Custom local soil blend: slate, trap, perlite, and DE. Thoughts?

[Veebs]

I live in coastal Carolina, far from the land of so-cheap-its-practically-free pumice, so I’ve been looking into options that I can source locally.

Here’s what I’ve devised (but haven’t yet tried) and my rationale. Would love some feedback

- Trap Rock: Similar to basalt (which is close to pumice) in terms of drainage and aeration—locally available and works well as a pumice alternative.

- Slate: Adds drainage and keeps the soil structure stable, so it doesn’t shift or settle too much.

- Diatomaceous Earth: Holds moisture and nutrients, with a high Cation Exchange Capacity (CEC) to keep nutrients available to the roots.

- Perlite: Lightens the mix and boosts aeration, keeping the soil from getting too dense.

This mix uses what’s locally available while still covering all the bonsai essentials.

I’m thinking either equal parts for all or a double part of perlite to reduce some weight.

Thanks in advance for your feedback.

 

[Deep Sea Diver]

Greetings!

Hmm…. I fear this ship is heading into heavy seas! A make your own media strong is on the horizon.

The very first hard lesson I learned as a rookie, besides to keep my scissors in my pocket, was to get known media components and stick with certain blends. This cuts down a really huge variable on the horticultural side. And that is a big rule in bonsai, keep the variables down.

So we did choose to bite the bullet and go with akadama, pumice, lava and biochar as the key components for all trees in the latter stages of development, except azaleas… but I clean and recycle everything. So no outlay in a couple years now…. And have never needed to look back when it comes to media,

Based upon this experience honestly would say one would be better off with just shelling out and buying the pumice, then recycling it at each repot. Since it doesn’t breakdown, at some point depending on the size of your collection, the outlay is minimal.

Can’t speak much about the first two selections, other than they are both variables we wouldn’t want to introduce into our media.

… except Slate out here is nothing like pumice in weight, shape or water holding capacity. Your’s must be different.

Have used diatomaceous earth and not super fond of its grain size, particle shape and high cec, but would likely work in initial stages of development. Others swear by it.

Am presently testing perlite and coco coir blends (be sure to sift the coco coir first!,,.) for some trees in initial development. Works ok on JBP, JRP and Junipers. Not so good on deciduous trees imho… but ok. Big issue is the perlite always wants to float, so one has to be very careful when watering not to blow it out. We had to put a layer of large pumice or lava on top to hold it down.

Anyways, fear I haven’t been much help…. Sorry, but media discussions on BonsaiNut can be very dreadful. Everyone has their favorite media and all swear that their’s is totally the best. So it’s a fraught with danger deal.

Good luck
DSD sends

 

[Shibui]

Trap Rock: Similar to basalt (which is close to pumice) in terms of drainage and aeration—locally available and works well as a pumice alternative.

I have no idea what 'trap rock' is like but basalt is nothing like pumice apart from having igneous origins. Pumice is full of tiny holes which can absorb water and nutrients. Basalt is extremely dense and hard. If trap rock is like basalt it should add long lasting particles and weight but not much else to the soil mix
Slate is also quite hard but tends to fracture into flat pieces. It may be suitable to add long lasting particles and weight but won't contribute much else to your soil mix.
DE is not only for CEC and water holding. The particles are durable so if they are a good size they'll also help with aeration.
Perlite is a great horticultural material. Much more like pumice IMHO but even lighter. Perlite has a tendency to float out of the mix when it is watered so not always great in a bonsai mix.

Not saying the components won't work. We can grow good plants in almost anything if we put in enough work and enough water. I'd be a little worried about how quick such a mix will dry out in summer but you should not have any problems with root rot.

Like all new ideas, try it out in a small way on a few expendable plants first rather than putting all your eggs into the one basket.

 

[rockm]

All of the above what @Shibui said. Trap rock isn't porous and pumice is quite porous. Slate is a poor ingredient, not angular or porous enough.

If you're in coastal Carolina, look around at agricultural supply stores. Chicken grit (crushed granite poultry grit, in starter grade--do NOT use crushed shell or scented pigeon grit) is a pretty decent ingredient. I used it for a while when I was making by own soil. You can also look around for Turface, used in baseball fields. It is porous and holds onto water and nutrients. Another ingredient is swimming pool filter sand (Mystic White is the brand to use, crushed quartz, sharp edges). Composted pine bark mulch is also useful as an organic ingredient for deciduous trees. It's soil as Clay Buster or similar, at landscape nurseries to break up clay soil and amend them with lighter soils.

FWIW, if you have fewer than a dozen trees, it's not worth making your own soil. Searching and finding decent ingredients is a chore. It's not really as cost effective as it might seem. It takes gas money and a few dead trees to add up to a downside.

