Conceptual question about roots on rocks

[HoneyHornet]

So you know of the practice of planting on top of a rock or slab when you make that thick muck and literally press your roots into it and putty it over with more muck…
So my question is how does that actually WORK… there is no aeration in that planting setup so how does that work out

 

[LittleDingus]

So you know of the practice of planting on top of a rock or slab when you make that thick muck and literally press your roots into it and putty it over with more muck…
So my question is how does that actually WORK… there is no aeration in that planting setup so how does that work out

Admittedly, I have not slab grown anything myself, but this is not my understanding of how it works. My understanding is the thick muck hardens to form dikes within which normal bonsai soil is used. The muck just looks more natural and is a surface that algae can grow on. The tree's roots grow in normal bonsai soil.

Basically, the muck forms the pot's outer walls...or terraces...or plateaus...

 

[HoneyHornet]

Admittedly, I have not slab grown anything myself, but this is not my understanding of how it works. My understanding is the thick muck hardens to form dikes within which normal bonsai soil is used. The muck just looks more natural and is a surface that algae can grow on. The tree's roots grow in normal bonsai soil.

Basically, the muck forms the pot's outer walls...or terraces...or plateaus...

I mean that makes sense to me but I’ve literally seen videos I’m pretty sure of people planting on top of a tall mountain shaped rock and I’m almost positive they literally Mucked the roots to the rock
I could be mistaken I mean I wouldn’t do it that way myself and there’s more than one way to do some thing but I just could’ve sworn I’ve seen that in fact I think it’s in one of my black and white Bonsai books

 

[ShadyStump]

I've not done it yet myself, but my understanding is that you're essentially trying to create conditions similar to air layering, only you already have roots to work with.
The roots are draped over the rock, then moist soil pressed in over them so they have something to grow in, then it's all wrapped to hold the whole mess to the rock. You have to use the, "muck," as you call it because otherwise the soil won't hold in place on steeply angled or even vertical rock sides. As the roots grow they find their way into the crevices and pores of the rock, eventually adhering to it, and elongating down into the more traditional soil at the base of the rock. After the roots are set into the soil under the rock, the wrapping id removed and the old, "muck," can be washed away by watering or removed intentionally, revealing the roots underneath.
When done with slabs (again, haven't gotten there yet but it's on the list) the same thing is sometimes done if the slab is at a steep angle, or the there are no sides to hold the soil in.

This is my understanding from a little bit of research. I may be trying out both this year if I find the components that prompt it.

 

[Dav4]

Bonsai rock plantings, where the entire root system is confined ON the rock structure, shouldn't be confused with root over rock plantings, where the roots of the tree grow on and adhere to the rock surface before eventually entering a pot with bonsai soil. Muck is generally used for the former planting. It can be used to build a perimeter wall to hold regular soil, perhaps on a slab, but with many slab and rock plantings, it comprises 100% of the existing soil for the planting, and the roots happily colonize it and live in it for many years. There are several different recipes for muck, but sphagnum moss and clay seem to be the most important ingredients. The combination seems to create a medium that both retains it's form and doesn't wash away, holds moisture but drains well. Ultimately, these plantings tend to dry out more quickly then plantings in ceramic containers. Here is a Hinoki Cypress muck slab planting at the Smith Gilbert Gardens in Kennesaw GA... 25 + years old when the pic was taken, never re-potted and looking great.

 

[Shibui]

It is difficult to separate all the different types of rock plantings and the different techniques used for each.
Slab plantings: A flat rock used as a 'pot'. Muck 'walls around the edge of the planting area help retain the potting soil. Roots are confined to the potting soil inside the muck walls.
Root Over Rock: Roots grow over and down the rock into bonsai soil in the pot. Again, roots are growing in bonsai soil. In older references I have seen muck used to paste the roots to the rock in the initial stages while the roots grow and thicken while the rock and roots are buried in a container of bonsai soil. The muck eventually disappears when the tree is raised to expose the roots. My experiences with this technique were not favorable. Roots seemed to be damaged in the process or rotted due to staying too wet. No muck works better for me.
Root ON rock: Tree or trees are planted on a larger, usually taller rock to simulate a mountain or cliff. Roots are confined to small hollows or ledges and do not usually extend down into a below. The small size of the planting hollows makes it impractical to use bonsai soil. Bonsai soil also dries far to quick when in contact with rock in such small pockets. This is where planting roots in muck can be used. The much retains moisture and nutrients far better than bonsai soil so the tree can survive through a hot day. The muck pockets dry out most days so the roots don't rot as they would in larger pockets or pots in similar soil. These root on rock plantings are rarely if ever repotted.
Root on Rock is a very specialized style. Trees and grower skills are pushed right to the limit to maintain the trees. Root on Rock plantings are often placed in a suiban of water to maintain humidity and prevent premature drying out during hot days. I have one small rock planting with 3 shimpaku planted on the rock where the roots started out in muck pockets. Over the years the roots have now extended down the rock into the suiban of gravel so now it's not quite Root On rock any more. I don't have access to my photos today and limited internet to upload anyway but will try to remember to post a pic when I do.

