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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 7:20 pm 
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I love mounted phals. Impossible to lose to root rot. I am slowly converting all of mine to mounts (cork, tree fern, or hardwood planks).

But the observation about aeration mentioned here is not really as accurate as it might seem. The causes of root rot are more complicated than lack of air. I have had phals with roots immersed in a jar of water for years now, with lots of nice underwater root growth. Zero aeration. The roots in the water are several years old. And this is with mottled-leaves phals that are usually said to need rapid drying after watering. Others have made similar reports in this forum. There are also observations of wild phals dangling their roots in streams with no ill effects.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 9:22 pm 
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phalaenopsis wrote:
hmm. that's interesting to hear. i don't have a greenhouse, nor do i grow in clay yet, so it's interesting to hear this. so, do you mean that even though the pot sizes are different (but the diameters are the same), the shortest pot dries the slowest? that implies that clay is much better at wicking water away from sphag than it is for sphag to hold onto water. could be true, since sphag does require a lengthy amount of time to "soak" before it softens, which means that the ability of the moss to soak is much less than that of, say, a kitchen sponge.

i might hold off growing in clay pots then, because i would like to keep my deep watering interval around 7 days or more.

the other thing i would worried about is the salt buildup on the clay surface, especially with fertilizer. you would probably have to leech much more with clay than with plastic.


yeah tahts what im saying. doesnt seem right, but thats what Steve (and I) have observed...

i grow some in sphag in clay and its usually about a week before i have to water. so you would be alright. i also like the sturdiness.

if you repot frequently enough, i dont think the salts would be too much of a problem.

phalaenopsis wrote:
ok, i found a possible rebuttal to my notes above. Al, from the orchid exchange posted on facebook the following with a picture of an unpotted orchid with great root growth:

I have removed the pot to check the roots. They are in good shape except for a bit of root death in the center of the root ball where most of the fern roots are growing. This is always the case. Live orchid roots almost always head toward the space between the potting media and the pot and wrap around and around this zone. Notice this root wrapping is concentrated most heavily around the upper rim. These are the sweet spots in an orchid pot. Even in potting media that is not overly decomposed, you find this pattern. The center of the pot has the least air movement. Roots suffocate as easily as they drown. In any pot larger than a 6" pot I often invert a smaller pot inside the rootball to keep wet stagnant media out of this dead inner space where roots don't really want to grow anyway. When repotting I try NEVER to push all the live roots toward the center of the pot where they will surely suffocate or drown if they were used to the airier perimeter.

so maybe aeration around roots is important.
phalaenopsis wrote:
ok, i found a possible rebuttal to my notes above. Al, from the orchid exchange posted on facebook the following with a picture of an unpotted orchid with great root growth:

I have removed the pot to check the roots. They are in good shape except for a bit of root death in the center of the root ball where most of the fern roots are growing. This is always the case. Live orchid roots almost always head toward the space between the potting media and the pot and wrap around and around this zone. Notice this root wrapping is concentrated most heavily around the upper rim. These are the sweet spots in an orchid pot. Even in potting media that is not overly decomposed, you find this pattern. The center of the pot has the least air movement. Roots suffocate as easily as they drown. In any pot larger than a 6" pot I often invert a smaller pot inside the rootball to keep wet stagnant media out of this dead inner space where roots don't really want to grow anyway. When repotting I try NEVER to push all the live roots toward the center of the pot where they will surely suffocate or drown if they were used to the airier perimeter.

so maybe aeration around roots is important.


thats interesting! thanks for sharing! yeah in most cases aeration is important in phal roots...


loujost wrote:
I love mounted phals. Impossible to lose to root rot. I am slowly converting all of mine to mounts (cork, tree fern, or hardwood planks).