 

[horibonsai]

I think you are referring to expanded slate. It's more of a substitute for lava but will work in conjunction with your mix. The NC Arboretum uses expanded slate in its soil mix. I would recommend this if you can't get pumice. Stalite is the company that extracts and makes this in NC.

 

[Deep Sea Diver]

Not sure what the issue is….

Try General pumice this is 3 gal 3/16 delivered price

3/16" SIZE - 3 GALLON BAG GARDEN PUMICE — General Pumice Products

Our 3/16" size is our most popular, and the most versatile stone, perfect for medium-large pots & containers. Typically we recommend the 3/16” size for pots/containers over 4” in size (or over a half gallon). It is also the perfect size to add to your garden beds, whether succulent, veg

www.generalpumice.com

Cheers
DSD sends

 

[Glaucus]

Actual rock pieces like basalt or slate are NOT pumice substitutes. They are inert and basically take up no water. Though it depends a bit on how smooth they are. Smooth pebbles eroded by water would be the worst. Crushed up rock would be better. But many rocks shatter into smooth surfaces, I believe. They have no porosity and their purpose is to create air pockets and to make the substrate mixture more heavy and look better than say using perlite. You want stuff to provide CEC, water retention, and fine porosity that allows finer roots to enter the substrate particles. Once you have that, you can add other inert filler like coarse sand or if you need larger air pockets, chunks of slate. That said, you generally want the particles of the different materials to be the same size. So you don't get air pockets inside your slate chunks that get then filled up with the much smaller coarse sand.

 

[WavyGaby]

Does anyone else have experience using Stalite in their soil mixes? Its abundant here in NC and cheap. Ive used it for a couple of years on trees in development and everything seems ok. The specs indicate it has a similar CEC as akadama. Moisture appears to be between pumice and lava. The PermaTill expanded slate specs from their website is:
Sterile and Inert; Durable, High Compressive Strength; Particles contain 50% additional porous surface area; 26.9 me/100g CEC for enhanced nutrient retention; 6 - 10 % moisture retentive.

Akadama CEC is between 21 and 31 me/100 g with 20-30% moisture retention
Pumice CEC is between 1 and 15 me/100 g with 10-20% moisture retention

 

[Deep Sea Diver]

It’s worth a try.

Looked like a good lead to research, so down the rabbit hole once again in search of a potential El Dorado of Bonsai media.

There is always the hope we can find a better media in the US to sub for Akadama. I’m sure it’s possible. The latest geologist search came up with Oregon volcanic material as the best potential fit. Anyways for the newer folks, Akadama is a clayish degraded volcanic mineral that is porous, holds water, yet gives it up easily, has a slightly acid pH and breaks down in a way which causes roots to scale down over time.

This is the fact sheet most often mentioned in bonsai discussions, showing a CEC of about 31.4, a slightly negative pH and high water retention… but doesn’t mention root scaling.



So in hopes Stalite is a home run product, did a little checking and discovered it’s an expanded slate product. Stalite is heated to 2,200 degrees F (1,200 degrees C), similar to those expanded shale products used in hydroponics. Except its surface is rough like a pumice.

Production — Stalite

www.stalite.com

One note: the data I found shows a 6 - 10 % moisture retentive per Stalite Environmental. (https://staliteenvironmental.com/soil-amendment). Perhaps the company has a slightly different process. The cost I found for medium size pebbles of Stalite was 31.00 for a 4 Qt bag.

It would be good to test drive this component, subbing it for akadama one for one, and see how it works. Please be aware an issue we had with expanded slate products in the past were its hardness… so it does not scale… and being hydrophobic when dry.

Cheers
DSD sends

 

[Bonsai Obsessed]

Does anyone else have experience using Stalite in their soil mixes? Its abundant here in NC and cheap. Ive used it for a couple of years on trees in development and everything seems ok. The specs indicate it has a similar CEC as akadama. Moisture appears to be between pumice and lava. The PermaTill expanded slate specs from their website is:
Sterile and Inert; Durable, High Compressive Strength; Particles contain 50% additional porous surface area; 26.9 me/100g CEC for enhanced nutrient retention; 6 - 10 % moisture retentive.

Akadama CEC is between 21 and 31 me/100 g with 20-30% moisture retention
Pumice CEC is between 1 and 15 me/100 g with 10-20% moisture retention

I have used Stalite in my soil mix as an akadama substitute for 4 seasons now and have seen good results, it’s abundant and not price prohibitive. Down side is it’s heavy, especially in large trees but it does hold the pots down. Up side it doesn’t break down in the pots ever die to humidity or watering which is a problem I had with akadama in coastal South Carolina. I use it in my basic mix for all my trees that are coming out of raw development and going into pots - my basic mix is 40% Pumice, 40% Stalite, 10% lava rock, 10% oyster shell. I alter it appropriately based in the tree species and the growth stage - for example if I have a Maple going into refinement I will add akadama to that trees mix to help with root structure. I highly recommend the Stalite, I’ve seen no horticultural drawbacks from using it and many benefits.

