Sphagnumaphobia

[isurus79]

Originally Posted by Fairorchids

Re Bark (Orchiata)
Virtually all orchids outgrow their container in 2-3 years. Thus, I do not see any reason to spend $ on a 'premium' bark. Also, I have had people tell me, that while Orchiata does last long, the pH starts to change after a few years.

The money is well spent since it allows you to simply drop the old pot into a new one without removing the plant. For Cattleyas, they just walk out of their pot (as you well know) and into the new one. I've also heard the pH changes over time (including from Fred Clarke), but I've never noticed any decline in my orchids, many of which have some part of their roots in 5 year old orchiata.

---------- Post added at 08:17 AM ---------- Previous post was at 08:17 AM ----------

This is an excellent thread, BTW. Thanks for getting it kicked off, Keith.

[Mr.Fakename]

Originally Posted by Ray

Speaking of compacting, that is one thing I have never been able to wrap my mind around: how do nurseries get away with really compacting the sphagnum? More compact means less air space, so I’d think that the moss would saturate and suffocate the roots, drying very slowly. What am I missing in that equation?

You're missing hyaline cells. Sphagnum is mainly made up of dead, porous cells that act as water and gas reservoirs.

They are surrounding photosynthetic cells, and provide them with everything they need to perform.

Sphagnum has evolved to dynamically alter its surroundings to trap nutrients/water and also release them as needed, and also wick the contents of hyaline cells evenly throughout the plant.

So when some cells start to dry, surrounding cells give it moisture, their surrounding cells give them moisture and so on; pulling fresh air and distributing it evenly.

Of course this system works better on live moss, but stays functional in our plant pots.
Fascinating stuff, really.

[Roberta]

With regard to the pH change of Orchiata, it may depend on the water. Fred Clark of Sunset Valley Orchids has observed that - apparently the product is calcined to maintain neutral pH and for Fred, that leached out in a few years leading to a lowered pH. The Kiwi bark that he uses and sells is also New Zealand pine bark, but doesn't have that treatment and works better for him. BUT... he uses RO water exclusively. I tested the hypothesis on my own Catts... Tested the water running through the pots that really, really needed repotting and compared to the (city) water that went in. It dropped the pH from 7.8 to about 7.5. A few organic acids are no match for my calcium-loaded tap water. So like anything else in the potting medium discussion, "It depends" on other factors.

[Shadeflower]

Originally Posted by Mr.Fakename

You're missing hyaline cells. Sphagnum is mainly made up of dead, porous cells that act as water and gas reservoirs.

They are surrounding photosynthetic cells, and provide them with everything they need to perform.

Sphagnum has evolved to dynamically alter its surroundings to trap nutrients/water and also release them as needed, and also wick the contents of hyaline cells evenly throughout the plant.

So when some cells start to dry, surrounding cells give it moisture, their surrounding cells give them moisture and so on; pulling fresh air and distributing it evenly.

Of course this system works better on live moss, but stays functional in our plant pots.
Fascinating stuff, really.

I honestly do not think it has anything to do with any of that.

It has to do with mass.

Did you ever play softball when younger with those soft spongy balls? Well if you carry on playing with them in the rain they get soaked and take days to dry.

Take a tennis ball on the other hand, dunk that into a bucket and it will be dry an hour later.

Why? because the tennis ball is lose and fluffy. The softball is big and compressed.

So the smaller the moss ball the more compressed it needs to be otherwise it dries as fast as a tennis ball.

The bigger the moss ball, the more it acts like the wet softball which is less good.

So it's all got to do with the size, small moss balls dry faster and need to be compact, big moss mounds need to be loose and airy.

[isurus79]

Originally Posted by Ray

Speaking of compacting, that is one thing I have never been able to wrap my mind around: how do nurseries get away with really compacting the sphagnum? More compact means less air space, so I’d think that the moss would saturate and suffocate the roots, drying very slowly. What am I missing in that equation?

You just have to try it yourself, since it really works! Super compact spag dries almost as fast as bark.

For a thought experiment, you could think of a super compacted sponge in a cup. The amount of of water absorbed by the sponge is a tiny fraction of it's actual capacity, which is why it dries so quickly. Same with spag. There's still enough airflow, most likely because there isn't nearly as much water in the pot.

---------- Post added at 10:30 AM ---------- Previous post was at 10:28 AM ----------

Originally Posted by Mr.Fakename

You're missing hyaline cells. Sphagnum is mainly made up of dead, porous cells that act as water and gas reservoirs.

They are surrounding photosynthetic cells, and provide them with everything they need to perform.

Sphagnum has evolved to dynamically alter its surroundings to trap nutrients/water and also release them as needed, and also wick the contents of hyaline cells evenly throughout the plant.

So when some cells start to dry, surrounding cells give it moisture, their surrounding cells give them moisture and so on; pulling fresh air and distributing it evenly.

Of course this system works better on live moss, but stays functional in our plant pots.
Fascinating stuff, really.

Oh wow, this is interesting! I'll have to read more about this.

[K-Sci]

Wow, the responses on this thread are even better than I had hoped. Ray's description of a love-hate relationship with using sphagnum is pretty much why I made this post. I kept all my orchids in bark mixes for decades moving anything that came in sphagnum into bark the first time new growth started. I recently thought to change some over to sphagnum, but didn't get the greatest outcomes.

