Hi Larry,
I saw your post and wanted to share a couple of observations, just noted yesterday actually. I am in the process of repotting a lot of junior plants which had been last done the end of April and beginning of May. Funny thing is I just e-mailed a couple friends last evening about this same thing.

Two different potting mediums were used, coir and one formulated with Pro-Mix. I also had two kinds of coir mix: one already prepared purchased from a vendor last fall, but as I only had little bit of it I made some up myself from a coir brick. I did rinse the coir in the one prepared myself several times having read about higher salt content cautioned by someone either on this forum or elsewhere.

I marked the little pots indicating which mix was used so I could compare. All of these were cared for and fertilized the same way.

What I noticed is that root systems from both mixes were robust and healthy, so no problems there. Also, the centers of all of these appeared okay. Perhaps the ones planted in coir mixes were a tiny bit tighter but not enough to note a real signicant difference, but again this was just for a short period of time.

Where a real distinct change was noted was in the color. The Pro-Mix potted ones were a nice darker green color while the coir ones were somewhat yellowish in appearance. Three of these have dark green foliage descriptions(Kris, Summer Carnival and Cathedral). Both Summer Carnival and Cathedral were in the coir mix while Kris was in Pro-Mix. Kris was a nice dark green. The other two were more yellowish appearing. The other young plants had various colors as descriptions(meaning medium green, variegated, etc.)but most seemed more yellow tinged or off color planted in coir. I don't know if this is from a ph thing or caused from fertilizer absorption being altered in some way or some other reason.

This is certainly not a long term experiment, just some observations made from last springs repottings based on a short period of time.

Unfortunately, I did not note which coir produect was used, already fixed or one mixed by me. Anyway, I have decided not to use the coir anymore. I don't have anything planted in a terrarium so maybe my response isn't really answering your question.

Good question! - Elaine

Hi Elain,

Thank you so much for relaying the information on your little test study. This is really the stuff I wanted to know about. It's quite discouraging though. I know that coir lasts a long time without breaking down. That makes it ideal for terrariums as one does not want to have to do a soil change very often. I don't want to have to change the planting in this terrarium for at least five years. For those of us who grow gesneriads, we are very aware of the breakdown of spagnum. Spagnum will just not be a desirable potting medium for that long. I'm also not getting any response in my question about coir in the terrarium forum. I'm afraid that they are completely sold on the stuff.

This leads me to the question of what to use for the substrate that does not contain coir or spagnum? I definitely do not want to use anything with soil. Oh well, I am still in the design phase and have time to research this a bit further.

Thanks again for responding to my question.

Larry

Hi, Larry. That was one of the major things the study showed; plants grown in coir (with the potassium salts rinsed out) were stunted and yellowish. *Not* healthy-looking. At all. They're currently studying to find out why this is. Go them!

Korina

Larry - hello,

I keep my episcias in a terrarium. Since I want to take them out from time to time, I keep them in their own pots. I made a lining on the bottom of the fish tank from tghe thick layer of an inexpensive sphagnum moss - picked it at Paulino's - then saw a better grade at Echter's - it is for lining hanging baskets. It is more brown then the orchid grade sphagnum. But so far - it looks quite natural, episcias in a fish tank grow well and mostly cover the surface and I get the benefit of the moss antifungal properties.

I tried to put the soil, soil mix with sphagnum etc. - looks like the set gets overgrown and looses attractiveness before the soil deteriorates.

Cheers

Irina

Hi Irina,

I sure hope I am able to meet you at the gesneriad show in two weeks!

This isn't in response to anything anyone has said. It just occurred to me that I need to be a little more clear about what kind of terrarium I am going to make. It's basically going to be a rain forest terrarium. It's pretty small so there won't be a lot of plants, but I'm hoping to have one terrestrial bromeliad along with some epiphites like tillandsia and an epiphitic miniature peperomia. Maybe a small columnea and an episcia if it doesn't grow too large. A miniature African Violet would be nice along with some microminiature sinningias.

