Success with potting mix exp.

[MichaelS]

This spring I experimented with a potting mix idea which was rolling around in my head. I wanted a reliable long lasting mix for azaleas mainly but also tried it with gardenia and dwarf kumquat. It obviously had to be acidic. Kanuma is out of the question.
I used washed and screened scoria (red lava) and peat moss. The scoria typically has a pH of about 8 (way to high) and a very low CHC and the peat a low pH of about 4 and a very high CHC. I assumed that mixing the 2 would bring the acidity to the right level (about 5-6) The proof would be in the growth response. I used scoria of between about 2 and 5mm with all traces of fines and dust thoroughly washed out. To this I added about 15% (?) peat moss straight from the bag. That's proper sphagnum peat NOT coconut. I added enough peat to slow down the drainage just a little (tested) and stopped adding after that. Into this mix I planted several azaleas and dwarf rhododendrons ( which can be difficult at the best of times ) after cleaning the roots. The growth of these has been outstanding. In fact, it's the best they have ever performed. They where top dressed with some low P osmocote and a little nutricote (higher P) with nothing else added. The colour of the leaves has never been better and the plants seem to have rooted strongly into this mix. There is no need to worry about a slumping or decomposing mix which always sets the plants back after a while. It remains to be seen how the second year in this mix goes but everything points to continuing good growth. In hindsight, it would probably be better to add some Iron and copper to the mix but even without this they seem to be doing very well. My small Rh kiusianum in particular looks like it has finally woken up from a thirty year potting mix nightmare and has grown more this year the previous 10! Another thing about the mix is that I have not yet seen wilting so it holds quite a bit of water. I have not measured the pH of the mix after some months of use but at the moment there really does not seem to be a great need to as the growth is still very good.
The next step is to try other species and in particular I will try it out on some natives with a possible pH adjustment. This medium would probably suit thirsty species or growers in dry areas.

 

[Wires_Guy_wires]

Good obervations, thanks for sharing!

 

[Anthony]

Michael,

here is what works for our Azaleas [ since 1980 ]

5 mm silica based gravel
Canadian peat moss / has perlite which can be sifted out.

Every 5 years we cut off a % of soil and add new mix.

Mind you this is the coarser azaleas that can grow around Louisiana.

I also add- more success to you!!!!!!!!!
Good Day
Anthony

Scoria = Crushed red brick [ porous ] ?

 

[GGB]

I'm really glad to read this today. I was just about to experiment with my own, nearly identical, soil mix. And coincidentally, I was trying to remember Anthony's words of advice to me. I balked on doing this last spring but still have tons of black lava laying around. I'm almost done over thinking the amount of organics to add after this last record breaking rainy year. but anyway... Thanks for doing the experimental leg work for me. Please update in the future especially if you start planting other genus in this mix

 

[Anthony]

@GGB ,

peat moss holds 15 times it's weight in water.
However it still has to compost.
Takes under 4 months if growing indoors [ Carl Rosner, IBC New Jersey ]
The reason why fine powder filters out the drainage holes or clogs bonsai pot soil.

Compost holds 20 times it;s weight in water.
In the next stage of decomposition it clumps together.

5 mm Crushed red brick also is porous and holds water.

5 mm Silica based gravel is non-porous.

So for say the tamarind we combine brick with gravel but
never more that 3 parts organic.

Transplanting is done in our 6 month dry season. By the wet season
the tree / shrub has mastered the soil.
So there is no water problem.

The soil components are indestructable, and promote fine
feeder root growth and free drainage with a water bank.
Clay or clay type ingredients will encourage fat roots.
We see this with our island's high clay soil terrain.
Trinidad is a giant lump of very plastic yellow or red clay.
Good Day
Anthony

Molto Importante -
**** As usual test on Expendables, not the mothers.*********

 

[bonhe]

Thanks for sharing information.
I am glad that more modern bonsai people in the hot dry areas using organic in their soils! I have been extensively using pine bark and ground fir for more than 5 years with good result ! Most of my soil contains pumice: mini pine bark and ground fir with 1:1:1 ratio. I use this for all my deciduous trees. This year, I use Tee-N- Tuft instead of ground fir. I will see if there is any difference in growth.
Thụ Thoại

 

[MichaelS]

Michael,

here is what works for our Azaleas [ since 1980 ]

5 mm silica based gravel
Canadian peat moss / has perlite which can be sifted out.

Every 5 years we cut off a % of soil and add new mix.

Mind you this is the coarser azaleas that can grow around Louisiana.

I also add- more success to you!!!!!!!!!
Good Day
Anthony

Scoria = Crushed red brick [ porous ] ?

Yes scoria is very porous! But you can vary the WHC with particle size to some extent. (or add your quartz gravel to do the same)

 

[MichaelS]

Thanks for sharing information.
I am glad that more modern bonsai people in the hot dry areas using organic in their soils! I have been extensively using pine bark and ground fir for more than 5 years with good result ! Most of my soil contains pumice: mini pine bark and ground fir with 1:1:1 ratio. I use this for all my deciduous trees. This year, I use Tee-N- Tuft instead of ground fir. I will see if there is any difference in growth.
Thụ Thoại

Yes I have always used pine bark/sand but sooner or later it breaks down to dust and you get a saturated lower root zone or water repellence. I wanted something which would not slump after a few months and would accept water more evenly. Pine bark in moist cool environments like azaleas enjoy also seems to attract pests like millipedes and slaters which eat it. I often find half of it missing from the bottom of the pot!

 

[bonhe]

Yes I have always used pine bark/sand but sooner or later it breaks down to dust and you get a saturated lower root zone or water repellence. I wanted something which would not slump after a few months and would accept water more evenly. Pine bark in moist cool environments like azaleas enjoy also seems to attract pests like millipedes and slaters which eat it. I often find half of it missing from the bottom of the pot!

I don’t know what kind of pine bark you have, but mine, it still keeps its shape after 5 years!
Thụ Thoại

 

[Hyn Patty]

Big difference in the climate of Southern California and most other places. I would expect your bark to last a lot longer there with how warm and dry it gets, even with daily watering. Out here it'll not last long with 90 to 130 inches of rainfall a year. It's going to be interesting while I sort out what is the best mix in my climate in the coming year or two.