Half bare rooting technique

[FiestaRed]

I found reference to "half bare root technique" in a YouTube video which led me to a search on Google and eventually to a post on here in 2019.

I would like to learn more about this technique but can only find a reference to "Boon" and as I'm in the UK, don't really know what that is. Any help or advice would be greatly appreciated.

 

[Scorpius]

Remove up to half of the top half of substrate and replace with bonsai substrate. Let grow for at least a year. After roots have filled in the bonsai substrate you are safe to remove the bottom half of the rootball. Hope this makes sense.

 

[markyscott]

I found reference to "half bare root technique" in a YouTube video which led me to a search on Google and eventually to a post on here in 2019.

I would like to learn more about this technique but can only find a reference to "Boon" and as I'm in the UK, don't really know what that is. Any help or advice would be greatly appreciated.

It is a technique advocated for by Boonyarat Manakitivipart used on yamadori to replace the field soil that performs poorly in bonsai culture with a faster draining and coarser media and a much higher air filled porosity. This technique is used on collected tree species for which significant field soil is retained around the roots at the time of collection (primarily pines and junipers). It is generally not used on tree species that can tolerate bare-rooting at the time of collection (I.e., elm, maple, etc) as these are generally potted directly in a higher performing medium.

The technique is exactly how it sounds in the name - bare root 1/2 of the tree (ensuring you get deeply beneath the rootball) and replace the substrate leaving the other 1/2 untouched. Then let the tree grow for a couple of seasons allowing the root system to become well established in the new medium. Then bare root the other 1/2. If Boon is uncertain about the health of the tree, he sometimes only bare roots 1/3 at a time.

There are detractors, but Boon has advocated this technique for many years. I‘ve done it many times myself and can document that, at least in the cases I’ve worked on, I’ve seen positive results.

Bare rooting the other 1/2 of the rootball on a Western Juniper.

 

[Srt8madness]

HBR is done per side, not top or bottom, as Mark's picture shows. The idea being the tree retains vigor from relatively undisturbed roots while filling the new substrate with roots. Perhaps unsurprisingly it's used when switching substrates (like field soil to bonsai aggregate).

 

[Scorpius]

HBR is done per side, not top or bottom, as Mark's picture shows. The idea being the tree retains vigor from relatively undisturbed roots while filling the new substrate with roots. Perhaps unsurprisingly it's used when switching substrates (like field soil to bonsai aggregate).

I've seen it used on trees that are in tall nursery pots to get the root ball down to a manageable height.

 

[River's Edge]

HBR is done per side, not top or bottom, as Mark's picture shows. The idea being the tree retains vigor from relatively undisturbed roots while filling the new substrate with roots. Perhaps unsurprisingly it's used when switching substrates (like field soil to bonsai aggregate).

There are some who advocate top and bottom and indicate they have had success with that approach. I believe the key is to suit the particular species and condition. My approach is to deal with the weakest areas first, leaving the stronger areas of root growth to aid in recovery, before completing the process in a subsequent repotting or two. and also important to do 1/3 at a time if deemed appropriate.
One further comment that I always take into consideration.
" a weaker tree will rarely improve if left in the conditions that weakened the tree"

 

[bonsaichile]

Remove up to half of the top half of substrate and replace with bonsai substrate. Let grow for at least a year. After roots have filled in the bonsai substrate you are safe to remove the bottom half of the rootball. Hope this makes sense.

This is wrong. You bare root the sides. It makes no sense to bare root the top half

 

[Scorpius]

This is wrong. You bare root the sides. It makes no sense to bare root the top half

See comment five in this thread.

 

[bonsaichile]

See comment five in this thread.

I call BS. Nursery trade is not the same than bonsai needs

 

[Shibui]

There's another HBR variation that cuts pie slices out of the root ball to half bare root.

Note that HBR is only needed for species that resent or don't recover quickly from root pruning. Pines, junipers and other conifers are the main culprits. Most deciduous trees have no problem at all with total root reduction and complete change of soil so no need to waste time and effort on HBR for deciduous species, azaleas or tropicals

 

[FiestaRed]

There's another HBR variation that cuts pie slices out of the root ball to half bare root.

Note that HBR is only needed for species that resent or don't recover quickly from root pruning. Pines, junipers and other conifers are the main culprits. Most deciduous trees have no problem at all with total root reduction and complete change of soil so no need to waste time and effort on HBR for deciduous species, azaleas or tropicals

Thanks for the reply Shibui. It was on a Juniper repotting video that I first heard of HBR. In my rush and inexperience to repot a couple of garden centre Junipers I bare rooted them and will now be lucky if they live.

