AusBonsai

Hi all,

This may sound really simplistic but.....

What is a drainage layer?

What is it for?

What does it really do?

Is it necessary?

Do you use one? If yes why? If no why?

Grant

I reckon this explains it really well Grant
http://bonsaiwonders-art.blogspot.com/2 ... ayers.html
After all the talk on the international boards about a coarse layer inhibiting drainage it was great to finally see what they where suggesting explained.

I am not so agreeable with the attitude of the author suggesting that a coarse layer will actually impeded drainage but think more in the way that it is a way of manipulating the water table which I think could be very useful and is why the Eastern masters have long done this in practice. Also the article does not go into detail what happens when the layers are progressively larger. Arthur recently told me that the Japanese are using the mediums in a mixed size.
IE. Top layer is small and fine next layer is small and medium. then a layer of large and medium. So what happens to the water table here I guess it would gradually fade down to nothing at the bottom. Sounds dam good to me.

Sometimes in is just to stop the smaller particles falling out of big holes and that is OK too!

Seeing the "drainage layer" is a Japanese concept could it have something to do with the mix they use? Could it be mislabelled or misinterpreted?

Grant

I would say it is a given it could be misinterpreted. I think even the guy writing this article who has a vast knowledge of the facts behind this has misinterpreted his own information
But I am not sure I follow what you are suggesting?

Sorry I edited my first message as you posted your last That can't help

What I am getting at is; Is the drainage layer there in the first place to allow all the fine particles and silt to be washed out of the Akadama/Kanuma mix? ie allow the water and silt to drain away from the soil mix? The larger particles on the bottom layer would allow this; a homogenous finer mix would not. The methods the Japanese use seem to be trying to keep the mix open and draining.

It is however a drainage layer but in another sense?

Grant

Edit: Just read the other thread and thought that was what you meant!

If you are suggesting that the coarse layer enables the dust to escape through the drainage layer in the first flush watering I would think it would come out anyway. I have used the akadama in small pots with no drainage layer and just flush them out at potting just the same.

I have wondered why they suggest that this will only happen at the first watering. IE Get dust out in the first watering or it will stay forever. Surely normal watering over the first few weeks would have the same affect as watering continuously at the first watering. As in surely there is nothing that happens to the pot in the first week or so that will stop any dust being able to be washed out.
Maybe with the soft type akadama it settles down (compacts) pretty quickly, but I have not noticed this with the hard akadama we have been getting!

As the soil ages though maybe the coarse layer at the bottom would help in this regard. But I also tend to think that once you are at this stage the roots should be giving the soil it's structure anyway.
Also I wonder what happens to the roots in a coarse bottom layer after some time. That is where the roots tend to gather in the end. I think Jamie suggested that when the roots take up the space in a coarse bottom layer the water table will again drop to the bottom of the pot. Which was good thinking

As Jamie said it would be great to pick the brains of a Japanese Master over this as there are so many variables. I wonder if you would get a in depth explanation or just that it works so I do it?

My guess is it is more about manipulating the water table and then space for roots to occupy as it fills the pot! Although it could have advantages like you suggest!

Bretts wrote:Edit: Just read the other thread and thought that was what you meant!

If you are suggesting that the coarse layer enables the dust to escape through the drainage layer in the first flush watering I would think it would come out anyway. I have used the akadama in small pots with no drainage layer and just flush them out at potting just the same.

I have wondered why they suggest that this will only happen at the first watering. IE Get dust out in the first watering or it will stay forever. Surely normal watering over the first few weeks would have the same affect as watering continuously at the first watering. As in surely there is nothing that happens to the pot in the first week or so that will stop any dust being able to be washed out.
Maybe with the soft type akadama it settles down (compacts) pretty quickly, but I have not noticed this with the hard akadama we have been getting!

They have a summer monsoon wet season and tip the pots on the side for a month or so to help drainage. Every bit helps and by flushing out as much of the silt as possible it may help it not get waterlogged?

