# Mega rockwool cubes



## monocotman (Oct 26, 2019)

these turned up from a hydroponic store off eBay when I thought that I was buying mini cubes. They are about eight times the volume of the mini cubes.
No good for smaller phrags but maybe ok for the big stuff. This is my biggest plant and I repotted it into this medium about six weeks ago when the plants came into the house after the summer outside.
The new growths were a third grown and any check due to repotting would have been easily seen.
There was no check at all, in fact the growth rate seems to have accelerated!
The same thing has happened with a plant of cardinale ‘birchwood’. The growth is excellent and I’ll put more plant in it when they reach a large mature size,
David


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## NYEric (Nov 13, 2019)

Cool, and you might not need any inorganic material in you mix to keep air spaces.


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## monocotman (Nov 13, 2019)

Eric, 
I potted the flowering Mem.Mariza Rolando into this mix a couple of weeks ago. It’s not skipped a beat or dropped any flowers. Still looks fab.
It a great growing medium so far and the air spaces must be quite large. 
Anyway the ