I like that it is made from recycled glass and made in the USA. I was going to get some a few months ago, but I got Geolite instead, which I have not yet even opened yet. I'll have to grab a bag next time I'm near the Hydro Shop.

You should rinse it well when you first open it up - there's lots of fine dust in the bag from sitting in storage and being tossed about during delivery. This is the one thing I think is worthwhile to remove (as opposed to sifting the bark and/or peat moss, which I didn't bother to do). I had actually forgotten that!

It's an important point also that this IS recycled glass and you don't want to breathe any of that - just as you don't want to breathe any of the dust from the gritty mix ingredients. Just wear a regular 99c dust mask when you first open the bag and rinse the dust out of it, after that I've not bothered and the dust doesn't seem to recur.

It can also have sharp edges straight out of the bag, but I always wear gloves for this kind of thing anyway. And the edges get worn down over not too much time.

Last year I used growstone in some mixes but I cannot really tell if it is doing any better than either 511 or gritty. I had been pretty happy with both 511 and gritty mixes but we do not have the same blazing heat as you have.

Apparently there are smaller size available too but I could not find it locally here. They have three sizes: The small is too small size range (less than 1/8), the medium is more towards larger size (1/8-3/8) than desirable for bonsai and then there is the really large 3/8-3/4 inches. I think I got that last time.And the coarse size seems good as a substitute for perlite in 511 type of mix.

I think I will try to see if I can get the medium bag here. Looks and sounds promising.

Even before I got sick this past winter, my Growstone mixes were doing better than the gritty-like. And I was doing my best to be scrupulous about keeping up with the maintenance.

However when I talked to the ag research prof about their gritty-like mix, one thing they told me was that in their research, their gritty type mix (which doesn't use any Turface) needs to be watered with a fine, widely dispersed spray so that you don't get little rivers running through it leaving dry patches behind. This is fine in a greenhouse, especially since they do water reclamation (this is a desert after all, we try not to waste too much water here - at least those of us who eschew green grass lawns do, LOL!).

However, on shelving in my closet - not an option. So I was floating the pots with the gritty mix. Well not really FLOATING so much as putting in a bucket of water where they promptly firmly seated themselves cuz them suckers is HEAVY even in small pots.

The big advantage I see in the Growstone mixes is they are just easier to care for, the one expensive ingredient in it (the Growstone) is reclaimable and reusable for YEARS (I actually haven't opened my last bag of Growstone because I can just recycle) and it avoids, or at least vastly mitigates, compaction. No other mix I have ever used has been so compaction free.

If you keep on top of things and have better facilities than a closet full of fluorescent lights and plants (it was at least ventilated - where I am now I have LOTS more space so the closet is a thing of the past) then gritty mixes may be fine for you. Mind you from my experience a Growstone mix is still better, at least for what I do, but that doesn't have to mean that gritty mixes must all therefore always be terrible. And I suspect using it with cacti and some specialty plants with very specific demands as far as pH etc. may be trickier than what I've done with it.

But for those of us who are home growers with less ideal circumstances would be better served going to a Growstone mix.

There are lots of "professionals" who use similar mixes based on natural pumice, which is pretty much the same sort of unobtanium as is the Turface. So I think there is lots of room for testing out Growstone mixes in a variety of situations even for breeders of rare or difficult plants, and certainly Bonsai growers who have tried the stuff have had some good results.

However keep in mind that Growstone is NOT an exact duplicate of pumice. I think it is BETTER in many ways, but it is different. Pumice tends to be roundish. Growstone is pretty much rectangular with actual edges. Growstone is actually far more porous than most pumice, which seems good to me but perhaps there are situations where that would be a problem. Growstone weighs less. Growstone pH has yet to be established - I sent email to the company twice (not recently, too busy and/or too ill) and never got a response on that question.

