Author Topic: Results of an Unscientific Air Pot observation  (Read 9243 times)

cray13

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Results of an Unscientific Air Pot observation
« on: June 26, 2011, 07:54 AM »
After three years I finally wrapped up my "experiment" with growing pre-bonsai using Air Pots.  

I did my best to employ the elements of the Scientific Method I learned back in middle school.  However, please realize that my "results" are basically at best a casual observation... please accept the preceding as my disclaimer.

The Question:
Are Air Pots worth the investment over standard nursery pots for growing Japanese Black Pine for Bonsai?

The Research:
Here is some background information on Air Pots.

Advertised benefits of Air Pots from a Wholesale Nursery perspective:
  • Eliminate root circling
  • Reduce growing time in the nursery - more roots = faster growth
  • Double the shelf-life of nursery stock - you can leave the plant in the air pot longer
  • Reduces losses

Now for some details... some great visual media here.
How Air Pots work

The Hypothesis:

A Japanese Black Pine seedling planted in an Air Pot should have a more fibrous root system and exhibit no root circling.  This should also allow for a more efficient root system resulting in better top growth as compared to planting in a standard nursery container.

The Test:

On May 12th, 2008 I planted one year old Japanse Black Pine Seedlings of similar size in a one gallon nursery container, a pond basket and a one gallon Air Pot using the exact same porous bonsai soil mix.  The seedlings were watered and fertilized exactly the same and also received the same amount of sunlight each day.  These seedlings were originally sown in 2007 using the root pruning method described in another post

For redundancy I planted a total of six seedlings, two for each of the three container types.

Variables
  • One Gallon Standard Nursery Container
  • Pond Basket
  • Air Pot

6 seedlings from May of 2008 ready to be potted.


Container comparison
Image with containers



The Results:

Any variation of top growth regardless of container was indistinguishable.  All the seedlings were comparable with no container showing a clear advantage.  This was my first sign that most likely the root growth would be very similar as well.

To inspect the root growth, on April 17th, 2011 I repotted three of the six seedlings choosing one from each type of container.  

Root circling:
The Air Pot performed as expected with regards to root circling.  There was no evidence of root circling at all.  The pond basket and nursery container both exhibited root circling at the bottom of the container.  

Root volume:
The Air Pot and the nursery container appear to have the most root volume with no clear winner between the two.  The root system on the pond basket had much less volume and was clearly the weakest.

Root fibrosity:
The Air Pot and the nursery container clearly have the most fibrosity with the nursery container actually showing a slight edge over the Air Pot.  Again the root system in the pond basket is obviously much weaker.

Air Pot Images:

Air Pot -No root circling-


Air Pot - Root System


Nursery Container Images:


Nursery Container -Clear evidence of root circling-


Nursery Container - Root System -


Pond Basket Images:


Pond Basket - Root Circling -


Pond Basket - Root System




The Conclusion:

Air Pots may not be worth the extra cost.


However, I do feel I may not have allowed enough time for the air pruning affect of the Air Pot to contribute to the trees growth.  None of the containers had yet reached a stage of being root bound.  If the Air Pots perform as advertised I will not have to repot them as many times as I will a tree grown in a nursery container.  It will be interesting to see how dense the root system may become if I delay repotting and allow the air pruning to work.

Before the experiment I had already purchased the Air Pots and currently have over 75 pines growing in 1 and 3 gallon Air Pots.  I will make a point of revisiting this post in a few years to update the progress of these Air Pot grown pines.  Perhaps my opinion will change given more time to observe the results.  Either way, I'm fairly certain the Air Pots will perform as well as the nursery containers.  As for pond baskets, they are awkward, not strong enough and from my observation performed poorly.

See following posts for a few more images.






« Last Edit: June 26, 2011, 08:19 AM by cray13 »
 

cray13

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More Images
« Reply #1 on: June 26, 2011, 07:58 AM »
More Images:
 

cray13

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More Images
« Reply #2 on: June 26, 2011, 07:59 AM »
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cray13

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Even more images
« Reply #3 on: June 26, 2011, 08:01 AM »
More Images
 

Buffrider

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Re: Results of an Unscientific Air Pot observation
« Reply #4 on: June 26, 2011, 10:10 AM »
Hmmm. Nice experimnt. From this I think I'll stick to nursery pots. Thanks for this.
 

Larry Gockley

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Re: Results of an Unscientific Air Pot observation
« Reply #5 on: June 26, 2011, 01:20 PM »
Good to read about your experiment. Have never read about air pots before. I do however see an uncontrolled variation in your test. The total soil mass was considerably smaller in the pond basket, and that coupled with the increased exposure to air, might have required that pot to be watered more often. I sometimes use pond baskets, but they are flimsy and do get brittle in the sun in a few years. My biggest complaint with most pots in general, and nursery pots especially, is that for bonsai purposes, they grow root masses that are more vertical, and in bonsai, we want a more horizontal root mass. Why grow a deep root mass that will have to be bottom pruned when the time comes to put it in a bonsai pot? Thus the continued search for the perfect root training pot. The mesh type sides and bottom are a good start, IMO, because the roots self prune. Quite often, especially for a collected tree, I make my own pot, lined with mesh and to the size and shape of the future bonsai pot. Thanks for the post. Very interesting. Larry
 

gtuthill

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Re: Results of an Unscientific Air Pot observation
« Reply #6 on: June 26, 2011, 05:20 PM »
Thanks for taking the time to make this comparison.  The other variation i have seen used (and am about to try myself) is the collander pot. 