 

[Shibui]

Have just been reading another thread along similar lines where another grower points out that not only is root reduction hardiness dependant on species but also on age.
There's no problem bare rooting and severe root reduction for young pines and junipers. I do both to seedling pines and rooted cuttings of juniper and JBP every year with almost no reduction in growth rates. Young trees will cope with far more root reduction and bare root than their older siblings and parents.
Knowing what can be achieved with different species at different time of year at different stages in the life cycle is a matter of experience and research. Suffice to say that most plants will cope with way more than we initially give credit for.

Often failure is not due to the initial root prune but to subsequent care or conditions but the root reduction is the obvious scapegoat for any death or damage. Given you are a beginner it is likely your junipers are young and will cope well with whatever (probably) mild repot you have given them.

 

[Srt8madness]

Thanks for the reply Shibui. It was on a Juniper repotting video that I first heard of HBR. In my rush and inexperience to repot a couple of garden centre Junipers I bare rooted them and will now be lucky if they live.

That's how a good chunk of us newer (read internet) generation got into bonsai. If they die, you've gained experience, if they live, you've gained experience.

 

[bwaynef]

Repotting

I've recently started to approach bonsai more seriously, ...actually seeking (regular) instruction. Recently, after learning how to repot in person (instead of just watching videos/DVDs, reading about it, and looking at pictures), I decided I'd try to capture every step of the process. What...

www.bonsainut.com

Surprisingly, I'd go back and add a few things to that thread. HBR technique is mentioned in the 2nd (real) post in that thread. Most of the important parts have been touched on in this thread. The key, and I didn't harp on it enough in the thread linked above, is to get the old soil out ALL THE WAY TO THE TRUNK on the half you're barerooting. This process can take a lot longer than you might think. (Sometimes it goes surprisingly quickly too.)

One thing I don't see mentioned is that for the half not being barerooted ...on a reasonably healthy tree, its treated like a regular repot, so you're still trimming the rootball and still trying to incorporate better soil into the extremities.

 

[Maiden69]

I only have one HBR experience with JBP, and in my case I will not do that again. I know Boon, Scott, Adair and many others have good results with it. I did a HBR on my first nursery bought JBP, a 1 gal JBP that arrived with close to a 1" trunk. The HBR was done the spring of 2021. Growth pretty much stopped, in contrast, this spring I did what Ryan at Mirai recommends on my 2 other JBP, I cut all the roots close to the trunk and cleaned out the rootball nicely without disturbing the soil immediate close to the trunk, planted them in the same Root Pouch that I planted the first pine. Growth exploded literally, I have a multitude of 12" plus candles that have extended in the last 2 months. You can't really distinguish in this pictures, but the pine that I did the HBR is the one circled in yellow, which was done in Spring 2021, the other 2 pines to the right were done this spring 2023, and the growth is absurd in comparison.

This Mirai technique is a two step, just like the HBR technique. In the HBR you address the 2nd half of the rootball a few years after. In the Mirai, you address the center part a few years after. I guess I will need to do an update next year when I move the first JBP to a pot or a slightly bigger Root Pouch.

 

[Tele]

I saw it done in this video.

 

[Scorpius]

I call BS. Nursery trade is not the same than bonsai needs

Some of us purchase material from where we can find it and sometimes that is nursery material. I'm happy you have such high quality yamadori and material from bonsai professionals so readily available near you.

 

[bonsaichile]

Some of us purchase material from where we can find it and sometimes that is nursery material. I'm happy you have such high quality yamadori and material from bonsai professionals so readily available near you.

That is not what I meant at all. Read again

 

[Scorpius]

That is not what I meant at all. Read again

I don't have to. You made your point and so did I.

Nursery material is a viable option for bonsai. Nursery grown plants are usually in tall containers and using the half bare root technique is a viable option to safely reduce the height of a root ball drastically so it will fit into a bonsai pot.

 

[rockm]

I've seen it used on trees that are in tall nursery pots to get the root ball down to a manageable height.

Unclear what you mean. Barerooting or reducing? Half bare rooting a tall root mass doesn't really reduce the height...?

To reduce height on nursery trees in tall pots (And most any other nursery sourced tree) I just saw off the bottom 1/3 to 2/3 of the root mass to start. If it's deciduous, I also bare root.