I am so enthusiastic about my Growstone mixes. And its been getting harder and harder to get good material for container mixes - last year my local Home Despots and Lows both stopped carrying anything even remotely resembling pine fines at all, and all the peat moss I can get locally is that super fine stuff they think you're going to stick in a lawn spreader and spread all over your lawn. Vermiculite hasn't been available for decades. I hate perlite with a bloody passion and have never used it and don't understand why anybody else does - all it does it take up space in the mix, it isn't porous, it doesn't make air available to roots, it doesn't hold water, it doesn't hold nutrients, and it floats to the top and looks ugly. It floats because it is lightweight and there are "air pockets" inside it - but roots don't grow into it so that oxygen is not available to plant roots. None of which really matters since HD and Lows have both stopped carrying the big bags of coarse perlite anyway so even if I wanted it I couldn't get it.

Growstone mixes are saving my garden a$$.

Container culture is always by a balance between what plants want and what humans want or do not want. It is great that you found your sweet spot with Growstones. What I am not clear about is how you are using it. Are you using it in pure form without anything else? I presume you are using the GS2 version which is between 4mm and 9mm particle size. Or the larger one - GS3?

Perlite is definitely one of the components I do not like much. Because it disintegrates and floats to the top. It does hold significant water but mostly near the surface and not inside. Plants can be grown in pure perlite too. And with care most of it can be recovered when repotting. It does need a mesh or something to hold it down in the pot and the pot needs to be anchored too.

Turface and grit are both pretty durable and reusable like lava and pumice. I have not seen any significant degradation of turface myself. In bonsai world people also use pure turface, lava or pumice for certain plants. For most bonsai the weight of the mix is a good thing. The pots are shallow and so the weight of the soil helps the plant to stay put. Wiring/Anchoring of the plant is still needed though.

Watering gritty or bonsai mixes is a learning experience. Water will run straight down in any well aerated mix. I bet it does the same in growstone too. The basic trick is to water gently and slowly. Indoors I use a long narrow spout watering can and water plants like a "scanner". To me it is not a big deal and not every plants needs watering at the same time. So I am not in a rush anyway. A newly repotted plant in gritty mix does need some extra attention initially when the plant is establishing itself in the mix. But if it is done when it growing fast this initial phase is about 2-4 weeks.

Next spring I will use growstones and try it out as a substitute for turface.

Lastly may be it will be interesting for many too see pics of your plants in growstone based mix.

Unless crushed, perlite does NOT disintegrate. It can be washed and reused and holds up indefinitely.

Where is all this misinformation coming from???

Disintegerate is not the right word - it implies it happens on its own. But perlite does not hold up indefinitely either. That is also a piece of misinformation. Poking the soil when packing in around roots while potting and bare rooting using a root rake both mechanically damage/crush perlite. Perlite crushes easily - big lignified roots crush perlite as they grow. I have yet to see perlite still intact as it was day 1 in a 511 mix.

Added: For outdoor plants I can also think of freeze-thaw cycle doing a number on perlite.

Well, I have used it for years (25+) in my potting mixes and unless I step on it, it does not disintegrate or crush. So yeah, I consider that as indefinitely :-)) And most perlite resources will tell you the same: "it does not rot or otherwise deteriorate but continues to function in the growing mix".

Zensojourner, thanks for sharing that info. Hope your health is better. I might have to give some a try. I wonder if PH is a positive factor somehow. Definitely lots to consider.

Perlite IS easily crushed. I've never met a piece I couldn't crush between my weak little fingertips. Every time I buy a house plant it comes in a mixture with perlite in it. I hate the stuff. It does NOT hold water - you will get some apparent "wetness" that is just surface tension. If it DOES hold water - there is research that shows the smaller crunched up sizes will hold water where the coarse grade basically does not (other than surface tension) - then it isn't contributing to aeration. Because plant roots do not grow through it they have to grow around it. Internal air pockets not open at all to the outside have absolutely no effect on aeration. Plus it floats to the top and moves around in the mix. And its ugly.

I've been gardening indoors and out for over 50 years now. In all that time, perlite has never been of any use to me. If it works for others, keep on doing what works for you. I've just never ever seen any positive benefits from using it. If that makes me a perlite bigot, so be it.