Apparently many phalaenopsis growers use sphagnum. The last full size phalaenopsis I got from Hausermann's a couple years ago came in a 7 inch plastic pot with firmly packed moss. When I went to repot about a year later I found that all the roots below the top inch of the media were dead despite my attempts to water only when the sphagnum was just shy of becoming crispy. Subsequent to this I've planted one full size phal into moss, but left it loose as Ray and Kim suggest.

Kim, you said that if water pools on top of the sphagnum then I have it too tight. Water could not pool on top on this one, but this experiment isn't complete as this phal is very slow growing and not yet established.

With the exception of my Neos which are wound with traditional mounds a strand at a time (photo #1), I have been packing the sphagnum tightly copying what I see for many of the phals I've purchased that look like the attached pic (photo #2). These are often in moss packed rock hard. Some, like the one in this photo have so many roots I can't even get a finger in to check the media. Fortunately, these usually come in clear plastic pots so I can check them visually. Perhaps tightly packed moss only works for small pots such as these.

Leafmite, I think you are spot-on concerning the use of premium or better spagmoss. I've tried others and have an area of my garden that is mulched with product that was too crummy to use in the greenhouse. I have a good supply of the Premium Spagmoss now, but finding this stuff is tough and the prices are insane. The super-premium uniformly long fiber Spagmoss I use for Neos sells at prices that rival silver, apparently due to the extreme covid politics in Australia and New Zealand.

Isurus79, I am an Orchiata fan as well. I'm wondering if the growers who have problems with acidity use Orchiata that is too fine without something like foam peanuts in the bottom of the pot. I fill pots 1/4 to 1/2 way with peanuts so there is a lot of air space and the media core will be able to dry. I attached a photo of my Bryan Wheeler 'Grandson', which has been potted up this way. It is now in a 10" pot and is growing and flowering like a weed. Incidentally, last time I posted a photo of this plant some people marveled at the lack of stains on the outside of the pot. I recently noticed that this pot, though ceramic, doesn't sweat.


I'm out of time for now. More later.

-Keith

[Roberta]

I am very fortunate in having a nearby (relatively) nursery-supply store that usually has the good sphag. So I stock up when the supply starts to run even a little low in case they're out of it the next time that I go there.

[Leafmite]

I keep a supply of good quality NZ sphagnum on hand, too. When I get low, I order more.

[isurus79]

Those are some great looking plants, Keith!

[K-Sci]

There is a very interesting discussion above about hyaline cells, moss mass, compact sphagnum vs loose dry times, and related topics. Here's my take.

Sphagnum leaves are composed of a geometric pattern of photosynthesizing cells that enclose bundles of long narrow structural/capillary hyaline cells which are dead at leaf maturity. The cell walls include protein antibodies that account for sphagnum's antiseptic qualities. Unless sphagnum is extremely saturated, the long hyaline cells with holes along their sides contain both air and water.

The capillary action of the hyaline cells accounts for sphagnum’s ability to move moisture uniformly throughout the moss mass. I see this effect with Neofinetia where the pots have legs, but a single strand of sphagnum hanging down into pooled water can cause the media in the entire pot to become dripping wet.

Although this is speculation on my part, it seems likely that the hyaline cells provide channels for air movement throughout the mass when the moss isn't saturated. I'm convinced that this is why root suffocation doesn't occur with sphagnum even when the moss is very wet. In poor quality sphagnum or as the sphagnum breaks down, the hyaline cells are disrupted and the moisture and air distributing properties are lost, making root suffocation much more likely.

What about the effects of packing and mass size?

For a given packing density and the same uniform moisture distribution, a large sphagnum mass will dry more slowly. This is inevitable because the volume of a sphere (for example) increases by r cubed (4/3 πr^3), which is faster than the r squared rate of increase in surface area (4πr^2). The same holds for all relevant sphagnum mass shapes.

What about drying rate and packing density?

Moisture is held in sphagnum between strands and within strands. If the pots are the same size, the evaporation surface areas is similar. Tightly packed sphagnum has fewer large areas between strands to hold moisture and more fine capillary spaces in the hyaline cells. It is speculative, but it stands to reason that loosely packed sphagnum can hold more moisture than packed sphagnum because of the larger spaces between leaves/stems/strands. Holding more moisture would cause it to dry more slowly for the same evaporative surface are. The drying rate would be similar if both the loose and tight packed media contained identical amounts of water.

What about dry times for bark and sphagnum?

In my experience the sphagnum hard packed in my small phalaenopsis dries in 10—14 days where those in bark dry in 5-7 days in my current winter schedule. This is true for those in Besgrow and even more true for those I grow in an Orchiata and LECA mix. However, how long it takes for sphagnum to dry will very heavily depend on how much water is applied when watering. If I watered my phals in hard-packed sphagnum filling the (intentionally shallow) basin above the moss and allowing it to soak in only once, it will be dry in a couple days. I usually fill the basin 2-3 times. However, I often receive plants with very deep basins above the moss. Filling the basin even once can result in soggy moss.

-Keith