Pros and Cons of Grodan rock wool mini cubes

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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!
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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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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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
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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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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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

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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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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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
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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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.
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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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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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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@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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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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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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@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 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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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.
 

musa

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