100% Pumice and Montezuma Cypress

AaronThomas

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stability is granite grit.
Okay... I use DG for my bougies. Arizona is essentially a huge granite pit so I mine from the back yard. Have to use a mask due to the risks of contracting Valley Fever(like I need to worry about catching something else these days)
Which would you suggest for better water retention DG or Lava? ... I have both black and red. From all I have read Montezumas are essentially desert tolerant Baldies to put it simply.
Thank you
 

River's Edge

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My point was that straight pumice is used (and particle size selected) to allow rapid establishment of a root system, not to create fine ramification. I don’t think you’re recommending that the OP use straight pumice, either.
You are correct in that it is not my number 1 choice for fine ramification, however I am pointing out that if the proper particle size is selected than it is acceptable and can be used. One would need to adapt fertilization and watering techniques to account for the low CEC capacity of pumice as opposed to the use of Akadama or Kanuma. This could also be accomplished with a low percentage of selected size and structure of organic particles such as Pine Bark. I would limit the amount to 5% or less and be strict about the structure and condition of the material. I would also expect to have to repot more frequently to compensate for the decomposition of the bark. However the Bark would add important PH and CEC capacity to the mix.
 

River's Edge

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Okay... I use DG for my bougies. Arizona is essentially a huge granite pit so I mine from the back yard. Have to use a mask due to the risks of contracting Valley Fever(like I need to worry about catching something else these days)
Which would you suggest for better water retention DG or Lava? ... I have both black and red. From all I have read Montezumas are essentially desert tolerant Baldies to put it simply.
Thank you
Lava has pore like structure , whereas DG does not. Water retention rates are higher for Lava in general. This of course will depend on the source and quality of the product. Pumice and Lava are generally close in water retention capacity and Decomposed Granite has less retention than both Pumice and Lava.
My source of Lava has sharper edges than the pumice, and the granite is smoother edges. This is another factor in root formation.
I dislike the white appearance of Pumice, thus mix the black lava and darker grit for Bonsai mix in show trees and further refinement display.
 

Leo in N E Illinois

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Nothing wrong with using a bark mix. IF you remember to REPOT every 2 to 4 years. Bark is no good if you want to go 5 to 10 years between repotting. If you repot the ones in a bark mix, they should pick up growth and maintain it for a couple years, then time to repot again. Bark is dynamic, it changes its structure over time. This can be good, especially if you are growing trees that need acidic conditions, as bark breaking down becomes more acidic. Not so good when you don't need the acidic conditions. Also, 50% bark is pretty heavy. For my pines I usually keep bark around 10 %, and for spruces and hemlock I keep bark around 25% component. Blueberries are the ones that get the 50% bark & 50 % peat moss.

For a bark mix use a HIGH NITROGEN fertilizer. 20-20-20 is NOT high nitrogen, in fact it is poorly balanced, or not balanced at all in terms of what the trees actually use. I use a 13-1-4 fertilizer with good results, it has a long list is micro-nutrients too. PM me if you want some, I occasionally package and sell what I use.

Pumice is great. If it is working for you, keep using it. No need to change a good thing.

DE- I would never use any component at 100% of a mix. Pumice is the only exception I make. Everything else I use as a mix. DE is great, but I have never gone over 25% DE as a mix component. When I tried 100% DE, the results were not good, at least in my conditions.

Granite, Decomposed Granite, and crushed Quartzite - None of the particles hold water internally. THeir water holding is just the water film on the outside of the particles. A granite mix will be a dry mix. You are in Arizona in not the place I would ever tempt fate by using a dry mix, unless I were raising cactus. Also, granite is heavy. A 5 gallon nursery pot could weight 75 pounds. I'm too old to be throwing around that kind of weight. As a component it is good for "drying out" a mix. I have used it as a 25% component in one of my earlier pine mixes, but I have since gone to pumice, just because I got tired of straining my back moving trees around.
 

KiwiPlantGuy

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Hi all,
Seeing this has gone into more of a soil discussion I thought I would ask for an opinion about Leca (clay) balls as a component (10-15%) or substitute for Akadama as I can’t source that here. In a country of Volcanoes Lava rock is difficult apart from 7-25mm size. Pumice is easy sourced thank goodness.
I realise the balls don’t have any rough edges but they don’t breakdown so non-organic mix would last longer between repots etc.
@Leo in N E Illinois, or @River's Edge have an opinion?
Charles
 

River's Edge

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Hi all,
Seeing this has gone into more of a soil discussion I thought I would ask for an opinion about Leca (clay) balls as a component (10-15%) or substitute for Akadama as I can’t source that here. In a country of Volcanoes Lava rock is difficult apart from 7-25mm size. Pumice is easy sourced thank goodness.
I realise the balls don’t have any rough edges but they don’t breakdown so non-organic mix would last longer between repots etc.
@Leo in N E Illinois, or @River's Edge have an opinion?
Charles
I used Leica balls for a period of time ten years ago and found they did not break down. However it was difficult to get similar particle size and I did not like the shape for Bonsai purposes. The ones I had were too large for practical purposes except bottom drainage. Their shape when combined with other substrate did not work well. Smaller particles compacted easily on top of them and created drainage issues! The last comment would be that I found them rather expensive, unless sifted out and reused. I ended up placing them in the bottom of my wife's outdoor planting pots along with larger gravel for stability and drainage layers.
As you can probably guess I would not recommend them for Bonsai purposes. Much better options available!
 

AaronThomas

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Want to thank everybody again for all the great information. Whether it was the correct decision or not I bit the bullet and decided to repot the three trees that were in the 50/50 bark mix and replaced with 100% pumice. I can reevaluate the substrate again next season... I really just wanted to get the trees out of the bark. This year I will keep a close eye and will fertilize as needed with the help of @Leo in N E Illinois.
I will say this… Even though there has been die back and the trees have been slow to push green… The amount of roots growth was nearly double the growth of what I grew in pumice last year. So strange that the pumice trees are leaving out and doing so much better than those in bark. However I will also add the roots growing in the pumice seem to grow much thicker than the spindly spider leg roots that were growing in the bark.
Little late in the season to be reporting MC so hopefully they will all recover nicely in the shade for a week or so.
Found these little critters in one of my larger pots… If I were on a survival reality program I would probably eat these bad boys. Green scarab beetle larva… Beautiful as adults ugly as can be as grubs.
C94275F2-6D82-4D59-B3E7-5DE769BB1998.jpeg
 
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