Root Death

[Ray]

Originally Posted by K-Sci

Isn't one of the main advantages to S/H avoiding work like this?

I guess that depends upon one's understanding of the meaning of "constant flushing". My way of dealing with S/H pots is to fill them rapidly to the top and let them drain. That results in a "frequent" flush, if not continuous, returning it to your preferred chemistry. Folks who simply top-up the reservoir most of the time and do such a flush less frequently are letting their plants "sit in a cesspool" as far as I'm concerned, because the reservoir chemistry starts changing pretty much immediately after you water.

I'll add that "S/H" has several definitions, if you will. I refer to LECA in a pot having drainage holes in the side and a reservoir. Another "take" is the 3-component pots, with outer pots, mesh culture pots, and gauges. A "frequent flush" is much easier in my setup.

Let me ask your opinion on this. Do you think the often heard statements that the roots of some orchids such as C. walkeriana or Tolumnia will die if they don't dry quickly after watering?

My observation of my own plants and those of others make me think that it's not a 100%, universal thing, because there is a lot more to "orchid culture" than watering.

Like many, I assumed, for example, that tolumnias were impossible in the constantly wet, S/H culture - they sure as hell wouldn't grow that way for me - and their natural conditions would seem to support that....then I met a grower in Ohio who was doing just that!

I think that if the grower can easily and continuously provide "just the right" conditions (whatever that means), any plant can adapt.

[K-Sci]

Originally Posted by SouthPark

That's a nice workable method. Over here, I have only used plastic opaque pots in the tropics with very good (and lots of) drainage holes down the bottom - works nicely too. I just do something along the lines shown in this pic here .... Pic Link.

Sometimes - I use much larger pots than usual, and only use smaller media for the surface region (depth of my own choice) with relatively small orchids (such as seedlings, or some juveniles) - otherwise, I just use one sort of media purchased with some average size.

I've had two walkers in scoria slightly larger than a peppercorn for two years. They're growing like weeds with no indications of any sort of root issues. I used the smallest terracotta slotted pots possible.

Even though the image shows watering toward the rim or outskirts of the pot ----- that doesn't strictly need to be followed. I just dump most of the water at the outskirts, and have the choice to add water further in.

What is the goal of the arrangement in your photo. I'm not sure I'm understanding.
-Keith

---------- Post added at 06:24 PM ---------- Previous post was at 06:13 PM ----------

Originally Posted by Ray

I guess that depends upon one's understanding of the meaning of "constant flushing". My way of dealing with S/H pots is to fill them rapidly to the top and let them drain. That results in a "frequent" flush, if not continuous, returning it to your preferred chemistry. Folks who simply top-up the reservoir most of the time and do such a flush less frequently are letting their plants "sit in a cesspool" as far as I'm concerned, because the reservoir chemistry starts changing pretty much immediately after you water.

Oh. I thought the cesspool method was standard procedure. The two seedling I'm experimenting with are in a plastic tray with water 1" deep. I overflow the tray watering with everything else twice per week, but don't empty the reservoir. The roots are in good health and, in fact, these two plants didn't lose them transitioning.

I think I need to go back and re-read the S/H stuff on your web page.

Like many, I assumed, for example, that tolumnias were impossible in the constantly wet, S/H culture - they sure as hell wouldn't grow that way for me - and their natural conditions would seem to support that....then I met a grower in Ohio who was doing just that!

Maybe you should have tried some KelpMax. (j/K, I would imagine that you did)
-Keith

---------- Post added at 07:47 PM ---------- Previous post was at 06:24 PM ----------

Originally Posted by Ray

In that context, it seems obvious that the smaller the particles, the smaller the voids, so more of the open volume is occupied by water, leading to stifled gas exchange/suffocation (choose one).

You are right in saying that with a small sphere size surface tension will come into play causing gaps to filled with water rather than air. Also, gas impermeable spheres will reduce the cross sectional area available for diffusion. Both these factors will have a stifling effect.

