Why do bonsai pots have large drainage holes ?

[Bonsai Hunter]

What is the thought process behind having just 1 or 2 large holes, instead of multiple small holes ?



The large holes seem to unnecessarily force the usage of mesh screens. If the wire holes are increased in number to match the drainage area of the bigger hole, wouldn't the drainage remain same as before ? Then mesh screens can be completely avoided. Any thoughts on the design aspect ?

 

[Paradox]

For ceramic pots, it is much easier to make. Small holes can become clogged with soil and keep things too wet because it doesnt drain.

 

[jeanluc83]

It also comes down to math and the number of small holes you need to equal the area of a single large hole.

For example consider a 1" diameter hole

3.14 * (1/2)^2 = 0.785 in^2

Now consider a 1/4" diameter hole

3.14 * (1/8)^2 = 0.049 in^2

You would need 16 1/4" diameter holes to replace the area of one 1" diameter hole.

When you get pots with multiple drainage holes it is easy to see why large holes are used.

Considering a piece of drainage screen costs about $.03 and can be installed in about 30 seconds I don't see where you would really be saving by using small holes.

 

[sorce]

Surface tension will keep water in the small holes....

The copper wire allows water to use capillary action to exit the pot.

Sorce

 

[M. Frary]

This is just one of those few times when a larger hole is preferred over smaller holes.

 

[Bonsai Hunter]

Thank you all for your inputs.



Clogging - But a large drainage hole is never used directly. After placing a mesh over it, the
effective hole size becomes tiny. In this image, the wire hole is not that different from the holes of
the mesh. And if clogging was a real issue, then people would not be growing bonsai in anderson flats
,colanders or air pruning pots having a mesh as a floor, would they ? So, I am not sure about this.



Surface Tension - If that is not a problem with tiny holes of Anderson trays, colanders or air pruning
pots having a mesh as a floor then why is it a challenge for the wire hole to drain water ? If the large
hole were to be sealed with duct tape, would the water not leak out thru the wire holes ? Has anybody
tried that and found it to be true ?

Ease Of Manufacturing - In the case of handmade pots, sure, punching 1 hole is easier than
punching 16 - individually. But if the potter has a block of multiple cylinders, 2-4 presses are enough
to easily create 16 small holes. If the pot making is mechanized, it is just 1 press. And just google "ceramic colanders". It is very common. Can you imagine a car manufacturer not installing AC or a music system in their product because it sure is easier to manufacture ?

Savings - I agree the effort, time and money is not much per hole. But when you add up all the holes of all
your pots and factor the repotting over the years, I can't help wondering why the pot manufacturer could not
design a better pot and eliminate the need for a mesh screen completely. Why create a problem and then
solve it ? Why not avoid it totally with a better design ? The plastic bonsai pots have solved it by integrating
the mesh design into the pot itself - mesh & pot are one piece.

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

 

[Paradox]

Clogging - But a large drainage hole is never used directly. After placing a mesh over it, the
effective hole size becomes tiny. In this image, the wire hole is not that different from the holes of
the mesh. And if clogging was a real issue, then people would not be growing bonsai in anderson flats
,colanders or air pruning pots having a mesh as a floor, would they ? So, I am not sure about this.

The thing is the mesh is over a much larger area than a small hole would be so there is no way it can get clogged. The soil particle sizes we typically use would very easily get stuck in 1/4 inch holes and clog them making the pot have effectively have less drainage. Ive never had a pot clog unless there was a very fine, tight mat of roots that grew along the bottom of the pot. That would have caused problems with both designs.

There is no collusion with the mesh or screen industry to make people use screens over the drainage holes of bonsai pots.

Surface Tension - If that is not a problem with tiny holes of Anderson trays, colanders or air pruning
pots having a mesh as a floor then why is it a challenge for the wire hole to drain water ? If the large
hole were to be sealed with duct tape, would the water not leak out thru the wire holes ? Has anybody
tried that and found it to be true

An Anderson flat is has a HUGE surface area compared to most pots (at least shohin size and smaller) and the entire bottom is effectively mesh. It does not look like the picture you posted of the holes in the bottom of the pot.

Another thing with all those small holes, I can imagine that the pot could crack easier between the holes from the stress of the soil and tree, not to mention heating and cooling.

Honestly, these types of pots have been used for 3000 years. You only think that more holes are a better design and that a large hole is a problem. Its not, it works just fine and has for a very long time. If there was a better way, I would think the Chinese, Japanese or modern manufacturing would have come up with it.

If you want to use a pot like that, get a bunch of plastic pots and drill the bottoms with holes and have at it.
I will stick with the tried, true and works instead of trying to reinvent a wheel that I dont need to reinvent.

 

[Solange]

Agree with the points already made above. And I'll echo and emphasize what paradox hinted at - Many small holes makes a pot easier to break.

