Pine Potting Question

[AndyJ]

I'll look for your thread to address your specific questions.

But, since it is appropriate for this thread, a bit about "half bare rooting":

You will not see much, if any, description or instructions about "half bare rooting" (HBR) in any book. To the best of my knowledge, this technique started with Boon. I may be wrong about that, if so, I apologize in advance. But, until I started studying with Boon, I had never heard of it, and I've been doing bonsai 40 plus years.

Bare rooting deciduous trees just before the bud out has long been a standard procedure. They appear to do just fine. Conifers, however, don't like it, and it can seriously set them back or kill them! That is one of the reasons imported conifers are so expensive: they are bare rooted when shipped, and then reported upon arrival here in the US. Unfortunately, many don't survive being barerooted.

Conifers prefer a free draining soil when kept in bonsai pots. Newly collected yamadori, and even nursery grown trees often have soil that provides inadequate drainage, or stays too wet. This can cause either root rot, or there can just be no active roots at all in the part of the root ball closest to the trunk.

So, this old "mountain duff" in the case of yamadori, or old worn out potting soil in the case of nursery material needs to be replaced. Soil close to the bottom of the trunk needs to be replaced? How do we do that without bare rooting the tree?

HBR:

Start off doing a regular "repot" procedure. Then, determine which half of the rootball is the "weakest". Bare root the weak half. Leave the strongest part untouched so it will continue to sustain the tree while the weak part regenerates. If the tree is really weak, don't do a full "half". Do a third, or a quarter. The object is to begin replacing the old soil with new hood bonsai soil, but not kill the tree in the process.

You've heard the old joke, The Doctor comes into the waiting room and tells the family that "The operation was a success, but the patient died"... We don't want that!

So, using root hooks, bent tip tweezers, chopsticks, etc., remove as much soil as you can on the weak side, and get up under the trunk and get the old soil out from under 1/2 of it. Wash it off with a gentle rinse of water. Don't pressure wash it off! Try to leave the other side as undisturbed as possible.

Then pot in a pot, or box, or colander, being sure to get new soil back into where you removed all the old soil, leaving no air pockets. Use chopsticks, but don't overdo it! It's easy to break what few good roots you have with over enthusiastic chopsticking! Backfill with soil, and settle it in by giving the pot a few taps with the meat if your fist. Water throughly.

In a couple years, do the other half. If you only did a third, you only have to wait a year to do another third.

Now... The question has come up: "What about watering?" Should I water for the new soil? Or the old soil?

The answer: it's virtually impossible to overwater good bonsai soil. The drainage is such that excess water will pass right through. Therefore, water according to the needs of the old soil. Certainly, if the old soil is really water retentive, and you don't need to water very often, you may need to make sure the new soil. Usually, the problem is the old soil is so compacted that water doesn't penetrate into the center of the rootball. In this case, you need to water a lot do that the old rootball gets some water. The new soil will let any excess drain on out.

Now, why isn't this in any of the books? For the most part, the books discuss how to repot existing bonsai that have already been growing in good bonsai soil. In Japan, they grow their nursery stock in bonsai soil, so a switch over isn't needed.

Finally, don't forget that a HBR is still considered major rootwork. It's best to give the tree a rest after that to let it build a good strong root system. If you have a good root system, then you can be more aggressive with other training procedures. The fact that you needed to do a HBR is an indication that the tree is weak, and so it would be better to wait until the tree is stronger to do anything else.

Hi folks.

Dave post in his literati JBP > https://www.bonsainut.com/threads/jbp-literati.21109/page-3

@Dav4 - just read through this from start to finish. Great progress and nice tree at the end! Hope you don’t mind me jumping on to ask a question about HBR that @Adair M has explained here? Apologies if this has already been discussed in another thread - please can you point me in its direction?

When you discuss the HBR process, I understand that this means you remove 50% of the substrate in order to remove any ground soil that might still be present but is it also to maintain the trees roots too? Do you take this opportunity to try and enhance the trees roots and try and arrange them radially? Do you also cutback the roots? If you do, how much are you cutting back? Do you just nip the tips? Or are you cutting back, say, 50%?

Also. How do you manage the move of a pine from a big training pot (pond basket, colander, etc) and into a bonsai pot? Given that pines don’t like root work? A development tree maybe in a pot that is, say, twice as big as the bonsai pot you want it to go in. What is the procedure for reducing its football to make it small enough to fit the pot?

Thanks all

 

[Dav4]

A half bare root re-pot is basically going to refresh approximately 50% of the soil in a root ball. It can be field soil or old and compacted akadama based soil and is something that will need to be done to trees that have been kept in a pot for a long time, but definitely not at every re-pot. You should always work the roots to improve them when you re-pot, so this does mean you're cutting and positioning roots to make the overall rootage better. It's true that you can't be as aggressive with root work on a pine as with a maple, but you can certainly reduce the overall volume in a healthy tree by a fair amount to move it into a smaller container... reducing the root mass over several re-pots and good soil are the keys. Don't forget that the whole point of keeping a pine in a colander is to increase root ramification to allow safe root reduction to move it into that smaller pot. I'd say a healthy pine can routinely have close to 25-30% of it's roots removed at a re-pot, but I've removed over 50% in one go without issue. Ultimately, each tree/situation will be different and you'll develop a feel for how much work/root removal/root ball reduction is appropriate.

 

[AndyJ]

Thanks @Dav4 that’s brilliant. I’ve yet to do a repot on any pine as have been very nervous about overdoing it and killing the tree! Your explanation clears things up quite a lot.

So if you’re doing an HBR and trying to arrange roots better, what do you do with those roots that have grown into the half of the rootball you’re not touching? Do you just pull them free and hope they’re not damaged? Do you leave them? Or do you cut the root at the point it goes into the other half? (Hope that makes sense?)

 

[Adair M]

Thanks @Dav4 that’s brilliant. I’ve yet to do a repot on any pine as have been very nervous about overdoing it and killing the tree! Your explanation clears things up quite a lot.

So if you’re doing an HBR and trying to arrange roots better, what do you do with those roots that have grown into the half of the rootball you’re not touching? Do you just pull them free and hope they’re not damaged? Do you leave them? Or do you cut the root at the point it goes into the other half? (Hope that makes sense?)

No.

When you do a HBR, you start by prepping the roots and rootball just like you would do without doing the “half bare root” process.

Then, you pick a side to HBR. could be any side, left, right, front or back. Choose to bare root the weakest side. The remainder of the rootball, the non-bare side, will sustain the tree while the bare side regenerates.

To bare root your chosen side, use root hooks, chopsticks and water to as gently as possible remove the soil around the roots. It’s important to get up under the base of the trunk as best you can. This is a rather tedious process.

When putting it in the pot, be sure to get new soil into all the voids you created. When using chopsticks on the new soil, don’t do a lot of vigorous stabbing, rather insert the chopstick into the soil, and wiggle it back and forth, all the while pushing soil into the void you’ve created. This back fills the empty space under the trunk. Too much “chopping” injures the roots.

Be mindful over the next month or two that water will drain very quickly thru the HBRed section of the roots. So give plenty of water to the non bare rooted side since those roots are still sustaining the tree until the bare rooted side has recovered.

Do the other side a year later.

 

[AndyJ]

Brilliant! Thanks @Adair M thats clearer - I think I’ve got it!