The other thing that is worth considering is the surface the pot is sitting on, and how freely water will drain away from that. 

The theory being with airpot /pond baskets/ collanders being that the root tips that reach the air dry out, die and the roots branch further back creating ramified roots.  If the roots in one of these is circling at the bottom, i suspect it is because the tips never had a chance to dry out.

Just a thought  :)

Any ideas for free draining benches?
 

MatsuBonsai

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Re: Results of an Unscientific Air Pot observation
« Reply #7 on: June 26, 2011, 06:13 PM »
While I've not tried the air pots, I have had great success with the Inomata Green Plastic Colanders from Chef Tools (9" and 11 1/2").
 

cray13

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Re: Results of an Unscientific Air Pot observation
« Reply #8 on: June 26, 2011, 06:15 PM »
Thanks for taking the time to make this comparison.  The other variation i have seen used (and am about to try myself) is the collander pot. 

The other thing that is worth considering is the surface the pot is sitting on, and how freely water will drain away from that. 

The theory being with airpot /pond baskets/ collanders being that the root tips that reach the air dry out, die and the roots branch further back creating ramified roots.  If the roots in one of these is circling at the bottom, i suspect it is because the tips never had a chance to dry out.

Just a thought  :)

Any ideas for free draining benches?


You are absolutely correct about the root circling and the soil not draining completely.  However, I'm fairly certain the water was able to drain away from the pot.  The material in this experiment was placed on "free draining" benches... My bench surface is 1/4 inch wire mesh.  

 

cray13

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Re: Results of an Unscientific Air Pot observation
« Reply #9 on: June 26, 2011, 06:23 PM »
Good to read about your experiment. Have never read about air pots before. I do however see an uncontrolled variation in your test. The total soil mass was considerably smaller in the pond basket, and that coupled with the increased exposure to air, might have required that pot to be watered more often. I sometimes use pond baskets, but they are flimsy and do get brittle in the sun in a few years. My biggest complaint with most pots in general, and nursery pots especially, is that for bonsai purposes, they grow root masses that are more vertical, and in bonsai, we want a more horizontal root mass. Why grow a deep root mass that will have to be bottom pruned when the time comes to put it in a bonsai pot? Thus the continued search for the perfect root training pot. The mesh type sides and bottom are a good start, IMO, because the roots self prune. Quite often, especially for a collected tree, I make my own pot, lined with mesh and to the size and shape of the future bonsai pot. Thanks for the post. Very interesting. Larry

You are correct about the soil mass and this most likely had an affect on the pond basket grown tree.  I guess my main complaint with the pond basket is the same as yours... they're just not sturdy enough.  

As for soil depth, I think having a deep pot is ok when you're in the pre-bonsai stage and you are trying to get trunk girth and quick growth in the early stages.  I agree, once you have the trunk built it is time to reduce the root mass and overall depth to get the tree ready for a bonsai pot.  

The nice thing about the Air Pots is that the volume of each pot and it's depth is actually adjustable.  The way the pot is designed you can move the bottom up or down to vary the depth of the pot.  With my three gallon Air Pots I actually only use half the depth of the pot.  So I have a 10" diameter pot that is only 5-6" in depth.  I also used to build wooden boxes with mesh bottoms and sides.  However, I decided it was too much work and have dropped putting mesh in the sides... I only mesh the bottom of my boxes now.  Unfortunately... a carpenter I am not.

Below is an image of some of my boxes before I've added the mesh lining.
« Last Edit: June 26, 2011, 06:25 PM by cray13 »
 

Alain Bertrand

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Re: Results of an Unscientific Air Pot observation
« Reply #10 on: June 27, 2011, 02:31 AM »
Very interesting post, thanks for sharing.

I would challenge the sentence « more roots ==> more growth ». This is true only if root surface (i.e. water and mineral nutrient absorption ) is limiting. When it is not, as roots consume photosynthesis products, more roots means less aerial growth. You can find evidence for this in the scientific literature targeting horticulture professionals.

Also, I don't care much about pot depth. To me, what is important is the direction of root growth in the limited area around the trunk that will not be cut away at the next re-potting.
 