I really am not familiar with what orchids are grown in. Is it just pure spagnum? After doing a little bit of research over the last day I am leaning towards a bark, vermiculite and perlite mixture. It seems like the world loves to put gravel in this mixture, but I am not a big fan of gravel in soil. Although gravel would look a lot more natural than perlite. I'm kind of brainstorming here. lol

I may very well put some of the gesneriads in pots and plant them in the medium. That is especially true for the African violet. Even with that I don't want to have a poisonous environment leaching into those pots. Since I'm a little ways away from getting plants (I'm looking at Rob's violet's terrarium plants) I have plenty of time to research this soil thing and be sure that I am left with a medium that I am happy with.

Larry

Hi Larry,

I tried vermiculite as a bottom layer. It actully looks quite attractive - kind of silvery. I would think that the fish tank with gravel would be too heavy to handle. The best episcia for terrarium will be Silver Skies. It stays compact, doesn't catch rot too easily and blooms bright red from time to time. Roots to everything it touches - except gravel I think. I kept a hare paw fern in a terrarium for some time - now this thing needs to find a new home, takes half of the shelf - but when it was small it was quite attractive in a set. And Gloxinia Lindeniana - now called Gloxinella - was good there - leaves are very attractive. Sinningias look OK. Micro-minis - if you keep your tank wery wet, otherwise - just minis. I put S. Amizade in a tank with episcias - and it bloomed there and still looks nice. The only problem - if they go into dormancy, you need to extract them from the tank- otherwise the tuber will rot.

Looks like you are already having fun. It is always work in progress - you can change it afterwards. Many times.

See you at the Show. To my regret I do not have anything to bring this year. My gesneriads are still suffering after move to the new house.

Irina

Hi Larry,

Just lurking around here, am curious abt Coir myself, so I read this thread. When I saw you said "I know that coir lasts a long time without breaking down." I figure I'd best let you know I have found just the opposite!

I tried some Coir for my Hoyas & initially they responded very well (maybe 1/3 coir, 1/3 pumice & 1/3 plain HP mix). To my great chagrin, a year later they started looking bad, yellowing, going somwewhat limp, etc., generally looking pretty crappy. On unpotting, I found that the Coir had broken down very badly, into a sawdust- like yuck, which stayed either too dry, or when kept moist turned into G_d awful muddy mush.

I do keep some small terrariums (currently w/ an Episcia, potted in my AV mix, I think), never tried Coir in that. The Coir I did try was in open pots w/ Hoyas, some plastic, some clay.

Importantly, the above breakdown was in just one year's time. Since you said you'd prefer not to unpot it for a few (5 ?) yrs. I thought I'd better give ya a holler. I quit using Coir for the Hoyas, just use it abt 25% of it in my mix for Haworthias, which seem to really like it & so far haven't had any problems.

If useful to know, the Coir I used came in small dry, compact disks, which one moistens to reconstitute. That's all I can think of for now, other than to say if it were my plan, I'd think twice abt this. FWIW

(PG) Karen

Karen -

I do not think anything should seat in the same medium for 5 years. The fish tank would look like a swampy landfill. And smell the same.

Since my hoya experience is limited - I had one, it was on a sunny window, bloomed all the time, soaked the curtains with the sugary nectar on a regular basis - then I left and my Mom promptly killed it. So I do not know how often you should repot hoya. But seems to me if you will be doing once a year - you can use coir. I guess the same is with a fish tank - if I would be replacing it when it started to rot it would be OK.

But I remember that Korina found a link that showed that coir can actually work as a mild herbicide and suppress the growth... oops - away with the coir.

Happy Hoya Growing to you

Irina

Hi Irina,

I agree abt the 5 yr. business.

But Hoyas like to be potbound (or at least tight in the pot) to bloom (so I keep hearing). So I don't pot them up, rather I change their mix abt every 2 yrs., sometimes every yr., depending on how/what the plant's been doing. If you don't already know, GW has a Hoya Forum, pls. come on by, you'll find friendly & knowledgeable folks there & learn a lot too.

Karen,

People here are exceptional on all forums I checked.

I moved to the house where there is no natural light to talk about. May be enough for spathiphyllum. So whatever can get under the fluorescent lights - survives, the rest needs to find a new home.

