# Pros and Cons of Grodan rock wool mini cubes



## Bob in Albany N.Y. (Jul 12, 2020)

I've been hearing about these for sometime now. Was hoping that members here can share their experences with this media. Want to hear both the good and the bad. Please be sure to include your growing conditions and locations. Such things as, can you pot up without removing the cubes? Does the roots grow threw the cubes. Can the cubes be reused. Do they hold salts? What group of orchids are you using it for? How often does it need to be changed, once a year? How often do they need to be watered in your conditions? Do you need to still sit them in an inch or two of water for phrags? 

Thanks to all members that take the time to inform the rest of the members on this forum.


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## Duck Slipper (Jul 12, 2020)

I have used gro cubes as a part of a potting mix...I have used it as a mix with gro cubes and perlite. Currently a kovachii and a Fritz Schomberg potted up in cube/perlite mixture. 
Yes the roots kind of attach or grow through it but it doesn’t really matter because it doesn’t decompose. I have never reused it, but a plant can stay wetter longer in it, before repotting. In fact, probably considerably longer. 
It definitely has benefits and unique abilities as a potting media.


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## abax (Jul 12, 2020)

In my very humid greenhouse growing conditions, I get any Phrag.
that's in Grodan out as quickly as possible. It stays too wet too long.


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## monocotman (Jul 13, 2020)

Whereas in my indoor conditions with much lower humidity than Angela, it is an amazing medium for phrags. I water the plants about once a week when the water in the trays has dried out,
David


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## southernbelle (Jul 14, 2020)

Bob in Albany N.Y. said:


> I've been hearing about these for sometime now. Was hoping that members here can share their experences with this media. Want to hear both the good and the bad. Please be sure to include your growing conditions and locations. Such things as, can you pot up without removing the cubes? Does the roots grow threw the cubes. Can the cubes be reused. Do they hold salts? What group of orchids are you using it for? How often does it need to be changed, once a year? How often do they need to be watered in your conditions? Do you need to still sit them in an inch or two of water for phrags?
> 
> Thanks to all members that take the time to inform the rest of the members on this forum.


Jerry Fischer at Orchids,Ltd. says phrags and miltoniopsis love the grow cubes. His mix is 65% cubes, 25% perlite, 10% charcoal. I use 55/35/10 and next mix will add oyster shell. He also uses bark for phrags, but not moss, as he says it tends to be too acidic. I now grow phrags and miltoniopsis in my main level of my home high 74 day temps with air circulation, 45-50% humidity, very bright East windows, because my grow room (under LED lights) was too warm for them to be happy at 84 degrees in summer. 

I water when the cubes on the surface just start to dry (phrags). The cubes, according to the manufacturer are 50% hydrophilic and 50% hydrophobic, so technically hold ½ air. Jerry says their shape causes good air spaces in the mix, especially with the perlite. 7 days is a little long for me to go, but my phrags are in small pots being rehabilitated, right now. I feel as though they stay wet, as the cubes do not dry out visibly below the surface, but there is good root growth with them (I use clear plastic). 

If you search a previous thread I started in April/May "Advice, please re Phrags", if my memory serves me, PeteM posted pics of a small Fritz Schomberg he bought at the Paph Forum the same day I bought one. These were not well rooted. I downsized mine which was in bark, to bark, he downsized his experimenting with grow cubes mix. His results after just a few months were remarkable per his photo--I almost lost mine!! I've since repotted in grow cubes and moved it to cooler temps. 

Re repotting without removing the cubes. Yes, according to Jeff Morris of Charlottesville Orchid Soc. who exhibits many CCM awarded specimen phrags (many of the same plants get CCMs every year he exhibits) in large (2 gal and larger containers) because the cubes never break down, he just removes the pot, puts it in a bigger pot, adds cubes around the outside/bottom and (in large pots) adds a couple of inches of bark on top to keep algae from growing. His theory is phrags don't like their roots disturbed, so they are very happy with this system and his plants certainly are a testimony to that! 

