Sphagnum - Loose or Packed Tight?
 

Whenever I use sphagnum alone as a medium, I tend to keep it a bit loose in the pot - packed enough to support the plant, but not tightly compressed like we see from large nurseries.

I have never understood the "physics" or "mechanics", or whatever you want to call it, of tightly packed sphagnum. (Those of you who know me well must understand my consternation at that!). When saturated, there is absolutely NO free air space in the pot, so it seems to be a great way to kill roots, yet the plants I acquire that's are potted that way seem fine. Is is due to the growing conditions they were in? I suppose that's it, as those plants do not remain "fine" if I don't repot them.

What is it that makes it "good" for some?

I have heard some speculate that the highly-compressed moss simply cannot hold much water, so between plant absorption and evaporation, dries out quickly, but if that's the case, what must the growing conditions be to result in that fast drying. It sure doesn't happen out on my deck.

Good question. I've always wondered that myself. Especially wondered how the grower got the moss so tightly packed in there to begin with. Maybe just barely had roots going to start with that grew down in?

In my care, with one packed in moss, the plant does "okay." But when I repot, the roots at outside may look great but the middle is usually rotted roots and barely surviving roots. I always thought that was because of lack of air flow. But if, as Ray says, speculation says the tightly packed moss quickly dries, it may be the individual's culture... if I have something in moss, I soak the heck out of it each time I water, then wait until pot is light before resoaking. Sometimes two or so weeks plus before resoaking. Perhaps that's where my rotten middle of pot roots is initiated.

Unpopular opinion: I love sphagnum moss for Cattleyas. There I said it.

Confession #2: I do pack it pretty firm.

Confession #3: It rarely gets a chance to dry out in my rainy summers.

Now for the context. Sorry, this is going to be long winded.
This all started when I was talking to Dr. Courtney Hackney when he came to speak at my orchid society. I had some questions about the Rupicolous Laelias and some mini Catts. I was struggling with them and he mentioned trying sphagnum with some reasons behind it. I looked up an article from the St. Augustine Orchid Society, read about it some more, and gave it a whirl.

If the sphag is in a basket or a very shallow pot I usually don’t pack it. I do not use sphag on any of my blooming size, or near blooming size, standard Catts (that are not recent divisions). I also do not use sphag in plastic pots.

I do use it packed pretty darn firmly, it’s definitely compressed, for many of my orchids- My few potted Phals, some of my Sarcochilus, rupicolous Laelias, my two mini Catts, and basically anything else that is in a 3” clay pot or smaller, though I am still using sphag from some orchids in larger pots. I love it for getting my divisions started. I like using for the usual suspects like Bulbos and Catasetums, but those are moisture lovers anyways.

I’ve tried it a few ways and they all seem to work. One is wrapping the entire root ball in sphag, I wrap it till it’s larger than the pot size and then “gently” cram it in the pot. Or I collar it by wrapping the strands of sphag around only the top half of the root system till it’s bigger that the pot opening and cram that in as well. For my Phals that are in larger cylinder shaped pots, I stuff some peanuts in the center of the roots, wrap sphag around the roots and stuff that in the pot...

None of this sounds very gentle, but it has been working great. I do make sure to wrap the moss, like you would if you’re wrapping a Neofinetia, and not just stuff wads of moss in the pot with my fingers. The moss is not rock hard once I get it in the pot, but it is definitely very firm. It holds the orchids upright and if the pots are smaller (I.e. lighter), I can lift the whole thing by the base of the plant. All of my things get watered every day in the summer. Sometimes all day, for several days, with our rain. I will try to remember to take some photos of the root systems next spring (and when I start repotting my Sarcs this fall) and post some pics. These have had some awesome looking root systems with no signs of rot.