No hoya for me. To my regret.

Thanks

Irina

Hi Karen,

Thank you very much for telling us your experiences with coir. That is very interesting to hear about it disintegrating after one year. In that case, there is no reason to use it over a spagnum based soilless medium.

Irina,

You may be right. Five years may be too much to expect out of a terrarium before needing to put down a fresh substrate. I'm sure that it will be difficult to do though. It will probably be looking very nice by then.

Four more days until the gesneriad show! I am planning on being there at 1 p.m. on Saturday. I hope to see you there.

I should also congratulate you on your new house. I hope you get many years of enjoyment from it.

Larry

Larry -

I volunteered to be there at 8.30 to do the clerking. 3G is a small group, needs good people. Please think about it.

Thank you, Larry. It is a beautiful ranch, 40 years old. We removed the carpet upstairs already - it was peed through by dogs - beautful hardwood floors under - could you believe?
Now - basement have a shag carpet in Broncos colors - and it smells...

See ya Saturday

Irina

PS - Think what you want for your terrarium - episcias?

I should stop by this forum more often!

I was just looking at my last batch of seedlings yesterday and noticing very yellow leaves over all. I was thinking heat and too much light might be the culprit because I ended up increasing both this summer, but now that I think back, I believe I mixed coir into the mix. I decided to try it as it rewets more easily than peat, and I am a chronic underwaterer.... I might try repotting back into a coir-less mix to see what happens.

Larry - don't know if you got your orchid medium answered. Orchids are grown in anything from mud mix to chunks of clay. I could probably list a couple of dozen mix and mounting materials that are common - just let me know if you want more info.

I would not recommend a bark mix for the terrarium because it will mold and rot quite quickly. In a humid terrarium, I would guess: cork walls will hold up fairly well, most woods would manage a few years or less depending on the wood, serious hardwoods would last much longer, tree fern chunks I would guess 3 years.

Have you considered hydroponic materials like diatomite (I recently started trying this) or expanded clay pellets like Leca or Hydroton? I have been toying with the idea of somehow making a terrarium substrate that is mainly the hydroponic material, but with pots or baskets of dirt mix buried into it. I would keep an inch of water in the bottom - essentially a semihydro setup. I even thought that a pot of sandy peat buried to be bottom could share the water reservoir and support a carnivorous plant.....

Then the issue becomes salt buildup. Even using distilled water, the hydroponic medium would have to be leached because of fertilizer and the peat mix. I'm guessing that with very little fertilizer, and if algae remains low, then at most I could go for 2 years before a leaching is required.

Now that I think about it, I think I know someone who had a sealed terrarium with long fibre sphagnum moss in the bottom - the moss turned into layers of live moss of various types, and I think he said he hadn't done maintenance in a few years? He had carnivorous plants in it. On the other hand, the lowest layers of live moss would be rather disgusting.....

Just some more chatter to add to the thread ;-)

Just bumping this up for a new grower....

I wonder if they have done more studies to find out the why of this? It's a bit strange, especially because coir works well with other plants. What makes the physiology different? Huh. It's been three years, so maybe there is more research now. If I get time, I'll do some searches to see what I can find out.

Thanks again for the bump.

I do not use fine soil-like coir, I bought some of the coir chunks and added perlite and chunky vermiculite. I started a bunch of leaves and small plants and then moved them into this mix. I am not having problems but am concerned about the salts. Should I repot?

I haven't done many searches yet, but a few. I have found several places selling AV potting mix that has coir in it. Huh. So, it is being used by some people. Now, they may be unhappy people! Or, maybe they've figured out something. Not sure. I'm still hunting for info.

One article I just found, linked below, says that the research is mixed. This Dutch article mentions that they have had encouraging results using it and acknowledge the negative findings from Germany. Salt was the problem.

It sounds to me as if the salt content may vary in them (based on the article. That might account for differences.

I found several references of people using coir and being happy with it.

Here is a link that might be useful: Dutch Research

I was looking for something else related to a fertilizer I'm using on my veggies, and I came across this about the coir that Botanicare offers, "Q: What is so unique about your coir fiber?
A: Our coir fiber has very low salt content, is aged a minimum of 18 months and has finished its decomposition stage. In addition, it is not chemically treated, has an extremely high air content, has extra long fibers and is double sifted to reduce dust."