Re accumulating salts, yes, so every 3-4 weeks flush with clean water, no fertilizer (per Jerry). So the last week of the month, they get clean water. I do not sit my phrags in an inch or two of water. Some do, but it has never worked for me (I killed my first Jason Fischer doing that when I went away for 4 days, it was still moist when I returned, however, declined rapidly after that.) I've not noticed my roots growing through the cubes, but I see a lot on the outside of the mix through my clear pots, but I don't pick apart the mix when repotting, so they might. Hope this helps. Look up the thread, a lot of comments there will be helpful and Pete M's photos speak for themselves!


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## Ozpaph (Jul 17, 2020)

con - cant seem to find them anywhere in Oz....................


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## southernbelle (Jul 17, 2020)

Ozpaph said:


> con - cant seem to find them anywhere in Oz....................


have you tried online? Very light so should be minimal shipping. Our garden center had them, but they closed. In VA Fifth Season Gardening does not have the grow cubes but can order them. They are reasonable and ship. Talk to Patrick
www.fifthseasongardening.com


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## PeteM (Jul 17, 2020)

I'm still experimenting with these, I have yet to get through an entire growing season. I have seen strong root growth in young and or rootless phrags transferred from bark mixes, this was in winter and spring during cooler conditions in my grow area. Currently I am cycling to a warmer night time low and many of my phrags have slowed down a bit. So I have not transferred additional phrags to the cubes.

Two of my phrag divisions of 'Spot On' are in the cubes (repotted in the winter) and are currently still blooming.. but have looked a bit stressed, I believe it's the higher temp and increased light from the position on the grow bench. The leaves were yellowing (very light light green all over) a bit, so I just moved them to a lower light and cooler grow environment next to the evaporative cooler (another experiment). It also might be the grow cubes needing to be replaced. I have not repotted any of my plants that are in grow cubes yet, I was hoping to get through the summer.

Other orchids that are thriving right now in grow cubes / perlite mix. THRIVING. Catasetum, have come out of their dormancy this spring and taking up large amounts of water, root growth is strong in aircone pots. Habenaria, have also come out of dormancy and are thriving in the cubes. I would say, any orchid that needs large amounts of water during it's growth cycle would be a good candidate. If I remember to get some pictures I will post. Hope this helps.

Pros: relatively affordable, available in the states form hydroponic stores in large quantities for close to $40 for a very large bag. Very light weight, so might be less expensive to ship if you need to. Inorganic, running it a bit wet for a bit longer without rot issues maybe possible. I plan to use it to replace all my sphagnum moss. 

Cons: wet it before you use it as some of the information I found has it as an irritant for people with allergy sensitivities. Also wear thick gloves when working with it. I have found thin nitrile gloves are not thick enough and I still feel the rockwool on the back sides of my hands, I do use the back sides of my fingers sometimes when tapering down during repotting. Nothing big, just a slight scratching. Salt accumulation? TBD. I fertilize almost every day with a hand pump spray at the roots at very low levels of PPM (50). I run RO water and flush with RO hose about 15 minutes after spraying. I also have been experimenting with growdan cubes and phrags in net pots (kovachii). So far so good. once I get into the next cooler growing cycle I should have more results on this front.

added some images below. I should also mention I use a heavy layer of styrofoam peanuts at the bottom of all my pots. This might also change depending on results.


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## KateL (Jul 22, 2020)

I have been using the Grodan cubes for 1/2 of my slightly bigger kovachii seedlings. The others are in sphagnum. They are under shade cloth, open to rain, as well as frequent watering in a climate that is undoubtedly too warm to be ideal. I sprinkle the media liberally with oyster shells and dolomite to keep the pH up a bit. I haven’t killed them all, so that’s a plus. I haven’t grown any to blooming size yet either, although I have a couple that might be getting there. I have not drawn a conclusion yet on the media. So far, the sphagnum seems to be as good as the cubes, as long as I keep it relatively fresh. I am thinking about trying to plant them shallower and flatter (maybe like Tom K’s tray method, if I can find something that works), as the last one I repotted (from cubes to cubes) had all of roots right near the surface. Going to check out a couple more before I decide it’s a pattern.


