Bonsai Pot mix research driving me crazy (Melbourne)

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Bonsai Pot mix research driving me crazy (Melbourne)

Post by aaronspain »

G'day all!
Long time lurker, first time caller (???), all that stuff!
It's coming to that time of year, when I finally have the free time to start training a few random Junipers I bought from "the place with the sausages out the front" a year ago, and some eucalypts, callistemons and hakeas obtained from work in the wholesale nurseries. I started my collection about 10 years ago with a few items from Gardenworld/Collectors Corner, and started working on a couple of junipers I'd grown from cuttings, but never actually properly planted a specimen in to a real "bonsai pot" (as opposed to a typical 200mm black nursery growing pot).
I'd like to start properly potting some specimens this year, so that I can say I actually HAVE "a real bonsai", but I'm hitting a brick wall when it comes to availability of materials for the mix. I understand that it needs to be free-draining to provide aeration, have good water retention, and offer a decent amount of cation exchange capacity. My pre-bonsai growout pots have mostly been a mix of coir peat, builder's sand, composted pine bark, perlite/vermiculite, some 2mm scoria/pea gravel, and a pinch of "water saving crystals" (ie. polyacrylamide), which has served me well in terms of growth and ease of watering.
I've come at a crossroads in that I've been pulling my hair out trying to find suitable media for my actual bonsai pots (not growing pots, I mean the actual Bonsai pots):
- Diatomite (used to exist in 2-4mm granular form, but now I can only find powdered form for livestock mineral supplement)
- Zeolite (exists in the Woolie's cat litter orange bag, and can get from, but it's in NSW. I have a couple of hundred kilos of this stuff, but it's <1mm in size and came from a pool filtration system)
- Akadama (nope, stupidly expensive to import. Is there anything similar that breaks down over a few years to allow root ramification?)
- Debco's Bonsai Mix (the one apparently designed by the Koreshoff's. All the mentions of this on the forums are from 2011 or so. Debco was bought by Scott's, and Scott's only makes the Osmocote branded "Bonsai Mix", which is basically just regular composted pinebark with polyacrylamide, so completely useless)
- Decomposed Granite (this is frustrating, because I live five minutes away from a damned granite quarry in Lysterfield, but I can't find DG in Melbourne! Does it need to be granite, or will any inactive gravels do as ballast?)
- Coir peat (this stuff is awesome, and I'll probably be using it forever as a water retention media)
- Compost (composted pine bark works well, but I don't feel comfortable repotting and trying to get new roots to grow in a media with anything higher than a 10% portion of composted cow manure, so I prefer to just add fertilizer later down the track)
- Sand (Coarse propagation sand seems to work well for providing drainage and ballast, but that's about all it's good for)

The tubestock I've purchased from Yarra Valley Nurseries (ie. the nursery wholesaling to the big shop with the sausages), seems to be pinebark with no grit, with some slow-release fertilizer balls mixed in, so it basically looks like it's the Bio Gro product from AGS (Australian Growing Solutions, who used to be Debco before they split retail from wholesale/commercial). Great for growing out, not great for ramification and eventual development of shin roots in a training pot.
The shohin bonsai you can get from the shop with the sausages, I'm pretty sure they come from Collector's Corner / Paradisia Nurseries, who make great stock, but when I looked at the top layer of soil, it was GLUED. Somebody had put so much glue in to the top layer that I couldn't even pick one of the rocks off with my fingernail. It looked like they'd used 3-5mm shale as a mulch. Since the big shop with sausages is closed to the general public and they're empty, I grabbed the nearest hose and poured a little bit of water from it on to the topsoil: it just ran off the top. It's as though they've been bottom-watering the plants. I don't think I'll be doing that, thanks. I can understand why it'd be easier to mass produce and ship plants where the soil won't fall out, but you've got actual plant-delivering couriers for that, and you don't need to pack them up in cardboard boxes.

Is there anybody out there in Melbourne, possibly a member of Nursery & Garden Industry Victoria (NGIV) who knows of wholesale suppliers that'll sell at least the components I can use to make a decent mix for keeping natives in a bonsai pot? I'm going crazy here. I can buy wholesale from places like Plantmark, Warner's, Southern Advanced Plants, Paradisia, AGS, GCP, etc., as I'm an apprentice horticulturalist for wholesale nurseries, do some maintenance work on the side, and operate a sole trader operation for selling at markets (and yes, I'm branching in to Bonsai, but will mostly only be selling hardy natives and junipers to the general public).
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by rodm »

