Pumice as substrate..

[fredman]

So, I did some practical tests to see how long pumice and composted pine bark holds onto moisture. Its beginning of summer here. Temps range roughly 60-70 F. (15-21C)

Used 3.5 ounce (100 gram) of both. Both are roughly 1/4 inch size. Wrapped in netting as photo above. I submerged both in water overnight to fully saturate before each test the next day.
Bark weight saturated... 4.5 ounces (127 gram). Pumice... 5.5 ounces (157 gram).

Test 1....Hung indoors (closed garage) in a draft less area (cloudy damp weather). Bark took 34 hrs. to loose all its moisture. Pumice...50hrs.

Test 2.... Hung outside (on a big bonsai's horizontal branch, why?...seemed the appropriate thing to do) in a shaded/well drafted area (sunny windy). Bark took 7 hrs. to loose all its moisture. Pumice...12 hrs. (recorded weights every hour)

Test 3.... Hung outside (washing line) in full "blazing" NZ sun (windy). Temp all day...77F (25C) with the wind chill.
Bark took 4 hrs. to loose all its moisture. Pumice... 8 hrs.

Both the bark and pumice looked "dry" to the eye very quickly. I was amazed when I weighed them the first times. What surprizes me, is that the pumice takes up much more moisture than the bark, and holds onto it for much longer to. I always thought the bark fracture in the mix is the one that diffuses the moisture in time. Now I see its actually more the pumice.
The last test is the most interesting to me. The pumice turned white and looked bone dry, yet it held onto the moisture for 8 hrs. When I walk past a pot now, that looks dry although I know I watered it recently, I know for certain there is moisture in there...
Also very interesting is the steady rate the pumice released moisture. Bark weight declined rapidly and sometimes irregular, but the Pumice steady and at the same rate with every test.

 

[sorce]

I know for sure bark makes my DE dry faster. Cuz it breaks up the "neighbor wicking".

Its Probly the same with pumice.

I think that why straight works better.

Sorce

 

[SU2]

Hopefully it's not too 'against the grain' to bump this thread but I've just gotta know how realistic a worry this is:

You might try adding the sphagnum to the top rather than mixing it so it doesn't rot in there.

Have never heard this advisement before and would really appreciate any thoughts on it, I use only small amounts now (some top-dressings but usually as a ~5% substrate component in many of my mixes), however I'm going to be re-potting a lot of trees soon and was actually planning to increase the amount of sphagnum I use (fantastic CEC and water-retention with a low pH- perfect attributes for an additive for my needs!)

Maybe @Eric Schrader means over really long time periods ie something that's in refinement and isn't getting re-potted every year or two? The top-dressings I've made still look ok ('rot' is an interesting word to use here anyways, 'rot' is really decomposition which is inherent to all organic substrates so FWIW I'm taking the quoted statement to mean 'rots/decomposes faster')

Thanks for any insight on this additive, I use the type from Home Depot that's tan, long-strand sphagnum (want to be sure nobody is thinking of those brown, dusty 'peat moss' bricks that people use for starting seeds) like this stuff:


Thanks for any thoughts I don't want to go buy another bag in anticipation of going closer to 10% in my mixes if it's decomposing at a much faster rate than I'd thought!

[edit- FWIW the general mix I make is, roughly, 40% perlite, 35% DE, 20% lava, and ~5% organic like bark or sphagnum. Am also intending to increase the DE/decrease perlite, as well as decreasing both of those to add more lava]

 

[tree4me]

This year I potted a few junipers from nursery pots into straight 3/16" pumice I got from here...https://www.generalpumiceproducts.com/. I see how it goes over the next few years with a heavy feeding regime and attention watering. I have a moisture meter may start taking measurements day to day and see how quick it dries. not very scientific but should give a general idea.

 

[SU2]

This year I potted a few junipers from nursery pots into straight 3/16" pumice I got from here...https://www.generalpumiceproducts.com/. I see how it goes over the next few years with a heavy feeding regime and attention watering. I have a moisture meter may start taking measurements day to day and see how quick it dries. not very scientific but should give a general idea.