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## Silverwhisp (Jul 22, 2020)

KateL said:


> I am thinking about trying to plant them shallower and flatter (maybe like Tom K’s tray method, if I can find something that works), as the last one I repotted (from cubes to cubes) had all of roots right near the surface. Going to check out a couple more before I decide it’s a pattern.


 Kate— What has worked for me are bulb pans (“Plant Pie“ trademark), and bonsai forest trays, from eBay seller takashima_bonsai.


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## PeteM (Jul 22, 2020)

I have added a significant amount of styrofoam peanuts to the bottom of many of my larger pots to simulate this reduction in pot size and then you can adjust the depth accordingly by plant.


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## KateL (Jul 22, 2020)

Silverwhisp said:


> Kate— What has worked for me are bulb pans (“Plant Pie“ trademark), and bonsai forest trays, from eBay seller takashima_bonsai.


Thanks, Patricia! I just ordered a couple to try!!


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## Silverwhisp (Jul 22, 2020)

Great! The bonsai trays have a gazillion holes.... Right now I’m using a bulb pan for my adult besseae- it’s got pretty good drainage, too.


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## Tony (Jul 25, 2020)

I use them with perlite and or LECA for nearly everything and love them. I can water every day during the hot South Carolina summer without having to worry about rotting roots. Here are some roths seedlings one year apart:


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## Linus_Cello (Jul 25, 2020)

Tony said:


> I use them with perlite and or LECA for nearly everything and love them. I can water every day during the hot South Carolina summer without having to worry about rotting roots. Here are some roths seedlings one year apart:


 
What is your winter culture for the Roths? Do you have a GH or windowsill?


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## Duck Slipper (Jul 25, 2020)

I have some Phrags in a 4 parts Orchiata, 1 part charcoal, 1 part perlite, 1 part cubes for two years now. The cubes hold more moisture and the Orchiata takes longer to break down...All others, Paphs. and Catts. are in 4 parts Kiwi bark, 1 part charcoal, 1 part perlite. I ordered a good sized bag of cubes from Amazon.


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## tomp (Jul 25, 2020)

Silverwhisp said:


> Kate— What has worked for me are bulb pans (“Plant Pie“ trademark), and bonsai forest trays, from eBay seller takashima_bonsai.


Just looked at the “plant pie” info and they look like an interesting concept. Could you please say more about what you might or would or would not use these for. Thanks


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## southernbelle (Jul 25, 2020)

Tony said:


> I use them with perlite and or LECA for nearly everything and love them. I can water every day during the hot South Carolina summer without having to worry about rotting roots. Here are some roths seedlings one year apart:


What % perlite in the mix?


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## Silverwhisp (Jul 25, 2020)

tomp said:


> Just looked at the “plant pie” info and they look like an interesting concept. Could you please say more about what you might or would or would not use these for. Thanks


Right now I’ve got an adult Phrag. besseae in one. It’s very happy. If my Mexipediums ever take off, i.e. , multiple spreading growths, I might consider using a Plant Pie for them.


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## PeteM (Jul 25, 2020)

Tony said:


> I use them with perlite and or LECA for nearly everything and love them. I can water every day during the hot South Carolina summer without having to worry about rotting roots. Here are some roths seedlings one year apart:



thanks for the pictures and info.

How often do you find you need to repot with this mix? Maybe you already have a system to repot every year or sooner? I’m curious to see what Interval has worked best for phrags, paphs, other orchids if you have any in the same mix.

Is there anything specific that you look for to indicate that the mix has deteriorated and you need to repot?

Are there any other recommendations, like things to Absolutely avoid When using this mix, that might have led to unfavorable results? Thanks!


