Perched water tables-myth?

[UNOCAN]

Whoa tin can, back the truck up. "Even Harry got it right", no well said.

Harry

Jeesh Harry, I just got back on here...let me warm up to you first

 

[UNOCAN]

Not quite a closed case by any means. What we have heard is that a drainage layer is really not necessary anymore because of the free draining soil mixes we use today, but how does this apply to perched water tables?

In short, it doesn't, because if we use a free draining mix consorting of particles of the same size there can not be a perched water table. So, as Walter says, there is no worry.

But....

There are many who still use a drainage layer consisting of larger particles than the mix above it and advocate doing so. The perched water table comes in where the two differing particles sizes meet. Contrary to popular belief, the larger particle layer does not increase or hasten drainage, it in fact impairs it.

Simple physics tell us that this happens where water adhesion occurs at an area where surfaces change size and/or texture.

All this can be solved by eliminating the practice of using a drainage layer at all, which a vast majority of bonsaists and container gardeners have done.

So, the question put forth "does a drainage layer cause a perched water table" really hasn't been addressed yet, however we have learned that using uniform particle sizes in or mix without a drainage layer negates the worry completely.


Will

All true Will, well said

 

[Rick Moquin]

So, the question put forth "does a drainage layer cause a perched water table" really hasn't been addressed yet, however we have learned that using uniform particle sizes in or mix without a drainage layer negates the worry completely.

No! the perched water is caused by the density of the substrate itself and not the drainage layer. Think of the sponge as a containerized substrate.

A drainage layer of a couple of inches would be beneficial if the pot did not have drain holes and you didn't water profusely (flood the pot) as we do. In the latter case, their would still exist "perched water" in the substrate if you did not flood the pot.

It's the pot size that is important along with the type of substrate and tree uptake. Perched water will exist regardless but the time it exist in the pot will be minimal if the 3 conditions aforementioned are met.

 

[Chris Johnston]

THE STORY SO FAR

Here's my question. It had more do do with perched water tables in bonsai pots than the makeup of drainage layers.

In the interest of brevity, I'll leave out all the nonsense. I can't believe someone told me I was the guy who started all that trouble on the internet. Where are you, Rob?

Since the myths are being bunked or debunked, what about perched water tables? The main argument against a drainage layer has been so-called "perched" water tables. Has it really been shown that a bonsai pot with a drainage layer "perches" water?

Chris,

I have supporting evidence and I will post such when I have time.
Will

Thank you. When will we get to see it?

I think of the drainage layer not as a layer of different sized particles, but of a layer that is composed entirely of material that will not easily degrade. Akadama, fir bark and all organic material will decompose over time. The drainage layer in my pots is made up entirely of pumice or lava rock, and is the same size as the soil above it. That way I can be sure that a few years down the road there is still a structure to the soil on the bottom of the pot. That said, the breakdown of components above likely clogs the structure anyway.

This has been my understanding of drainage layers ever since I graduated from the most basic of basics in bonsai. There are still a lot of folks, however, practicing bonsai from Naka I and Naka II among other basic info that is largely outdated in the 21st century.

my take, plain and simple.

When we used soil in our bonsai pots we had to have a drainage area. And there was a theoretical danger of perched water tables. I think it never was a danger really anyway.
Nowadays we use modern substrate. This has the particle size that the drainage used to have. Actually modern substrate is drainage area all through! There is not need to have an additional part for drainage anymore.

What many don't know: You must use the same particle size throughout. Meaning if you add some finer soil, organic or whatever to rough particles you will indeed sooner or later have a drainage problem because the finer particles will clog the areas between the large particles and will meet at the bottom of the pot. I remember when I 'knew' that I had to add some 'real' soil, meaning compost to akadama because the tree 'must' have some feed in the soil. All wrong! The nutrients come with feeding. It is absolutely correct to have substrate with no nutrient contents at all.

Perched water tables are a thing that play no role in bonsai anymore if they ever did.

Thank you, Walter, for addressing the actual question factually and forthrightly.