Not sure how they know it's low salt, but I assume they test it in some way. A place like this might be an option for someone who felt the need to not use peat.

I know this is an old thread so it may be that things have changed. I'm deciding whether to make my own seeding mix our buy it. When I looking at Pro-Mix ingredients, I saw that it contained coir. Maybe it didn't at the time of this post. Unfortunately, it also contains peat, which I'm trying to stay clear of as I know the peat bogs serve an important purpose for things like breathing. :-) It's hard to find anything else, though!

The idea is to use a Canadian sphagnum peat, not a sedge peat. Canadian is renewable... depending on the harvesting technique, sedge peat harvesting is NO-NO.

I do not think there is a media that is totally renewable. We are inhaling valuable oxygen, exhaling carbon dioxide contributing to the global warming... we are driving the cars - not bicycles - to work, we eat meat ... and cows produce GAS...18% of methane is contributed by cows... but if we stop eating meat and start eating vegetation, we will be producing a lot of GAS...

So - everything in moderation. Your small collection of AVs is going to use some peat - and produce some oxygen.

Not following the vegetarian remark, unless it's a joke about beans. I've been a vegetarian for 40 years and I swear I'm gas-normal. :-) I've never apologized for living, either. We all leave a footprint.

I appreciate the fact that Canada has sat on the peat industry, but there's a great deal of difference between putting it all back and restoring the habitat. There's a lot of controversy over whether or not it's even possible; the water table has been changed, the soil has become nutrient rich, and species may or may not have been destroyed. All this is a small matter compared to the real problem: peat bogs are the most efficient carbon sinks on the planet, period. Nothing else touches them. Now, more than ever, we need every inch of carbon sinks we can get. That's my #1 reason for avoiding it.

My other reason for not wanting peat in my seed mix is that I hate it. It stays too wet, then dries out and becomes hydrophobic. It has no nutrient value (which is-actually- fine for seed-starting), is acidic (sometimes good, but not for everything) and retains any pathogens the living moss might have had. By me, it's a lousy soil addition. I always lose seedlings in peat.I'd much rather use clean coir.

Coir, of course, isn't an innocent. You have to find a sustainably sourced product and then figure in the environmental impact of shipping across the globe. Upside is that it's very light and compact, so can be shipped efficiently. There is no perfect solution.

You can replace peat with smallest size rock wool cubes. They won't deteriorate, you can flush the salts out with water and your mix of rockwool perlite vermiculite will be extremely long lasting.

Why I am against using coir - because even if it is not salty low quality coir - it will start deteriorating with time and will kill your plants. The gesneriads require evenly moist soil - which is conducive to a coir decay. Orchids require more of the drown- drought cycle to imitate the natural epiphyte watering routine - so the coir will last longer.

The fact that your peat dried up to the point it became hydrophobic - was just a sign that your watering should be more frequent.

I am not insisting on peat - more of it - it is not working that well in the tropical climate. Plus having a strong opinion about preserving our planet is very good.

Though we contribute much more to the climate change by driving every day - than using a bale of peat in a lifetime.

BTW, Larry - The answer is YES, soaking and straining absolutely leaches the salt. Find one that's OMRI certified (from a sustainable source) and since they've gone to that much trouble, they're likely to have leached it as well. I think adding a cal-mag fertilizer will obviate any salt problem anyway - though Gardens Alive swears that theirs has no such problem. I've read remarks about high phenols in coir stunting growth. A lot of hydroponics growers and seed starters swear by it, but it's something to look out for. Not everyone agrees, obviously. I think it must partly be due the source of the coir.

It's true that rockwool will last a long time - possibly forever. It's not a natural material and won't decompose easily. If you do use it, wear a good mask. It works pretty much like asbestos in your lungs. I used to use it, along with hydroton until I learned a bit more about them. Now I'm leaning toward coir and growstones for hydro and coir for seeding and a bit in the garden bed, but it's a "we'll see" situation.