To my knowledge Root On Rock is the only place where confining roots to muck is appropriate however, as most of us are aware, different conditions and different care can allow a vast range of different planting techniques and soil types to be used successfully so it is theoretically possible to plant trees in pure muck provided you can manage the water and trees appropriately. Personally I'd only resort to muck planting in extreme cases where bonsai soil will not work.

 

[Frozentreehugger]

It is difficult to separate all the different types of rock plantings and the different techniques used for each.
Slab plantings: A flat rock used as a 'pot'. Muck 'walls around the edge of the planting area help retain the potting soil. Roots are confined to the potting soil inside the muck walls.
Root Over Rock: Roots grow over and down the rock into bonsai soil in the pot. Again, roots are growing in bonsai soil. In older references I have seen muck used to paste the roots to the rock in the initial stages while the roots grow and thicken while the rock and roots are buried in a container of bonsai soil. The muck eventually disappears when the tree is raised to expose the roots. My experiences with this technique were not favorable. Roots seemed to be damaged in the process or rotted due to staying too wet. No muck works better for me.
Root ON rock: Tree or trees are planted on a larger, usually taller rock to simulate a mountain or cliff. Roots are confined to small hollows or ledges and do not usually extend down into a below. The small size of the planting hollows makes it impractical to use bonsai soil. Bonsai soil also dries far to quick when in contact with rock in such small pockets. This is where planting roots in muck can be used. The much retains moisture and nutrients far better than bonsai soil so the tree can survive through a hot day. The muck pockets dry out most days so the roots don't rot as they would in larger pockets or pots in similar soil. These root on rock plantings are rarely if ever repotted.
Root on Rock is a very specialized style. Trees and grower skills are pushed right to the limit to maintain the trees. Root on Rock plantings are often placed in a suiban of water to maintain humidity and prevent premature drying out during hot days. I have one small rock planting with 3 shimpaku planted on the rock where the roots started out in muck pockets. Over the years the roots have now extended down the rock into the suiban of gravel so now it's not quite Root On rock any more. I don't have access to my photos today and limited internet to upload anyway but will try to remember to post a pic when I do.

To my knowledge Root On Rock is the only place where confining roots to muck is appropriate however, as most of us are aware, different conditions and different care can allow a vast range of different planting techniques and soil types to be used successfully so it is theoretically possible to plant trees in pure muck provided you can manage the water and trees appropriately. Personally I'd only resort to muck planting in extreme cases where bonsai soil will not work.

What I don’t get is the standard belief is shallower the pot the worst the drainage this makes sense to me . But in Japan you see them all the time planting a forest on a natural rock or a slab with a muck wall and no drainage holes . Makes no sense to me plus I’m still bitter found a real nice flat rock and broke it in 3 parts trying to drill drain holes in it

 

[ShadyStump]

What I don’t get is the standard belief is shallower the pot the worst the drainage this makes sense to me . But in Japan you see them all the time planting a forest on a natural rock or a slab with a muck wall and no drainage holes . Makes no sense to me plus I’m still bitter found a real nice flat rock and broke it in 3 parts trying to drill drain holes in it

Like he said, it's water management. You can't depend on excess to run off like in a pot, so you have to water differently, and use a soil that will disperse the water more evenly.

 

[Shibui]

What I don’t get is the standard belief is shallower the pot the worst the drainage this makes sense to me . But in Japan you see them all the time planting a forest on a natural rock or a slab with a muck wall and no drainage holes . Makes no sense to me plus I’m still bitter found a real nice flat rock and broke it in 3 parts trying to drill drain holes in it

My experience is that rock plantings use water way quicker than pots. My take is that natural rocks are more porous than fired clay pots. Water in the soil is soaked away by the rock and evaporated to the air. Even with no drain holes the rocks drain moisture away much quicker than pots with drain holes. In the early days I tried planting on slabs but they either did not thrive or just died in summer from dehydration. I was not able to water enough to keep slab plantings alive and healthy.

I feel your pain about the rock. I found a great slab around 3 feet long by 2' wide but less than 1" thick which is ideal because thicker slabs are so heavy and difficult to manage. It would have been ideal for a forest planting. Carried it a couple of miles all the way down off the hill. Nearly home when I put it down to climb through the fence and it broke in half.............

 

[Frozentreehugger]

What you are saying about water management and rock dehydration makes a lot of sense . At the end of the day seems over complicated and easy to screw up the everyday care . That’s why seems more logical tone to use drainage holes and treat it as a normal bonsai water technique . But I don’t have 800 years ofJapanese trial and error behind me .