This is speculation, but the only reasons I can think this works in my environment are: It’s hot. Very hot. Day and night. Most of my orchid get pretty annoyed at me if they get dry in 100° heat, even with the high humidity. Moss keeps things pretty hydrated. With the moss being constantly damp throughout the summer, that makes the clay pot wet, the wet clay pot keeps the roots slightly cooler, the Catts and Sarcochilus seem to especially appreciate that. Clay pots are breathable, I figure that can help keep things from getting too soggy by wicking some moisture out. That’s why I don’t use plastic. My stuff gets watered way too frequently for that.


Supposedly, the fibers of the moss are better supported when used more tightly. Too lose and the fibers can hold too much water and collapse on themselves. I’ve seen this in my baskets where I have used sphagnum moss loosely; it breaks down quick, turns into slim, some moss falls apart and the rest of the fibers can actually become a sludge brick if I wait too long to replace and refresh it. When I repot my firmly packed pots, the very top part of the moss has some algae on it, but otherwise the integrity of the rest of the moss throughout the rest of the pot is great. Even if I wait a more than a year to repot. I also soak my pots first for a good hour or two before repotting. Again, the very surface of the moss is pretty wet, the rest of the moss is damp like it would be if you soaked some moss and then wrung it out.




I apologize for the long post and a summary is: These are just my observations. I like using it packed tightly in clay pots, where it doesn’t seem to hold too much water, and remains just airy enough to not rot the roots. here is that article I mentioned for anyone who hasn’t read it https://staugorchidsociety.org/PDF/S...ySueBottom.pdf

Absolutely. It is interesting that some situations appear very counter intuitive. I often wondered about that too in the past. I recall once reading somewhere - that the firmly packed spaghnum itself can behave on-the-whole a big wick.

If air-circulation is very good, then the water in the tightly packed spaghnum can disperse - wicked around through the mass. And if air circulation is good around the plant and also through maybe many big holes in the pot at the bottom, then a slow flow or movement of water and air etc can be maintained.

The grower must provide a suitable amount of water during the watering, and must have a suitable frequency of watering. They have to sort this out, or work it out for themselves under their own growing conditions. Too much water will definitely lead to saturation, and undesirable things that follow from that.

Too little water, and the water might not get down into the depths (middle and lower part) of the pot.

Catasetum nursery growers use this tight spaghnum method. Some do it for Cattleya - seedlings and all.

The tightly packed spaghnum 'system' is a system. How it all works and how it is controlled is often up to the grower. If the spaghnum is primed (pre-wetted), then one way to keep this system under control is to periodically add maybe suitable amount of water, to keep the system moist. Good air circulation is beneficial as always. An important thing is to know roughly what might be going on inside at the different layers or levels of the pot. This applies to any kind of growing media.

For myself, I've only recently begun to grow catasetum in scoria - 5 mm average diameter scoria. I haven't grown for long enough yet in this media. My current method with my catasetum is fairly tightly packed scoria, with big scoria rocks piled below the spaghnum mass, and around the sides of the spaghnum mass - all in a pot. So the spaghnum is surrounded by scoria. I don't know if it's necessary to do this, but the catasetum type plants have no problem with it.

I just prefer inorganic - scoria.

It does seem to serve a purpose for the shops. Basically with the spagnum packed tight the roots won't dry up. They won't be getting much light, won' be growing much and thus won't be breathing much either.
They are not like animals although even some animals don't need much air either so not much air is needed when the plants are in shop "stasis".
Once the roots are packed that tight the spagnum cannot be wetted - pretty much guaranteed root rot every time.

But without the shop having to worry about watering, the plants will survive for a month without any care and attention so it's beneficial for the shop - not the customer.

Quite important to know this when giving out advice about spagnum which is not a great medium for uk growers anyway

I always just figured the moss became more tightly packed when new root growth compressed the sphagnum. I also figured that roots growing into sphagnum were adapted for that medium and that growers allow the sphagnum to dry between waterings; that the water retentive nature of sphagnum was financially beneficial to growers. The biggest root rot issue I see with sphagnum is when there is a original sphagnum core that was never removed and filled in with bark or less water retentive medium. In this case the core never dries out and rots the roots at the base of the plant.