 

[Joe Dupre']

I've had good success with about 30% Tractor Supply SafeTSorb. It's a little small, but doesn't break down, holds water and nutrients and has nice color.

 

[Desert O'Piñon]

At the risk of attack...
I think the right mix is the mix that works, and the wrong mix is the one that doesn't. That said, there is a reason certain products/materials are used so commonly. But, the "typical" well-draining mix hasn't been very successful for me, and I attribute that to my climate. There aren't many of us crazy enough to attempt bonsai in such arid heat. I'm going to be experimenting with DE, coco coir, chicken grit, barks, and perlite in different mixes and ratios. When summertime humidity is less than 20%, disease is not an issue, generally speaking. The trees I've killed (other than by ignorance) were due to the inability to keep them from drying out. So I am trying to balance water retention with aeration.
Just a noob sticking his uninvited 2 cents into the conversation.

 

[WavyGaby]

It’s worth a try.

Looked like a good lead to research, so down the rabbit hole once again in search of a potential El Dorado of Bonsai media.

There is always the hope we can find a better media in the US to sub for Akadama. I’m sure it’s possible. The latest geologist search came up with Oregon volcanic material as the best potential fit. Anyways for the newer folks, Akadama is a clayish degraded volcanic mineral that is porous, holds water, yet gives it up easily, has a slightly acid pH and breaks down in a way which causes roots to scale down over time.

This is the fact sheet most often mentioned in bonsai discussions, showing a CEC of about 31.4, a slightly negative pH and high water retention… but doesn’t mention root scaling.

View attachment 581094

So in hopes Stalite is a home run product, did a little checking and discovered it’s an expanded slate product. Stalite is heated to 2,200 degrees F (1,200 degrees C), similar to those expanded shale products used in hydroponics. Except its surface is rough like a pumice.

Production — Stalite

www.stalite.com

One note: the data I found shows a 6 - 10 % moisture retentive per Stalite Environmental. (https://staliteenvironmental.com/soil-amendment). Perhaps the company has a slightly different process. The cost I found for medium size pebbles of Stalite was 31.00 for a 4 Qt bag.

It would be good to test drive this component, subbing it for akadama one for one, and see how it works. Please be aware an issue we had with expanded slate products in the past were its hardness… so it does not scale… and being hydrophobic when dry.

Cheers
DSD sends

Good info. Thanks for elaborating. That table and another from the San Diego Bonsai Society is what I was going off of as well. SDBS also shows a couple other variables in its use like appearance, cost, and mositure as grams per 300ml. Not sure but i think you can divide this quantity by 3 to get percentage.

I used 50/50 pumice/stalite last year on several pines, two being 26 year old 5-6 ft tall field grown trees. They are looking good so far. I still have field soil in there, so not much data yet.

 

[WavyGaby]

I have used Stalite in my soil mix as an akadama substitute for 4 seasons now and have seen good results, it’s abundant and not price prohibitive. Down side is it’s heavy, especially in large trees but it does hold the pots down. Up side it doesn’t break down in the pots ever die to humidity or watering which is a problem I had with akadama in coastal South Carolina. I use it in my basic mix for all my trees that are coming out of raw development and going into pots - my basic mix is 40% Pumice, 40% Stalite, 10% lava rock, 10% oyster shell. I alter it appropriately based in the tree species and the growth stage - for example if I have a Maple going into refinement I will add akadama to that trees mix to help with root structure. I highly recommend the Stalite, I’ve seen no horticultural drawbacks from using it and many benefits.

Sounds like its going well! Makes sense

 

[Bonsai Nut]

In NC you have expanded shale and expanded slate. They have slightly different properties. Neither is going to get you to pumice, but they are definitely better than crushed granite (ie chicken or turkey grit).

 

[Joe Dupre']

A lot of things work. I'm amazed at the soil used in India and China. It sometimes looks like red clay mixed with sand.

 

[Deep Sea Diver]

In actuality we find many different medias can grow decent bonsai. The one thing I do know is many can grow better in mainline bonsai media than others once in ramification. Differences in secondary development are not as readily apparent, it’s with ramification and time where these differences really start showing.

That said, things get really complicated as care, bonsai practioner and styling can make a really big difference in health and growth. In addition, at the ramification level, there are a number of media components that can be used to good effect. European bonsai, especially Spanish bonsai practitioners are case in point. In addition, @leatherback has created some really excellent trees and seem to recall he uses zeolite vs akadama as a key component.

Finally, this discussion reminds me of a media survey of near 40 azalea bonsai hobbyists I did on BN about five years ago. Of these at least 60% used kanuma in some greater or lesser percentage in the media to grow azalea bonsai with. However, when asked specifically, all respondents stated their media was the best for growing azaleas in…. maybe that was true?