 

[HoneyHornet]

Noticing my OP lacked any real depth or explanation , I was working and literally randomly popped my phone out to post it and it’s just a little vague for me now

First off Thanks to all input and answers lots of great info as always,
And to try and clarify maybe where I was coming from; I understand when and why they would use the method, as steep rock surfaces can not hold soil, -by the way I was primarily referring to root ON rock where the muck is the entirety of soil used-,i was mainly pondering just how it seems so contradictory to the typical soil conditions we strive for, since a mix that is claylike and can bond to a vertical wall is like the opposite of free draining lol

- but to kind of start answering my own question using the info provided, it definitely makes sense that water management is the ticket:,because typically when for instance if a soil is too mucky in your pot, when it dries out it will be like a brick, allowing none of the conditions the roots need and therefore can smoke your tree…and if it is consistently mucky it will also hinder the conditions the roots require and can also smoke your tree-
So the same thing applies to these plantings, I understand why they are often found in a waterscape type thing where the humidity can consistently feed the conditions needed

 

[BrianBay9]

What you are saying about water management and rock dehydration makes a lot of sense . At the end of the day seems over complicated and easy to screw up the everyday care . That’s why seems more logical tone to use drainage holes and treat it as a normal bonsai water technique . But I don’t have 800 years ofJapanese trial and error behind me .

It all depends on the shape of the rock you're planting on. If it's a relatively flat surface the water will run off, even if you make "soil dams". Your challenge here would be making sure the planting doesn't dry out. If your stone has a planting pocket with some depth to it then, yes, you probably want to drill a couple of drain holes.

 

[Sae Nguyen]

Bonsai rock plantings, where the entire root system is confined ON the rock structure, shouldn't be confused with root over rock plantings, where the roots of the tree grow on and adhere to the rock surface before eventually entering a pot with bonsai soil. Muck is generally used for the former planting. It can be used to build a perimeter wall to hold regular soil, perhaps on a slab, but with many slab and rock plantings, it comprises 100% of the existing soil for the planting, and the roots happily colonize it and live in it for many years. There are several different recipes for muck, but sphagnum moss and clay seem to be the most important ingredients. The combination seems to create a medium that both retains it's form and doesn't wash away, holds moisture but drains well. Ultimately, these plantings tend to dry out more quickly then plantings in ceramic containers. Here is a Hinoki Cypress muck slab planting at the Smith Gilbert Gardens in Kennesaw GA... 25 + years old when the pic was taken, never re-potted and looking great.

View attachment 421662

How does that work being "never repotted" for 25 years? I know Walter Pall doesn't repot (or very infrequently) but what does that do to the trees?
How long can roots go with no new soil?

?

 

[Dav4]

How does that work being "never repotted" for 25 years? I know Walter Pall doesn't repot (or very infrequently) but what does that do to the trees?
How long can roots go with no new soil?

?

Apparently, the tree roots are eventually air pruned as they reach the outer edge of the muck, then regrow... rinse and repeat... this constant rejuvenation keeps the roots healthy enough to avoid the need to be re-potted as frequently as they would in a conventional soil filled container. I'm also sure that eventually, the planting would need to be taken apart as the trees grow over time.

 

[Shibui]

This is my attempt at root on rock planting.
The roots were originally confined to clay/manure/sphagnum muck pockets but have now merged together and down under the rock.
The pot is a shallow suiban (no holes) about 1 cm deep filled with gravel around the rock. After watering the tray fills with water but by the end of the day that has all evaporated so the roots have water for part of the day but air for the remainder. The trees seem to cope OK with that regime and it has grown well since 2016.


before trimming


after trim.

 

[HoneyHornet]

This is my attempt at root on rock planting.
The roots were originally confined to clay/manure/sphagnum muck pockets but have now merged together and down under the rock.
The pot is a shallow suiban (no holes) about 1 cm deep filled with gravel around the rock. After watering the tray fills with water but by the end of the day that has all evaporated so the roots have water for part of the day but air for the remainder. The trees seem to cope OK with that regime and it has grown well since 2016.

View attachment 421870
before trimming

View attachment 421869
after trim.

Cool I like the scene , that rock is really great, does the water in gravel tray pull water all the way up to the top or does it require some misting? I mean I see you’ve had it going for some time now obviously it works lol ,I watch these videos where they build these live scenes in a big tank with running waterfalls and stuff and they use what looks like terry cloth strips as a wick to pull water from the bottom pool up to the mountain peaks, they pack it into crevices and muck it in and they often moss over it etc, just sharing in case it helps for future planting arrangement

 

[Shibui]

Initially the whole thing was watered several times each day to make sure all the roots had moisture. One of the benefits of clay muck is that it holds moisture for longer than more open mix so trees panted in it survive with less water. This now just gets the same watering regime as other bonsai - morning and evening in warmer weather, once a day in mild temps and natural rainfall during winter.
Now all 3 trees have roots that reach down into the tray so they have access to water for even longer between watering. I guess the clay will also wick moisture up a bit like the towelling you mention. Th rock in this is only 20 cm tall so not too far for the roots or water to travel. Bigger plantings and different climate may require different techniques