Interesting post, all. I follow a method similar to SaraJean. My phals, Oncidiums, and zygos are in a moss mix, some in pure moss. Always in clay pots. My theory is that the clay breathes, so the roots get more air. I have a ceiling fan running, so air circulation is good, I often have to water every two days. As Ray has previously mentioned, I will fill the saucer and let the plant suck up the water. More often, though, I water from the top as the moss approaches dryness. I do not pack it in when repotting but, I do press it in firmly. When it's cold, I run the phals drier. I have never had root rot and some of these plants are very old.

Another scenario is change of hands - from one grower to the next. The grower with their new plant - especially a beginner - might not know the details or watering schedule or amount. Or not know how to make the necessary adjustments or tweaks in the new growing conditions. Such as popping in too much water, and drenching the media (without knowing what's happening under the bonnet - aka hood).

I have such doubt regarding the topic of this discussion too. Hopefully what i get to know can help out at least a little here.

When i repot, i consulted one of the local nursery here. He says tight moss will help to make sure the water in the moss is distributed evenly within the pot due to the nature of the moss that wicks water. Which will assist in judging when to water.

Loosely pack moss will have issues where the top layer of moss is dried and crispy but the lower moss are still moist. This might leads to root rot if the grower mistakenly continuously water it based on the dryness of top moss.

Therefore finding the balance or correctly compact is important.

Sphagnum allergy
 

When I first started repotting new phals, I did not connect
orchids or any of the media with causing me to have asthma. I have not had asthma for a few years and first blamed it on my cat, the outdoor weeds my dogs track in, but finally narrowed it down to the moss. I search on the web for same and found a few things that cited moss allergy but none in connection with orchid repotting or growing in moss.
Any one else have this allergy?:waving

I know sphagnum can have mold issues and you have to be somewhat careful about handling it if have you breaks in the skin and should avoid inhaling the dust when it’s dry. Mold allergies are pretty common. Maybe it’s the fungal spores present rather than the moss itself you are reacting to?

If the sphagnum is nice and wet when working with it, I think potential problems are minimized. If dry, the dust could be hazardous, I have heard of people having respiratory symptoms from it. (I never have, and I use lots of it, always damp) For that matter, the same deal with perlite, only potentially worse - when mixing it in with bark, a good idea to spray it down first with water so that you don't get a snootful of fine silica dust.

I seem to have the allergy and asthma when I am working with the sphagnum wet. I am getting rid of all my moss except for the two that I have in ICU.
ps love your link with info and photos

I agree with getting rid of sphagnum if it’s causing you respiratory issues. For those cases where you find yourself having to work with allergens or dusty media you want to avoid inhaling, those little n95 face masks are pretty handy and work well.

Sphagnum allergy
 

I have mask and gloves. Retired RN, just have to remember to use them:rofl:

My dad used a spaghnum/bark mix (about 3:1) for all orchids in his retail nursery. He also used a potting stick (piece of thick broom handle) to hammer it in tight.

At Silva Orchids & Waldor Orchids, they use mostly a bark mix, but they also use potting sticks to pack it tight into the pots.

I use a lot of spaghnum/bark mixes, primarily for:

• Plants in 3" or smaller pots.
• Vanda baskets.

However, I only press it in with my fingertips.

I think it's a very good practice (ie. what you do). I heard and read of real cases where people just touch dirt from the garden or potting media, and contracts something very nasty that gets in through a cut or something.

In general, there's no issue without doing all of this - as we know. But eliminating the chance or risk altogether with protection will get a thumbs up from me.

I can't speak to the hydro-physics of tight moss (sorry Ray!) but loose moss stays wet and soggy, while tightly packed spag doesn't. The effects are that simple.

Additionally, high quality spag tightly packed in (I don't even wet it when potting my Catasetums) lasts for years, and I water every single day during the growing season. I unpotted several Catasetums that had outgrown their pots a few weeks ago and the moss was as fresh as when I packed it in about a year ago. Many will get repotted next next year and will still have good looking moss.