I used to make a mix that was mostly vermiculite, peat, and bagged potting soil (which was the only way I was getting suitable bark into the mix, basically this was as close as I could get to the original Cornell mix, minus the perlite which in my experience didn't do anything) and the one thing I didn't like about it was how quickly the vermiculite broke down and led to compaction. The Growstone mix is superior to that.

Actually I wouldn't argue with you if you said gritty mix was superior to that for you and whatever you grow - but I did well with it for whatever reason, while my as close-to-gritty-as-I-could-manage was decidedly inferior to anything I've ever used before. But don't tell me it must be inferior to your gritty mix for all purposes if you haven't given it a fair shot.

While we're at it, I don't see the Growstone as a Turface-replacement. I see it as a far superior ingredient to perlite in Cornell and Cornell-like container mixes. It's still not a 1-1 equivalence, but rather a different way to compose a container mix that solves a lot of problems many of us have with gritty and gritty-like mixes.

Sieving. Breaking down chunks of bark that are too large. Trying to find the ingredients. The weight. The rigorous attention to detail involved in watering and providing nutrients appropriately. As an alternative to the 5-1-1 mix, Growstone mixes seem to avoid any noticeable compaction for at least the 3 years since the last repotting. Or perhaps the compaction just doesn't matter given the porosity to roots of the Growstone.

About 80% of my remaining curry leaf trees should be repotted now - noting that none of those are the ones that were started and grown in my gritty-like mix. Probably should have done it at the beginning of spring, but ... illness. I was lucky I got them moved outside before I hit the skids again, LOL!

Every gritty-type mix I tried took HOURS to compose. Sure, there is equipment out there that eases many of these tasks - but as a small home grower most of that equipment is out of my price range. It killed my back too. But with the Growstone, I scoop using 2 gallon buckets, Growstone, peat, and bark (I was actually using Mountain Magic Soil Pep) or Growstone and a potting mix (to which I may add a bit of peat moss if it seems light on that), then I just run my (gloved) hands through it and toss it around to mix it up until it "looks right" and eh, voila - she is done!

The one pre-prep thing I have to do is rinse the Growstone when you open the bag. I got some coarse vinyl window screen or nylon or whatever the flexible stuff was and made a bag of it and dunked it up and down in a big plastic tub and shook it around some. It is so lightweight that even weak ancient no-energy me could do that without getting all worn out.z

Somewhere I actually do have the ratios I was using for the Growstone mixes but at some point I just got a feeling for what "looked right". Probably not all that helpful to people who want to repeat the mix, LOL!

I'm using the middle size Growstone, GS2. But I intend to give the GS3 a try. Obviously not THIS year. Particle size doesn't seem to matter with this substance when mixed with potting soil or peat/bark. The roots grow right through it so it is no impediment. I won't say that the GS3 is just as good without trying it but I think its worth giving it a try. It may work with some plants and not others, or the size of the plant may matter. I want to see.

Plants CAN be grown in nearly anything, including perlite. It just depends on how much effort you are willing to put into it, and at my age and my physical condition, that would be as little as possible, LOL! For one thing perlite won't hold nutrients so there's a whole world of chemical adjustment I just don't want to get into.

Turface does not reliably hold up over time. Some batches do, some don't, according to the research scientist I spoke with a few years back. Also quite frankly nearly everything that goes into gritty mix is too small in particle size. INCLUDING the Turface, which I have never been able to lay hands on anyway. I had some of the car store oil absorbing stuff and tested it through freeze-thaw cycles and discovered that it does break down over just a couple of weeks I think it was. Now if you live in the tropics, or your plants are all HOUSE plants, that is unlikely to matter (freeze thaw that is). And that was calcined diatomaceous earth, not Turface (calcined clay). But even so - explain to me, if you please, how you sterilize mass quantities of Turface to reuse it? HINT: I'm not autoclaving it and I won't put it in my pottery kiln either, LOL! (JK - I don't have a pottery kiln. Though I would like one.)

