Why are standard Nursery Pots more popular than Air Pruning Pots ?

[Bonsai Hunter]

Roots need oxygen for development & I no longer use pots that have poor drainage and aeration. An air pot, like the one below, would fit between the the square pot & colander, as it has less pot surface exposed to air. Cost & watering issues need to be factored in, though and planned for.

 

[Bonsai Hunter]

1 Big Hole vs. Many Small - drainage speed test



I feel air pruning is more relevant to bonsai than gardening or tree nurseries bcos compact roots are important to us, apart from the aethetic aspect of roots. Trees in training pots or grow pots should ideally have an air-pruning feature, self made or bought. That is not the stage to slow down growth, else it would not be called a grow pot, would it ?

Ideally, bulb pans with perforated side & bottom should be available at the same price as the regular type. Yes, maybe some of the tree & bonsai nurseries are taking shortcuts but even tree nurseries benefit by air-pruning. They might cost more, though they shouldn't.

Anthony, I am surprised that you got better results with air-pot. A colander has more of the pot surface exposed to air than an air-pot and should have worked better. Please post some pics of your test if possible. Nice looking tree.

 

[Anthony]

@Bonsai Hunter ,

firstly we use colanders for ground growing, after 1 to say 3 years, you can lift the plant and colander out of the soil with
no real disturbance as the roots go.
Just set aside for a few months and tree naturally regenerates fine feeder roots.

Additionally [ for apartment dwellers ] we have a test running on the colander within a colander technique seen in
Bonsai Today.
The idea being - the roots still have root run and trunk /branch growth is encouraged.
Will let you know in 2 or 3 years how that went.

We first ran an air-pot against a normal pot. To see what would happen.
Result was the air pot grew much faster [ trimmed 3 times ] and because we used only as much soil as the normal pot,
the root examination after a year showed the tree in the air pot was so filled with roots that it looked like wood.

[2] Second test - a metal colander and a plastic colander against an air pot.
The air pot enhanced feeder root growth so much that the tree placed into a Bonsai pot had trouble handling
the full sun due to too much foliage.
We had to thin it out.

When we next test, we will see if we can change the air pot to a rectangular shape, to act as the pot for the Bonsai
,lifting the plant out for temporarily placing in an exhibition bonsai pot, when exhibiting.

However, the ground growing makes everything so easy, that we will most likely abandon the air pot.
We have several sizes of air pots from a seller on Amazon.

For whatever reason the colander just does not do as the air pot does. So we use colanders only for ground
growing [ presently ]

Could not presently find the images with plastic colanders in use.
As I make more time I will look for those.
Here are the others.

All soils are our standard 5 mm inorganic and sifted aged compost done by volume. 2 inorganic to 1 organic.

Give me a few days to locate the plastic colander image and the tree in the images presently in a bonsai
pot.

It would be a waste of time to air pot a ficus as it's roots already handle air in nature.
Good Day
Anthony,


First test - speed of growing ---------- air pot at this stage has been trimmed three times for long shoots.
The soil volumes are the same ------- note placement of tape.
Trees were the same age. Full sun and next to each other.
This air pot design is well researched as science goes.

Note our air pot clay pot ----------- doesn't quite do as the air pot - chuckle.




close up and look at the holes you can see the inorganic material of the soil.




second test - full container of soil - had to be pruned 4 times.



defoliated



metal colander

 

[markyscott]

Anthony. Did you notice how different the soil volumes are between these pots? It looks like your nursery container is a 4" seedling container (which holds about a quart of soil) whereas that air pot you're using might be a full 1 gallon pot. I can't tell what the soil volume is in the colander, but it's dimensions look different as well. Can you tell us how you're sure that it's the holes in the side of the container and not the difference in volume that led to the differences in growth rate?

Scott

 

[Anthony]

@markyscott ,

I believe you missed the 1st image with the tape showing where the soil was. Soil content was measured by filling the 4 inch seedling pot and then
filled into the air pot. The one batch of soil mix was used for both containers soil mix .

Look closely at the second image, the holes where the soil is, are coated white.

Additionally, see how the base is attached in Bonsai Hunter's air pot image just above.
Hope this helps.
Good Day
Anthony

* Image of metal colander with measurement coming .

