Hi Folks -
I have about 2 dozen trees in nursery cans (some quite large) that will be repotted this spring. As this is the first repotting and akadama is so expensive, I was hoping to get by with the following components: pumice, pine bark mulch, diatomaceous earth (oil-dri), and turface.
Any suggestions on ratios for those to make a basic mix (that can be modified based on the species)?
I have used a mix of pumice and pine bark to grow trees in early development such as you have listed. I generally use about a 50/50 mix for broadleaf deciduous trees and 67/33 mix for conifers that want to be a bit drier. I screen both to keep the particles between 3 and 9 mm, although I will keep some larger particles for large pots and smaller ones for small pots. I have used oil dry in about a 50/50 mix with garden soil in grow bags in the ground and was pleased with the results. I know some folks swear by turface, but I believe that pumice is a much better choice since it is more porous. I have also mixed in aged steer manure at up to 20% for both my grow boxes and in the grow bags - normally replacing some of the bark or soil. I like to keep the aggregate content fairly high so the root system is easier to take apart and trim when repotting.
I usually agree with marty but don’t in this case. If this is their first repot, do you save your old soils that might be high in akadama? go with that. there is always the chance of introducing pests with old soils and of course weeds galore but it works well for an initial repot if you don’t want to use fresh soil blend. I have started using more akadama with all my trees and am seeing better results. better growth and more resilience too pests. need to repot more often though as they tend to produce a lot of rootage. akadama is so expensive that I have started saving old clean soil rather than throwing it in my garden which I used to do. now just the really dirty soil goes in the garden. You also need to start looking at your roots and get rid of what you can safely do to produce good base flare and eventually go into a shallower pot.
Good point about recycling used bonsai soil. I normally sun dry it in the summer and rescreen.
For 1st repots out of nursery soil, I use 50% pumice, 25% akadama, & 25% lava.
I’ve been thinking about experimenting with 100% pumice.
What are you using for pots?
How deep?
That would drive the mix
If back into nursery can 75-85 pumice, 15-/25% spag peat moss, worm castings added to this as directed.. Pines like it on the dry side == less peat Maples would like the higher peat to retain moisture.
If cement mixing trays or deeper bonsai pots 100% pumice or 50/50 pumice/ lava it is a cost thing but it will dry out very fast and require water almost everyday or multiple times a day in the hot summer. (You could also use the above mix of peat, pumice, worm castings) Peat will hold moisture and nutrients.
Turface is often hydrophobic, it is a weird material. You could use pine bark but remember it turns toxic after about year 3 so it depends on how quickly you plan on repotting, less then 3 years go fo it, Longer than that Ryan warns about its toxicity and other issues.
Green zeolite will be my new akadama replacement due to it cec but it is not cheap to get the larger particle sizes and in low ph the aluminum may become plant available like Akadama which is not good.
If less then three years to repot, they will pretty much grow in anything that provides a balance of water and oxygen.. longer then that it becomes tricker as far as your choices go.
Old soils dried in the hot sun or cooked in a shed all summer long to dry and kill pathogens can be used as well but if this is your first round, IDK how much old soil you have left but it can be resifted and washed, you could even wash it with hot water if you wanted to kill or knock down what could be living in it.
If old soil smells rancid do not use it.. It must have been washed & dried immediately after you were done with it.. If left to sit around wet in a bucket or bag it will grow nasty stuff and smell rancid.
My shed is used as heated storage for trees in the winter and it dries my soils in the summer as it gets ripping hot in there, a garage, shed any place that gets hot can be used to dry soils for reuse..Of course drying in the sun would be better but that depends on your climate, rain etc.
Peter Chan out of the UK plants trees in pumice, peat, loam mixes in bonsai pots. I do not believe Ryan would support this, once outside of the traditional Boon mix you are off on your own.
Akadama has massive amounts of aluminum which is not good and it has large quantities of maganese which can become problematic as it breaks down, but it has been shown to stunt growth..
Remember the Japanese use akadama because it is there!! They are not importing exotic soils.. akadama is local dirt.
With pumice as your base you could only go wrong if what you added held too much moisture or was high in unwanted things.. For example a lot of coco coir is high in sodium which is not good..
Just my thoughts, take it or leave it..
Here’s one last opinion to consider! Not sure what part of the country you live in so that makes a huge difference on what soil components you might have available. As was pointed out akadama is the native soil available in Japan, it’s the primary soil used - just happens to have some unique characteristics that make it excellent for bonsai. I’m in the Deep South, I only used akadama on trees that are in final refinement stages and then only as 1/3 of my mix, for all the reasons already mentioned.