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## southernbelle (Jul 25, 2020)

PeteM said:


> thanks for the pictures and info.
> 
> How often do you find you need to repot with this mix? Maybe you already have a system to repot every year or sooner? I’m curious to see what Interval has worked best for phrags, paphs, other orchids if you have any in the same mix.
> 
> ...


The beauty of rockwool is that is does not breakdown, as it’s not organic. That’s why phrags love it, as you can just pot on and not disturb the roots. That’s what I’ve been told by growers of huge specimen phrags. Mine have not been in it long enough to need larger pots. You do need to rinse with clear water every month or salts can accumulate with it, though.


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## cpmaniac (Jul 25, 2020)

I'm really enjoying this thread...lots of useful information. I've used regular clay bonsai pots. They are heavy and it's difficult to add drainage holes. Those plastic pots are on my list.

This Phrag. kovachii has been in Grodan Mini-Cubes plus charcoal and Growstone GS-2 for five months:








I use the Growstone for Phrag. kovachii, fischeri, and some kovachii hybrids. For others, the mix has perlite.
Cheers,
Paul


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## Linus_Cello (Jul 26, 2020)

Love the Sarrenicia. Wish I had more sun for these. (Tarnok seems to do ok with part sun)


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## southernbelle (Jul 26, 2020)

cpmaniac said:


> I'm really enjoying this thread...lots of useful information. I've used regular clay bonsai pots. They are heavy and it's difficult to add drainage holes. Those plastic pots are on my list.
> 
> This Phrag. kovachii has been in Grodan Mini-Cubes plus charcoal and Growstone GS-2 for five months:
> 
> ...


Paul, how often are you watering in the Grodan cubes? Also, at what day temp are you growing phrags; particularly besseae hybrids?


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## cpmaniac (Jul 26, 2020)

southernbelle said:


> Paul, how often are you watering in the Grodan cubes? Also, at what day temp are you growing phrags; particularly besseae hybrids?


I water kovachii, besseae and the like daily - others two or three times a week. The maximum greenhouse temperature is normally 78 F, but hits the low 80's during extreme heat waves. The area in the direct path of the swamp cooler output stays below 75F. 

I have a lot to learn about phrag. cultivation...Phrag. besseae in bud after a two year hiatus is a nice surprise here!

Cheers,
Paul


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## PeteM (Jul 26, 2020)

cpmaniac said:


> I'm really enjoying this thread...lots of useful information. I've used regular clay bonsai pots. They are heavy and it's difficult to add drainage holes. Those plastic pots are on my list.
> 
> This Phrag. kovachii has been in Grodan Mini-Cubes plus charcoal and Growstone GS-2 for five months:
> 
> ...



those roots look great. Well done. How old is that plant? I’ll have to try the grow stones, I picked up a bag after reading a thread but only throw a few in here and there. do you also have holes in the pot on the bottom or just at different intervals around the sides?


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## musa (Jul 27, 2020)

It seems to work well, Paul!
Did I understand that right, Growstone is puffed glass? It is not common here. What is the advantage vs. pumice? Wouldn't be pumice better for calciolous slippers?


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## southernbelle (Jul 27, 2020)

cpmaniac said:


> I water kovachii, besseae and the like daily - others two or three times a week. The maximum greenhouse temperature is normally 78 F, but hits the low 80's during extreme heat waves. The area in the direct path of the swamp cooler output stays below 75F.
> 
> I have a lot to learn about phrag. cultivation...Phrag. besseae in bud after a two year hiatus is a nice surprise here!
> 
> ...


With roots like those I’d say you probably will have more blooms if light is good and fertilizer is balanced.


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## cpmaniac (Jul 27, 2020)

PeteM said:


> those roots look great. Well done. How old is that plant? I’ll have to try the grow stones, I picked up a bag after reading a thread but only throw a few in here and there. do you also have holes in the pot on the bottom or just at different intervals around the sides?



