AusBonsai

At the moment, I have about 10 trees in large plastic pots to help them grow as big and fast as possible (ground growing is not an option currently) that will need to be repotted this season.

What do people generally use for the soil mix to keep costs down but also mange to keep their trees healthy and thriving?

Example are JBPs if they were to be potted in a bonsai pot, I could use the more expensive stuff like akadama or pumice etc but for big ugly black pots, what could I use during the development phase to keep costs down but still provide health for the trees?

Thanks and I look forward to reading your views / experiences.

Hi mate
Try using a good quality premium potting mix eg Searles. I use it quite a bit for growth in grow pots
Cheers RodM

I've never grown JBP in large plastic pots so don't really have personal experience/advice to pass on but in general they like a well-draining, "open" mix that can provide plenty of air. With that in mind, something that offers a coarser texture which doesn't hold water seems like a good place to start. I'd be looking at "Cacti Mix" variants as these get the closest to these kind of qualities when you look through the generic ranges available at mainstream nurseries. I still find it can hold a lot of water compared to mixes based around pumice/akadama etc but as an off-the-shelf solution, it might be a place to start. Be sure to provide a good aeration layer in the bottom to help with air flow mentioned.

I second the quality commercial potting mix. In the past, I used Debco 'Tub and Terracotta' which is based on larger chunks and seemed to be good, especially for larger pots. I guess some other brands have a similar product but I don't have personal experience.

Cheaper potting mix can be a lottery. Some are OK, others I've tried are terrible and we had many problems. If you are paying less than $10 for 25 litres, chances are it won't be great.

Our club members compared different brands of cacti and succulent mix a few years ago and found a really wide variation in those too. Just because it says cacti on the pack does not mean it actually has great drainage.

Having said all that, the larger the pot the less important it seems to be to have great potting mix. It's more a case of matching watering and care to the potting mix you've used.

Thanks for sharing and yes I do need to get the mix as free draining as possible as large plastic pots can hold too much water with the wrong mix.

I did look into this further and sandy loam seems to be a good addition for a variety of trees and mixed with perlite, coco coir or vermiculite in varying quantities could be good for what I need.

Approx $10 a bag or $80 for a cubic meter (55 bags) which is a lot for a small time bonsai fan

And Shibui thank you very much for the Chojubais, small leaves and they've been popping that orangey red flowers all over.

Very happy!

I use my standard "Kens Mix" 40% Akadama, 40% Pumice 20% Zeolite, in all my pots whether plastic grow pots or Bonsai pots.
the Main reason is consistency and drainage, but also the dreaded curl grubs infestation with organic soils in pots

I find it cost effective as whenever i repot, i wash and reuse up to 80% of the mix each time and just add a handful of fresh akadama in each year. The pumice and Zeolite never break down and the Akadama is good for at least 3 years

Ken

Fantastic to see Vets still here and sharing knowledge and experiences!

Thanks all

hydroponics shops are your friend, they sell big bags of perlite cheap along with coco coir, pine bark, etc.
mix the above with appropriate sized scoria and sand from a landscape soil supplier, then slow release fert from bunnings.... easy

Awesome, will be sure to add hydroponics stop over on my shopping list

Canberra folk tend to use Martin's native potting mix - it drains well, holds moisture well, and keeps its structure for a couple of years. We buy it in by the pallet load - clubs are good for that.

Gavin

Yea this stuff normally 15 bucks it’s actually on sale atm. It’s decomposing bark and is great. I use it in my mix and use it 100% for trees in large grow pots. The bark pieces range in size. It’s holds water well dries fast and is chunky enough to provide oxygen. It’s not like other orchid bark I’ve seen this stuff in decomposing black bark


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Like Ken said it’s not much use if curl grubs are an issue. And you will definitely see fungus gnats with the orchid bark. A surface layer of corse diatomaceous would fix but those issues.


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Why not use pumice or akadama or whatever the usual mix you use in your bonsai pots?

If you want good fibrous root growth, then it is a no brainer. I use pumice based mix for ALL my trees. Even the ones in black nursery pots, colanders, foam boxes, and half wine barrels.

If you are developing the tree and focusing on fattening the trunk and growing great nebari then the most important decision is what substrate you use.

Yes it is more expensive, but it is worth every cent, and you can reuse pumice to keep costs down over time

Tried searching for pumice in Melbourne and all are quite far and postage is expensive.

Scoria is more accessible for me, so would a mix of say scoria, coco coir and sandy loam be good for pines?


Did come across this on the web:

Pumice (3/8" grain size)
Porosity = 31%
Air-filled porosity = 26%
Water-filled porosity = 5%

Scoria (3/8" grain size)
Porosity = 40%
Air-filled porosity = 20%
Water-filled porosity = 20%