Sphagnum cells are is permeated with channels that can pass moisture or air. This could be seen as an explain for why sphagnum can be very wet without negatively affecting roots. Unfortunately, the resistance to root damage could also be attributed to sphagnum's antiseptic qualities so the forgoing isn't meaningful evidence.



At any rate, there are a couple things that bother me about the stifled gas exchange idea.

First, on one occasion I inadvertently left a mature phalaenopsis pot fully submerged in water for around 24 hours. When I found it, I was sure the roots would have been killed, but the plant wasn't affected. Why?
Option 1: It take longer than being saturated for a day or two to suffocate roots.
Option 2: There is a different cause or another ingredient to root death that wasn't present (and isn't present in submerged S/H roots).

It is easy to assume that the answer is Option 1, but I'm a scientist by training and there are other factors to consider.

Second, if the gas stifling due to water fill between particles is the only factor, it would necessarily follow that reducing the amount of water to levels that would prevent the gaps from being filled (i.e. only moistening the media) would virtually preclude root rot. I've never tried watering with measured volumes of RO, so I have no idea if this would happen.

-Keith

[SouthPark]

Originally Posted by K-Sci

I've had two walkers in scoria slightly larger than a peppercorn for two years. They're growing like weeds with no indications of any sort of root issues. I used the smallest terracotta slotted pots possible.

At what stage were they provided with the pepper corn sized scoria? It certainly is known that orchids can develop roots that adapt to various sorts of environments - where the new roots or extensions of roots grow into a particular media.

But - as for planting a full-grown walker that already has established roots into pepper corn sized scoria - and expecting those established roots to survive ------ very slim chance to no chance I reckon. This is assuming the media stays relatively wet - and the roots remain relatively wet for relatively long periods of time.

But that's ok. If a grower finds a particular method works conveniently and reliably for them for years - decades - then no problem at all.

[SouthPark]

Update - I meant slightly-larger-than-peppercorn-size scoria. Or roughly around pepper-corn size.

[Louis_W]

Originally Posted by Ray

I guess that depends upon one's understanding of the meaning of "constant flushing". My way of dealing with S/H pots is to fill them rapidly to the top and let them drain.

Ya I think I flush about once a week and top up in between. I'm not sure if S/H is less work as far as watering goes for me. I'm motivated by other advantages like the airflow, even moisture, inorganic media, and perhaps most of all the seemingly nonexistent transplant stress. That' last one is pretty relevant to this conversation because as long as you keep the new water level exactly the same as the old one there seems to be almost not change in root conditions. Just remove a solid block of roots and LECA and put it in the new container. No rot and no removal of stale media. Someone did suggest that LECA has a expiration date which was slightly alarming... hopefully it is longer than the natural lifespan of the roots. However long that is... 5- 10 years? Less? More? Probably depends on the species.

[K-Sci]

Originally Posted by SouthPark

At what stage were they provided with the pepper corn sized scoria? It certainly is known that orchids can develop roots that adapt to various sorts of environments - where the new roots or extensions of roots grow into a particular media.

They were both mature plants. They've been growing in it for at least 3 years. I knocked one over last year and did see quite a few roots before I put the loose scoria back. From those I could see, there was nothing unusual about where the roots were in the pots.

I said the scoria was "a bit larger than peppercorns". When I took the photo I concluded that the scoria is better described as the size of canned peas. Photo attached.

But - as for planting a full-grown walker that already has established roots into pepper corn sized scoria - and expecting those established roots to survive ------ very slim chance to no chance I reckon. This is assuming the media stays relatively wet - and the roots remain relatively wet for relatively long periods of time.

There were no indications of die-back.

But that's ok. If a grower finds a particular method works conveniently and reliability for them for years - decades - then no problem at all.

The scoria was an experiment I tried because I received a C. leopoldii from Odoms (I think) that was growing wonderfully in the same scoria (still is). The pots do drain very quickly, and there are a lot of foam peanuts to assure air from the bottom. Having no visibility to the pot moisture other than the terracotta exterior being moist, I water them on the same schedule as plants in bark. This probably means they get good and dry between waterings.

