zaterdag 16 januari 2016

article: A durable bonsai substrate as replacement for akadama and peat

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A durable bonsai substrate as replacement for akadama and peat 

Substrate in stead of soil

The term substrate offcourse implies it is mainly composed of inorganics. More than 5 years ago, after thorough reading and researching all kinds of sources, substrate was the choice I made. I will not elaborate on the pros and cons of mainly (approx 50% and up) organic soil, I can however share the main reason why I do prefer inorganics: Total control. I consider this a big plus if it comes to feeding and watering my trees. It is all about diminishing the risks, the ‘can-go-wrongs’. I know better how my substrate will behave, than I would with mainly organics. No more soil that contains too much salts, and the risk of getting the PH of my substrate all out of balance is lower too. No more rootrot in soaking wet and clumped soil.
Besides ‘total control’ there are offcourse a number of other reasons: I no longer depend on akadama, I now use more durable (no peat, no turf) compounds, my main compound has better properties than akadama on many aspects, it is more affordable, it does not break down,...

Durable alternative for peat and akadama
Most brands of potting compost still rely on peat or turf. Peat mining has significant environmental impacts. Mining to date has opened up extensive areas of swamp with an extensive free water area now replacing what was a shrubland/rushland peat deposit. Damaged swamp filtering function, damaged ecosystem, destabilization of hydrology, etc. Swamp areas with peat deposits carry/are one of the most specific habitats. If I can replace peat or turf with an equally good (or better) more durable alternative, I happily use this alternative. This is why I use cocopeat for the organic part in my substrate (max. 20%). It is a byproduct, it does not break down as fast, and it is a good water and nutrient absorbant.

Besides peat-based soils, most bonsai enthusiasts use akadama-based soils. For sure, one of the first things a beginner buys has got to be akadama. All shops I know of will advertise akadama as basic. Offcourse this is due to the fact that akadama is traditionally used in Japan. There was no need for westerners to ask questions, the use of this material was/is just copied, the akadama imported. That is all fine, but questions finally begin to rise due to the fact akadama gets more sparse, more expensive. For me personally, I just wanted to know if there were other materials that can do the job just as fine, or better, why not ask this question, why not learn lots of things while searching for alternatives.

My current and new formula

I’ll immediately get to the point.

Current formula

Natural zeolite (clinoptilolite) granulate, medium (2-5mm), depending on the size of the pot I’ll mix it with small (1-3mm) and/or big (5-10mm) to come to an overall 70 to 80%. The other 20 to 30% is cocos compost. This comes in rough bits of coconut bark and fibres, or in fine compost. The rough cocos I don’t use because I don’t have huge sized pots nor do I have pines (only 1 shohin). Depending on how thirsty my (broadleaved) tree is, I’ll mix the 20 or 30% cocos. The more smallsized particles of zeolites, the more moisture your substrate will be able to hold. This very simple and basic substrate mix I’ve been using for several years (since 2010) with satisfying, good or very good results.

Easy watering, easy feeding. When watering, water abundantly until it runs out from underneath the pot, overwatering this substrate is impossible unless you’ve used way too much cocos in combination with only the small zeolite granulate. U can use liquid chemical fertilizer but I prefer liquid organic fertilizer, in combination with 1 or 2 times organic fertilizer in granulate for hedges (that contains mycorrhizae spores).

New formula

Because I’ve found new studies/info about crop growth in pure zeolite substrate, indicating an initial strong growth followed by a decline or stagnation in ‘strong’ growth (sheer biomass production), I decided to re-evaluate or update my substrate mix. In all studies however, zeolite as such, proves to be a highly effective growth and root stimulator, along with other advantageous characteristics (more below). The new substrate will be a bit more work and effort (or fun) to mix it together, and there is the initial cost of buying all the ingredients.

The mix in the table underneath is usable as standard mix for all broadleaved trees in small to midsize pots, with use of Zeolite. The small granulate makes sure enough moisture can be retained. For very big pots, or pines/spruces I suggest you adapt the granulate size of your compounds, but do not exclusively use bigsize particles in all your compounds, at least use 1 midsize granulate compound.

