Summer Repotting of Chojubai and Princess Persimmon

[Eric Schrader]

I'm not anti-lava, just lazy. I don't know what advantage lava has over pumice, so I only use pumice and it's one less material to stockpile.

Since you're a technical guy - you should explore that a bit.
Here are a couple relevant bits from "Soilless Culture: Theory and Practice" 2e by Raviv, Lieth and Bar-Tal:

Pumice is an inert aluminosilicate material composed primarily of silica and A1-oxide but also may contain metal oxides, calcite or salts. Pumice has no buffering capacity and possesses a very low surface charge, derived mainly from carbonate and metal impurities. Caution is required when applying fresh pumice material because high concentrations of Na may be initially leached.

Tuffs (lava) have permanent and variable charge surface characteristics resulting mainly from amorphous materials. Tuff exhibits a significant buffering capacity and may absorb or release nutrients, especially P, during the growth season (Silber et al., 1999; Silber and Raviv, 1996). The chemical stability of tuff depends on the mineralogical composition.

So my takeaway is that the differences are in the residual minerals that will leach and their ability to hold nutrients. Total porosity is similar as are the water retention curves. And based on the numbers alone (which vary from one source to another!) lava is actually a better substrate than pumice because of the nutrient retention factor.

Empirically, I would note that myself and many others find that performance of lava and pumice as media is significantly improved by washing prior to use. I assume this removes much of the excess salts that would otherwise be present in high quantities in the container. The practice of drying to bone-dry and then sifting is essentially to the same purpose but less effective.

I have been using neither for a while in favor or perlite, which does not leach minerals. But this is actually turning out to be a problem because it's so inert that once other soil components (Coco in my case) break down a bit the soil is totally inert.

 

[Gabler]

I'm reminded of this thread, which produced this chart:

 

[NaoTK]

Since you're a technical guy - you should explore that a bit.
Here are a couple relevant bits from "Soilless Culture: Theory and Practice" 2e by Raviv, Lieth and Bar-Tal:





So my takeaway is that the differences are in the residual minerals that will leach and their ability to hold nutrients. Total porosity is similar as are the water retention curves. And based on the numbers alone (which vary from one source to another!) lava is actually a better substrate than pumice because of the nutrient retention factor.

Empirically, I would note that myself and many others find that performance of lava and pumice as media is significantly improved by washing prior to use. I assume this removes much of the excess salts that would otherwise be present in high quantities in the container. The practice of drying to bone-dry and then sifting is essentially to the same purpose but less effective.

I have been using neither for a while in favor or perlite, which does not leach minerals. But this is actually turning out to be a problem because it's so inert that once other soil components (Coco in my case) break down a bit the soil is totally inert.

Thanks for this.

I don't know what my soil (or water) pH is. I never cared to check because I don't have growth issues. If using lava can correct pH and get demonstrably better growth then that is one reason to shelp myself to the lava pits and sift lava.

So why not, I will test my current pHs and the impact from using 3x miracle gro. And then see what incorporating lava does.

edit: here's my water report. I also read that miracle gro can lower pH

 

[Eric Schrader]

I hope I didn't hijack this nice thread on Chojubai and PP with the soil stuff....lol.

I'll be doing a test repot of a couple persimmon later this week. The buds are already forming along the branches so I'm hoping that means it'll be fine.

 

[NaoTK]

I ordered pH test strips and tested my growing situations:

My water straight from the tap is 7


I tested two of my soil types that I use: One is straight pumice that had miracle grow applied every week this year, and the other is pumice + akadama with miracle grow applied all year. Both were 6.5ish


I was expecting more basic results necessitating lava experiments, but I'm pleased with how things are now. I read that miracle grow can bring down the pH so that might be it.

edit: there you go, regular strength miracle gro solution is off the charts acidic. So I am using it to bring down my pH essentially

 

[Ruddigger]

Helps to have nice water. Mine is between 8 and 8.5

 

[actionflies]

Helps to have nice water. Mine is between 8 and 8.5

Add Miracle Gro per Nao's test.

 

[namnhi]

I ordered pH test strips and tested my growing situations:

My water straight from the tap is 7
View attachment 512017

I tested two of my soil types that I use: One is straight pumice that had miracle grow applied every week this year, and the other is pumice + akadama with miracle grow applied all year. Both were 6.5ish
View attachment 512019

I was expecting more basic results necessitating lava experiments, but I'm pleased with how things are now. I read that miracle grow can bring down the pH so that might be it.

edit: there you go, regular strength miracle gro solution is off the charts acidic. So I am using it to bring down my pH essentially

View attachment 512022

Nao,
My water is very hard so which Miracle Grow fertilizer are you using?
Thanks,

 

[actionflies]

Nao,
My water is very hard so which Miracle Grow fertilizer are you using?
Thanks,

Miracle-Gro Water Soluble 4.25 lb. All Purpose Plant Food (24-8-16) 3020506 - The Home Depot

Miracle-Gro Water Soluble All Purpose Plant Food instantly feeds vegetables, trees, shrubs, and houseplants to grow bigger and more beautiful than unfed plants. Simply feed them every 1-2 weeks. The formula

www.homedepot.com

 

[Darth Masiah]

my tap is usually in the high 7s. after adding Jacks professional 202020 at about 3 grams per gallon, the ph is almost always around 6. jacks hydro a and b at 3/2 g per gal also puts my ph around 6. this fall im using jacks hydro 0 12 26, and it also brings the ph close to 6.

