Water & Oxygen Balance With Conifers

Today I visited a local grower who has been growing some materials in his farm for over 25 years and some of the JBP are absolutely powerful (5" plus trunk). After placing a few orders to be dug up in the coming spring, we started talking about repotting. He said the soil in the farm are mostly red clay and they fall loose very easily during the digging process and that made me worry that I may not have an intact root ball with enough native soil next year. However, the owner and another hobbyist told me they actually bare rooted and washed these JBP’s without any issue. As a matter of fact, these JBP just kept growing like nothing happened. This made me wonder about why we hear conifers should not be bare rooted. After all, balance of water and oxygen is the key and the native clay soil is the opposite of that. Ryan has said in multiple videos that with nursery stock or collected materials, the roots will grow into the APL mix because it is superior to clay or other organic soil. So why don’t we replace all soil in one go? Is it just to preserve beneficial bacteria? If so, then there are products that will promote beneficial bacteria to colonize. Can we just use that and get all fresh soil in the pot to promote better root growth?

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I can’t speak for Ryan but I think the never bare root advice is especially important for old yamadori that has been growing in the wild with certain beneficial bacteria and fungi. You can’t always replace it with an inoculant because the off the shelf innoculants might not have what the tree has been growing with over the past hundred years or so.

Furthermore the fungi has physical structure and if you destroy it and reinnoculate, it’ll still take time to rebuild to the same levels that the tree needs.

As for nursery and stock field grown material, I don’t think they rely on the fungi and bacteria in the soil quite as much (yet) and can probably handle a bare rooting in the initial repot.


Thank you. I have noticed that when repotting pines, i tend to see a lot of white fungi presence if the trees were grown in pots. However, when I dig pines out of the ground, there tend to be much less white stuff around the roots. So maybe when the roots aren’t restricted, they don’t rely on micro organism as much? Also it could be that because roots are circled around the pots, the fungi presence becomes much denser?
Anyway, it is good to know that field grown pines especially when they are super strong can handle repotting with much less native soil.

A couple of things to consider:

Regarding the fungi, there are 100s of different species that may or may not colonize the container and not all of them are visible to the naked eye. So, just because you can’t see them doesn’t mean they aren’t present.

Second, there are definitely nuances between yamadori and field grown stock. Field grown is going to be very vigorous when first dug which increases the likelihood of success with a more invasive repot. Can you have success bare rooting? Sure. Is it the best practice for guaranteeing success? Probably not. Even if your success rate is 90%, are you willing to lose tree number 10?

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I agree that yamadori is very different and the root that come with yamadori are usually very limited. However, the “not bare root conifers” mindset is generally applied to all scenarios I believe. And I wonder if it is causing unnecessary panic in this hobby.
Also, I don’t know if this has happened to others but I am one that suffered from the “never bare root a pine” concept. I dug up a JBP that had been growing in the backyard for 8 years this spring and because I was afraid of bare-rooting, I kept the core rootball intact and filled the sides of the pots with bonsai soil. Later I found out that the clay soil was extremely difficult to water through. Back then I was not a Mirai member yet so I didn’t think of poking holes in the clay to get water through. But I think if I simply shaked off the clay before potting it up, the pine would have grown much stronger. That’s what happened to the other JBP I dug up at the same time. The only difference was the soil was so loose almost all of the clay just shook off when I lifted the tree. To my very surprise, this one grow super strong and even bud back all the way to the base within one inch of the root line. The new needles are over 5" long. I really think having all the roots in good soil made all the difference but I have no scientific proof.

There’s a big difference between not bare-rooting and leaving as much soil as possible. With each re-pot, you should remove progressively more of the field soil. Ryan’s mantra with conifers (especially pines) is “Never bare root, always leave some portion of the root mass untouched.” But this doesn’t mean that you don’t significantly work the roots when re-potting.

The key to merging two different soil components (native soil and particulate bonsai soil) is not to leave a clean boundary between the two. Water will not tend to pass through boundaries of two different soil types easily and therefore the particulate matter will drain freely and the clay will hold water which will not pass into the bonsai soil on the outside. This causes all sorts of water/oxygen imbalance in the pot and does not promote new root growth.

As mentioned, bare-rooting conifers is not advised as it removes the natural microbiobes in the soil which can not necessarily be simply replaced with inoculation. It can work in a young, strong tree but it is not a sustainable technique.

The better technique is to remove a proportion of the native soil and where that soil meets the new bonsai soil, lightly break up the root boundary and cut the tips of the roots to promote callusing and new root production. Be careful not to do the second watering (after soaking the soil post repot) too soon. You want to let the soil dry out (not bone dry) sufficiently as the initial watering causes the callusing and the subsequent high oxygen content (in the drier soil) is what stimulates the new roots to grow.

Then when you come back on the second repot you lightly clean out the top, sides and bottom, preserving the new root growth, and clean out the central portion of old native soil (cutting tips of roots again to promote callusing and new growth) and replace it with bonsai soil. That way you’ve cleaned out all the native soil in two repots and you haven’t had to bare root at any point.