That plant is a division I received 5 months ago. It went right into that mix. I put a couple holes in the side almost midway up, and a few in the bottom, much like they do at OL.


musa said:


> It seems to work well, Paul!
> Did I understand that right, Growstone is puffed glass? It is not common here. What is the advantage vs. pumice? Wouldn't be pumice better for calciolous slippers?



I don't know about pumice. I'll have to investigate. I didn't attend the 64TH Paphiopedilum Guild this year, but in the summary published in the current issue of "Slipper Orchids" or the "Orchid Digest" quotes Glen Decker recommending Growstone as an additive to his mix for Phrag. kovachii. Also, some time ago, OL grew their kovachii and some others in straight Growstone: 

The problem is Growstone is no longer manufactured. It is hard to find now, especially in the smaller GS-2 grade.

Cheers and good growing,
Paul


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## southernbelle (Jul 27, 2020)

I’ve got 3 or 4 bags of both sizes of Growstone if anyone close by is interested. I’d pass it on at cost, as it has been discontinued by the company. I don’t know why. It is expanded glass. I used it for a couple of years and decided to change to perlite. Many use it and like it and I had no problems, but it (supposedly) has to be soaked and rinsed before use or (I think) can cause ph issues. Ray mentioned that once in a thread comment, and I found the soaking to be a pain. There are some who grow in straight Growstone and are very happy with it. Terry Ros has had great luck with it.


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## richgarrison (Jul 27, 2020)

As Paul mentioned above Glenn said he uses it in his kovachii to manage pH up a bit as they have been advertised to like... I've attempted to accomplish the same thing by just adding a butt load of chicken grit... appears to be working but i don't have a good experiment going to truly validate efficacy...

@PeteM are you by any chance growing any coelogynes in a mix containing the cubes? i'm trying them in a few plants just as an additive as well in some dendrochilums as an additive, Having reasonably good luck in oncidium intergeneric hybrids, but it'll take a few years before i know that's a formula that works for me...


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## Silverwhisp (Jul 27, 2020)

@PeteM are you by any chance growing any coelogynes in a mix containing the cubes? i'm trying them in a few plants just as an additive as well in some dendrochilums as an additive, Having reasonably good luck in oncidium intergeneric hybrids, but it'll take a few years before i know that's a formula that works for me...
[/QUOTE]

Not Pete here, but I’ve got a Coelogyne cristata var. grandiflora that is deliriously happy right now in a 50-50 mix of cubes and green tree moss that I gathered from a woods.


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## cpmaniac (Jul 27, 2020)

southernbelle said:


> I’ve got 3 or 4 bags of both sizes of Growstone if anyone close by is interested. I’d pass it on at cost, as it has been discontinued by the company. I don’t know why. It is expanded glass. I used it for a couple of years and decided to change to perlite. Many use it and like it and I had no problems, but it (supposedly) has to be soaked and rinsed before use or (I think) can cause ph issues. Ray mentioned that once in a thread comment, and I found the soaking to be a pain. There are some who grow in straight Growstone and are very happy with it. Terry Ros has had great luck with it.


I'm only using the Growstone as an additive to the mix for my kovachiis and kovachii hybrids. Phrag. fischeri reportedly prefers a higher pH, so I'm using some Growstone with it as well. I just give it a light rinse when making up the mix. I use it pretty dry and water after the plants are potted.

I'm using perlite for my other phrags and paphs.

Cheers,
Paul


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## musa (Jul 28, 2020)

I hope that isn't going too off topic but as it is an artificial potting medium as well...
I read, too, that Growstone is not any more produced. Nevertheless there is an other product which is expanded glass: A friend of mine used pebbles of expanded glass as an isolation layer underneath the lowest floor of his house. So it seems under another brand and purpose such a product still exists.
Do you think that might work for orchids, has anybody some experience with it? Of course it might be treated in some way to make it water resistant as it is done with perlit, too...