(10-12L or 1 bucket)

1.       Zeolite small (1-3mm) mixed with Zeolite medium (2-5mm) or bigsize (5-10mm), in equal parts 

I use small and medium (50%+50%) together as my standard (unalterable) part in my substrate.

2/5 (2 x 2 to 2,5L)

2.       Vermiculite (1-4mm)
This is expanded/exfoliated Vermiculite, a natural mineral, which is already widely used in horticulture. Lightweight, good qualities, and has a natural brownish look useful for esthetic aspect.

or replace with pumice mediumsize

1/5 (2 to 2,5L)
3.       Lava small (0-3mm) mixed with
Lava medium (4-7mm) in equal parts

or replace with zeolite small
or replace with pumice or zeolite medium
1/5 (2 to 2,5L)
4.       Cocopeat (brand: Ecostyle)
or use Cocosol (DCM)
or use Cocover (DCM) which contains more rough bits of bark and fibres, for pines or very big pots)
1/5 (2 to 2,5L)
Dried cow manure pellets
(= soil improver, not fertilizer)

Mix it in when repotting in early spring, a handful in midsize to bigger pots. In substrate, it helps to bring in essential bacteria faster. The fertilising aspect of cow manure is very low to unexisting.

Other dried livestock manure. Be careful with manure containing a substantial amount of poultry manure, this has really high NPK.
1 handfull
Organic Fertilizer granulate for Hayes/Hedges (brand: Ecostyle)

Mix it in when repotting in early spring. The Ecostyle (brand) fertilizer contains a certain amount of myccorhizae spores/gramm, this is the main reason I add it. Apply most of it in the substrate closest to the roots.
Any other organic fertilizer.

Do NOT use chemical fertilzers as your standard fertilizer if you want a healthy soil life with mycorrhizae.
½ to 1 handfull

Picture below:
1. Vermiculite 1-4mm
2. Lava (reddish-brown) 4-7mm
3. Cocopeat
4. Lava (grey) 1-3mm
5. 50/50 mix of small and medium Zeolite

Mixed together
=> (depending on esthetic preference) To finish off the topsoil I could cover with a mix of both lava portions and the vermiculite portion.

How to mix
Use an oversized bucket/tub (masons bucket) about twice the size of the volume to mix. Decide on the measuring standard you’ll use (in the table above I mention parts of 2L to 2,5L, for a volume of 10 to 12Liter). U can use an old dustpan as unit volume per part? I normally first mix the smaller granulates, than add the cow manure pellets and half the volume of organic fertilizer pellets (use the other half in the substrate surrounding the roots). Then I add the bigger granulates and mix again.

Repot every 2 year, with trees that have a lot of rootmass. This I recommend because roughly and irregularely shaped granulate can be quite difficult to ‘comb’ out from between the rootmass when repotting.  Rough and irregular does however stimulate rootgrow, and caption of nutrients and the smaller particles of your substrate. Fill the pot for 1 or 2cm, put the tree on the substrate, use the other half of the organic fertilizer pellets with mycorrhizae in the substrate surrounding the roots, water as soon as you covered most of the roots, then fill with the rest of the pot with substrate, water again abundantly. I don’t use chopstick I use my fingers to gently comb and push in the substrate between the roots (tap the pot every once in a while when filling between the roots). Don’t forget to wire the tree into the pot, especially younger trees who’s rootmass often isn’t developed enough to be able to support the tree on its own.

The compounds Zeolite and Vermiculite

Because lava and pumice (bims in Dutch) are wellknown, I will not elaborate on them any further. The only thing I could point out it is that there are several types of ‘lava’, eg in my substate mix you can see the reddish-brown lava granulate and the small grey lava fraction. Check the PH, and if the lava has been washed. Up to you to decide if you want to use pumice as either 6th compound or in stead of e.g. the lava fraction. This will not really make a huge difference. The small lava fraction I find very convenient, in colour, in adding weight, adding smaller particles to surround the soil with and yet not loose the aereating function.