You seem to have a few issues to sort out and if you source through the internet you will find plenty of places to get this info. You also find a lot of information to answer most of your questions on this site if you take the time to check it out :reading: ;)
Cheers RodM
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by Phil Rabl »

G'day aaronspain. I see you don't belong to a bonsai club - as you say in your profile: Bonsai club: "none, unfortunately". I am 100% confident that if you joined a local bonsai club you would fined loads of help with the questions you have raised.
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by evan »

There's no point going to wholesalers unless you are growing significant amounts of stock. Most places won't sell you less than 1 cubic metre amounts of anything. If you go to a proper bonsai nursery and see the mix they use (Bonsai Sensation in Narre Warren for example), you'll find that most use standard mixes ordered with a higher percentage of prop sand than normal (from places like Australian Growing Solutions). But again the problem would be minimum order amounts from custom mix places.

I would be simplifying down your mix and using something similar to other established small time bonsai growers. Most will have 2-3 ingredients, usually consisting of scoria, pumice, diatomite, akadama, or orchid bark (everyone has their own mix, so whatever works for you is best).

I use personally use scoria with either akadama or orchid pine bark. Best place that I've found to get scoria in Melbourne is Van Schaik's Bio Grow, but minimum order of 1 cubic. Akadama is available enough in Australia nowadays due to multiple importers, and there really isn't anything that comes close to it if you want that breakdown. And only orchid bark that is worth using is Orchiata, which can be found at a few different suppliers.
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by SquatJar »

I don't see the point of sand or granite chips in a bonsai pot, seems to me they just take up space without providing anything back. Minimal/no AFP, water holding capacity or CEC.

From your choices I'd be starting with the tried and true 2/3s inorganic 1/3 organic and adjust from there. Say 1/3 zeolite, either woolies or one of the horticultural brands, 1/3 your 2mm+ scoria and a 2-5mm organic of your choice. For coir you'll probably end up sifting a lot away, also best to rinse it in case it's full of salt. I'd be looking at a chunkier potting mix/pine bark for a budget option, although again, you'll probably be sifting a lot away. Safest option is the small orchiata pine nuggets.
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by Stu »

You will find many conversations on this. Can make the head spin because of all the alternatives.
Oology (Damien) can provide materials and has provided pre-mixed.
I use plumber's scoria or blue metal screenings (1/2 cu.metre from garden supplies), Woolies cat litter (2 parts), pine nuggets and coir peat. It's about as cheap as I can find.
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by shibui »

Every serious bonsai grower has their own favorite potting mix. Most of them will tell you that theirs is the only one that will work. Now they cannot all be correct given the widely differing mixes used. What is correct is that we can grow good bonsai in a wide range of mixes provided the care matches the mix or vice versa.
Let's look at the components:
Akadama: I agree that importing some soil from halfway across the world is foolish. There is nothing magic about heat affected clay, it is just a locally available material that has properties suitable for growing plants in pots under Japanese conditions. Look for locally available alternatives.
Decomposed granite: Is just a hard, heavy mineral component used to maintain drainage and air filled porosity. If you can't get granite any rock will do. Crushed, with sharper edges seems to give the mix better properties than rounded water worn grit but at a pinch any grit will do the job.
Zeolite: relies on very limited sources here and is only available when a pit is operating profitably. It provides grit but has some CEC ability.
Compost: composted pine bark is not compost. Compost as I know it is well broken down organic matter and smaller particles can cause problems in pots. I would avoid compost in potting mix unless you know your care can cope with it as part of the soil mix.
Composted pine bark: is screened to provide particles that aid Air filled porosity and water holding capacity. It gradually breaks down as the mix ages so may even provide some of the features of the fabled Akadama. 6mm screened composted pine bark can be a useful component of bonsai mixes. 'Orchiata' seems to be the commercial source for bagged 6mm pine bark in small lots.
Sand: coarse propagation sand is a good component of bonsai mix. Yes it provides drainage and ballast both of which are critical components. My mix has 30% propagating sand for just those reasons.
Scoria: provides particles that aid drainage and AFP and some CEC. Use it as part of the grit component if you can get it. Not available in all areas and seems to be increasingly difficult to source as existing pits are exhausted. Pretty sure that what we know as scoria is what Americans call 'lava rock' and it is a big part of American bonsai soil mixes. I believe that scoria is still available around Melbourne but 6mm is harder to find than the usual landscape size.
Pumice: is another big one for American growers. Lighter and more water retentive than scoria and does not break down like Akadama. probably useful if you can source it at reasonable prices. I think the closest source is New Zealand.
Commercial 'bonsai mix': Most of the specialist bonsai nurseries have their own mix made locally from local ingredients. Being in the industry you should be able to talk to any of the suppliers about replicating one of those mixes. Those mixes obviously work for the nurseries who use them. You may need to alter care to match the mix but they will still work. Bio Grow was quite open with me about the mixes they regularly made for some of the local nurseries when I was looking for sources. Min order is usually 1-2 cubic metres but you may be able to source individual components in smaller quantities.