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## richgarrison (Jul 28, 2020)

Silverwhisp said:


> @PeteM are you by any chance growing any coelogynes in a mix containing the cubes? i'm trying them in a few plants just as an additive as well in some dendrochilums as an additive, Having reasonably good luck in oncidium intergeneric hybrids, but it'll take a few years before i know that's a formula that works for me...



Not Pete here, but I’ve got a Coelogyne cristata var. grandiflora that is deliriously happy right now in a 50-50 mix of cubes and green tree moss that I gathered from a woods.
[/QUOTE]

AHHHH lucky you.... my luck with moss is limited (mainly top dressing or mounts)... and i've abandoned it as a moisture retaining additive. For me and my habits/conditions, i've proven that i can't keep it beyond 8-10 months without having to change it out...


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## PeteM (Jul 29, 2020)

Silverwhisp said:


> @PeteM are you by any chance growing any coelogynes in a mix containing the cubes? i'm trying them in a few plants just as an additive as well in some dendrochilums as an additive, Having reasonably good luck in oncidium intergeneric hybrids, but it'll take a few years before i know that's a formula that works for me...



Not Pete here, but I’ve got a Coelogyne cristata var. grandiflora that is deliriously happy right now in a 50-50 mix of cubes and green tree moss that I gathered from a woods.
[/QUOTE]

Fantastic. No, I actually don't have any in my collection. I do have 2 stanhopea that are next in line for the growdan chopping block.


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## PeteM (Jul 29, 2020)

musa said:


> I hope that isn't going too off topic but as it is an artificial potting medium as well...
> I read, too, that Growstone is not any more produced. Nevertheless there is an other product which is expanded glass: A friend of mine used pebbles of expanded glass as an isolation layer underneath the lowest floor of his house. So it seems under another brand and purpose such a product still exists.
> Do you think that might work for orchids, has anybody some experience with it? Of course it might be treated in some way to make it water resistant as it is done with perlit, too...


interesting. Do you have the name or link to the product? Thanks, would be worth looking into.


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## musa (Jul 29, 2020)

Hi Pete, I just did some research, there are some producers like Geocell and Glapor.
Unfortunately their products are described as waterresistant, because the single bubbles in the glass are closed. They absorb only 10 % water in relation to their volume. Growstone has probably a more open structure to store more water. Nevertheless I'll try to get a sample of that stuff.
There was mentioned expanded glass also for storage of dangerous liquids. I suppose In that case a high absorption af liquids is wanted. I couldn't find more info about that material.
Sorry, that dosen't sound to promising...


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## eds (Jul 29, 2020)

There are sintered glass materials produced as filter media for fish and also ceramic media that are definitely open-pored. They might be worth a look as a substitute if the grow stones are no longer available. I certainly wouldn't buy siporax or bakki house media but cheap knock-offs instead!


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## southernbelle (Jul 29, 2020)

cpmaniac said:


> I'm really enjoying this thread...lots of useful information. I've used regular clay bonsai pots. They are heavy and it's difficult to add drainage holes. Those plastic pots are on my list.
> 
> This Phrag. kovachii has been in Grodan Mini-Cubes plus charcoal and Growstone GS-2 for five months:
> 
> ...


How do you punch the holes in your pots? And where do you get the deep clear pots?


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## cpmaniac (Jul 29, 2020)

southernbelle said:


> How do you punch the holes in your pots? And where do you get the deep clear pots?


Hello southernbelle, The pot in the photo is a one quart freezer/soup container. My wife has been packing leftovers in them for my son for years. I stole a few and used them for sundews (Drosera) and Paphs. More recently, I saw Jason Fischer recommending them for Phrags and they work well. Check out his blog for kovachii. For even larger plants, the tall seven inch white Hydro pots work well, or the one gallon Plant Warrior pots. The holes are made with a soldering iron. I put a just couple holes in the sides almost halfway up, and a few in the bottom. I use a fan to be sure the fumes are directed away from me. 

Cheers,
Paul


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## PeteM (Jul 30, 2020)

southernbelle said:


> How do you punch the holes in your pots? And where do you get the deep clear pots?


