Bonsai substrate mix for dry climates.

Ujjawal Roy

Ujjawal Roy

Yamadori
Messages
64
Reaction score
49
Location
Mumbai, India
USDA Zone
12
Greeting, everyone! I'll soon be shifting to a city that falls under USDA zone 12-13, the temps can go as high as 43°c in the summer months and the climate of the place is quite dry as it is away from the shoreline. My new house has a balcony which will receive morning sunlight till around 12 and then late evening sunlight. My trees will stay in the open balcony so it's semi-indoors I guess. If you all could suggest me some substrate ratios then that'd be awesome 😊 I have crushed clay pots, perlite, pumice, vermiculite and volcanic pumice stone at my disposal and would like to use an inorganic substrate mix as organics have already caused a lot of problems in the past (just maybe i can get hold of some coco husk chips as an organic component if needed) . Thank you in advance for your time and suggestions!
 
Our friend from the Las Vegas desert swears by an open inorganic mix to prevent boiling.

Sorce
 
Sounds like the trees will be shaded during the hottest part of the day.
When I wanted more moisture retention in my mix, I added Douglas Fir Bark chips to the lava and pumice in equal parts.
Now I use that mix for every tree I have.....minus my JBP which will be getting akadama when the time comes.
 
In Southern California I used pumice or pumice/lava in the majority of my trees.

In cases where I was concerned about drying, I would add chopped pine bark nuggets - trying to find pine park pieces that were as small as my other soil pieces. But at the end of the day, I still watered twice a day - early morning and late afternoon.
 
just.wing.it said:
Sounds like the trees will be shaded during the hottest part of the day.
When I wanted more moisture retention in my mix, I added Douglas Fir Bark chips to the lava and pumice in equal parts.
Now I use that mix for every tree I have.....minus my JBP which will be getting akadama when the time comes.
Click to expand...
Coniferous bark isn't available here, can I use vermiculite or coconut husk chips instead of Fir bark chips? I was thinking of using 50% crushed clay pots + 20% perlite + 20% volcanic pumice stone + 10% vermiculite. I want to water it once a day atleast during summer time.
 
Bonsai Nut said:
In Southern California I used pumice or pumice/lava in the majority of my trees.

In cases where I was concerned about drying, I would add chopped pine bark nuggets - trying to find pine park pieces that were as small as my other soil pieces. But at the end of the day, I still watered twice a day - early morning and late afternoon.
Click to expand...
Do you use horticulture grade pumice? If yes then does it retain moisture for a good amount of time? My biggest problem with the soil that I make is that the perched water table stays wet for 2-3 days whereas the top layer dries up. So, I water my plants as I've read that keeping the perched water table replenished with fresh water does not drown the roots as the fresh water has more oxygen and it pulls in air behind itself while watering, and still, I'm getting terminal leaf dieback, stunted growth issues on many of my plants.
 
Coco coir or chips can hold water for too long.
Fir bark or chips is better. Beech chips are cheap but they suck.

Your stunted growth can be a result of many things, as is the case with dieback; high salt concentration is one possible cause. Since you're relatively new to bonsai, it could also be that you just messed with the roots a little too much.
 
Wires_Guy_wires said:
Coco coir or chips can hold water for too long.
Fir bark or chips is better. Beech chips are cheap but they suck.

Your stunted growth can be a result of many things, as is the case with dieback; high salt concentration is one possible cause. Since you're relatively new to bonsai, it could also be that you just messed with the roots a little too much.
Click to expand...
The last time I re-potted few of my trees I used a mix of volcanic pumice stone and some kind of stupid bone meal compost that smelled like chemical fertilizer; maybe it's the bone-meal crap that's affecting the roots and I'm unable to properly diagnose the problem. And thus, I want to use inorganic substrate and feed exogenous nutrients to it later on.
 
Cypress187 said:
Is this bonsai jargon I never heard of? 😜
Click to expand...

@just.wing.it ...it's HVAC jargon!