 

[Anthony]

Hee hee, nice one Bonsai Hunter.
Never really thought about it.

Have had Paradox's situation, roots clog the hole.

From what I read, it is supposed to be better to have several large holes than a multitude of small ones.

Plus before we use a pot, we wet the inside and observe how it drains. If need be, we compensate
with a hole to handle an internal lean.

Keep on thinking and questioning, my good man.
Good Day
Anthony

* Large pots can be fired in quartz or alumina or have supports placed under the base, depending on
how you fire. Same for fine China or Fine Porcelain - think thin translucent walls ----- no need to burn
down a whole forest for the Emperor to get a tea bowl.

 

[sorce]

Has anybody
tried that and found it to be true ?

This may sound quite dickish....but I assure you it's only in jest....

Have you!?

Maybe you should have before asking these questions!

Nah, I'm with Anthony....thinking of any sort is good.

We should just do the experiment.

The experiment in my head goes......

Well, if I poke an invisible hole in a water bottle and squeeze it, water will come out.
But if I don't squeeze, it will stop.

Water WILL come through the wire hole, but only as it is forced to break the surface tension. When the water gets low enough to stop pushing out the hole, too much water will still remain in the pot.

The Flats are placed on rocks, utilizing capillary action again.

The holes in mesh are 1/8in deep at most.
The bottom of a pot is more than 1/8in deep. The hole will be more of a cylinder.

Larger than a quarter inch, we'll be back to using mesh. Hell, at a quarter inch we'll lose soil, so it has to be smaller. 3/16in.

But drop one rounder piece of lava in a 3/16in hole.....add on the "lip" at the top of the "punched hole", and surface tension is not allowing water to pass freely.

It doesn't matter how many times you multiply it by. It won't drain freely.

Or breath....

You ever breath through a straw to see what emphysema is like?

I'd rather breath through a meshed hole.

But that is only the experiment in my head.
And that's not the only thing going on in there....
6 folks are having a conversation right now.
2 high, 2 tripping, and 2 scholars.

They disagree....

It's a mesh, I mean mess!

Sorce

 

[jeanluc83]

Another thing with all those small holes, I can imagine that the pot could crack easier between the holes from the stress of the soil and tree, not to mention heating and cooling.

The firing of the pot could also induce cracking.

We need more potters in the group to answer these kinds of questions.

 

[aml1014]

I agree with sorce here. Say you have 16 1/4 holes, that's equivalent to a single 1" hole. So now let's say we actually want 11 1" drain holes, that would be 176 drainage holes. I have several pots with lots of large drainage holes like this scenario. I do also have pots I've made with a bunch of holes drilled in the bottom and as @Paradox pointed out, under weight it has caused stress cracks over time. Admittingly they are made of plastic and not ceramic but honestly I still feel like it would be more fragile.
Plus I like @sorce 's example. Breathe through a straw then brethat throught a large hole with some mesh over it. Pretty easy to imagine.

Aaron

 

[markyscott]

"Good drainage" starts and ends with the soil. The size, shape, or number of drainage holes is close to irrelevant. Water needs a hole to get out. That's pretty much it.

http://www.bonsainut.com/resources/introductory-soil-physics.29/

Scott

 

[sorce]

close to irrelevant.

Except for 3/16in holes and 1/4in ball bearings.

Sorce

 

[Bonsai Hunter]

Thanks guys. I hope I am not coming across as argumentative. I do have some opinion on this topic and also want to know what the community here thinks about this. I just have 1 yr experience in this hobby and that too restricted to plastic bonsai pots, not ceramic. I do not have a drill, else I could experiment on some cheap terracotta pots first.

Thank you Sorce for elaborating on the surface tension part. Now its beginning to sink in Kind of like a 2d hole vs 3d hole. My experience with plastic bonsai pot was in 2d only. And hence, clogging with soil & roots in a 3d hole is a new concept to me. My justifications with fabric pot have now turned to dust !

However, as requested, I do have a video showing drainage test -

Fragile pot - yes I too felt the same till i saw images of ceramic colanders. they seem strong enough and one of the makers says it will last for years unless banged on something. Besides, here are some pots with many holes. I doubt if it is any more fragile than a pot with a single hole. The holes I was proposing are much smaller and more spread out. Hence, I am doubtful if it will be weaker in any way.

Clay pot - drilled

http://www.fukubonsai.com/1a6z9.html


http://www.bonsai4me.com/Basics/Basics_Repotting2.html


https://yamadori.co.uk/tag/thor-holvila/#jp-carousel-5763


https://peterteabonsai.wordpress.com/2012/07/23/namako-ceramic-pottery/



Paradox, anderson tray & colanders ARE a vast improvement on the ancient bonsai pot designs. Welcome to air pruning, superior drainage & superior root aeration Thats what I approximated, in my video too.