Growstone won't hold up "indefinitely" either - but after 4 years its still not noticeably changed from when I first mixed it up. And I don't need to go poking pencils or knitting needles or chopsticks into my mix because the nature of the Growstone ensures plenty of aeration.

Also in the interest of experimentation, I topped some of the plants with bark mulch and left some unmulched. In the mulched pots, the Growstone did not float to the top. In the unmulched pots, some Growstone did rise up - apparently as a result of watering disturbing the top layer of the soil allowing some Growstone to float up. Nowhere nearly as bad as perlite does and it took more than 2 years for this to be visually obvious. Simple solution is to mulch, which has other benefits as well anyway.

You've got a point about the positive aspects of weight in a shallow bonsai planting. It might also be helpful to stabilize very large plants in very large pots in high wind conditions. But I'm not doing any of that - I am growing garden plants and curry leaf trees in fabric pots that I need to frequently schlep in and out. This past week temps have dropped to the freezing point and well below the 50F that is safe to leave my curry leaf trees out. My guys do better when I can put them out after temps rise above 50F and take them back in before it drops below that.

Next week temps will be in the 70s again (it was 44 today, and low 30's last night, and we got hail and sleet). But overnight temps next week will still be in the 30s with a few 40s projected, even when it approaches 80F in the daytime. So my guys will do better outside during the day well into October here, but I have to bring them in every evening, and doing that with a much heavier gritty mix is simply beyond my capabilities. Certainly not in the fabric pots I favor! Even if it were not - I would STILL prefer the Growstone mixes. They've just been way more bullet proof for me.

@pete - contrary to what some people espouse, I'm quite fond of peat moss. I suspect that the amount of peat moss I use is in excess of what most people would even consider. I have considered the possibility - nay the likelihood, LOL! - that the highly acidic peat moss is being counterbalanced by any alkalinity that may exist in the Growstone. Or, since I rinse it well before use, that washes away the smaller particles that are far more likely to leach into the mix and change the pH. Or or, perhaps bleaching it to sterilize it xcounteracts any putative issues with pH. Or or or my tap water is pretty durn alkaline to start with - around 9 I think - so maybe THAT is what is moderating peat acidity. Or or or or, maybe all of that adds up to more than the sum of its parts. Or or or or or - none of that is true at all, LOL!

I really can't say as I do not have access to adequate methods or equipment to actually test that. I do know it has been working for me.

Seriously, I was on the verge of giving up on container growing ANYTHING, due to failure after failure with the gritty and gritty-like mixes, including the fact that Turface remains unobtanium for lots of us. I did have one guy get snotty with me several years ago - he sent me a link to a purported supplier of Turface in the area in which I lived at the time. I did check it out, and they would be HAPPY to sell me the Turface - a pallet load (about a ton I think, or maybe only half a ton) at a time.

Even the 5-1-1 was not possible due to not being able to find affordable pine fines. Since vermiculite (in the very coarse grade I always used, you could still find the fine grade which is useless for anything other than seed starting or rooting IMO) disappeared decades ago, I was down to peat moss and potting soils which I DID make work - but really never liked and certainly wasn't going to work in the High Sierra Desert. It just wouldn't hold enough water to withstand the aridity without getting waterlogged. The worst of both worlds, you might say - dries out too quickly in the upper region while remaining a swamp at the bottom.

The Growstone mixes have changed all that.

I hate Pearlite too, its too small and dusty. Unless you can find BIG CHUNKY pearlite, it IS usless. I got a name brand from a big box store and it was 1/16" to dust... a half a bag of dust.

Exactly what are you doing with your plants that your pearlite gets crushed after it's potted?!?!

I'm going to try the growstone though, I will give it a fair shake. I subbed the pearlite with DE (NAPA 8822 and Opti-Sorb) in my 5-1-1 last year, due to my salvias in pots that were very water hungry...probably from being in pots that were a bit too small. It worked very well, and pending the deconstruction and analysis after I take the pots down, I'll probably never use pearlite again.

That being said, Pearlite DOES work.