I came up with a mix that works excellent for both grow out and refinement work and it’s extremely versatile. I can reuse old soil season after season by baking it in a large roasting pan over my fire pit. (it’s a fun activity for winter afternoons). I use 20% pumice (American), 20% lava rock, 50%expanded shale (trade name Stalite Regional product) 10% crushed oyster shells ( another regional product). This mix turns out to have very similar CEC to akadama based soils, doesn’t break down in my super moist, humid climate, and nearly guarantees I can’t overwater. The big plus is it’s very cost effective, and once sifted and roasted easy to sanitize for reuse as nothing breaks down quickly. As always you can augment with pine bark to increase water retention, and Taylor to specific species but over the past 7 yrs this has been my go to soil at my nursery when pulling field materials with excellent results. Good luck with your trees!
I have never used expanded shale as it is not common in the Northeast.
Does it have CEC?
Thanks CP
Over the years I have tried all the soil ingrediencies you mentioned and more. I have found that there is no substitute for Akadama, Pumice, Lava (APL) for refining trees. There are no nutrients so you control growth with fertilizer and the Akadama gets finer over time so finer particles gets finer spaces so finer roots. I usually use 1:1:1 for conifers and 2:1:1 for deciduous. I am in Charlotte, NC zone 8A with short wet springs and hot, high humidity in summer. That is why I use more drainage than for the Pacific NW. You may be able to pre order/ buy larger quantities of Akadama from some place if you can piggyback on their big order. Some clubs arrange an annual big buy.
Pumice is great, it has a high CEC.
Lava is light in weight and holds more moisture than sand. I often use Stalite (Permitil, Vole Guard, expanded slate, expanded shale) as it is made near my home and is cheap. Stalite is denser than lava so for large pots it can get pretty heavy.
Pine bark is great for nursery pots. I am able to get partially composted PB. I mix up a large batch of nursery soil which is mainly PB and Stalite (from the producer I am able to buy CA 9 size which is about 1/8 inch) 1:1 plus fertilizers. PB breaks down over time releasing nutrients and getting finer for finer roots. It can get too fine and become bog mud which can restrict air in the roots.
As an intermediate development mix I combine the APL and Nursery to 1 part Akadama, 1 part Pumice, 1-3 part lava or Stalite, 1-5 parts PB.
I do not like Turface, oil dry, Cat litter etc . Any trees I have bought that came in large amounts of Turface died over the winter. As I remember the Turface instructions said no more than 15%.
This is a very interesting discussion. I am 10 years into my bonsai journey but not to this level of soil knowledge (although have listened to apical streams and have been experimenting basic soil ingredients with good results, and viewed basic videos on library). May I ask CMP: Why does pine bark create toxicity after 3 years? I may have missed that Ryan discussion as only about 1.5 years member. If you can direct me to a particular video in the library, I would appreciate it!
Permatill is a regional product, readily available in the south east produced in North Carolina. It’s used a lot in the green roof movement. It has a CEC of 26.9 which isn’t to bad. It’s a bit heavier than akadama but not terrible. For the price savings I get and the quantities I use at a small nursery it pays for itself easily.
I don’t have the video, just send them a email. He is clear in many Q&A about it. Nursery’s use it knowing the item will sell and be planted in the ground within a certain time frame. It is cheap and provides excellent drainage & maybe moisture retention which is why they use. It seems to be standard knowledge among USA bonsai growers that it turns toxic after a while..
I think it is absolutely fine in the short term and many folks have success with starters, pre bonsai etc. You would have to search the web or the library to get more info. If you look at Ryan’s repot strategy he is going out as long as 8-10 years on some of his trees, so naturally you would need a soil that has that type of longevity.
We are all learning and many folks don’t use Akadama on cheaper stock, starters, pre bonsai etc. due to the cost, and in some climates cheap Akadama can’t survive the winters well. Look to Peter Chan in the UK or even Corin Tomlinson both will plant in organic soil in a bonsai pot, which is taboo here..
It is all very interesting to me, basically if it works do it, if it doesn’t change your approach
Good luck in your adventures.
Thank you Chris, for the clarification. I use several different prepackaged bonsai soil mixes, some have a small % organic component, usually fir or pine bark, which prompted my concern. Now I understand the post referred to 100% organic nursery soil so that makes more sense.
Thank you so much.
This seems like a great choice but it does not seem to be readily available in my state. I think I found a source online, thanks for the information.
Happy Holidays
Yeh it might be tough to come by, it is a regional product but it is widely used for the green roofs so that might be an avenue to locate some. Good luck. Happy holiday season.
I would think putting used soil on a metal tray over hot barbecue coals would get the temps high enough to kill pathogens and weeds. 165 degrees Fahrenheit should do it?! Though I think bonsai growers aren’t as fussy about that sort of thing as are orchid enthusiasts. 
I’ve had good results transferring trees out of nursery pots into Anderson flats or wood boxes with screen drainage on the bottom to get them beefed up a bit more before putting them into ceramic bonsai containers. I use mostly pumice with some lava and akadama mixed in. The trees love it and most grow really well with this technique.