankly I can’t remember how I came to that conclusion – but I’m guessing I “tested” it by itself rather than in a mix with peat and bark. And I don’t grow bonsai.

    However at this point I’m totally sold on using Growstone in a container mix, at least for the plants I grow – eg garden veggies, houseplants, and my beloved M. koenigii.

    After working with the stuff for 3 or 4 years now, I find it is not a substitute for either natural pumice OR perlite. It is its own thing with its own characteristics that allows me to make up a well drained, highly aerated, moisture retaining container mix.

    Despite living within a few miles of some of the largest pumice deposits in the continental USA, I have never been able to obtain natural pumice in large enough quantities to directly compare its characteristics to the Growstone (GS2 btw). But I can say that the isolated small quantities of natural pumice I have been able to come across were smoother (more rounded edges where Growstone has quite sharp edges right out of the bag) and the natural pumice, while lightweight relative to its size when you consider that it is a rock, is still heavier than the Growstone. EG, the Growstone seems to be more porous and to have better aeration than the samples of natural pumice I had access to.

    I can’t speak to issues of pH and my ideas about WHY this stuff works so well for me may be totally off base. But Growstone mixes have been a miracle for me, as my access to suitable components to make up container mixes has just about disappeared altogether by now. My local Home Despot no longer carries even the not-very-good approximation of “pine fines” I had been using, and I haven’t been able to get vermiculite (coarse grade) for almost 30 years now.

    “True Gritty” as espoused by one guy who dominates every hobby gardening site on the internet has been impossible for me to evaluate as I have NEVER found a place where I could get just one bag of Turface. That guy buys it by the pallet – of COURSE he thinks it is cheap and easily available. And the Tapla-approved gritty-like mix I did manage (using the 8822 calcined DE product) did not pan out for me. Granted, it was not “true gritty” and my plants did go through ridiculous repeated neglect – yet the Growstone plants are doing fine while the transplants from gritty mix struggle to catch up (and that’s from when I was on top of things, even before the collapse of this past winter). And everything I didn’t get out of the gritty-like is now dead.

    After 4 years working with Dry Stall both in gritty-type and peat/bark compositions, I find it NOT to be very useful – especially when compared to a mixture using Growstone. The stuff has had the life crushed out of it, it is heavy for its size, and the particles, as others have mentioned, are just too small.

    But the Growstone has given my gardening new life. It works well even with the crappy super-fine peat moss that is all the local Home Despots and Lows carry any more. Compaction continued to be an issue in mixtures that used Dry Stall, weight continued to be an issue, moisture retention continued to be an issue. None of those are issues with the Growstone as I have been using it.

    I’m sold on it.

  59. Soj says:

    BTW – I forgot to mention – Growstone is reusable virtually forever. I would guess you could continue to reuse it until repeated handling has broken it up into pieces too small to be helpful any more, a process I guess would take about 20 years depending on how often you repot and recycle it for reuse. I pay about $35 for a bag of the stuff (the larger size bag they make, I forget the quantity) but given I can reuse it easily that doesn’t sting so much as it did at first. In fact I’ve never had the need yet to open my remaining bag of the 4 I originally bought because

    There are basically only 2 reasons to repot (can’t say about bonsai but for more plebian types of container plants at least) – excessive compaction, and plant growth requiring a larger pot or division into multiple pots.

    After 3 years in the same (fiber – as in fabric) pots, compaction is STILL not an issue, and despite my repeated neglect of late, most of the plants originally planted in the Growstone mixes are ready for potting up. M. koenigii has a tap root when grown naturally so typically isn’t repotted a lot and switching from plastic to fiber pots seems to have helped to naturally “air” prune that tap root and encourage upper growth even in a pot. Lots of m. koenigii in pots get real leggy. By and large I seem to be managing to escape that with the Growstone mixes in fiber pots.

    All my long-term plants, btw, are M. koenigii (curry leaf tree). Container veggies only stay in the mix for one growing season.

    Anyway. To sterilized and recycle the Growstone – float the spent mix in a large tub. Most of the spent organic matter will fall to the bottom and the still usable Growstone will float on the top. Just scoop it out and throw it in a bucket of bleach water to sterilize, rinse, and reuse.

    Also, straight out of the bag Growstone is quite dusty. Keeping in mind it is made of recycled glass, wear a dust mask when working with it. Rinse it well – I made a “bag” of the coarsest window screen I could find and just swished it around in water and tossed it about some and the vast majority of the dust washes out.

    The edges can be quite sharp as well – recycled glass. But I always wear gloves and would recommend doing the same when working with it. And the edges do wear down over time to a degree.

  60. This is arguably your most relevant blog post…thank you!!!

  61. I have been pondering your observations. Years ago, my young son wanted to grow an eastern red cedar, Juniperus virginiana, as a bonsai. I put a small plant, that survived mowing in a neglected yard, in a spare gallon pot with turface mixed with some potting mix. This eastern red cedar has been surviving on my deck, in this pot, without watering for years. I checked the roots and they look healthy. The potting mix has all decomposed, or washed away, and all that remains for the roots to grow in is turface and some residual perlite.

    I used turface when I created my rock garden. As I am planting in my rock garden, there are always roots from maples that have encroached. Every year, I take a narrow spade and cut into the soil surrounding these rock gardens to sever the encroaching tree roots. However, there always continues to be more tree roots that have grown into the turface. It is apparent to me that maples have no trouble rooting into turface.

    I left some propagation flats outside that contained either a turface mix or potting mix. The flats have been largely abandoned in the midday shade of trees. Various plants established themselves in these propagation flats like sedges and Saint John’s wort. During a period with little rain, the plants in the flats containing turface were stressed but survived. In contrast, the plants in the flats containing only potting mix dried up. If these plants have not been killed outright, they will have to grow back from their roots.

    I can see how turface would not be appropriate for certain plants that live in arid conditions. Some of the plants in my rock garden have done poorly when transplanted into turface, which I water often in the heat of summer. These plants did much better when they were grown in sand. However, I think turface definitely has a place in horticulture when plants need to survive during periods without watering for as long of period as is possible.

    • crataegus says:

      Thanks for your observations. Turface changes significantly when mixed with other things, particularly the water shedding problem with overhead watering. There one might use it. Water holding particles are many. Perlite holds a ton of water, then becomes so light it floats away. Yet horticultural perlite grows some amazing root systems, and it’s no wonder that it’s a preferred particle for horticulture. Not that it looks very nice, but it might be worth a try in your situation in flats, mixed with something like potting soil. When I lived in Arizona I was amazed how good the root growth was in perlite. But it seems good in nearly every climate. Thanks again for the comment.

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