Bonsai substrate mix for dry climates.

[Adair M]

Water doesn't pool in my substrate but it creates a muck on the lower layers of the pot where the roots start rotting eventually...

Then your substrate is of poor quality.

Or, it’s time to repot if the water stops draining.

I’m confused... at first you asked how to keep your soils more moist in hot weather. Now you’re saying they stay too wet?

 

[Leo in N E Illinois]

I would not use vermiculite in your inorganic potting media. If you need more water retention coconut husk chips are good.

Note: uniform particle size is important. For a 3 mm particle size mix, the size range really should be 2 mm - 4 mm, no large pieces, no fine pieces. If you are getting a perched water table in your pots, your your plants need immediate repotting into a media with uniform particle size. I do not put a coarse "drainage layer" in my pots as this can be the cause of "perched water table". I get better drainage with a totally uniform particle size media.

I cover drainage holes with wire mesh, eliminating the need for a "drainage layer".

A coarse media, with uniform particle size, can not be over watered. It will breathe, supplying oxygen to the roots. This is important in hot climates.

 

[Ujjawal Roy]

Then your substrate is of poor quality.

Or, it’s time to repot if the water stops draining.

I’m confused... at first you asked how to keep your soils more moist in hot weather. Now you’re saying they stay too wet?

It is of poor quality and that's why I want to make it better and at the same time not overdo the drainage as I don't want my plants to dry out completely between watering as I'll be moving to a drier city in a few weeks. I am just preparing my soil with the help of your experience so that atleast my plants can survive till I can make the best possible mix out of components that are available locally

 

[Ujjawal Roy]

I would not use vermiculite in your inorganic potting media. If you need more water retention coconut husk chips are good.

Note: uniform particle size is important. For a 3 mm particle size mix, the size range really should be 2 mm - 4 mm, no large pieces, no fine pieces. If you are getting a perched water table in your pots, your your plants need immediate repotting into a media with uniform particle size. I do not put a coarse "drainage layer" in my pots as this can be the cause of "perched water table". I get better drainage with a totally uniform particle size media.

I cover drainage holes with wire mesh, eliminating the need for a "drainage layer".

A coarse media, with uniform particle size, can not be over watered. It will breathe, supplying oxygen to the roots. This is important in hot climates.

Noted. No vermiculite from now on, I'll most likely go with coconut husk chips. Thank you for the advice!!

 

[Ujjawal Roy]

Vermiculite is really bad, it breaks down and creates a mush, its not good for bonsai

I did not know this earlier, while sifting it I thought its a good moisture retaining particle for my mix. But, form now on I'll not use it anymore, I can already see it's getting dusty when it gets dry. Thank you so much!

 

[Leo in N E Illinois]

Vermiculite is useful in "potting soils" which are not good for bonsai use. It is not evil, it is actually used for it's cation exchange capacity, but it is too soft for bonsai use.

 

[Ujjawal Roy]

Vermiculite is useful in "potting soils" which are not good for bonsai use. It is not evil, it is actually used for it's cation exchange capacity, but it is too soft for bonsai use.

I'll skip the vermiculite. Can you suggest some other materials that retain moisture (other than pine bark as I can't get it here)? Can activated charcoal help?

 

[Adair M]

No.

The best mix is totally inorganic. Don’t use anything that has ever been alive. No bark, wood chips, etc.

To retain moisture, the spaghnum moss layer ON TOP of the actual soil will work.

 

[Ujjawal Roy]

No.

The best mix is totally inorganic. Don’t use anything that has ever been alive. No bark, wood chips, etc.

To retain moisture, the spaghnum moss layer ON TOP of the actual soil will work.

Roger that!! Thank you very much!

 

[Oleg]

I did some tests on soil components when I switched to inorganic by weighing the components dry and then again wet, by far the most retentive were Turface (which you cannot get) and Diatomaceous Earth can you get that.

 

[eryk2kartman]

Try Sanicat Pink - cat litter - its moler clay same as Diatomaceous Earth
Also Tesco has one, but not sure if they are available there
Sanicat you can get on Amazon

 

[Ujjawal Roy]

I did some tests on soil components when I switched to inorganic by weighing the components dry and then again wet, by far the most retentive were Turface (which you cannot get) and Diatomaceous Earth can you get that.

Sadly I don't have access to granular DE here. They sell it only in powdered form to kill insects. I think crushed clay pots are somewhat similar to turface maybe not as good as it but somewhat similar. Maybe clay pots are made of calcined clay, for now i'll just break those pots and make 3-5mm chips and use them for water retention. Thank you for the suggestion

 

[Ujjawal Roy]

Try Sanicat Pink - cat litter - its moler clay same as Diatomaceous Earth
Also Tesco has one, but not sure if they are available there
Sanicat you can get on Amazon

Searched for sanicat, it's unavailable here. Amazon charges for delivery from other countries is two folds costlier than the product itself

 

[Alcam]

Vermiculite is useful in "potting soils" which are not good for bonsai use. It is not evil, it is actually used for it's cation exchange capacity, but it is too soft for bonsai use.

I've been reading lots about vermiculite lately, and it seems like it would be a fantastic add to a soil mix for deciduous trees, as long as it's added in moderation.

I'm trying it this year with a Japanese maple forest (year 2 trees), with a mix of high-quality pumice, lava rock, and vermiculite. I only put in around 10-20% vermiculite, so I'm hoping its high CEC and water retention ability will be great for them, since they will use lots of water during the growing season.

 

[sanjay]

I think it's red clay that's baked. Turface is restricted in my country and akadama is just too expensive for me.
The crushed clay pots soak up a good amount of water and if I break them while they are still wet, the inside if also dark in color.
Here, in India, people use lots of organics like compost, cow manure and all the other finer organic matter with red garden soil and maybe some perlite and sand but this mix gets compressed too quick for me and the roots start to rot. I've even seen stem rot on my trees due to such soil mixes. All this is so confusing. Help me, help!

Red clay baked (BRICK CRUSH) is pours and great for drainage, its actually 80% of what I use in my mix and I live in Telangana it is way hotter and dry here, I used to use organic mix like vermin compost two years back but as soon as summer hits they dry up faster and compacts and in monsoon I could not not tolerate the root rot, so I started to use crushed brick 8 kg , coco coir (wet) 1kg and 1kg compost for 10 kg soil mic mix them well and wash the coco coir till all the salts are washed away and it drains well and it works great for me. AKA is red DAMA is clay so that is AKADAMA for japan.