# Potting mix trial



## Rick (Jun 5, 2011)

I picked up a small compot of a dozen sukhakulii seedlings (before I started the sphag / basket system) November or Decmeber 2010.

I've always been intrigued by how some folks seem to have no problem with this species in virtual potting mix on windowsills, while I've torched about a couple dozen BS and seedlings, doing "all the right things".

In this latest iteration, I planted the 4 size matched, healthy seedlings in a sand heavy, Orchiata bark mix, and 4 in a mix of sand hydroton balls, and potting mix (similar to FAFRA). I watered the potting mix plants less, but other wise everything is the same.





The bark mix plants on the left, potting mix plants on right. The only decent roots on the potting mix plants are the ones that were in the live moss that started growing on the surface of the mix. The bark mix has more roots that went deeper into (some to the bottom) of the pots. Foliage is lighter for the bark mix. 

I just transferred the potting mix plants to the sphag basket system. They are at a root deficit compared to the bark plants, but we'll see if they take off and surpass the bark mix plants in a few months.


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## JeanLux (Jun 6, 2011)

Interesting experience Rick!!!! What was the diff. between the 'potting-mix' and the 'bark mix'? Jean


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## PaulS (Jun 6, 2011)

JeanLux said:


> Interesting experience Rick!!!! What was the diff. between the 'potting-mix' and the 'bark mix'? Jean



I was about to ask the same thing. Sorry, Rick, they both sound quite heavy to me. Shame you didn't have one lot in straight Hydroton, that would have been a fascinating comparison.

Do you have pictures of the mix as well?


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## Ernie (Jun 6, 2011)

JeanLux said:


> Interesting experience Rick!!!! What was the diff. between the 'potting-mix' and the 'bark mix'? Jean



Looks to me like "potting mix" is a "dirt mix"- maybe something like sphagnum peat mosserlite (~1:1)?


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## NYEric (Jun 6, 2011)

I was going to ask, "What is 'potting mix'?".


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## Rick (Jun 6, 2011)

NYEric said:


> I was going to ask, "What is 'potting mix'?".



Sorry

"potting mix" is that FAFRA (peat/dirt/compost) like stuff you by for potting up standard terrrestrial plants at you basic garden center. It usually has a little pearlite in it too for aeration.


Although we orchid people call our bark, CHC, ......potting mixes, the definition for the rest of the horticulture world is pretty standarized to that fine black peat based stuff you get at Home Depot for your african violets.

As noted I heavily ammended the potting mix with sand and hydroton balls.


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## JeanLux (Jun 6, 2011)

Ok, thanks Rick!!! Jean


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## NYEric (Jun 6, 2011)

Ahhh! Potting soil! I get it. I never would use that for paphs!


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## Rick (Jun 6, 2011)

NYEric said:


> Ahhh! Potting soil! I get it. I never would use that for paphs!



Well typically I wouldn't either, but I had some successes (and others) with FAFRA mixes, as long as you are veeeerrrryyyy careful with water. Also I had some big jumps in paph growth with sand addition. Then seeing some in situ pics of suks growing on rotting logs or other heavily composted systems, I'd thought I'd combine them up for another try.

This is a better test than most (uses more than 1 plant in paired controlled conditions), and shows it still ain't no good.

So the trial continues as a race against the sphag/basket system.


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## paphioboy (Jun 6, 2011)

NYEric said:


> Ahhh! Potting soil! I get it. I never would use that for paphs!



You will be surprised.. I have seen pictures of callosum grown straight in the ground, blooming their heads off..

Nice little experiment, Rick... I agree with the observation that bark-grown plants always tend to look yellower than plants grown in other organic mixes. Wonder why...


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## SlipperFan (Jun 6, 2011)

Interesting experiment. We used to use something called Faferd -- not sure of the spelling. I wonder if it's the same. Once it dried out, it was very hard to re-wet.


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## Rick (Jun 7, 2011)

SlipperFan said:


> Interesting experiment. We used to use something called Faferd -- not sure of the spelling. I wonder if it's the same. Once it dried out, it was very hard to re-wet.



