Keeping old soil

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Ollie

Yamadori
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I understand that, when in refinement, it's generally best not to bare-root a tree, and work in a little soil around the edges every repot.

And I understand that soil breaking down over time (particularly akadama) helps produce fine roots and ramified branches.

However, doesn't this mean that over time your root ball gets a wetter and wetter (and thus hypoxic) centre compared to the peripheries of the root ball? Doesn't the akadama in the centre just turn to mush?

Similarly, when collecting trees, doesn't "keep as much field soil as possible" create a soggy core compared to the bonsai soil you add around it?
 
Adjust your watering accordingly as you would do for any other condition that effects water needs such as rain, wind, sun or lack of these.
One size does not fit all.
 
But wouldn't you still need to water when the edges (newer soil) dry out, when the centre will still be wet? Thus always keeping the centre too wet?
 
First, when repotting an older established bonsai, you do much more than "take a little off around the edges". Depending on the species, you either do "half", or you do all the way around. You tease out old soil quite a way into the root ball. Yes, you are supposed to leave the "shin", or central root ball unmolested, but this area is not much larger in diameter than the trunk itself. So repotting old trees is more aggressive than "just a little off the edges". In the case of older pines, and other conifers, only one half of the root ball is given this treatment at a time, then the other half is done 2 or so years later, after the recovery from the first half.

With older established bonsai, the central core is mostly pumice, or pumice and akadama. This does not form an "anoxic mass" as it is not organic, there is nothing there that can rot. Pumice retains good water & air penetration. Akadama gets finer and finer, but at its most decomposed it is more like a fine sand, than it is clay or muck. Yes, soaking so that the new and the old soil are completely wet is important.

As to "Keep as much field soil as possible" is just not true. The goal is to keep fine roots intact, without breaking. The goal is not to get "as much soil as possible". The goal is to collect as many roots as possible. If you could bare root without damaging roots, that would be more ideal. Unfortunately bare rooting in the field, without damaging roots in the process is not easy to do. I found with deciduous trees, bare rooting for late winter collecting is preferable to keeping a lot of native soil.
 
Thanks very much, I understand it better now - think I misconstrued various bits of online information.
 
I don't use akadama anymore.
I use a blend of pumice, lava rock and something I can't ID. I do this because akadama breaks down in one or two years here and I prefer keeping most of my trees in the same soil for more than 2 years.
 
I've also been using more and more pumice. I know some people swear by and get great results with akadama, but it is pricey and I've seen issues with it breaking down, at least for certain types of trees. Pumice has a great balance of water retention and aeration. Different sources rate it's CEC from moderate to pretty good, and it seems using humic acid every once in a while should help that. I've also been exploring different size particles from 1/8th inch for small or more refined plants, as well as for top-dressing, to 3/16th inch for more medium since plants or when I need better drainage. I was using 1/4 inch, but I felt that was bigger than necessary for the size trees I'm keeping.

When your repotting, your probably taking off the top, bottom, and sides of the soil then replacing some or all of what you removed with fresh soil. Some people will remove 1/4-1/2 of the soil in the main/core rootball if they feel a need to revitalize the soil, so the rootball has fresh soil every 3-5 years (sometimes longer) depending on how often you need to repot it, basically just cleaning out a wedge each repot.
 
You can also use kittydama instead of akadama, that doesn't break down and should be available in England. It's sold as cat litter but a specific type, you find a lot on which types are good. I use that mixed with bark for all my trees.
 
Ollie said:
Thanks very much, I understand it better now - think I misconstrued various bits of online information.
Click to expand...
I'm trying to do the same as I'm a total newb. This site really has helped me so far because there is so much conflicting/confusing info out there.
 
Bnana said:
You can also use kittydama instead of akadama, that doesn't break down and should be available in England. It's sold as cat litter but a specific type, you find a lot on which types are good. I use that mixed with bark for all my trees.
Click to expand...
I think that is similar to turface in the US. Some plants really liked it. I think it is a good additive for cec and water retention without reducing aeration. I'm minimizing my use of it next year
 
Soil wars: there is a huge range of strongly held opinions on potting media components. Any discussion is liable to bring on a flame war. However. I will try to touch of few more topics without getting people too worked up.

FIrst: every "formulation" of potting media requires a unique water and fertilizer program. If you understand how to water and fertilize your chosen potting media, you can very successfully grow a nice tree. If you don't understand the product you are using, you will be doomed to less than ideal performance out of a product or potting media formulation.