Grant

Bretts wrote:As the soil ages though maybe the coarse layer at the bottom would help in this regard. But I also tend to think that once you are at this stage the roots should be giving the soil it's structure anyway.
Also I wonder what happens to the roots in a coarse bottom layer after some time. That is where the roots tend to gather in the end. I think Jamie suggested that when the roots take up the space in a coarse bottom layer the water table will again drop to the bottom of the pot. Which was good thinking

As Jamie said it would be great to pick the brains of a Japanese Master over this as there are so many variables. I wonder if you would get a in depth explanation or just that it works so I do it?

My guess is it is more about manipulating the water table and then space for roots to occupy as it fills the pot! Although it could have advantages like you suggest!

As the soil ages it would definately help it get more air to the roots as the layers fill up with silt and roots. However the Japanese person I was speaking to said they don't use the largest Akadama; they sell that to the foreigners.
Also one PM said when he was in Japan they didn't use a drainage layer except in the largest pots.

Grant

i wish i could of copied and pasted that night it come up

ok from the way i understood the water tables and the reason why the japanese do it is the manipulation of water tables. as we know with a finer mix throughout the pot the water table or saturation point will rise up the pot accordingly as to how much retension is applied by the particle size. going in layers from a large layer on the bottom to the finer layers in stages to the top lowers the water table therefore not actually given the mix a more free draining situation but it has less water retention due to water tension.

hope i havent lost ya all yet!

my theory behind why the japanese are still practicing this method is not as for the drainage of the pot with a coarse layer in the lower section but the manipulation of the water tables. when a tree has been root pruned and repotted we want it to dry out sufficiently enough every day so it will extend and grow roots right? right!
as the trees root system grows and starts filling the pot, through the more medium layers and then the coarse layer in the bottom, in theory the root system will have a lot more fine feeder roots filling the spaces, in theory what this does is minimise the amount of "coarse" area to a more "fine" area with the roots filling the spaces, this will maniuplate the table again and raise it, but this will only happen once the tree has reached a stage where the amount of water retention by the smaller spaces available with the higher water table (still with me? ) and the tree will be able to take that amount of moisture in between each watering there fore giving it sufficient "dry" time.

so in conclusion to my theory as to why this is done, a coarse layer system used when a tree is repotted that has less of a root system will need a lower water table, which the coarse mix gives, as the trees root system grows and fills these gaps of the coarse layers the water table will rise because what is happening is basically the root system and fine roots fill the spaces of the coarse layer and then that layer basically becomes like a fine layer, which in turn will rise the water table, giving more moisture available but at that stage the tree should be capable of using that amount of moisture given to the tree daily, or whatever the watering schedule is!

i hope that made sense to you guys, it did to me!

jamie

HI Grant,

I use a drainage layer in my growing pots and in deep bonsai pots, simply as a way of conserving sieved potting mix. I find the roots are happy to grow in this courser material. I also use a large layer of cobble sized stones as a bottom layer in large plastic pots, then another layer of course stuff and then potting mix; as potting mix simply pours out of these holes. I find I often have to tip shallow pots up on an edge to get them to drain properly in spring and autumn, but I've not put a drainage layer in them.

I think a perched water table is very possible in a bonsai pot, if deep enough, however this will subside once roots grow down into the lower layers, as they will act as wicks for water.

Another way of looking at it , and this is something that is often overlooked in the water table debate, is that drainage of a mix is related to depth of potting mix and the size of the largest pores. If you only have a 5cm deep pot, you will have a mostly saturated soil, if you use a 2-5mm graded mix, after watering. The bottom 10mm, or so, will most likely be completely saturated, this water can only be removed by roots. If there is a period of reduced transpiration, a wet week for instance, it might take days for the lower medium to become dry, this region of the pot is where a lot of roots end up and it will become anoxic quickly. Adding a layer of course material, a drainage layer, will allow air along this medium-pot interface via the drainage holes. I can see an advantage in a drainage layer in this scenario.