Scott, I totally disagree with you. Good drainage & aeration starts with the pot. Soil comes later. Making fast draining soil is good but to put that into pots having poor drainage & aeration just seems like taking 1 step forward and 1 step backwards. I will take you on this, in the other thread of mine which I am yet to get back to. I have gone over your soil thread. Every time I prepare a great speech, life hits me and then I have to pick up my words again and remake my lines

 

[Anthony]

Hmm, well if you check the pots ability to drain before using. you can drill a hole
where the water might be moving more slowly.

But remember if the pot is porous, the day is windy, the soil is not moisture retentive, the tree is thirsty. full sun .......................
You have to take many things into account.

You can also take stainless steel mesh make a pot that fits into your - exhibition pot - for showing, you can just grow
in a metal container all of the time, but so much extra inventory.
Which is why we abandoned the idea.

Bonsai Hunter, since we have a dry season of 6 months, and we repot at the beginning, the water retention bit never became
a problem, and as I typed before, we check the pots before use.
Great discussion, mooooooooooooorrrrrrrrrrrrrrrreeeeeeeeeeeeeee,
please.
Good Day
Anthony

 

[markyscott]

...Scott, I totally disagree with you. Good drainage & aeration starts with the pot. Soil comes later. Making fast draining soil is good but to put that into pots having poor drainage & aeration just seems like taking 1 step forward and 1 step backwards. I will take you on this, in the other thread of mine which I am yet to get back to. I have gone over your soil thread. Every time I prepare a great speech, life hits me and then I have to pick up my words again and remake my lines...

I suppose the point of confusion is that bonsai folks often use the term "fast draining" to describe better quality soils. It's a poor choice of words. "Fast draining" as you elegantly show in your video, is related to many factors - the arrangement of drainage holes being one (there are other factors as well). That's why it's such a poor quantity to measure soil quality with. The problem is that the rate of gravity drainage is completely irrelevant to the water saturation in the soil after the drainage is complete. Once that water drains, the only thing that determines how much water and air remain in the soil - the air-filled porosity and water-holding capacity - is the soil itself. It doesn't matter if the soil is in a pot that takes 2 seconds or 20 seconds for the water to drain away - the AFP and WHC will be exactly the same after gravity drainage.

I won't bore you with my qualifications or why you should accept that I speak from a position of authority on this matter. I suggest instead that you do the experiment yourself. What you showed in your video is that more holes = faster drainage. I accept that as fact, but you have not demonstrated that the AFP and WHC are a function of "drainage speed". In this post, I describe how one can build a device to measure the quantities that are known to be important - the AFP and WHC. Repeat those experiments with the same soil and a different number of drainage holes. If you do so, we'll have something to talk about. If you choose to just disagree with the physics, we probably won't.

Anyway - give it a go. When you're done we can talk about air-pruning.

Scott

 

[Solange]

Fragile pot[/B] - yes I too felt the same till i saw images of ceramic colanders. they seem strong enough and one of the makers says it will last for years unless banged on something. Besides, here are some pots with many holes. I doubt if it is any more fragile than a pot with a single hole. The holes I was proposing are much smaller and more spread out. Hence, I am doubtful if it will be weaker in any way.

Ceramic colanders don't face freezing. Small holes are more susceptible to freeze damage. Ceramics become much less strong with many holes. I can fire a stoneware pot with many small holes and one with regular holes and smash them but I doubt you'd believe me. It seems you are out to prove your point and justify your youtube video questioning "intelligent" pot design. What is apparent, regardless of your motives, is that you are unfamiliar with the physical qualities of the material you are concerned with.

 

[MichaelS]

Scott is completely correct. The important aspect of drainage with regards to horticulture is the water that REMAINS in the substrate AFTER drainage, not how fast the water drains. This mainly depends on particle size and to a lesser extent (in practice) on the porosity of the particle itself. Obviously having just very small holes interferes with drainage because of the potential blockage, but who is using a pot like that? Put another way, you can use a pot with the whole bottom being a mesh (50% or more as open space) but his won't make the slightest difference to the quantity of water which drains from the pot. Also, the ''aeration'' also has nothing to do with drainage holes. It has everything to do with particle size as air moves through the substrate by diffusion from the atmosphere. The larger the particle size, the faster the diffusion of air. (and the quicker the drying) Compared to the surface area open to the atmosphere at the bottom of the pot, trees get most of their air from the top down.

 

[Mike Corazzi]

My daughter made and fired a special pot for me some years back.
She put 4 ...small... holes (not knowing anything about bonsai)
The pot continually got waterlogged.
I tried drilling some more holes with a masonry drill.
Worked fine until the last hole.
Then it broke in half.

Hated to lose the pot because it was a nice ....looking... one.

(hmm...reading this post, OF COURSE it broke on the LAST hole. Sorry bout that. )