Bottom line, use high quality moss and pack it in. I'll let Ray (and other smart folks) figure out why it works.

Steve, your moss source?

I assume it never gets wet. The process of moistening the center of a really tight ball of moss is to soak it. For a long time. Spraying and misting will never fully wet a really tight packed moss ball.

I admit I am confused about how it works with air exchange

This professional catasetum grower has moist sphagnum, and packs it like he does in the video : Click Here

That's pretty much my method.

I use besgrow: Spagmoss Sphagnum Moss - At the Root of Healthier Plants | Besgrow

---------- Post added at 06:26 AM ---------- Previous post was at 06:21 AM ----------

Me too, but with dry spag.

---------- Post added at 06:30 AM ---------- Previous post was at 06:26 AM ----------

Here's a bit of pure speculation for you. I think tightly packed spag can't expand with water in the same way as loosely packed spag.

A thought experiment would be to take a single dish sponge and put it into a cup or aluminum can (stronger than a cup) and get it wet. Then put three sponges in the same sized vessel and wet them. I bet the inability for the three sponges to expand would mean they absorb less and dry more quickly. Yet there is still a ton of air space in the "mix."

Maybe it's kind of like - loose sphagnum probably allows for pools of water to be formed among the media. That is, when enough water gets on the bits of the loose sphagnum segments, the water and loose sphagnum combination can form localised layers or pools/clumps of water through out the pot region. And when you have some (or a lot) of these water clumps, then it becomes a bunch of pools.

Pathways, directions and speed of aerated water movement in the media and pot will be affected by the pool regions. Perhaps the more pools there are, or the bigger these pools are, the more it affects the movement (or no movement) of oxygenated (aerated) water, which the roots (or parts of roots) need to survive.

The non-uniformity of this loosely-packed water soaking media could mean significant variability (variations) in aerated water moving activity - some regions might have slow water movement - or hardly any aerated water movement.

But - when the sphagnum is firmly packed and the medium approaches a tighter network or has more uniform water spreading and propagation (movement) properties throughout - working collectively as a wick, then aerated moisture/water can keep propagating (at some desirable rate) without getting hung up too much in any particular region - provided the amount of water we add each time (when it is time for watering) doesn't overload the system - in which case - drowning of roots could still occur.

When packed firmly, the water that is being evaporated (away from the surface of the pot and through holes etc) probably pulls/draws the water from the inner regions (of the packed sphagnum) much more uniformly than loose sphagnum - maintaining some 'suitable' rate of water movement throughout the pot. And - as we know - moving water (even slowly) that contains oxygen, will sustain the roots. But water moving at too slow a pace, or hardly any movement at all (if any medium gets water-logged or saturated) can result in roots somewhere in the pot running out of oxygen, and dying.

The key factor is - adequate oxygenated water movement. The roots generally occupy a fraction of the region of the pot/medium. So we can assume that there will be lots of oxygen carrying water in the medium. The main thing is that the oxygen carrying water in the various regions of the pot keeps moving adequately around any roots regions, and also keeps moving adequately in general - to avoid stagnation. Firmly packed sphagnum can provide the necessary conditions for this needed water movement.

If there is pooling of water (eg. water-logged loose packed sphagnum), then the movement of oxygenated water in the medium might have more variability in speed and directions of movement. Sections of roots in certain regions might use up all the oxygen where oxygenated water movement is very slow (or none at all) - and the roots could take a bad turn after a while.

It could also turn out that loosely packed sphagnum is fine too. It likely depends on how much water we add (and how we apply it - such as controlled spray doses or pouring it into the pot etc), and how we control the system - so that water logging in any region(s) of the pot doesn't occur.

It may be harder to get things right (or do what we need) with loosely packed sphagnum - such as working towards keeping the bulk of the sphagnum moist (without water pooling, without saturation of any region) when watering the media.

Also, good air-movement in the growing environment is likely to help the movement of oxygenated (aerated) water along (better than still-air environment), as well as providing other healthy benefits for the orchids.