I think Faferd is the right stuff Dot. I need to go find the bag outside

Probably got used up on the tomato seedlings. They love it.:clap:


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## likespaphs (Jun 7, 2011)

fafard
i use several of their mixes at work
(for all you arabidopsis growers out there, the fafard superfine mix:turface {calcined clay} at 3:1 seems very promising!)
http://www.fafard.com/Home.aspx


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## paphioboy (Jun 7, 2011)

Who grows arabidopsis for fun?  Except scientists...


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## etex (Jun 7, 2011)

Very interesting experiment. Please keep us updated.

Perhaps the plants grown in bark are yellower/lighter due to the bark using up the Nitrogen in the fertilizer?


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## Rick (Jun 7, 2011)

etex said:


> Very interesting experiment. Please keep us updated.
> 
> Perhaps the plants grown in bark are yellower/lighter due to the bark using up the Nitrogen in the fertilizer?



No telling which component is getting exchanged. Or if there is just a significant pH shift. Could also be K, Mg, Ca, Fe, PO4 issues with differing ion exchange capacities of the different media (those also account for foliage color differences).


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## Jim Toomey (Jun 14, 2011)

It could be the bacteria on/in the bark are absorbing nutrients that the plants need... perhaps a dose of magnesium sulfate and potassium nitrite would green them up?


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## Rick (Jun 14, 2011)

Jim Toomey said:


> It could be the bacteria on/in the bark are absorbing nutrients that the plants need... perhaps a dose of magnesium sulfate and potassium nitrite would green them up?




All of them were getting shots of mag sulfate, and there's plenty of K and N in the weekly fertilizer.

From looking at various articles, the bacterial absorption factor of fresh bark is pretty small compared to the ion exchange capacity. Also there is probably more bacteria (per unit volume) in the potting soil than the bark. But no accounting for what species.


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## Ray (Jun 14, 2011)

From what I have read, the bacterial consumption of nitrogen in bark is negligible unless the bark is very well broken down, suggesting the population has had an opportunity to maximize. If the bark is THAT far gone, I would think the suffocating effect on the roots would be far more of an issue than a nutrient deficiency.


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## Jim Toomey (Jun 14, 2011)

Hmmm, so what is causing the "yellowing" or lighter color?


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## Rick (Jun 14, 2011)

Ray said:


> From what I have read, the bacterial consumption of nitrogen in bark is negligible unless the bark is very well broken down, suggesting the population has had an opportunity to maximize. If the bark is THAT far gone, I would think the suffocating effect on the roots would be far more of an issue than a nutrient deficiency.



And this mix was brand new at the start of this experiment starting in Winter of 2010.


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## Rick (Jun 14, 2011)

Jim Toomey said:


> Hmmm, so what is causing the "yellowing" or lighter color?



If the darker potting soil plants weren't in the pic for comparison I would suspect that most would consider the bark plants as having normal color (making the dark color of the potting mix plants the unusual color).

The bark mix was pretty straight forward and unamended. I can't say for sure that there was not some kind of supplemental nutrients in the potting soil, but it is hard to get potting soils that aren't amended with something.


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## PaulS (Jun 15, 2011)

My best guess at the cause of the yellowing is an iron deficiency, though there could be a lack of Zinc as well. Both are necessary for chlorophyll production.

This deficiency would be caused, or at least accentuated by the very high levels of manganese that is found in bark based mixes. This has an antagonistic effect on the uptake of iron and zinc by the plants. Commercial growers that use bark for things like Cymbidiums often have to be careful of their foliar iron levels.


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## Rick (Jun 15, 2011)

PaulS said:


> My best guess at the cause of the yellowing is an iron deficiency, though there could be a lack of Zinc as well. Both are necessary for chlorophyll production.
> 
> This deficiency would be caused, or at least accentuated by the very high levels of manganese that is found in bark based mixes. This has an antagonistic effect on the uptake of iron and zinc by the plants. Commercial growers that use bark for things like Cymbidiums often have to be careful of their foliar iron levels.



However in this trial I settle for paler plants with roots versus darker plants without roots.


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## PaulS (Jun 20, 2011)

Rick said:


> However in this trial I settle for paler plants with roots versus darker plants without roots.



I agree, but a dash of extra iron would colour them up nicely.


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