All my other walkers are either in pots with select large chunks of Orchiata, or in baskets with Orchiata, Orchiata and LECA, and one in LECA (an experiment). Photos attached.

-Keith

[Ray]

Originally Posted by Louis_W

Someone did suggest that LECA has a expiration date which was slightly alarming... hopefully it is longer than the natural lifespan of the roots. However long that is... 5- 10 years? Less? More? Probably depends on the species.

All materials build up minerals and wastes over time. How rapidly that happens is determined by what you're pouring on and how much evaporation there is.

Think of it at the gradient in scenarios from LECA staying constantly submerged in a sealed container of solution (i.e., zero evaporation) at one end, and LECA, upon which a solution was poured, then left to stand until all the solvent (water) evaporated, with that process repeated over and over.

In the first case, the content of the LECA will be identical to that of the solution and will never change. In the second case, 100% of the mineral content of the solution will end up in the LECA, then be added to and added to.

In "real life", there will always be some evaporation, so the LECA is bound to accumulate something, and periodic flushing does not extract it all.

[K-Sci]

Originally Posted by Louis_W

Someone did suggest that LECA has a expiration date which was slightly alarming... hopefully it is longer than the natural lifespan of the roots. However long that is... 5- 10 years? Less? More? Probably depends on the species.

Questioning the infinite lifetime claims sometimes heard (implied?) for LECA, hadn't occurred to me other than fleetingly. I only recently started experimenting with LECA, but probably wouldn't reuse it anyway.

The surface or interior of LECA 'plated' by hard or alkaline water minerals shouldn't be much different than the crusty surfaces of terricatta pots. A mineral residue that won't wash off is probably not very soluble, so I wonder what effect this would have. Fertilizer residue should, for the most part, be soluble and wash off, I would think.

-Keith

[SouthPark]

Originally Posted by K-Sci

I said the scoria was "a bit larger than peppercorns". When I took the photo I concluded that the scoria is better described as the size of canned peas.

Thanks for mentioning the size of the scoria and including pics. Roughly pea size is workable.

One of my C. Mini Purple orchids is currently flowering - which I had planted when it was mature/flowering size into scoria having similar average diameter. I think it was sold as 5 mm scoria - average diameter. But the 5 mm scoria doesn't go all the way down - as I think that full 5 mm scoria going too deep could lead to issues with air-movement down in deeper depths. I want to avoid having no (or not much) air movement.

The lower section of the pot has a fair bit of much-larger-size scoria --- eg. 15 mm diameter [pic link]

[Ray]

Originally Posted by K-Sci

Questioning the infinite lifetime claims sometimes heard (implied?) for LECA, hadn't occurred to me other than fleetingly. I only recently started experimenting with LECA, but probably wouldn't reuse it anyway.

The surface or interior of LECA 'plated' by hard or alkaline water minerals shouldn't be much different than the crusty surfaces of terricatta pots. A mineral residue that won't wash off is probably not very soluble, so I wonder what effect this would have. Fertilizer residue should, for the most part, be soluble and wash off, I would think.

-Keith

Being a Ceramic Engineer and orchid grower, I have looked into LECA a fair amount, and about 20 years ago, even helped a manufacturer in Europe design a better pellet.

Originally, LECA was invented as a concrete aggregate- a lightweight filler (and crack-stopper) allowed the construction of taller buildings - and it was later remarketed to horticulture. In concrete, the absorption properties were of little interest, but that, of course, isn't true for growers.

Not all LECA is the same - different shapes, surface morphologies and textures, and widely-varying porosities and internal pore communication, raw materials and additives used, firing schedule and quenching - so each one will have its own set of performance parameters.

The stuff that deposits on the surface is one concern, but the stuff that is absorbed and depositing internally should also be considered, as in most brands, even when unwatered for a long time, the interior still contains some liquid, meaning that the solution can be extracted once rewetted.