Also... I need to find out how you grow a field of Sarrenicia like that. I have a few in small pots, they look kind of scrawny on their own.. do you use a shallow tray or deep tub? any tips would be much appreciated!


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## southernbelle (Jul 30, 2020)

PeteM said:


> Also... I need to find out how you grow a field of Sarrenicia like that. I have a few in small pots, they look kind of scrawny on their own.. do you use a shallow tray or deep tub? any tips would be much appreciated!


Pete, the Sarrenicia are not mine. Someone else’s post.


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## Teresa Koncolor (Jul 30, 2020)

To me growstone and perlite seem pretty much the same except for size. How else are they different?


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## PeteM (Jul 30, 2020)

southernbelle said:


> Pete, the Sarrenicia are not mine. Someone else’s post.


Sorry, yes. I was hoping to catch him while he was responding to yours. :/


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## southernbelle (Jul 30, 2020)

Teresa Koncolor said:


> To me growstone and perlite seem pretty much the same except for size. How else are they different?


Growstone does not crush, perlite does potentially. However, growstone is pretty sharp. I didn't like soaking it, so switched. It also sticks to roots, much like bark, whereas perlite does not tend to as much. I have a lot of it, but plan to use it (unless someone wants it) in the garden to deter voles. Vole Bloc is a similar product that is expanded slate and totally inert, no rinsing, although it does leach dust. They don't like to scratch their noses when burrowing... Anyway, I have actually purchased cattleyas from Krull-Smith potted in (what appeared to be) Vole Bloc and nothing else.


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## Ray (Jul 30, 2020)

Perlite is chemically neutral. Growstones, being recycled soda-lime glass that has been foamed by the addition of an alkaline carbonate to the melt, has a high (basic) pH.


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## cpmaniac (Jul 30, 2020)

"Also... I need to find out how you grow a field of Sarrenicia like that. I have a few in small pots, they look kind of scrawny on their own.. do you use a shallow tray or deep tub? any tips would be much appreciated!"

I'm using plastic wading pools. Lots of cp growers around here use them. They attract mosquitoes, of course, so I add Mosquito Bits to kill the larvae. Interestingly, I recently discovered dragonflies are breeding in the pools. 

Flame Skimmer:




Cheers,
Paul


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## southernbelle (Jul 30, 2020)

Ray said:


> Perlite is chemically neutral. Growstones, being recycled soda-lime glass that has been foamed by the addition of an alkaline carbonate to the melt, has a high (basic) pH.


So, does soaking them take care of that?


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## littlefrog (Jul 30, 2020)

I might have missed something, did you imply that you grow drosera in rockwool? I'm actually looking for a new CP medium. Never thought about rockwool...

Rob


cpmaniac said:


> Hello southernbelle, The pot in the photo is a one quart freezer/soup container. My wife has been packing leftovers in them for my son for years. I stole a few and used them for sundews (Drosera) and Paphs. More recently, I saw Jason Fischer recommending them for Phrags and they work well. Check out his blog for kovachii. For even larger plants, the tall seven inch white Hydro pots work well, or the one gallon Plant Warrior pots. The holes are made with a soldering iron. I put a just couple holes in the sides almost halfway up, and a few in the bottom. I use a fan to be sure the fumes are directed away from me.
> 
> Cheers,
> Paul


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## cpmaniac (Jul 30, 2020)

littlefrog said:


> I might have missed something, did you imply that you grow drosera in rockwool? I'm actually looking for a new CP medium. Never thought about rockwool...
> 
> Rob


No, I just use the containers because they are tall. 
Cheers,
Paul


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## PeteM (Jul 30, 2020)

southernbelle said:


> Growstone does not crush, perlite does potentially. However, growstone is pretty sharp. I didn't like soaking it, so switched. It also sticks to roots, much like bark, whereas perlite does not tend to as much. I have a lot of it, but plan to use it (unless someone wants it) in the garden to deter voles. Vole Bloc is a similar product that is expanded slate and totally inert, no rinsing, although it does leach dust. They don't like to scratch their noses when burrowing... Anyway, I have actually purchased cattleyas from Krull-Smith potted in (what appeared to be) Vole Bloc and nothing else.