The mix I have been using for 10 years or so is a custom mix from Spotswood holdings in Yarra Glen. 80%composted pine bark 20% propagating sand with a little zeolite. As a commercial mix it also has some fertilizer, iron, dolomite and gypsum. They have been very helpful to me but, as a commercial supplier there is a min batch of 1 or 2 cube.
For those who want to make their own please be aware there is a lot of science in potting mix and the micronutrients can make or break a mix.

Ultimately the mix you use will be one that has readily available components that provide the necessary physical properties and don't cost an arm or leg. Just what that mix will look like will vary from place to place and person to person." onclick=";return false;
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by treeman »

aaronspain wrote: September 5th, 2021, 1:22 pm

Is there anybody out there in Melbourne, possibly a member of Nursery & Garden Industry Victoria (NGIV) who knows of wholesale suppliers that'll sell at least the components I can use to make a decent mix for keeping natives in a bonsai pot?
If you have an ABN you can (could) buy ''Orchiata'' seedling grade orchid bark wholesale from GCP. (3-5mm). It is not composted and does not need to be. It lasts a long time in the pot because it is not composted. It is aged however. (Bark King supplies raw graded bark in bulk I think - it will need to be aged and limed) To that you add coir in a quantity sufficient for your water holding capacity needs. To that you will need to add iron sulphate and copper sulphate (get back to me if you want precise quantities - I have them somewhere) and gypsum to supply Ca and S. pH should be around 6.5. To that you add a mineral component. Non alkaline quartz sand which you should be able to find fairly easily.
If you are just growing plants in standard plastic pots for training, order some quality potting mix for natives from your nearest supplier and use that.
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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by GavinG »

The simplest formula to get you started, that plants will do quite well in, in bonsai pots would be 50% good draining potting mix (sift fines if you must)(Martin's native mix is commonly used in Canberra)(where are you?) and 50% coarse grit - 1-4mm seems to work well. Propogating sand, granite, zeolite, diatomite, pumice, scoria - which? Any!!! Whatever you can get, that's practical. Then modify the mix from there as you find the need. The biggest problem I've had with potting mixes is the meathead at the end of the hose... There are thousands of "recipes" - which means that none of them are distinctly superior. What climate, what plants, size of pot, usual watering pattern - all of these things will affect your choices, and you will work out to suit yourself. But start simple. There's an enormous amount of information already on this site, enough to confuse Einstein.

Good luck,

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Re: Bonsai Pot mix research driving me crazy (Melbourne)

Post by aaronspain »

Sorry for the delayed response, it's taken FOREVER to get around to posting this.

I've gone with a mixture of several components, with varying mixtures depending on the tree. Most of what I've been training and styling has been Australian natives (callistemon, allocasuarina, eucys, banksias, lillypillys), so have been using more inorganic materials and less organics (about 75% inorganics). For the non-natives (buxus, euonymus, maples, boxelder, junipers) that I've been working on, I've been using at a rate of about 50/50.

Organics: 2-6mm graded/sieved aged pine bark, from a bag at "the store with the sausages" that costs about $6 for a 25L bag. I can keep the large chunks for mulch on top of regular pots, and the fines end up as one of the ingredients in the seed and cuttings propagation trays. It took me about seven or eight different types of potting mix from the shop before I found one without that horrible expanding crystal "water-saving" stuff, or cheap versions of osmocote, or even GIANT ROCKS. The $3 bags had rocks in them the size of my fist! Also, this pine bark doesn't smell like fresh pine, nor does it smell like anaerobic fermentation; it has a slight "earthy" smell to it, but not as strong as the thoroughly-composted pine chunks I've worked with from AGS.

- 2-6mm graded/sieved scoria, from a pallet load of some old bags I found hidden in the back of the big box store. Prior to this, I was crushing up the regular scoria I use for my aquaponics, which is about 10-20mm, and way too big.
- coarse propagating sand, also from the big box store. Grains are usually at about 1.5 - 2mm in size after sifting, and I can get about 40% of the bags in this useable grade.

All in all, it ends up costing about $1-2 for a plant in an oval 200mmW x 40mmH pot, with good drainage, some water retention, and the ability to distribute seasol and fertilizer pellet juices.
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