Why do bonsai pots have large drainage holes ?

Anthony

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On our side Marky is the pet name for a young boy :)
I thought you wanted to be very familiar with the group :)
Good Day
Anthony
 

MichaelS

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Bonsai Hunter,
I have already admitted I havent worked with ceramic pots but who in this forum has worked with a ceramic bonsai pot with multiple holes of the the type i illustrated ? Is there even one person ?


Yes me.
I have used a shallow clay pot as a training pot and I needed to put holes in it because there were none. I drilled many (maybe 20) small holes of about 1/4 inch. The reason I used a small drill is because I didn't have a larger one. If I had a 1/2 inch masonry drill bit I would have put in perhaps 10 or fewer holes. With a 1'' bit maybe 2 or three holes would be enough. Maybe even one. Point is the smaller the hole the more chance of a particle of soil or roots covering it and blocking it therefore you need more of them. It's practically impossible for soil or roots to clog a larger hole. Even with mesh over it. There's no doubt that multiple holes will work but it's not necessary. If it were, all pots would have them. Remember many millions of plants are grown throughout the world every year in ''normal'' pots with ''normal'' drainage holes. (the wheel has already been invented)

Now, I'd like to explain the concept of ''field capacity'' and ''pot capacity''. When it rains or when you water the ground, some water will be retained in the soil. When the soil can no longer hold any more water, it begins to drain. The field capacity of a soil is the water which is left behind immediately after drainage has stopped. Of course this doesn't last very long because plants and evaporation begin to remove it right away. Also, the water in the ground will drain more efficiently than from pots because there is nothing to stop it. Under a pot there is air. There is nothing to ''pull'' the water down further. This is the main reason we cannot use normal field soil in pots. It will hold more water and have less air in it than if it where in the ground. The more water held, the less air available to the roots. We therefore need to make our potting soil of a coarser structure to compensate for this fact.

Pot capacity or container capacity is the amount of water held in the potting mix immediately after drainage has stopped from the pot. The aeration (or the amount of air available to roots) of the potting mix is directly related to the amount of water held between the particles of soil. If we use coarse particles, more air and less water will be available. If we use fine particles, more water and less air will be available. The speed with which water is drained from the pot is of very little significance as long as the structure of the media in the pot is of the correct type for the plant. You seem to be obsessed with the speed of drainage. Let me give an example to help explain the irrelevance of this. Take a dry pot plant and put it in a bucket of water completely submerged.
Leave it for say 1 minute then remove it. Any harm done? Absolutely not. The ''drainage'' has taken 1 minute but there is no problem because the air is restored as soon as the pot is drained. Leaving it under water for 30 minutes will also not cause any problem. Now take a pot with a plant in it and block the drainage holes with something and fill it with water. Where is the drainage? There is none. No problem, after a few minutes you remove the blockage and ''aeration'' is restored. If it has one hole it might drain in 5 seconds. If it has 10 holes it might drain in 2 seconds. It makes no difference whatsoever to the health of the plant or to the amount of air available to the plant. That is completely due to the size of the soil particles.
I hope you can now understand that as long as water can efficiently drain from a pot in a reasonable amount of time, the speed with which it does makes no practical difference.

''Air pruning''. This concept was started in the advanced tree growing industry many years ago. There where containers designed with small cones all over the surface and a small hole at it's tip. Roots would enter the cone, reach the end and stop when coming in contact with the air. This would stimulate branching further back in the root system and the whole thing starts again. The reason behind this pot design was entirely to stop the circling of roots inside the container. This meant that the trees could be transplanted into the field without the coiled roots which are so much of a problem in the landscaping industry. It was a very good concept and it meant better and faster tree establishment and no root pruning needed.
Let's be clear though, air pruning has no practical advantage when it comes to the speed of growth in the short term. Anything that disrupts the growth of roots will inevitably slow the growth rate of the plant. In the long term, the advantage of potting a tree in a mesh pot means that it can be removed and potted on without needing to trim roots. This can be an advantage in training. Once a tree is in a display container there is no longer any need to air prune because we are no longer moving it up in pot size but maintaining and even reducing the root mass. The whole concept of bonsai maintenance is root pruning. It's this that keeps the tree going. Therefore air pruning at this stage is useless because we need to prune the roots regularly anyway.
I hope this clears thing up a bit for you..
 

markyscott

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...Now, I'd like to explain the concept of ''field capacity'' and ''pot capacity''. When it rains or when you water the ground, some water will be retained in the soil. When the soil can no longer hold any more water, it begins to drain. The field capacity of a soil is the water which is left behind immediately after drainage has stopped. Of course this doesn't last very long because plants and evaporation begin to remove it right away. Also, the water in the ground will drain more efficiently than from pots because there is nothing to stop it. Under a pot there is air. There is nothing to ''pull'' the water down further. This is the main reason we cannot use normal field soil in pots. It will hold more water and have less air in it than if it where in the ground. The more water held, the less air available to the roots. We therefore need to make our potting soil of a coarser structure to compensate for this fact.