Interesting, I'd always thought coniferous stuff like Juniper wanted more organic and pumice is pretty far from organics in key respects, it's low water-retention compared to high, has an alkaline pH (barely- 7-7.5pH is what I've seen quoted) compared to acidic organics, pretty low water-retention and considerably CEC/ability to hold nutes - I'd most certainly consider doing a lighter, more-frequent fertilization regimen in this type of setup!
(as to the moisture-meter, does pumice not have a visual that it's wet/dry? I've never used pumice but use lava rock extensively and had always thought the two were similar-enough that most properties would be similar...when it comes to lava rocks they're an awesome visual moisture-gauge!)

 

[River's Edge]

I have been using pure pumice in three of my grow out beds for the past four years. They have outperformed the beds that have a mix of sea soil and pumice. Keep in mind that my climate is fairly damp in the winter and hot and dryer for extended summer periods. Organic components often stay to wet for my situation. Zone 8b
I use organic fertilizer supplemented with slow release osmocote type preparations in the grow beds. I have had success with the following tree types. Trident, variety of Japanese Maples, JBP. JRP, Hornbeam. Zelkova. I also use pure pumice for all collected trees initially, Sub Alpine Fir, Hemlock, and Shore Pine.
After the grow beds i switch to various versions of Boon mix dependant on the species. The key variant is the amount of akadama for a particular type of tree. In some cases it is the amount of Kanuma or Kyru used. The basic three other components are black lava, granite grit and pumice.
I also vary particle size based on the results i am looking for with the particular species and stage of development.
Once we begin to understand pumice and get more familiar with its use, i believe it may become the primary soil for Bonsai. The biggest drawback i see is the color and to counter act that aspect i switched to black lava to give my soil mix a darker color, and a darker granite grit as well.

 

[tree4me]

as to the moisture-meter, does pumice not have a visual that it's wet/dry?

It does turn a light gray but can be difficult to tell. The meter is more to see if it will register a discernible difference day to day

I also use pure pumice for all collected trees initially

Treating a nursery grown plant like a collect tree was my original theory. I have read others do the same, collect trees and place in straight pumice. I though I'd try "collecting" from a nursery pot and use pumice. When I find it's time to place in a proper pot I'll use more of a Boon mix

 

[Adair M]

Hopefully it's not too 'against the grain' to bump this thread but I've just gotta know how realistic a worry this is:

Have never heard this advisement before and would really appreciate any thoughts on it, I use only small amounts now (some top-dressings but usually as a ~5% substrate component in many of my mixes), however I'm going to be re-potting a lot of trees soon and was actually planning to increase the amount of sphagnum I use (fantastic CEC and water-retention with a low pH- perfect attributes for an additive for my needs!)

Maybe @Eric Schrader means over really long time periods ie something that's in refinement and isn't getting re-potted every year or two? The top-dressings I've made still look ok ('rot' is an interesting word to use here anyways, 'rot' is really decomposition which is inherent to all organic substrates so FWIW I'm taking the quoted statement to mean 'rots/decomposes faster')

Thanks for any insight on this additive, I use the type from Home Depot that's tan, long-strand sphagnum (want to be sure nobody is thinking of those brown, dusty 'peat moss' bricks that people use for starting seeds) like this stuff:
View attachment 181149

Thanks for any thoughts I don't want to go buy another bag in anticipation of going closer to 10% in my mixes if it's decomposing at a much faster rate than I'd thought!

[edit- FWIW the general mix I make is, roughly, 40% perlite, 35% DE, 20% lava, and ~5% organic like bark or sphagnum. Am also intending to increase the DE/decrease perlite, as well as decreasing both of those to add more lava]

Eric does not use any organics in his basic mix. It’s Boon Mix: equal parts akadama, pumice and lava. Any spaghnum would be a top dressing, not a soil component.

 

[just.wing.it]

a lighter, more-frequent fertilization regimen

Just curious how you normally fertilize and what you would consider more frequent and lighter...