 

[markyscott]

There are lots of research papers on the use of air pots. AND some of them are even on species we care about. Here are some links:

http://depts.washington.edu/propplnt/Chapters/air-pruning.htm
http://www.fs.fed.us/rm/pubs_wo/wo_ah732_123_139.pdf
http://link.springer.com/article/10.1007/s11056-004-7364-6

The benefits of air pots these studies point to are that they:

• Promote branched root systems
• Encourage new roots to sprout
• Prevent roots from spiraling
• Prevent plants from becoming pot-bound
• Allow plants to remain in pots longer before repotting

None that I know make any claims about growth rates. In fact, some of the studies claim quite the opposite:

http://ria.asturias.es/RIA/bitstream/123456789/2165/1/Fiield performance.pdf

The patents (i.e., https://www.google.com/patents/US4497132) make no claim about growth rates - they are talking about root morphology. You can be sure that if these pots increased growth rate they would claim it in the patent. They don't. Specifically, they state that they're trying to avoid spiraling roots - a typical problem in container grown trees. Trees with spiraling roots are less stable when planted and the problem won't self-correct, potentially leading to long term problems for the tree. Particularly bad ones are culled. Avoiding culls while maintaining growth rates was where the whole shaving technique came from:

http://hort.ifas.ufl.edu/woody/documents/articles/EFG0901.pdf

In bonsai we don't have a spiraling roots problem because we repot regularly. When we repot we remove problematic and large unbalanced roots. Most broadleaf deciduous trees and tropicals receiving regular irrigation can recover from such severe root pruning without slowing their shoot growth.

http://hort.ifas.ufl.edu/woody/documents/articles/EFG0927.pdf

In short, I'm with Sawgrass - if you're growing your trees for bonsai and properly repotting regularly I see no benefit of air pots for broadleaf deciduous trees or tropicals being developed for bonsai.

Conifers, on the other hand, don't tolerate severe root pruning as well, so there is possibly a long term benefit in air pots for them when it comes time for root reduction to fit into a bonsai container. Notionally, you can build a large root mass (by planting in a big container) to support more rapid growth while maintaining a dense system of feeder roots that can be more easily reduced to bonsai container dimensions. Of course, this is conjectural and will never be demonstrated by research but it seems like it might make sense.

Scott

 

[markyscott]

1 Big Hole vs. Many Small - drainage speed test

View attachment 118662 View attachment 118663

I feel air pruning is more relevant to bonsai than gardening or tree nurseries bcos compact roots are important to us, apart from the aethetic aspect of roots. Trees in training pots or grow pots should ideally have an air-pruning feature, self made or bought. That is not the stage to slow down growth, else it would not be called a grow pot, would it ?

Ideally, bulb pans with perforated side & bottom should be available at the same price as the regular type. Yes, maybe some of the tree & bonsai nurseries are taking shortcuts but even tree nurseries benefit by air-pruning. They might cost more, though they shouldn't.

Anthony, I am surprised that you got better results with air-pot. A colander has more of the pot surface exposed to air than an air-pot and should have worked better. Please post some pics of your test if possible. Nice looking tree.

I know we often talk about "fast drainage" as if it's the end goal of our soil conditions. It is not. The most important factors are the air-filled porosity and the residual water saturation after the excess water has drained away by gravity drainage. It doesn't matter if it takes 10 seconds or 10 minutes for the water to drain away as long as the AFP is optimal after it's gone.

Consider your animation. If there were soil in the cups, would the residual water saturation in the cup on the left be different than in the cup on the right after the water has drained away? Which is more important, the 10 to 30 seconds the tree is exposed to high water saturations when it is being watered or the residual water saturations the tree has to survive with until the next watering?

The reason people often talk about "fast draining" soil is because, all else being equal, a faster draining soil is qualitatively more reflective of a soil with a higher AFP and lower residual water saturation (which is what we want). It's very clear that, as a general rule, less than 10% AFP and your soil is waterlogged - plant growth suffers. Too long under these conditions and plants will die (minus a couple of notable exceptions that have adapted to surviving these conditions). Increase your AFP and plant growth will increase. Ask yourself, what "drainage speed" is dangerous? What is good? Folks will think about it or not - plants don't care either way.

Scott

 

[markyscott]

@markyscott ,

I believe you missed the 1st image with the tape showing where the soil was. Soil content was measured by filling the 4 inch seedling pot and then
filled into the air pot. The one batch of soil mix was used for both containers soil mix .

Look closely at the second image, the holes where the soil is, are coated white.

Additionally, see how the base is attached in Bonsai Hunter's air pot image just above.
Hope this helps.
Good Day
Anthony

* Image of metal colander with measurement coming .

What fills up the rest of the space in the 1 gallon air pot?