I found my original "formula" for the Growstone mix.

3:2:1 peat-bark-Growstone

Yeah, that's a lotta peat. That's because peat is the ONLY ingredient I can find at all any more - I was using Mountain Magic Soil Pep for pine fines which it really isn't, but that's not locally available any more, nor is anything else in anywhere near affordable quantities - eg more than a quart but less than a dumptruck load.

When I couldn't get the Mountain Magic Soil Pep any more (which is more composted pine bark than actual pine fines anyway) I went to whatever bagged container mix I could find affordably that had no sand and as much bark in it already as possible plus peat until it "looked right" and used that at 4 to 5 parts to 1 part of the Growstone.

Pretty soon I was just mixing it all together until it "looked right". They all seem to have performed about the same. I may know better after I repot next spring if there were any differences under the mulch layer.

@mblan13

who thinks "pearlite" DOES work

Maybe "pearlite" does. But perlite does nothing of any value. (Sorry. Couldn't resist. Anyway.)

I'm sure that the reason you subbed in calcined DE for perlite, and now state you will never use perlite again, is because it was working for you, right? <VBG>

What am I doing that perlite gets crushed? REPOTTING. That's pretty much all it takes, LOL!

Coarser grades of perlite are also getting hard to find. Neither Home Despot nor Lows sells it any more, and I believe that is nationwide, not just my local stores. Of course you CAN get higher grades of cleaner perlite at hydroponics stores - at 3 or 4 times the (former) price. Actually you CAN get lots of this stuff for lots more money - my local "greenhouse" sells pine fines for about $60 a bag. Yeah. That's a no on that.

zensojourner

It is great for you to share your positive experience with grow stones...

Nobody is arguing with you against grow stones. But you do have some of the info about perlite mixed up. If you don't like it - NP, don't use it. Yes, it does float because it is so light. It could be substituted with pumice - but pumice is not as readily available to many (just as turface isn't to some) and many ppl do consider cost of material - you do too. Same with growstones - they are not inexpensive. I could say exactly same about vermiculite ("I hate it with bloody passion...") - I would never use it in a mix - that is what I think of it. But everything has its use (and so does vermiculite). All your posts are mostly rant against perlite...yet nobody is telling you/forcing you to use it. Do you know what total porosity and water holding capacity of any substrate is?

Btw, doing thaw-freeze test for turface (or any other substrate) is not to find out how it holds during freeze/winter. It is to find out if it will turn to mush or not. Freezing and thawing it will produce fast results instead of just wetting it and waiting for weeks or months to see how it reacts after subsequent watering. Some bags are of inferior quality (I have not have that experience yet), as are many of oil absorbent (any make). Cat litter is used a lot as substitute for turface - but one has to know which one to use and definitely do freeze/thaw test. So one should get proper info about any substrate and decide which one to use. And, as already pointed out, cost is important to many. There is np with using different materials, important is to know how they perform on their own and in a mix, and using them in proper proportions.

Many ppl are using LechuzaPon ready-made mix. They have great results - and yet, someone posted about having problem with a batch they purchased. It is very possible that batch happens to be defective in some way rather than saying all LechuzaPon is no good...

I use perlite a lot (can't get pumice easily). Have about 300 pots of succulents, and they are growing very well. Some mix is 50/50 grit/perlite, other perlite+grit in equal amounts + smaller portion of turface. I have potted some in a mix of grit+turface - any of them are doing well. These mixes are fast draining and well aerated. I keep all my plants outdoors from Spring to late Fall, and indoors during winter. They are all exposed to elements outdoors and get rained on (that is how they get watered most of the times! :) - I would protect some succulents if there was excessive rainstorm/many consecutive days of heavy rain.