 

[Goodbrake]

There is a surprising amount of literature on persimmon rooting and nitrogen storage. I think we can build some models about why persimmons suck at repotting and why summer repotting is better.

• Persimmons store most of their nitrogen in the roots in Fall.
• In spring, persimmons draw entirely on this root nitrogen to leaf out. Many other deciduous trees also do this.
  • https://www.sciencedirect.com/science/article/abs/pii/S0304423808002768 I can't access so if anyone has access please send me
    
    

    Frontiers | Nutrient Storage in the Perennial Organs of Deciduous Trees and Remobilization in Spring – A Study in Almond (Prunus dulcis) (Mill.) D. A. Webb

    The annual dynamics of whole mature almond tree nutrient remobilization in spring and the accumulation of nutrients in perennial tissues during the year were...

    www.frontiersin.org
• Therefore, if we cut the roots off in spring we are severely debilitating the persimmons.
• If we repot in summer, the tree is actively generating new growth and not relying on stored energy

I've said this before, but if you compare the leafing out behavior to say a Japanese maple, the Japanese maple will slow down its leafing out proportional to its root loss. Maples likely store more energy in the trunk and they certainly regenerate roots faster than persimmon.

@NaoTK do you still want a pdf of this paper?

 

[Goodbrake]

Here's the paper @NaoTK linked for anyone else who wants it.

 

[Goodbrake]

Here's the paper @NaoTK linked for anyone else who wants it.

I think there are a few main points to take home from this paper.

First, persimmon store the majority of their nitrogen in their roots during dormancy, so if you remove their roots, you're removing nitrogen.

Second, this nitrogen comes primarily from nitrogen absorbed from the soil the previous autumn, not leaf senescence, so there might be a reason to fertilize persimmon in autumn differently than your other trees, i.e. use more nitrogen.

Third, the nitrogen used during leaf out in spring is preferentially taken from reserves in the perennial tissue, not newly uptaken nitrogen from the soil, emphasizing that nitrogen lost to root pruning is difficult to replace by spring fertilizing.

 

[Gabler]

Second, this nitrogen comes primarily from nitrogen absorbed from the soil the previous autumn, not leaf senescence, so there might be a reason to fertilize persimmon in autumn differently than your other trees, i.e. use more nitrogen.

All trees should get nitrogen in the fall. The "no nitrogen in the fall" thing is a myth, like water droplets burning a tree's leaves.

 

[Goodbrake]

All trees should get nitrogen in the fall. The "no nitrogen in the fall" thing is a myth, like water droplets burning a tree's leaves.

Then if I'm reading this paper accurately, it's even more important for persimmon, since they aren't absorbing as much nitrogen from their leaves, compared to other deciduous trees.

 

[NaoTK]

Here's the paper @NaoTK linked for anyone else who wants it.

Thank you so much! Thanks for summarizing the paper as well.

Update on trees I repotted last summer: They are leafing out just fine this spring, despite freezing solid many times in the winter, just 4 months after repot. So Summer repotting does work.

I have been repotting a few persimmons this SPRING contrary to my advice, but in these cases there are a lot of roots in proportion to the leaves and I am not removing more than 25% of the roots. So far so good.

For more touchy trees I will be doing another batch of repots in Summer later this year.

 

[Goodbrake]

I would be interested in seeing if their carbohydrate storage is correlated with nitrogen storage (specifically if during dormancy they disproportionately store carbohydrates in their roots compared to the rest of their perennial tissue.) If so, summer repotting makes even more sense. If not, there might be some trade off between nitrogen and carbohydrates that should be considered when choosing repotting time, in addition to water demand on the root system.

 

[NaoTK]

I would be interested in seeing if their carbohydrate storage is correlated with nitrogen storage (specifically if during dormancy they disproportionately store carbohydrates in their roots compared to the rest of their perennial tissue.) If so, summer repotting makes even more sense. If not, there might be some trade off between nitrogen and carbohydrates that should be considered when choosing repotting time, in addition to water demand on the root system.

This paper suggests the answer is yes for most plants https://journals.ashs.org/downloadpdf/journals/hortsci/25/3/article-p274.pdf

Reading this paper I was reminded of a persimmon tree that was show down in California a couple years ago. It was defoliated in late summer so that the tree could be shown with only fruit. The tree went on to die the next year, presumably because persimmons begin carbohydrate storage late in the season after fruit set.

 

[NaoTK]

My hand wavey graph vs actual measurements

 

[Gabler]

So the takeaway is to repot in early summer when the leaves have hardened off and then fertilize well once the roots have recovered?