Many of the complaints around Akadama are due to the fact that we "Mericans" can not read Japanese. We often don't know what we are buying, if you can't read the label on the bag of Akadama. There are several grades, not only of particle size, but also degrees of hardness. Soft, Medium and Hard Akadama are the hardness levels I have "Been told about" because I can not read Japanese. I have had excellent results with "hard" akadama, even through our sub-zero Chicago winters. I have had terrible results with "soft" akadama, which can go to mush in one season. If you live in an area with below freezing winters, only purchase the hard grade of akadama.

Second, there is no "substitute" for Akadama. Its properties are pretty unique. There are many potting media formula that do not use akadama, but these are not "substitutes", they are simply different. It is best to think of akadama free potting media as simply being different. They require different watering and fertilizing. Just learn how to handle the mix you choose to use.

Sieves will improve virtually any mix. The more uniform your particle size, the better your potting media will breathe, the healthier your roots will be.

Humic acids, humates and fulvic acids are wonderful elixirs, and actually improve over time the structure your potting media. Humates can be obtained in seaweed emulsions products. Use humates as part of your regular fertilizer program and your potting media will survive longer without the need to be repotted, and you will have healthier roots.

In general, no potting media should be single component. If you use single component potting media, you pretty much are guaranteed to have problems. All turface, or all haydite, or all bark will cause problems. One exception possibly is all pumice. 100% pumice is the mix of choice for establishing newly collected conifers collected in western North America. It seems to work well.

Pumice is the single best component to be used as a part of a potting mix design. If you look at trees of high quality, at shows, you will find the vast majority have pumice in their potting mix. 25% pumice to 75% pumice is the common range. Pumice is great stuff. Difficult to source east of the Mississippi River in North America. Common in western north America.

Turface - this is a calcined (fired) clay. It is recommended by many as a potting media. The product website for Turface does not recommend using Turface as 100% component in potting media. The Turface website actually recommends not using it at more than 25% of a potting mix. Personally I have had trouble with any mix that is heavy in Turface. At moderate levels, 25% or less of a mix, it is really nice stuff. Some will not use it at all.

Horticultural charcoal - and or biochar - this is "good stuff", at bout 10% of a potting mix. Effect more than anything seems to be to encourage healthy mycorrhiza. If you can find it in the right particle size, use it.

Crushed Granite, Decomposed Granite and Crushed Quartzite - basically, inert rock. Holds very little water, mostly just adds weight to a potting mix, causes a potting mix to hold less water, dries out a potting mix. Recommended to not use as a "main body of the potting mix" component. Excellent for top dressing pots that are not going to be covered with moss for display. Some of the quartzite and decomposed granites have very natural colors that make for an attractive topping component to apply on top of your main body of potting media. If used in medium to large size bonsai pots, can quickly take the weight of a pot from a "one man" lift to a "two man required" weight.

Perlite - this is a man made product, quite similar to pumice in its chemistry and physical properties, but it is extremely light. Great stuff for a grow out container, especially if you are located where pumice is expensive. Use perlite instead. However, it is too light to use in shallow bonsai pots. So in nursery containers, perlite is great, in bonsai pots, use pumice instead. Perlite will leave your tree unstable and wobbly.
 
I do have the impression that the turface used in the US does look like the kittydama in Europe but is quite different. The kittydama I have (Linda moler) is quite coarse, therefore it gives better aeration than turface. I also read that turface can be a bit hydrophobic when dry, the kittydama I use is very hydrophilic, water is taken up immediately. So I do have the impression that they are quite different in some critical aspects.
 
Leo in N E Illinois said:
Depending on the species, you either do "half", or you do all the way around. <snip> In the case of older pines, and other conifers, only one half of the root ball is given this treatment at a time, then the other half is done 2 or so years later, after the recovery from the first half.
Click to expand...
You only need to half bareroot conifers when you're changing the makeup of the soil. (A collected tree to an inorganic mix, for instance ...or in rehabbing an old tree w/ a dilapidated soil mix.). This should be rarely done, and certainly not every 2 years. After the soil is completely changed out (after 2 HBRs), repotting every 3-5 years, ...maybe 8-10, depending on the level of development and quality of soil components you began with, the repots are of the take-a-little-off-the-edges (and bottom and top) variety.
 
Bnana said:
That's my experience too, but I read that turface becomes water repellent when dry resulting in very wet and dry parts in a pot (e.g. https://www.bonsainut.com/threads/dry-turface-water-resistant.10444/). I've never seen that with kittydama, but that comes from Denmark so probably slightly different composition and it's coarser.
Click to expand...
That's one reason why you don't use 100% turface. This is not a problem when at 25% and well mixed.
 
All soil threads are God's way of trying to keep trees in nature where they started out. ;)
 
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