Yes Vance, I think you are right. But since by my method the particles are the same size, it also doesn't hurt; When I repot trees a few years later I don't find that the ones with a layer of pumice on the bottom are miraculously better in some way...but you are also right about going the extra step. It takes so little extra time to do this little thing that could potentially have some benefit...so I do it.

This is such a lively board these days. I was just over at the new IBC board and there seems to be no activity. Maybe I'll post a photo!

Eric, Thanks again for wading in. Common sense without the need to dictate a universal answer. I like it!

What are your thoughts on the practice of using large particles in the bottom of the pot and smaller regualr particles ontop of that layer. This is what is commonly called and used as a drainage layer and is believed to cause a perched water table ontop of that larger particle area?
Will

Again, this is commonly called and used as a drainage layer among those practicing 50 year old bonsai technology.

When I first started doing bonsai, after I got to a point where I learned about soil and all that, we did not have such things as Turface, Akadama, Red Lava, or any other of the popular media used today. We made soil from collected materials just as carefully gathered as the trees we worked with. We would harvest clay from this area, Loamy soil from another and sand from yet another. We used Peat Moss and occasionally, agricultural sand could be found and used We would then have to sift this stuff down to get rid of the fines and use the particles that were left hoping that they would not break down too fast. They always did.

We of course used a drainage layer, mostly because the books said to do so, (Yoshimura's book) but the type of soil we were putting together more or less demanded it. Today, with the materials that we use, a drainage layer is not necessary. We even went so far as to level the bottoms of the pots by pouring a layer of cement in the bottom to establish a perfectly flat bottom surface with no pockets in the corners or random depressions anywhere else. Even when I was using a drainage layer I found that on repotting that layer was wet and colonized with roots anyway. So the question begs itself: Why bother?

Time in question here is late 50's early 60's.

Exactly, Vance. And you were collecting those things (or at least many Americans were) because of the soil recipes in John Naka's teaching and writing. His pages of soil recipes that varied by species are legendary.

Not quite a closed case by any means. What we have heard is that a drainage layer is really not necessary anymore because of the free draining soil mixes we use today, but how does this apply to perched water tables?

In short, it doesn't, because if we use a free draining mix consorting of particles of the same size there can not be a perched water table. So, as Walter says, there is no worry.

But....

There are many who still use a drainage layer consisting of larger particles than the mix above it and advocate doing so. The perched water table comes in where the two differing particles sizes meet. Contrary to popular belief, the larger particle layer does not increase or hasten drainage, it in fact impairs it.

Simple physics tell us that this happens where water adhesion occurs at an area where surfaces change size and/or texture.

All this can be solved by eliminating the practice of using a drainage layer at all, which a vast majority of bonsaists and container gardeners have done.

So, the question put forth "does a drainage layer cause a perched water table" really hasn't been addressed yet, however we have learned that using uniform particle sizes in or mix without a drainage layer negates the worry completely.
Will

That wasn't exactly my question. I asked, "Has it really been shown that a bonsai pot with a drainage layer "perches" water?" But speculation aside, what evidence is there that a drainage layer of any size particles perches water in a bonsai pot? Also, I was hoping for some evidence that even a larger drainage layer would perch water in a bonsai pot.

No! the perched water is caused by the density of the substrate itself and not the drainage layer. Think of the sponge as a containerized substrate.

A drainage layer of a couple of inches would be beneficial if the pot did not have drain holes and you didn't water profusely (flood the pot) as we do. In the latter case, their would still exist "perched water" in the substrate if you did not flood the pot.

It's the pot size that is important along with the type of substrate and tree uptake. Perched water will exist regardless but the time it exist in the pot will be minimal if the 3 conditions aforementioned are met.

Rick,
I understand and appreciate your point about the density of the substrate. Not sure I am in the same position about the rest of your post. Of course hypothetically, pots with no drain holes will perch water. They will also breed stagnation, so we don't use them.

So far we have had just a bit of good information. King Kong, I have generally enjoyed your posts at bonsaiTALK, but I don't recognize you over here. What's up? We already know what doesn't work. We've had folks, expert or not, speak to us pedantically and condescendingly before, and it never ends well. I haven't mistreated you in any way, so how about putting something out there without the extras?