 

[River's Edge]

Interesting, I'd always thought coniferous stuff like Juniper wanted more organic and pumice is pretty far from organics in key respects, it's low water-retention compared to high, has an alkaline pH (barely- 7-7.5pH is what I've seen quoted) compared to acidic organics, pretty low water-retention and considerably CEC/ability to hold nutes - I'd most certainly consider doing a lighter, more-frequent fertilization regimen in this type of setup!
(as to the moisture-meter, does pumice not have a visual that it's wet/dry? I've never used pumice but use lava rock extensively and had always thought the two were similar-enough that most properties would be similar...when it comes to lava rocks they're an awesome visual moisture-gauge!)

Pumice according to laboratory studies can have a range of PH from 6.6 to 8.3. It is generally considered neutral or 7.0. If it is being used for PH sensitive trees or shrubs then the PH of your particular pumice source may be important.

 

[Captkingdom]

FYI if you haven't tried it yet a good source for pumice can be a concrete block (aka CMU or cinderblock) manufacturer. It is often a componant of their lightweight block.
Lehi Block in Utah quoted me $30/pickup load last year.

 

[just.wing.it]

What the hell happened to @fredman ????
My man fall off the planet???

 

[BunjaeKorea]

Seeing as Jeju Island is an extinct volcano....a lot of bonsai growers use straight up pumice and that place has some of the best trees I have ever seen in my life.....only thing u need to worry about is drying and in NZ dont think u will have an issue....its not Ozzie land...

 

[SU2]

Eric does not use any organics in his basic mix. It’s Boon Mix: equal parts akadama, pumice and lava. Any spaghnum would be a top dressing, not a soil component.

Gotcha! Hope it's not decomposing in-full in like a year or something...I just re-potted a ~8mo old tree yesterday, the sphagnum that was in that mix still looked good ie very distinctly sphagnum-moss when I was un-potting the tree

 

[SU2]

Pumice according to laboratory studies can have a range of PH from 6.6 to 8.3. It is generally considered neutral or 7.0. If it is being used for PH sensitive trees or shrubs then the PH of your particular pumice source may be important.

This worries the crap out of me and isn't something I know what to do about...was told the at-home kits are off by too-much to be of use...think I'm going to get a basic kit anyways (damnit I hate this choice, if I get it then I may be working on false-positives yknow?) but I've read that black lava has a higher pH, and there's seems to be some degree of correlation between density and darkness ie the densest pieces in the bag don't have much bright red! So I choose based on that (I hand-sort my mix on a table before use ), hopefully I'm getting something that's at least somewhat acidic, the perlite is neutral, bark/sphagnum/leaf-mold/humus are all acidic, so am able to tweak it to a proper WHC and AFP w/o worrying much that, overall, it's alkaline/basic

 

[SU2]

Just curious how you normally fertilize and what you would consider more frequent and lighter...

Currently doing a 3 day rotation, day 1 is fertilizer (using 75%TBSP/gallon of 24-8-16, probably going to bump it back up to the full 1tbsp/gal of 24.8.16), day 2 I do an extra-heavy flushing (all days get more than 1 watering), day 3 gets epsom salts (because it just seemed to make sense to split that from the fertilizer, if I do it the day before fertilizer then I lower TDS in the liquid, and the Mg+ probably absorbs better especially w/o the iron that's in the miracle gro, although that's trace-level so may not matter...still seemed smarter to split those)

I have many plants in perlite, or perlite + lava rock, and have been doing lots of re-pottings (with many more qued-up right now!) that are including more DE and/or organics, so it's probably going to make for a situation where I water the 'looser' stuff with full strength fertilizer and then water that down for the stuff that's in better substrates (ie higher CEC and WHC))

 

[River's Edge]

This worries the crap out of me and isn't something I know what to do about...was told the at-home kits are off by too-much to be of use...think I'm going to get a basic kit anyways (damnit I hate this choice, if I get it then I may be working on false-positives yknow?) but I've read that black lava has a higher pH, and there's seems to be some degree of correlation between density and darkness ie the densest pieces in the bag don't have much bright red! So I choose based on that (I hand-sort my mix on a table before use ), hopefully I'm getting something that's at least somewhat acidic, the perlite is neutral, bark/sphagnum/leaf-mold/humus are all acidic, so am able to tweak it to a proper WHC and AFP w/o worrying much that, overall, it's alkaline/basic