There are many many types of ‘natural’ zeolite (do not use synthetical zeolites as they don’t carry micronutrients and tend to break down in prolonged acidic environments, eg when u do want to decide to use chemical fertilizer). Clinoptilolite is one of these natural zeolite, and perhaps the most commercialized and the one that is most used for horticultural purposes. In Belgium and the Netherlands it is marketed by some companies who import it, either from within the EU or from outside the EU. The clinoptilolite that is mined in Romania, Bulgaria, the Tchech Republic, Hungary, Armenia, Greece, is rather impure and contaminated with other minerals like quartz, feldspar… It has a purity of less than 80%. The most known companies that market it in Belgium and the Netherlands is about 80 to 82%. In the past however, I have obtained bags that contained 95% pure clinoptilolite. I suspect this comes from the Turkish mines. The reason why these companies do not import the 95% pure zeolite is for commercial reasons only: it inevitably contains a bit of dust, and this is not desirable for marketing as soil for birdcages, catlitter soil, etc. So people don’t want to get their hands dirty, but I do. When using the 95% pure, the dust had washed away with a few times watering, no big deal. Elas, another minus to the 80-82% pure zeolite is that it changes colour to a slightly light-blue colour when watered. This is not very attractive as topsoil, it adds to the artificial look.


This mineral (a silicate) belonging to the clay minerals in the Smectite-group, was originally mined and intended for usage in the building industry (as heat and noise insulant, levelling granulate..).For usage it gets expanded or exfoliated at high temperaties (800 to 900°C) to obtain its granulate-like soft structure.  It equally is an allready wellknown and widespread substrate within the horticultural industry and retail business.
Translating an extract of the description of the usage, characteristics and advantages of vermiculate from a distributor of ecofriendly  materials: “…these characteristics, combined with the low density and preservability against rot, encourage better sprouting, stimulate growth, and seriously decline fungal forming. Moreover, vermiculite is lightweight, aereates the soil, has a more or less neutral PH, acts simultaneously as an excellent water absorbant and drainage”. Perlite is perhaps better known and more frequently used in compost soils for horticultural purposes, but vermiculite has better absorbant properties, is a bit heavier, and has a natural brownish look as opposed to perlite having a pure white colour.


According to my initial calculation, the cost of my substrate should be about 8 EUR for 20L, but I'll keep it at max 10 EUR per 20L. That is far less than a bag of 16L hardgrain akadama. I say 'max' because some compounds are sold per kg and not per L, so I have to dubbelcheck and see e.g. how many liter lava is in a bag of 10kg. Vermiculite has a quite expensive initial cost (about 25 EUR) but then again it comes in bags of 100Liter so that makes it cheap again. Lava is about 10 EUR/10L, Zeolite is 12,5 EUR/25kg, cocopeat again about 10 EUR/40L.
So I can safely conclude this substrate is not only a more durable alternative for akadama and peat, it is also a cheaper substrate once you've purchased a supply of all the ingredients needed.

Cons of Zeolite?

  • ·         Allthough it makes your soil or substrate peat-free (peat is - still – a very basic compound of most compost soils, it is more and more contested because it is not durable and because of the drastic ecological impact), zeolite equally is a mineral that is mined, so there still is a certain ecological impact.
  • ·         The colour of the 80-82% pure zeolite is not very attractive/esthetical as topsoil covering in bonsaipots (offwhite or offwhite with few earthcolour speckling, and a light bluish when saturated). This can easily be solved by covering the topsoil with a separate mixture of the other compounds of the substrate described above, eg vermiculite mixed with the lava fractions (or bims).
  • ·         Zeolite is only sparsely distributed, by only a few companies/distrubutors, and it is almost always the 80-82% pure zeolite you’ll find.  Commercialization is limited in Belgium and the Netherlands as opposed to the rising recognition of zeolites in agro- and horticultural industries (e.g. greenroof substrate like Vulkagran-T, other specific substrate like Clinopti,…), and despite the many studies that have been published.
  • ·         Zeolite is relatively heavy , especially when fully saturated so this can be a bit of a problem with really big pots and/or in substrates that contain a very high percentile of zeolite (more than 50%). This can be countered by mixing in the very lightweight vermiculite.