Perched water tables have been one of the fears of bonsaikind for a long time. The question was put to Dave DeGroot some years ago here in Kansas City, which prompted me to do some of my own research.

I have potted trees both ways for years, with and without a drainage layer. Like so many, for some time I thought the drainage layer should be bigger than the rest of the soil. As time went on and I learned new techniques, All my soil particles came to be the same size instead of mixed. I've never noticed much difference in results with or without drainage layers as long as I was using a well-screened, loose soil mix (completely inorganic, by the way.)

Boon teaches using a very thin drainage layer of pumice only at the bottom of the pot. His soil mix is no smaller, it's all the same size. His trees are fabulously healthy, as are Walter's, who uses no drainage layer.

I've also done some Google research on the notion of perched water tables. Almost invariably, the results are:
A.) discussing water tables and spring formation in the landscape, which requires an impermeable shelf and a constant supply of water, or

II.) claims of perched water in bonsai pots without serious study or science, i.e., "of course a perched water table in your pot is a bad thing..."

3.) Two other instances of perched water tables: this post from IBC mailserver:
http://newsgroups.derkeiler.com/Archive/Rec/rec.arts.bonsai/2005-09/msg00144.html which seems to show some scientific basis, and the USGA recommendations for golf green construction.

With Walter, I'd have to say that very likely a "perched water table" has never been a serious concern in a properly constructed bonsai pot with proper soil mix.

It's interesting, though, isn't it, how much time and energy, bad feelings and ill will have been spent (and not only on this thread) over something so minor? Do it or don't do it. Just use proper soil, a subject over which there is unanimous agreement and no ill feelings wasted over the years.

 

[king kong]

It is all physics Chris, well mostly. Were you good at physics or like me skipped class. After a little reading, my opinion is that the term perched is a valid term and useful in certain circumstances but it has caught the chicken pox and is now spreading itself to the community from golf courses to the nurserymen's potted plants. The thing I would suggest Chris is start with the understanding of 'soil water' physics and work backwards...understand the big picture sort of thing. Then if you feel like pluggen in some flashy names, have at it.

 

[Rick Moquin]

Chris,

What I was trying to explain with difficulty was:

If a pot had no drain holes then a drainage layer (2 to 3 inches) would be beneficial providing the pot is not over watered so excess water can drain to this layer. Regardless, the substrate (regardless of composition) will still contain an amount of moisture/water because of surface tension etc... this is my understanding of perched water and has nothing to do with the ground perse. This can be readily seen in the sponge experiment where:

when laid flat and allowed to drain over a screen of some sort (a old fridge rack is perfect) allow all the water to drain out of the sponge; now

turn the sponge on its side and see how much water actually comes out of the sponge you thought was thoroughly drained; and finally

turn the sponge on it's length an see how much more water still remains of what you thought was a thoroughly drained sponge.

Now in Brent's article he uses this to explain the height of a given column of water in a drained pot or (perched water). Whereas, since this article we know that a shallow pot will reatin more water/moisture than a deeper pot of the same volume. Why? Because the sponge size never changed, did it? Therefore I confidently applied these conclusions in my bonsai practices with great results.

Back to the drainage layer, it is my opinion it is something that has transcended over time without a good understanding of new soil compositions and mechanics. I use an almost inorganic mix, perhaps only 5% bark at most. I have good quality pots with little to no places for the water to pool at the bottom. Yet when the pot is thoroughly drained, then tiped on it's side a good deal of water drains out why? Because of the height of the column of water has increased and tension in the substrate is now less. Still not convinced, on smaller bonsai, hold the substrate in place (with a rag etc... or wrap the pot and substrate in saran wrap) and hold the pot on end and see how much water comes out of the pot, from which you thought it was thoroughly drained.

I know we have discussed this before Chris, do I have anecdotal data? No, but I have offered an explanation that anyone can try in their own homes to convince or educate themselves of what is actually happening in a bonsai pot, with regards to water retention/drainage.