We might also need to consider what happens if the medium has some pathways of aerated water movement slow down considerably, or no movement at all --- maybe the possibility of some kind of unwanted bacterial activity or some kind of unwanted fungal activity in certain regions or pockets of media.

One other consideration - pot contents isn't going to be just sphagnum. After a while, there's going to be lots of roots. So how the water will move among roots plus sphagnum is something to consider as well.

In short, when inside the pot, we don't want sphagnum to have water looking watery - like this: Sphagnum - Wikipedia

just my 2c, I am still experimenting with sphag. I purchased a few nice standard cattleya divisions from notable west coast growers Steven Christofferson and OV orchids and saw they both use sphagnum (and sometimes with plastic pots). I asked both of them since I had previously been using a standard coconut husk or bark mix.

Slightly different but overall similar take home message: I was told to wet the sphag and to really squeeze the water out, and then pack it tight. (Also never to overwater, when in doubt wait a day or two). I like the fact that, instead of watering at fixed intervals or guessing when to water, now I let the plant tell me. Yes conditions will dictate how fast the pots dry but their growth patterns really impact how quickly they dry out. (I only use clay pots).

I read a Chadwick article about the benefits of sphagnum on cattleyas although they caution about using it on pots bigger than 4".

Knocked a few plants out of their 5" pots lately, root growth seems quite good overall. The top was crusty and algae laden but the sphagnum on the inside looked remarkably fresh. I think it is a world of difference using squeezed sphagnum packed tight versus the loose sphagnum which really soaks up water imo.

Jmoney -
First, Welcome!

Rather than getting hung up on the details of "which medium" and wet vs dry, packed vs loose, etc... take a step back and examine "what" you're trying to achieve. The "how" will vary depending upon your conditions. For Catts, no matter the medium or container the critical factor is being able to dry out between waterings, and lots of air in the root zone. So it depends on your ambient humidity, temperature, whether you are using plastic pots or open baskets, how frequently you water, etc. There is not one right way... Personally, because I am an enthusiastic water-er and mostly grow outside, I need to make sure that I have an environment where the plants can dry out. My best results come from using large bark, wood (best) or plastic (OK) baskets, and hanging the Catts, especially the larger ones (which exposes them to the breeze) Sphag wouldn't work well for me at all for that group. (It works great for orchids that need to stay damp like Oncidinae and PLeurothallids and Maxillarias) But if you live in a drier climate and/or don't water often, it might work for you.

I gather, from reading bits and pieces of this long thread, that you are mostly talking about catts. I use Roberta's method for most every other type of orchid. I have very good success mixing a touch of any bark, cut up corks etc. with my spagh. I wait to water until the top is crusty, then I drizzle water. If you pour it on, you'll be wiping the floor. For my oncids and phals, I will water from below about half the time. I have failures but, never from root rot. Also my 2c.

I think that's a good approach. I've definitely seen very successful cattleya seedling growth in orchid nurseries ---- with firm-packed spaghnum. As long as the spaghnum doesn't get super saturated, I really do think what people say is true ---- and makes sense ---- as in the firm packed spaghnum behaves like a sponge, and the water in there can get distributed around ------ and not form gluggy regions that could drown or smother roots.

Thanks Roberta! I have been using sphagnum for years but in the beginning it was very much a love/hate. (back then it was mostly phrags). Plants really perked up and put on a growth spurt, but after a year or so invariably they would decline. They were potted "loose" and when I finally got around to repotting it was a slimy mess with dead roots. I chalked it up to rapid breakdown of the moss and needing to repot earlier.

under my conditions the tight packing method produces totally different results. Not saying one is better than the other, and clearly depends on one's growing conditions and watering habits, but just saying the two are night and day in terms of properties...

I have also purchased from both OV & Christoffersen, and admire their results with the tightly packed spaghnum. Having read only the tail end of this thread, it appears that most are talking about large/mature Cattleyas. Size is an important consideration too.