Vole Bloc... will look this up! Thanks


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## Sky7Bear (Sep 7, 2020)

I have most of my orchids at present in one of a variety of semi-hydroponic mixes, all rock based (leca and monto clay mostly), and suspect that growing in rock wool is similar, though I haven't experimented lately. The advantage, of course, is that the medium doesn't rot, though pH change or salt buildup can be an issue if not cared for. However, I wonder, in the case of all orchid growing, including these, that we've forgotten what the "old growers" seemed to know--that lots of air at the roots was as important as enough water, and that the air/water balance is not the same for all genera in all media. I know that just adding an upside down net basket to the bottom and more holes to the sides seems to encourage good root growth, and too high a percentage of water in whatever medium is being used leads to rot (the primary disadvantage of all of the organic media, I think). Rands seemed to know this with his pots, as did the growers with the short terra cotta pots with slits on the lower sides. Perhaps the "Goldilocks principle applies-not too wet, not too dry, but just right.


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## Ray (Sep 8, 2020)

FWIW, I just repotted a couple of plants using Grodan Mini-cubes.

Warczatorea Heaven’s Bank went into straight cubes in an Air-Cone pot and Pescatorea Sandra’s First went into 50/50 cubes and LECA. Both have always done well for me in straight sphagnum, but I got tired of changing it out every 6 months or so, and believe it or not, it dried very rapidly indoors over the winter.

My “gut feel” Is that the 50/50 mix will be my longer-term preference as it will stay airier, but I’m trying to keep an open mind about the straight stuff.


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## SouthPark (Sep 8, 2020)

Sky7Bear said:


> Perhaps the "Goldilocks principle applies-not too wet, not too dry, but just right.



In general ------ definitely --- something like that. The old 'sweet spot' or 'sweet region' or 'suitable range' way of thinking. Otherwise ----- the other schools of growing, such as hydroponics ----- where some help may be needed too, such as aerating the water to keep the oxygen levels up at satisfactory levels.


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## Ray (Sep 8, 2020)

In case anyone else gets the urge to try them, before you mix cubes and LECA, wet them thoroughly so the mass of a cube and a rock are closer. If done dry, they tend to stratify instead of mix.


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## sergeharvey (Sep 9, 2020)

I have switched a few Phrags (bessae hybrids) to Grodan minicubes/large perlite in a 4 to 1 ratio and the roots are growing like mad. I will further evaluate in a couple of months. Salinity ranges about 200.


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## southernbelle (Sep 9, 2020)

sergeharvey said:


> I have switched a few Phrags (bessae hybrids) to Grodan minicubes/large perlite in a 4 to 1 ratio and the roots are growing like mad. I will further evaluate in a couple of months. Salinity ranges about 200.


You will want to flush with pure water once a month to avoid salt buildup, I've been advised.


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## NYEric (Sep 10, 2020)

I use grow cubes and moss on the top of the mix with stolonous Phrags. The roots grow on top of and around the cubes.

Pete M. showing off the Habs!


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## PeteM (Sep 11, 2020)

NYEric said:


> I use grow cubes and moss on the top of the mix with stolonous Phrags. The roots grow on top of and around the cubes.
> 
> Pete M. showing off the Habs!


Update, favorable results so far... waiting for one of the cubes to jump up and snap off the spike. 




Also, I new this summer Ophrys 'bee' orchids (2 different species) from the Tarzane Group orchids. I have no experience with these and.. lovingly threw the two dry little tubers into the magic cubes. I see a little green emerging from both pots.. Very much looking forward to this
.


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## Ray (Sep 11, 2020)

I just acquired an almost-mature Paph. rothschildianum and it got KelpMax-ed then potted up in a 50/50 LECA/cubes blend.


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