Pot capacity or container capacity is the amount of water held in the potting mix immediately after drainage has stopped from the pot. The aeration (or the amount of air available to roots) of the potting mix is directly related to the amount of water held between the particles of soil. If we use coarse particles, more air and less water will be available. If we use fine particles, more water and less air will be available. The speed with which water is drained from the pot is of very little significance as long as the structure of the media in the pot is of the correct type for the plant. You seem to be obsessed with the speed of drainage. Let me give an example to help explain the irrelevance of this. Take a dry pot plant and put it in a bucket of water completely submerged...

Thank you Michael. This is exactly what I tried to express in my resource. It's great for folks to hear the same message from another source.

...''Air pruning''. This concept was started in the advanced tree growing industry many years ago. There where containers designed with small cones all over the surface and a small hole at it's tip. Roots would enter the cone, reach the end and stop when coming in contact with the air. This would stimulate branching further back in the root system and the whole thing starts again. The reason behind this pot design was entirely to stop the circling of roots inside the container. This meant that the trees could be transplanted into the field without the coiled roots which are so much of a problem in the landscaping industry. It was a very good concept and it meant better and faster tree establishment and no root pruning needed.
Let's be clear though, air pruning has no practical advantage when it comes to the speed of growth in the short term. Anything that disrupts the growth of roots will inevitably slow the growth rate of the plant. In the long term, the advantage of potting a tree in a mesh pot means that it can be removed and potted on without needing to trim roots. This can be an advantage in training. Once a tree is in a display container there is no longer any need to air prune because we are no longer moving it up in pot size but maintaining and even reducing the root mass. The whole concept of bonsai maintenance is root pruning. It's this that keeps the tree going. Therefore air pruning at this stage is useless because we need to prune the roots regularly anyway.
I hope this clears thing up a bit for you..

Michael's comments about air pruning are exactly right. The only other thing I'd add is about culling in the nursery industry. As trees develop badly encircling roots in nursery cans they are culled. It's because these deformed roots are preserved in the landscape and the trees will never self correct. They look like this:

IMG_4681.JPG

Not good. So air-pruning was one of many different techniques used to reduce cull rates and improve the quality of root systems in landscape trees grown in nursery containers. Why do they cull instead of correct? Well, it's awfully expensive to send someone out in the field and work the root systems on a couple of hundred trees (let alone a couple of thousand). So air pots, ribbed containers, and many other specialized containers were developed. Or specialized techniques such as shaving. Or they just cull. Of course these specialized pots are more expensive, but they reduce cull rates. That's the trade-off in the nursery industry. There's another trade off that Michael mentioned. Trees don't grow as fast - canopy growth rates are slower in an air pot than in regular nursery containers. That slower growth rate has been documented in many studies.

So what does all of this have to do with bonsai? Well, very little really. Broadleaf trees are (or should be) regularly repotted. Large, deformed roots are removed. With proper root treatment these trees never develop encircling roots. So the problem that air pots were developed to address (encircling roots) are really not an issue in bonsai unless we're developing trees from nursery stock or we are neglectful of our trees during repotting season. Conifers may be different - they are repotted much less frequently during development. So there are far fewer opportunities to correct problem roots before they develop.

So for folks new to bonsai, I suggest focusing on learning proper root pruning techniques. I guarantee that none of my broadleaf trees have encircling roots. Do I grow in colanders or air pots? Yes - I've got a load of pines in them. They seem to have done fine. The ones not in them seem to have done fine too.

Scott
 
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Adair M

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And Scott has a huge olive in a wooden box. That leaks. :p
 

Eric Group

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Thank you all for your inputs.

View attachment 123745

.

I still feel the pot with multiple holes is a superior design & very practical. Any pot makers here ? What is your take on this ?

The take is simple: take an empty pot with a bunch of small holes, and one with a single, or a few large holes- pour water in and see which drains faster.
The one with large holes does every time.
 

Jarath

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Anthony

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Folks,

this is what we noticed with the tamarind in an air-pot and a normal pot, same % soil and sun exposure..
The air-pot grew faster and was pruned 6 times to the regular pot's one.

However when transplanted into a bonsai pot, the air-pot plant had way more branches and finer leaves.
Even today the tree maintains more leaves and branchlets, to the point we had to remove branches
because it kept drying out.

The air-pot did not influence the ageing aspect of the tamarind.
It seems to have made the tamarinds use of feeder roots way more efficient.

We are now going to see if the results seen above will be repeated.