Do I use a drainage layer? No!

For extra drainage after watering (I live in a wet climate) or heavy rains, I tip the pots on their sides. In the height of the summer (read hot and dry) I do not tip after watering (no need to), and prevents from watering several times a day.

I hope this explanation/information was useful...

 

[king kong]

Good effort Rick, you are getting warm. What is 'ground perse' please?

 

[king kong]

Let's have some fun with this one. For the person who 'nails it' I will send a skinny little tropical bonsai, on me, unless you are one of the four in the principal's office.

 

[Chris Johnston]

Good effort Rick, you are getting warm. What is 'ground perse' please?

I believe Rick was saying, ...ground, per se.

 

[king kong]

Thanks Chris, I am so stupid. Darn, that hurt his presentation a tad. And it can't be a newbie!

 

[Alain BERTRAND]

This link may explain some of the aspects of perched table (in fact it is a simplyfied version of a more elaborate article originally written by W.C. Fonteno, a big name in horticulture science, but I can't find it).

But, I think that W. Pall is right : we usually use too rough a substrate to get concerned with perched tables, anyway there is no point of using a drainage layer.

 

[king kong]

If someone tells me there is a Rhinoceros in my kitchen then I better find out what a Rhinoceros is. No Scientist help from MIT now. lol

 

[Chris Johnston]

I didn't start this thread to find out if I should be afraid of perched water tables. My point was to prove how such minor things can become such huge issues. My point has been proven.

Chris

 

[Anonymous User]

...anyway there is no point of using a drainage layer.

Exactly, and if such discussions as these can prevent someone from wasting their time, it has served a good purpose.

I do have more info, which I will post if I ever return home....



Will

 

[king kong]

I didn't start this thread to find out if I should be afraid of perched water tables. My point was to prove how such minor things can become such huge issues. My point has been proven.

Chris

Fooled the heck out of me, thought you wanted to know what a perched water table was Chris and I have a feeling you will never know, It's only water, no big deal.

 

[king kong]

So Kong brought the people down to the perched water, and the Lord said to Kong "You shall separate everyone that understands what the term perched water is" and Kong replied " the people are throwing spit wads, could care less and one gave me the finger.

 

[king kong]

my take, plain and simple.

When we used soil in our bonsai pots we had to have a drainage area. And there was a theoretical danger of perched water tables. I think it never was a danger really anyway.
Nowadays we use modern substrate. This has the particle size that the drainage used to have. Actually modern substrate is drainage area all through! There is not need to have an additional part for drainage anymore.

What many don't know: You must use the same particle size throughout. Meaning if you add some finer soil, organic or whatever to rough particles you will indeed sooner or later have a drainage problem because the finer particles will clog the areas between the large particles and will meet at the bottom of the pot. I remember when I 'knew' that I had to add some 'real' soil, meaning compost to akadama because the tree 'must' have some feed in the soil. All wrong! The nutrients come with feeding. It is absolutely correct to have substrate with no nutrient contents at all.

Perched water tables are a thing that play no role in bonsai anymore if they ever did.

Now is this information accurate? Well, lets say it is on the right track but still over simplified and missing details that should be addressed.

 

[greerhw]

Lordy, I thought I was hardheaded, but 57 posts and you guys haven't solved this mystery, yet. I think our Forefathers drafted the Constitution with less argument. I'm glad you guys weren't involved in that one. You would still be stuck "On we the people"
Harry

 

[Anonymous User]

The facts are obvious Harry, it just takes King Kong, the self proclaimed "god" a little while to catch up .....

 

[king kong]

Chris,

I have supporting evidence and I will post such when I have time.



Will

And the beat goes on and on and on. The facts, the supporting evidence, the science reports and we all sit and wait and wait and wait. The fact is, Mr. Heath has no snowball idea what this is all about so what do you do? How about stall for time and maybe they will go away, or team up with someone that seems like they know what they are talking about and act smart. You have plenty of time to throw mung Mr. Heath but to solve a problem.....I guess we will have to wait and wait.........