I use spaghnum (coarsely chopped), but only for seedling plants up to 3" pot size, and mixed with about 1/3 seedling size bark & charcoal. That mix is only used in 3" plastic pots with multiple slits in the sides; I pack it fingertip firm, but not hard. This ensures a 3-4 day period of fairly consistent moisture + some air flow.

For 5" & larger I use clay pots, with granular mix II (Catt size bark/charcoal & super coarse perlite in 2:1:1 ratio).

For 3.1/2" to 4.1/2" sizes I use clay pots, with granular mix I (1/2 the bark is seedling size).

For a few larger plants, I use baskets with Aliflor (Leca) clay nuggets.

With this size based selection, I can water everything in the greenhouse at the same schedule (twice a week in winter, three times a week in summer).

My dad, who was old school, used exclusively clay pots, always with spaghnum/bark mix (3:1) and tamped down as hard as he could with a potting stock. Plants grew fine, but it made watering a more cumbersome process, as you had to water pots of different sizes at different rates.

I am resurrecting this long thread, because the post above completely changed how I grow orchids.

I don't have a huge variety of plants and my growing conditions are my conditions, blah blah blah. That being said, I grow ever single one of my indoor plants in firmly packed moss as described above, and it is fantastic.

I was on the verge of giving up orchids because frankly the care was so time-consuming and stressful. Traditional media like bark was the worst, and my plants seemed to hate it, but even semi-hydro was ultimately a ton of work.

Switching to moss as described in Sara's post has been a revelation for me. The plants are growing beautifully, watering couldn't be easier. This method has completely changed how I approach the hobby, for the better! Thanks, Sara!

I heard a lecture on growing Phals in tightly packed moss. I took notes but haven't written them up yet. The gist is the moss is never completely soaked. When the top is crisp just run water over it for one second. That water diffuses through the entire moss ball, leaving it well aerated.

At repotting the moss is dampened but not soaked the night before. It should be flexible, not crisp, yet not feel wet. Wrap it around the roots to form a large ball and stuff it tightly into the pot. That person uses transparent plastic pots so she can see roots. Leave a generous gap below the pot rim for water.

I don't use moss because S/H works well for me. But without S/H I would use moss.

When I receive a new plant in moss I keep it until repotting at the appropriate time. Catts, Catasetinae and Oncidiums use water much faster than Phals. I do soak the moss for those. Note my growing area is warm to hot much of the year.

Alan Koch lectured he uses 7 different potting mixes for different plants to permit watering his hundreds of thousands of plants once a week. Moss is one such mix. He does soak it. I have bought Catts from him potted in moss.

That is similar to my experience.

The best part about watering sphagnum moss is that moss weighs almost nothing when dry. That makes it incredibly easy to tell exactly how much water is in the pot. Much more so than bark.

Unlike bark, firmly packed moss moss wicks moisture so well that surface dryness usually indicates the rest of the moss is almost dry as well.

I don't even feel the need to use clear pots with moss, although it is still nice to have them.

I cant believe that there is actually a thread on this and that I'm not alone in this. I have mild asthma and seasonal allergies which seem to have gotten worse since I started orchid hobby. Initially I didn't realize but over a period of time I've realized that when repotting orchids my asthma gets worse both with wet and dry sphagnum moss also I have allergic reaction on my skin in contact with potting media. Now I make it a point to wear long gloves to cover my hands when working with potting media as well as wear a mask to avoid inhaling allergens. Inspire.of my allergies I still love growing orchids.

I don't have the problem, but know others who do have allergic reaction to sphagnum. There are spores, which are allergens. Certainly, nobody should ever work with the stuff dry... having it moist will reduce what goes airborne. Another common potting material that can be an issue - perlite (sponge rock). It crushes to a fine powder, and it's silica... something that you don't want in your lungs. Again, spraying with water can reduce the dust, but also stayi8ng upwind and wearing a mask are good practices with it.

Almost no plants require one specific growing medium. You can find other media that don't affect your allergies. Most epiphytes can be grown in non-organic media like pumice, LECA, scoria/cinders or pebbles.

This is a good point!