Scott

 

[Anthony]

@markyscott

you can set the bottom part at any height. The bumps are also internal.

http://air-pot.com/nursery/wp-content/uploads/2014/05/Empty-trays-1-small.jpg

Perhaps for Bonsai growing ?

http://air-pot.com/nursery/news/page/2/

First time with this air pot Mark ?
Good Day
Anthony

* Remember they grow trees in them at 100 % compost - richest soil and with air and moisture retention

 

[markyscott]

@markyscott

you can set the bottom part at any height. The bumps are also internal.

http://air-pot.com/nursery/wp-content/uploads/2014/05/Empty-trays-1-small.jpg

Perhaps for Bonsai growing ?

http://air-pot.com/nursery/news/page/2/

First time with this air pot Mark ?
Good Day
Anthony

* Remember they grow trees in them at 100 % compost - richest soil and with air and moisture retention

I've used air pots and colanders, but not this brand. Some thoughts:

• The reference you gave is just a news article that gives an anecdotal account of peppers growing well in air pots, not a comparative study of canopy or root growth rates in different container types. I can point you to a number of studies (including the one I posted) that DO compare growth rates in different containers and with different hole configurations. The results are of those studies are not really that arguable and not even the manufacturer of air pots claims that growth rates are superior in air pots than in conventional ones. Don't you think that if there were studies demonstrating that growing in air pots was resulted in superior growth rates than conventional ones the manufacturers would be all over it in their patents and advertisements? They're not - they claim to reduce culling of nursery stock due to poor root development. That's what they do.
• Of course nurseries grow out trees in organic rich soil. It's cheap, mass produced and effectively drains as long as you're not using a shallow container. That's why nursery containers are so deep and not wide and thin. How that translates to bonsai culture where we're growing trees in a two inch deep container is arguable. But I'm assuming that you use an organic-rich medium in all of your pots so that's not a variable.

That's really all I have to say on the matter, but thanks for the exchange.

Scott

 

[Anthony]

@markyscott ,

no need to respond, I was just trying to show you how the air pot was attached and designed as I suspected
from your questions, it was new to you.

I can only pass on what I observed with this air pot design versus the 4" pot in the first shot.

No, the mix we use is equal to, or less than 1/3 aged compost to 2/3 - 5 mm inorganic material by volume.
Though we can add teaspoonfuls of aged compost if the mix becomes degraded to just inorganic
on the soil's surface.

What would probably make the difference is our air temperatures never cross 93 deg.F and then only hit that
high for 30 minutes of less. Humidity is around 50 to 70 % but can drop to 45 and go up to 80% with heavy rain.
We are listed as a marine modified climate and basically ------- a mild climate.
Our sunlight however is intense, but we are mostly cloudy and breezy.

The second address was only sent to you, as a general read, nothing more.

Good Chatting with you,
You also gave us a new test to try. Thanks.
Let you know the results in a year or two.
Good Day
Anthony

 

[Bonsai Hunter]

@Anthony

I like the experiments you are doing. From your pics of the metal colander, I understand why the air pot did better. The number of holes in the metal colander are too few and far apart, allowing the roots to dodge the exit holes. So they mostly do not air prune. A plastic colander like the one i have shown does not give any hiding place for the outer roots and they have to be air pruned. I had the same problem while melting holes in plastic containers, just like your self made clay air pot. For air pruning to work effectively, the total area of holes should be more than the pot area. At the minimum, it should be equal.

The air pot doesnt need so many holes and yet is effective bcos the bumps pointing inwards are guiding the roots to an exit hole, so it cannot escape, unlike containers that have a smooth inner surface. A nylon net bag is very effective at air pruning but is shapeless & loses water very fast. That way, I admire the air pot design - it balances air pruning & water retention.

 

[Bonsai Hunter]

@markyscott, @sawgrass

Thanks for your inputs. I will go thru your links & respond later. got to rush out now.

 

[Anthony]

No @Bonsai Hunter,

what you are seeing is the only image I could find on colanders. The test also included a plastic colander [ like the red one you have above ],
and a wire mesh colander.
Not to fuss as I make time, more images will follow.
Good Day
Anthony

 

[markyscott]

@markyscott, @sawgrass

Thanks for your inputs. I will go thru your links & respond later. got to rush out now.

Certainly. When I responded to your note, I was reacting to the statement "Good drainage and aeration begins with the pot, not with the soil". Most of the references I gave were about what the nursery industry uses air pots for and probably not exactly relevant to that statement. I repeat myself a lot on this topic and I don't want to pollute the main topic of this thread (the utility of air pots) with a soil discussion. So I'm going to make a new thread about basic soil physics. In it, I'll give you a brief overview of why I said what I did.

Scott

 

[Anthony]

@Bonsai Hunter,

here is the Tamarind from the earlier shots in a bonsai pot.
Tree has finer leaves and more branchlets than our other efforts.
Had to actually remove branchlets as there were too many for the soil to handle.
Good Day
Anthony