But the observation about aeration mentioned here is not really as accurate as it might seem. The causes of root rot are more complicated than lack of air. I have had phals with roots immersed in a jar of water for years now, with lots of nice underwater root growth. Zero aeration. The roots in the water are several years old. And this is with mottled-leaves phals that are usually said to need rapid drying after watering. Others have made similar reports in this forum. There are also observations of wild phals dangling their roots in streams with no ill effects.



i wish i had a greenhouse or somewhere i could take care of a mounted phal! its hard to water enough when you cant just spray with a hose and be done!

orchid roots grow tailored to the environment they grow in. so if an orchid is mounted and the roots are exposed to air and wood, they grow tailored to that environment. same for in sphagnum moss, bark, or any other media. also the same for water! when the roots grow into the water, they will grow suited to that environment. if you were to take a plant that had been mounted and put all those roots that are suited to being mounted and put them in water and keep them like that, those roots would surely die!

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 9:29 pm 
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If air about the roots is vital to the health of the plant would sh not be a death sentence? Me and moss have mutually agreed to go our separate ways.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 9:38 pm 
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ryan820 wrote:
If air about the roots is vital to the health of the plant would sh not be a death sentence? Me and moss have mutually agreed to go our separate ways.


thats where the roots growing tailored to their environment comes in. when you switch from conventional methods to semi-hydroponics, you loose most/all of the roots you had before. thats why you want to switch over when your plant is growing new roots!

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 9:59 pm 
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Several folks on this forum, including me, have stuck aerial roots of Phals and Cattleyas in cups of water, and they don't die. They actually seem happy, often making many branches underwater. I agree that soggy moss can get you into trouble, but I don't think we fully understand why. The explanation that "roots need air" is disproven by these experiments with phal roots living for years underwater. And again, the Phals I used in my experiments were the most sensitive to rot-- flat-rooted mottled-leaved ones.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Wed Sep 19, 2012 10:02 pm 
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loujost wrote:
Several folks on this forum, including me, have stuck aerial roots of Phals and Cattleyas in cups of water, and they don't die. They actually seem happy, often making many branches underwater. I agree that soggy moss can get you into trouble, but I don't think we fully understand why. The explanation that "roots need air" is disproven by these experiments with phal roots living for years underwater. And again, the Phals I used in my experiments were the most sensitive to rot-- flat-rooted mottled-leaved ones.

really? That's very interesting!!! I guess the whole thing about roots growing tailored to their environment isn't exclusively true! Guess the roots can adapt as well!!

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 5:51 am 
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All the advice above about aeration, wet spots, etc, is very good advice and it works. Don't get me wrong. But I don't think we fully understand why.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 7:35 am 
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I disagree that "roots need air" is disproven. All plants cells need gas exchange in order to conduct photosynthesis and respiration. In cases where roots have been completely submerged in water, they have adapted to that environment as Bob stated earlier. The reason the roots don't die is that the plant can close the stomata and gases are diffused through the loosely arranged cells within the plant tissue.

Root rot is caused by an infection of the root tissue by Phytophthora water moulds which grow through the tissue absorbing the necessary nutrients and destroying the tissue structure in the root preventing it from absorbing water and nutrients. While the Phytophthora zoospores need water to swim through the soil, I think either the chemistry or volume of just water prevents the zoospores from either reaching or penetrating the root tissue.

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 8:21 am 
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Yes, I should have been more precise. The water experiments don't disprove that root cells can go without gas exchange. But they do disprove the claim made above, that roots need pockets of air around them. They don't.

Jim, I think you hit the nail on the head: the Phytophthora biology is the missing element in the explanations given above. Maybe the shear volume of tasty mold substrate in sodden pot centers makes their population rise to the point where the plant's natural defenses can't keep up with the onslaught. And/or maybe changes in pH during the aging of media favor growth of Phytophthora. Maybe they can't grow in pure water. Maybe THEY need air!!!

What kills Phytophthora?


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 1:46 pm 
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Good cultural techniques and disease resistant strains are the most common controls in ornamentals. Some fungicides show some efficacy but I have no experience here. I did find a research article for ornamentals in Florida geared towards commercial plant production but it may gives some guidance. Since I no longer work in the commercial horticulture trade, I'm unfamiliar with the chemicals they discuss.
http://mrec.ifas.ufl.edu/foliage/resrpts/rh_93_3.htm

Cheers.
Jim

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 7:33 pm 
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great input! that maeks sense about the fungi Jim!