I feel I've explained this poorly,

Paul

63pmp wrote:HI Grant,

I use a drainage layer in my growing pots and in deep bonsai pots, simply as a way of conserving sieved potting mix. I find the roots are happy to grow in this courser material. I also use a large layer of cobble sized stones as a bottom layer in large plastic pots, then another layer of course stuff and then potting mix; as potting mix simply pours out of these holes. I find I often have to tip shallow pots up on an edge to get them to drain properly in spring and autumn, but I've not put a drainage layer in them.

I think a perched water table is very possible in a bonsai pot, if deep enough, however this will subside once roots grow down into the lower layers, as they will act as wicks for water.

Another way of looking at it , and this is something that is often overlooked in the water table debate, is that drainage of a mix is related to depth of potting mix and the size of the largest pores. If you only have a 5cm deep pot, you will have a mostly saturated soil, if you use a 2-5mm graded mix, after watering. The bottom 10mm, or so, will most likely be completely saturated, this water can only be removed by roots. If there is a period of reduced transpiration, a wet week for instance, it might take days for the lower medium to become dry, this region of the pot is where a lot of roots end up and it will become anoxic quickly. Adding a layer of course material, a drainage layer, will allow air along this medium-pot interface via the drainage holes. I can see an advantage in a drainage layer in this scenario.

I feel I've explained this poorly,

Paul

I don't you have explained it poorly.. I think allowing air into that lower layer is important. It is almost like an older method of air pruning of roots, before all the drainage holes in colanders and plastic pots became available..

Grant

Jamie wrote:i wish i could of copied and pasted that night it come up

ok from the way i understood the water tables and the reason why the japanese do it is the manipulation of water tables. as we know with a finer mix throughout the pot the water table or saturation point will rise up the pot accordingly as to how much retension is applied by the particle size. going in layers from a large layer on the bottom to the finer layers in stages to the top lowers the water table therefore not actually given the mix a more free draining situation but it has less water retention due to water tension.

hope i havent lost ya all yet!

my theory behind why the japanese are still practicing this method is not as for the drainage of the pot with a coarse layer in the lower section but the manipulation of the water tables. when a tree has been root pruned and repotted we want it to dry out sufficiently enough every day so it will extend and grow roots right? right!
as the trees root system grows and starts filling the pot, through the more medium layers and then the coarse layer in the bottom, in theory the root system will have a lot more fine feeder roots filling the spaces, in theory what this does is minimise the amount of "coarse" area to a more "fine" area with the roots filling the spaces, this will maniuplate the table again and raise it, but this will only happen once the tree has reached a stage where the amount of water retention by the smaller spaces available with the higher water table (still with me? ) and the tree will be able to take that amount of moisture in between each watering there fore giving it sufficient "dry" time.

so in conclusion to my theory as to why this is done, a coarse layer system used when a tree is repotted that has less of a root system will need a lower water table, which the coarse mix gives, as the trees root system grows and fills these gaps of the coarse layers the water table will rise because what is happening is basically the root system and fine roots fill the spaces of the coarse layer and then that layer basically becomes like a fine layer, which in turn will rise the water table, giving more moisture available but at that stage the tree should be capable of using that amount of moisture given to the tree daily, or whatever the watering schedule is!

i hope that made sense to you guys, it did to me!

jamie

That is all well explained and thanks. The trees need to survive many years and in many stages of growth in the one mix, and manipulating it sounds perfect.

Lots to think about and apply it to our own situation.

Grant

exactly right grant

if we manipulate the mixes we put our trees in to suit not just the new or a happy medium for overall i would expect that we could get better growth from them aswell

im glad that i explained it so people could understand my thoughts

Jamie

Hi Grant,
I use steel mesh on my growing benches and leave planty of space between my trees this allows plenty of air circulation around the pot, so I don't use a drainage layer in my soil. The mixes I use are fast draining anyway and are set up to be watered often during the growing season and to withstand the 6 weeks of fog, mist and drizzle that we get in July/August.

Cheers,
Mojo