I use lot of chunkier perlite in potting mix for other plants too (easy to find in hydroponic stores), even veggies that I grow in containers. I would actually use gritty mix if it wasn't heavy in big pots :) Perlite will float to surface eventually but not in a day or few, but I don't see it deteriorating as you said. I do not have (yet) 50 years of growing plants behind me so can't say how they will (mixes) perform after many years. Actually, I probably never find out since container grown plants need to be repotted eventually...so nothing is in same mix for many, many years :)

Edited to add: didn't see your last post as I was typing mine...have to read it yet but I find buying in bulk (from hydro stores that carries bigger bags) is actually more cost effective than buying smaller bags in any BBS ...and that is in Canada, where we pay more for everything -:(

Yeah - not "ranting" against perlite so much, and I wouldn't use vermiculite any more either. Neither are very good container components over the long haul. It (vermiculite) was just all I had access to at the time and it worked well enough but compacts too quickly. Perlite does nothing at all, but again - that's all that is available to some people.

And btw, talking about disinformation - perlite and natural pumice are NOTHING the same, not even functionally. Totally different. One substituted for the other is a wild change in composition and function. Might as well say you can sub peat moss for bark. Just because they're both organic doesn't mean they serve the same function. Anyway.

Growstone is just better and is not a "replacement" for anything so much as a component of a modified Cornell container mix in its own right that has worked well for me and the plants I grow, and allows me to eschew both perlite AND vermiculite entirely. And turface, and Oil Dri, and cat litter, and 8422 or whatever that number was, etc etc etc, LOL!

And oh yeah, that's the 1.5 cu ft bag that runs about $35 last time I bought any. And due to its reusability I still haven't opened the last bag I bought. They used to sell it in a 2 cu ft bag but I'll take what I can get, LOL!

I said nothing about perlite "disintegrating". That was someone else. I DID comment on its crushability, which is beyond denial and actually what the other guy meant when he said "disintegrating" (and later clarified himself).

What is perlite, after all? Basically tiny little irregularly shaped ping pong balls you put in your container mix. And they do all that buried ping pong balls would be expected to do - hold a bit of moisture on their exterior due to surface tension, take up space, float up to the top (yes, in a "few days"), until they are crushed due to weight/mechanical pressure and thence cease to be any use at all.

You CAN grow stuff in perlite. You can also grow stuff in plastic bits. There are lots of totally manmade substrates out there commonly used in hydroponics (actually Growstone is one of those). That doesn't make all of them equally useful in a container mix.

I'm not sure where the "many many years" thing is coming from. Of course plants need to be repotted from time to time (sometimes "time to time" is 25 years though - take snake plants for instance, that need to be pot bound before they will flower).

But saying "nothing is in the same mix for many many years" is like saying nothing is watered with the same water from one time to the next. Water is water. (and yeah I'm ignoring issues of pH and dissolved mineral content etc - but water coming out of your tap yesterday and today is more liable to be virtually identical than less).

Just because you water the plant next time with "different" water doesn't mean you've changed anything significant. Repotting into the same container mix doesn't change the fact that it is the same mixture (formula) you used before, even if all the molecules are different. So not sure what you're on about there.

Your experience is your own and as stated previously, if it works for you, great!! But just because you have had a different experience or what you consider an unsatisfactory experience using perlite, that does not justify making blanket statements about its ineffectualness or unsuitability for a container mix. Whether you care to admit it or not, perlite does offer considerable value to a container soil mix and that's why it is so often included in commercial mixes and is advised for inclusion in custom mixes. This is not made up stuff - perlite's ability to absorb water, maintain stability and add to aeration are highly documented.

It's great that there is an alternative product you like (or even prefer) and discussing it here brings that to light to other container gardeners as well. But it is a very specious assumption to determine based just on your single experience that it (the Growstone) is far superior to other similar products and that they in turn, are therefore worthless. Too many others have had equally rewarding results growing plants in more conventional soil mixes and are perfectly happy using the standard recommended ingredients.

zens

I respectfully disagree that plants should stay in same mix, without repotting, for many years - as you suggested 25. It is a myth that some/any plants need to be pot bound before they will flower. Same take years to bloom, some may never bloom, and others will bloom anytime. But keeping plant potbound and in same potting 'mix' for so many years will not make it grow to it's best potential - you are actually forcing them to 'think' they are going to die and they should reproduce....