Sounds fine to me. The intricacies of testing can be a pain. I have used digital electronic, sophisticated instruments that need cleaning and calibrating with neutral solutions etc. Bottom line they can all give an innacurate or false reading at times. Specially litmus paper that has been kept poorly or too long. After all that is said, a simple liquid Ph drop test by Wardley's or Hagen pet supplies usually works just fine. This is based on thirty five years of aquarium specialty and comparing the PH testers available on the market.

 

[River's Edge]

I have been using pure pumice in three of my grow out beds for the past four years. They have outperformed the beds that have a mix of sea soil and pumice. Keep in mind that my climate is fairly damp in the winter and hot and dryer for extended summer periods. Organic components often stay to wet for my situation. Zone 8b
I use organic fertilizer supplemented with slow release osmocote type preparations in the grow beds. I have had success with the following tree types. Trident, variety of Japanese Maples, JBP. JRP, Hornbeam. Zelkova. I also use pure pumice for all collected trees initially, Sub Alpine Fir, Hemlock, and Shore Pine.
After the grow beds i switch to various versions of Boon mix dependant on the species. The key variant is the amount of akadama for a particular type of tree. In some cases it is the amount of Kanuma or Kyru used. The basic three other components are black lava, granite grit and pumice.
I also vary particle size based on the results i am looking for with the particular species and stage of development.
Once we begin to understand pumice and get more familiar with its use, i believe it may become the primary soil for Bonsai. The biggest drawback i see is the color and to counter act that aspect i switched to black lava to give my soil mix a darker color, and a darker granite grit as well.

Just thought i should note the grit i prefer is called #2 Cherrystone by TCC products out of MN. comes in 50lb. bag. the black lava if from CanLava corporation sold as Tephragro also in a 50 lb. bag.

 

[SU2]

Sounds fine to me. The intricacies of testing can be a pain. I have used digital electronic, sophisticated instruments that need cleaning and calibrating with neutral solutions etc. Bottom line they can all give an innacurate or false reading at times. Specially litmus paper that has been kept poorly or too long. After all that is said, a simple liquid Ph drop test by Wardley's or Hagen pet supplies usually works just fine. This is based on thirty five years of aquarium specialty and comparing the PH testers available on the market.

Thanks for that, I wasn't going to bother with testing but in reading this I'm thinking to just get two brands of the generic liquid tests so I can run two at a time and average them and hopefully have an idea at least!

 

[SU2]

Just thought i should note the grit i prefer is called #2 Cherrystone by TCC products out of MN. comes in 50lb. bag. the black lava if from CanLava corporation sold as Tephragro also in a 50 lb. bag.

How do you find these types of products? Beyond home depot or walmart (and NAPA for my 8822 DE!) there's nowhere I know of to get these types of things....obviously you're not in my area but I just mean how do you find places 'like' a 'TCC Products'? I imagine it's a type of wholesaler/building-supplier or something? I'd really like to find something better for some of my aggregates, for instance w/ scoria I manually process it from 'lava-rock-mulch' bags, smash & sieve to 2 grades (~1mmm and ~2-7mm grades) It's (obviously) a major PITA, and with DE the only stuff I know how to get is the NAPA product which is poor quality in terms of particle-size (I get very little 'great' particle size, those bags are mostly smaller-sized pieces and tons of fines), would love to find a 'stone dealer' but the only one I've ever been able to locate on google-maps was a real underwhelming place (scoria 'smalls' are only obtainable if the pallet is close to empty otherwise it's the same size as standard scoria mulching rocks)

Would love knowing what terms to search for, or what professions/niches these types of suppliers cater to, so that I may get lucky enough to find another nearby who's got what I'm looking for!! (am aware that sized product is available online it's just too over-priced IMO!)