It's the evaporative cooling of a loose soil, watered frequently, that allows the core to stay boil free.
With no evaporative cooling in the core, the important part rots.

This is also a situation in which abandoning organic poop ferts in favor of liquid emulsions would be advised.

Sorce
 
If you are talking 43C, I’d be inclined to agree with some use of coco coir and or chips in your mix. At those high temps you are going to need all the water holding ability possible, consist with an overall porous media strategy.

I’m wondering about the entire climatology picture in Mumbai, also what type of trees you have?

Is Mumbai a very humid climate at times, with a strong monsoon? If so, I’d be concerned about ensuring your mix isn’t too water retentive and use some shade screens at sunny times.

Can you tell us a bit more?

Cheers
DSD sends
 
Ujjawal Roy said:
Do you use horticulture grade pumice? If yes then does it retain moisture for a good amount of time? My biggest problem with the soil that I make is that the perched water table stays wet for 2-3 days whereas the top layer dries up. So, I water my plants as I've read that keeping the perched water table replenished with fresh water does not drown the roots as the fresh water has more oxygen and it pulls in air behind itself while watering, and still, I'm getting terminal leaf dieback, stunted growth issues on many of my plants.
Click to expand...

Yes I use horticultural grade pumice.

When you water your bonsai, the water should immediately flow through the soil and out through the drain holes, leaving wet soil particles behind, but no standing water. If you water your trees, and the water appears to soak in (like a sponge), or worse yet, sits on top of the soil and has to slowly be absorbed, you need to repot and change out your soil. Yes, the top layer dries faster than the soil deeper inside the pot, but not enough to make a different (at least for me). It is a bigger issue immediately after repotting, but roots start to fill in the void spaces in the soil pretty quickly, and that will slow down the rate of desiccation.

Can you share photos of one of your stunted growth plants? Perhaps something else is at play.
 
Very new, but half the reason for my lack of success in bonsai has been my experimenting with making soils because, like you, I'm not able to purchase them.

Your crushed clay pots (terracotta?) will hold a little moisture, but probably not enough for once a day watering in a hot desert climate. You might try crushed brick along with it. Retains more moisture, but not as much as adding something like clay (akadam, turface, etc.), and will release it fairly slowly after it's been soaked thoroughly.
Another idea is to use your pumice and the like- the porous substrates- but mix them with just a little very fine all-brown-matter compost (composted leaves, paper, bark, etc. but no food scraps or manure). It will rest in the pores of the stone, but get washed from in between the stones, and will help hold moisture, but never directly against the roots.

Otherwise, some very fine coco husk in limited quantities should do the trick, like you were thinking. I would say no more than 25% of the mix, but less if you're also using clay pots and brick.

Please let us know what works. I'm always on the hunt for ways to keep my hobby affordable.
 
Deep Sea Diver said:
If you are talking 43C, I’d be inclined to agree with some use of coco coir and or chips in your mix. At those high temps you are going to need all the water holding ability possible, consist with an overall porous media strategy.

I’m wondering about the entire climatology picture in Mumbai, also what type of trees you have?

Is Mumbai a very humid climate at times, with a strong monsoon? If so, I’d be concerned about ensuring your mix isn’t too water retentive and use some shade screens at sunny times.

Can you tell us a bit more?

Cheers
DSD sends
Click to expand...
So, here in Mumbai things are quite chill. Temps go to about 35°c in winters and in peak summers it can go upto even 40 but it's humid. The new city that I'll be moving to is a drier place, the temps are usually higher than Mumbai and as for my trees, they will sit in the balcony the whole day, so, they will get morning to afternoon sun, indirect afternoon sun as the balcony is shaded on the top and evening sun from around 4:00 PM to about 7:00 PM. My trees are mostly local varieties so I think they are all either tropical or sub-tropical, mostly ficuses of various kinds, two delonix regias, one murraya paniculata and one bougie. I am aslo growing a grapefruit seedling.
 
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