I welcome any new information, anyone's experiences. But you are just throwing everything into same bag (like a garbage bag...) without, I suspect, having enough information. For example, I already asked if you know water retention and water holding capacity of any of the substrates mentioned? - you didn't answer.

As for water - I use collected rain water for most of the watering (or plants get watered by it when it rains...) And when I repot, I use (most of the time) new mix...I usually dump old one in a compost pile - and, surprisingly, when I use the compost (sometimes year or longer, later) - I still see the perlite in it! I really do not understand how you manage to crush it by repotting...are you hammering the potting mix down??? Anything could be crushed with enough force, even growstones...Yeah, if I spill any perlite and walk on it - it is crushed...

zens: I find it hard to follow your line(s) of argument(s) except that you certainly like growstones more than anything else. All I can say good for you.

Back to perlite. It is certainly a very useful component in soil mixes. It has good air porosity and water holding capacity approx similar to bark and pumice. On the other hand pumice has a much higher Cation Exchange Capacity (CEC), then comes bark and perlite is nearly zero in that regards. I suspect growstone is similar to pumice in this regard. Perlite in 511 mix serves to rebalance the bark (since bark pieces are generally flat and tend to compact) so as to create more air spaces which in turn reduces the perched water in the mix.

gardengal: Unless crushed, perlite does NOT disintegrate. It can be washed and reused and holds up indefinitely.

Have you tried that after removing soil from a tree in a pot? I have and these are the results from several years back; I started with coarse perlite in a 511 mix for a trident maple. The perlite is sifted with 1/8 screen. The rest is half under 1/4" approximately. After two years bare rooted the plant. Sifted the resulting soil first with 1/8 screen. By eyeballing about 25% of the perlite went right through 1/8 screen. About 75% of the rest went through 1/4 inch screen. So how did that happen?

Obviously not biological/chemical degradation caused it. You pointed that out also. So it has to be a mechanical/physical reason. I suggested several (in my mind very logical) reasons earlier. I do not consider this to be a problem as such. The perlite did its job while in the pot. But I cannot agree that it holds up "indefinitely" under normal working conditions. To me indefinitely would mean it is nearly 100% recoverable.

I do routinely sift used 511 mix and add a fresh batch of 511 for annuals with some extra perlite. In some ways it works out better since the used mix would have some leftover nutrients and is a lot less hyrophobic.

Last summer I planted a ninebark plant in 100% growstone with some controlled release fertilizer added and it did pretty well. It was basically a tiny rooted cutting when I received it, and it grew a few new leaves and stems while just sitting in the growstone in a big 4 gallon container outside all summer. I watered it maybe once or twice a week with my hard, 7.5ph well water.

I like perlite. Especially the coarse stuff. I’ll keep using it in my 5:1:1 mix.

A little misinformation going on about perlite in this thread.

I'd like perlite a lot better if I didn't still have PTSD from sifting the dust and fines out of the bag I bought last fall. But as much as I hate processing it, I can't deny its benefits. It's light, creates space between bark pieces, and holds water on the surface that the bark can absorb (at least that's my understanding of what goes on).

Maybe there's something wrong with me, but my 5:1:1 drains quickly enough that there's never enough water on the surface for anything to float. I guess it doesn't hurt that I sift out everything smaller than 1/8".

Anyhow, I just used the last 1/8-3/8" perlite I had left, so I'm faced with a search for a bag of coarse perlite that isn't half full of toxic, choking dust. I finally found a hydroponics store, so maybe I'll start there.

As for Growstone, it sounds great, especially because my health is pretty limiting these days, but as hard as it is to find good pine bark I plan to keep using what I'm using. If nothing else, it sounds like the amount of Growstone I'd need would cost as much as I've spent on just about everything except for Foliage Pro and lighting--Turface, pine bark (including the junk that got thrown away), grit, orchid bark, peat, pots, sieves, screen, buckets, and storage containers. Its hard to get past that when my plants are looking so happy already.