Owen Reich

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Re: Results of an Unscientific Air Pot observation
« Reply #11 on: June 27, 2011, 05:47 AM »
Thank you for posting your experiment.  I've heard Akadama was intended by a Japanese bonsai hobbiest  :).  I've evaluated about a dozen different "root pruning" pot designs from a variety of horticulture companies over the past 5 years; everything from propagation trays up to pots for 30 foot tall trees.  The air pruning pot in this experiment provided mixed results.  To keep it on topic for bonsai, three pots proved beneficial.  The Whitcomb or "Rootmaker" pots are ok, but you may mutter some expletives when you see the prices for one gallon to 7 gallon pots.  The design has small horizontal slits and tiered sides that decrease in diameter from top to bottom.  The next best are from a company called Tri-Tech Molded Products in McMinnville, TN called ARPACC pots.  They are better than the Whitcomb design as they have a lot more air exchange going on and are far less expensive.  The design has vertical slits for the entirity of the perimeter as well as the base; the base having "feet" as opposed to the Whitcombs.  They do however, tend to allow weeds to grow out the sides as Meehan's Miniatures can also attest.  The best by far are the Fanntum bags from Fanntum products in North Carolina.  www.Fanntum.com.  They are pretty cheap too. Alan Fann will also custom make any size or shape you want.  I will be using them for bonsai in the future with a diameter much greater than the height.  The fibrous roots produced by this pot are evident far deeper into the center of the pot and the zone of saturation is pretty small in the base.  The bottom of the pot is high durability felt and the wall is woven nylon.  I never ran into any issues with the base sitting on level weed fabric but a mesh bench can't hurt.  They are also green to reduce heat as black is the worst possible color. 
I have never used pond pots.  I have lined old Coke bottle carriers with mesh and been very happy with them as the are shaped like a bonsai pot and require no carpentry skills.  The colander method pioneered by the Japanese does work for black pine as i've tried a few and heard many positive comments from others.  As stated by the author of this post, those pines were still pretty small and hadn't filled the pots completely.  I'd try some seriously fast draining media (pure high fired Akadama,Turface,etc), water liberally, and liquid feed heavily as is done here in Japan and elsewhere. 
 

cray13

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Re: Results of an Unscientific Air Pot observation
« Reply #12 on: June 27, 2011, 05:59 AM »
Thank you for posting your experiment.  I've heard Akadama was intended by a Japanese bonsai hobbiest  :).  I've evaluated about a dozen different "root pruning" pot designs from a variety of horticulture companies over the past 5 years; everything from propagation trays up to pots for 30 foot tall trees.  The air pruning pot in this experiment provided mixed results.  To keep it on topic for bonsai, three pots proved beneficial.  The Whitcomb or "Rootmaker" pots are ok, but you may mutter some expletives when you see the prices for one gallon to 7 gallon pots.  The design has small horizontal slits and tiered sides that decrease in diameter from top to bottom.  The next best are from a company called Tri-Tech Molded Products in McMinnville, TN called ARPACC pots.  They are better than the Whitcomb design as they have a lot more air exchange going on and are far less expensive.  The design has vertical slits for the entirity of the perimeter as well as the base; the base having "feet" as opposed to the Whitcombs.  They do however, tend to allow weeds to grow out the sides as Meehan's Miniatures can also attest.  The best by far are the Fanntum bags from Fanntum products in North Carolina.  www.Fanntum.com.  They are pretty cheap too. Alan Fann will also custom make any size or shape you want.  I will be using them for bonsai in the future with a diameter much greater than the height.  The fibrous roots produced by this pot are evident far deeper into the center of the pot and the zone of saturation is pretty small in the base.  The bottom of the pot is high durability felt and the wall is woven nylon.  I never ran into any issues with the base sitting on level weed fabric but a mesh bench can't hurt.  They are also green to reduce heat as black is the worst possible color. 
I have never used pond pots.  I have lined old Coke bottle carriers with mesh and been very happy with them as the are shaped like a bonsai pot and require no carpentry skills.  The colander method pioneered by the Japanese does work for black pine as i've tried a few and heard many positive comments from others.  As stated by the author of this post, those pines were still pretty small and hadn't filled the pots completely.  I'd try some seriously fast draining media (pure high fired Akadama,Turface,etc), water liberally, and liquid feed heavily as is done here in Japan and elsewhere. 

Thanks so much for the information.  Go figure, I live in North Carolina so I'll definitely investigate the Fanntum product.
 

Larry Gockley

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Re: Results of an Unscientific Air Pot observation
« Reply #13 on: June 27, 2011, 10:20 AM »
Now that Owen mentioned coke bottle carriers, that's what I use quite often. They are actually the plastic carriers that the cola syrup is delivered to convenience stores, then discarded. I line them with plastic mesh or even nylon window screen. The tried and true method of planting a tree in the ground, on top of a piece of tile, is always a good way to go, assuming you don't live in an area that's experiencing a 100 year drought.  :-[  Larry
 

Treebeard55

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Re: Results of an Unscientific Air Pot observation
« Reply #14 on: June 27, 2011, 12:29 PM »
I've used the Whitman Rootmakers (TM) for a number of years now, with generally satisfactory results. The most persistent problem I've found with them is that, if a tree is in one too long, sooner or later roots grow to a size that blocks the slits from the inside, and then circling can begin. That's especially true with very fast-growing trees like some of the Ficus.

Aside from that, they've been pretty satisfactory, tho they're not magic.

Owen, thanks for mentioning the Fanntum items. That looks quite interesting!