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 7:48 pm 
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One element we never think about is the ecology of the micro-organisms in our potting material, or even on the leaf surfaces. These are complex and have an impact on plant health. Recently new techniques for fighting plant disease have involved spraying "nice" bacteria or fungi on plant leaves, which they colonize. Their presence keeps "bad" micro-organisms from being able to get started. I imagine potting material is a constant battleground as well, and cultural lapses (like severe drying) probably destabilize these ecosystems and let dangerous micro-organisms become abundant.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Thu Sep 20, 2012 7:50 pm 
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wow! that is something we as growers rarely ever think of! and ill bet your right. and if so, then its something that shouldnt be overlooked

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 Post subject: Re: Growing in sphagnum moss
PostPosted: Fri Sep 21, 2012 12:07 am 
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loujost wrote:
Yes, I should have been more precise. The water experiments don't disprove that root cells can go without gas exchange. But they do disprove the claim made above, that roots need pockets of air around them. They don't.


If you are referring to my statements, I think you have gotten confused about my statements. I don't think I was making the argument that the roots need "pockets of air" around them. First of all, not all phals are equal, after all, they come from different ecosystems, and thus are suited to grow in different environments and cultural conditions. Second, I have grown in s/h as well, in fact I had almost 90% of my collection in s/h about 3 years ago. since then, i have switched partly back to sphag, so I also have a lot of experience growing in s/h, and you can search for my valentinii on this forum that shows that s/h is definitely a medium that some phals enjoy being grown in. plants grown in s/h are not sitting in water--there is a constant movement of liquid wicked up from the reservoir below, and there is also constant evaporation from the reservoir solution coming off the clay pellets. third, just because roots are grown in water does not mean that there is not any oxygen around roots, nor does that mean that there will definitely be fungal or bacterial infection. water can carry oxygen molecules--this is well established, and roots growing naturally into creeks or rivers are subjected to constantly circulating water, which is often well oxygenated. another point on infection-- infection is more complicated than just having bacteria around--otherwise humans would be constantly "infected" by the bacteria from the gut. other factors to consider include entry of the bacteria, growth competition between bacterial colonizers, host defenses, virulence of the pathogen, inflammation by the host. if fungicide or pesticides are thrown into the mix, then you need to also consider susceptibilities and resistance issues. also, there are many more pathogens than just phytophthora out there that can cause infection.

i think that what i got from al's message is that there may be some quality that occurs at the interface at the top and bottom of a pot that roots find more favorable than at the middle. since there is a higher evaporation rate at both of these sites than the middle, that is the first thing i think of. this is not to say that roots won't grow in the middle--they just favor the top and bottom. going along that argument, then mounted plants would probably grow the best, but i would not be able to keep up with the frequency of watering that they would require. so for me, it is a tradeoff of what the plants would favor vs what i have time to provide.


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 Post subject: Re: Growing in sphagnum moss
PostPosted: Fri Sep 21, 2012 6:14 am 
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Don't get me wrong, I think the advice people gave above is really good and I agree with it. I am just trying to get at the reasons why it works. I want to say that the situation is more complex than some of the following statements suggest:

"...avoid roots sitting in water"

"The center of the pot has the least air movement. Roots suffocate as easily as they drown."

"...if you were to take a plant that had been mounted and put all those roots that are suited to being mounted and put them in water and keep them like that, those roots would surely die!"

It turns out that these things are not exactly true. Roots can sit in water without dying, even roots that grew up hanging in mid-air, and air movement (as opposed to gas diffusion through water) is not needed. Roots do not necessarily suffocate or drown when immersed in water. And the water does not need to flow.

Later when my camera charges I will post a picture of a counter-example to those statements: a flat-rooted Phal (supposedly the kind most sensitive to soggy medium) whose roots have been in water for years. The water doesn't flow; I haven't even changed the water for a year or so!!!


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