The tamarind in the colander, does nothing like above.
BUT the colander is very useful for ground growing.
Good Day
Anthony
 

Anthony

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Michael,

as the air-pot goes, isn't the idea to encourage more feeder roots, and not just stop the root circling ?

Will test with out plants able to densify through leaf and branchlet to see if we can do better.
Yes, I know there are also genetic limits, but curiosity.............................

Thus far the soil mix we use after 30 years does not encourage root thickening, [ touch wood ].
Save for Ficus p, which is immune to air-pots :):eek:

Now trying to find out why colanders do not do as the air-pot.
Good Day
Anthony
 

Anthony

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Scott, if that is a colander it's good.
But we got at from the air-pot looked like wood.
Good Day
Anthony
 

markyscott

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Scott, if that is a colander it's good.
But we got at from the air-pot looked like wood.
Good Day
Anthony

No colander. Ceramic pot, good soil and root work technique. I repot this every other year.

IMG_0117.JPG

Scott
 

Anthony

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Yes, very nice!!
We get similar with our trees.
Good Day
Anthony

* Not meaning to boast but our yearly repot usually comes out the shape of the pot and has to be cut back.

100_1555.JPG
 

Brian Van Fleet

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Yes, very nice!!
We get similar with our trees.
Good Day
Anthony

* Not meaning to boast but our yearly repot usually comes out the shape of the pot and has to be cut back.

View attachment 124012
This is a very nice Fukien tea, but there is nothing similar between these two root systems.
IMG_7647.JPG IMG_7646.JPG
I am enjoying Scott's posts; one mike drop after another.
 

Anthony

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That's because Brian, it's a solid mass [ fukien tea ] and has not been combed like Scott's.
See his background.
Good Day
Anthony
 

markyscott

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That's because Brian, it's a solid mass [ fukien tea ] and has not been combed like Scott's.
See his background.
Good Day
Anthony

The only thing done at the time of the picture is that the bottom of the rootball had been raked and trimmed flat.

Scott
 

Anthony

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Scott, Brian, to help clarify.

thinking about it, the fukien tea is about 18 inches tall and the pot's internal is 3.5 inches and
after a year we can lift the tree out of the pot. With no soil loss.

We cut off an 1" to 1.5" all around and then comb out for another 1 inch cut. Then repot for
new soil [ we reuse the inorganic ]

This year we tried all aged compost - dumb idea - shrub needs a % of peat moss in the mix for water
retention.
AND no stupid ideas like compost tea -------- back to 1/3 lawn fertiliser, one a week into moist soil.

Here it is when some of the IBC members suggested a shallow pot.
AND we [ as we say ] caught our tail by April to keep it watered properly.
By April in the deeper pot it takes a day to dry out, by October 1/2 a day and the rains save us.

By the way our soils are built on similar ideas to your notes on Bnut.

As I have tried to explain milder climate - No growth from Christmas to middle February.
Then the tree starts to master the pot and with short and these days few extensions of 4 inches.
Temp - 90 to 70 deg.F - highest 93 for less than half an hr and 66 on some days in January/February.

Almost all of our trees come out of the pot rootbound yearly [ like clock work ] Save for the Malphigia e.
it has to be dug out and will only have roots.
Will send images to Bnut after 2nd January, when repotting starts every year.
Good Day
Anthony

2008 and a great learning experience.

fukien tea 2.jpg
 

markyscott

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Scott, Brian, to help clarify.

thinking about it, the fukien tea is about 18 inches tall and the pot's internal is 3.5 inches and
after a year we can lift the tree out of the pot. With no soil loss.

We cut off an 1" to 1.5" all around and then comb out for another 1 inch cut. Then repot for
new soil [ we reuse the inorganic ]

This year we tried all aged compost - dumb idea - shrub needs a % of peat moss in the mix for water
retention.
AND no stupid ideas like compost tea -------- back to 1/3 lawn fertiliser, one a week into moist soil.

Here it is when some of the IBC members suggested a shallow pot.
AND we [ as we say ] caught our tail by April to keep it watered properly.
By April in the deeper pot it takes a day to dry out, by October 1/2 a day and the rains save us.

By the way our soils are built on similar ideas to your notes on Bnut.

As I have tried to explain milder climate - No growth from Christmas to middle February.
Then the tree starts to master the pot and with short and these days few extensions of 4 inches.
Temp - 90 to 70 deg.F - highest 93 for less than half an hr and 66 on some days in January/February.

Almost all of our trees come out of the pot rootbound yearly [ like clock work ] Save for the Malphigia e.
it has to be dug out and will only have roots.
Will send images to Bnut after 2nd January, when repotting starts every year.
Good Day
Anthony

2008 and a great learning experience.

View attachment 124034

It's a nice Fukien tea, Anthony.

Scott
 
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