Granted the survey responses were subjective… vs comparative side by side or against a standard… and that’s the rub. We see lots of folks who show us azaleas who believe they are in tip top shape. Yet compared to other trees we have known or work with, they aren’t… for various reasons.

So give this media a go if that is what you want to do. It’s your trees and your choice to take. My advice in this case is whatever you do, stick with it until it’s obvious things aren’t going well, otherwise keep using the media, develop your knowledge, skills and abilities and practice a lot.

Not meaning to be a killjoy, my usual advice, based upon experiences of those working beside us in the past years including a number of professionals, is stick with a mainline bonsai mix unless there is an incredibly powerful reason otherwise… varying only deciduous or conifer unless working azaleas or speciality trees. This keeps one of the very most important bonsai variables controlled.

Also in any case, please recycle the media, over and over, refurbishing ephemeral components as needed to keep costs minimized and the impact on the environment at a minimum.

Cheers
DSD sends

 

[leatherback]

In actuality we find many different medias can grow decent bonsai. The one thing I do know is many can grow better in mainline bonsai media than others once in ramification. Differences in secondary development are not as readily apparent, it’s with ramification and time where these differences really start showing.

That said, things get really complicated as care, bonsai practioner and styling can make a really big difference in health and growth. In addition, at the ramification level, there are a number of media components that can be used to good effect. European bonsai, especially Spanish bonsai practitioners are case in point. In addition, @leatherback has created some really excellent trees and seem to recall he uses zeolite vs akadama as a key component.

lol, I WAS trying to stay out of the debate!

I have as base mixture:

• Diatomous earth [sold as kitty litter] or other hard clay-like aggregate (seramis is readily available and sometimes -in clearance- affordable)
  This effectively replaces Akadama which I have found to turn into mush in 1-2 winters under MY [none] wintercare
• Pumice (Bought half a cubic metre 2 years ago which will last me a long time if I do not get a pervasive soil infection requiring full sterile restarts.
  The stuff I bought actually comes with 5-10% Zeolite mixed in, so that is in the blend too.
• Graded Pine bark
• Oil dry / Ground Hydro pebbles / turface / Underfloor Filler (I buy it as the latter, but I believe most of it is fairly similar stuff)
  Light-weight, VERY porous, VERY cheap and creates fibrous roots like nothing else. Is however on its own prone to turning hydryphobic so needs mixing with other components

As I reuse substrate, exact balance is unknown. I add a handfull of pine bark for those trees that like it more humid. And I add some of the floor filler if I need things drier.

For me, this works well.
I do not use akadama for a few simple reasons

• Bad experiences in my first years where I lost a number of trees, and I traced the cause back to the roots being unhealthy
• It stays wet VERY long. And under regular weather I typically have rain at least twice a week, most weeks of the year. In winter we can have rain periods where it never goes really dry for weeks.
• I am not sure shipping substrate from Japan makes a lot of sense if alternatives are available

I DO however know it makes a difference in the refinement stage. In fact, I have done a comparison growing a bunch of Elm seedlings in a range of substrates for a year. Results will be in a video, but in short: Akadama based blends had the shortest internodes under the same care than the other blends I compared. SO once my trees enter higher level of refinement I might jump across and start blending it in.

In the end, I think most people are not able to provide the care needed to get optimal results. Akadama is part of the puzzel, but not the one-stop solution to better bonsai development. There are loads of other components to tweak. I prefer to not worry too much about substrate, PH and fertilizer types. I feel those are the last 10% of the equation. ANd untill you have the other 90% pretty optimal, the difference is not going to be noticable in the trees.

 

[pandacular]

The very first hard lesson I learned as a rookie, besides to keep my scissors in my pocket

An aside, but I’m curious how exactly you carry your scissors in your pocket. I’ve learned to do so, and several bad (painful!) ways to do so.

… but I clean and recycle everything. So no outlay in a couple years now…. And have never needed to look back when it comes to media,

I would also like to learn more about your process for this, especially as repotting season approaches.

Am presently testing perlite and coco coir blends (be sure to sift the coco coir first!,,.) for some trees in initial development.

I’ve been using coco coir and pumice for my cheap blend for young plants because (at the risk of boasting to OP) pumice is just as cheap here as chunky perlite. I hate handling perlite because it flies everywhere! Still haven’t repotted anything out of it, but it handles reasonably well when doing early repots.

 

[isid]

I do not use akadama for a few simple reasons

• 
  
• It stays wet VERY long. And under regular weather I typically have rain at least twice a week, most weeks of the year. In winter we can have rain periods where it never goes really dry for weeks.

Is'nt it the same in Japan ? you think Japan is a dry country?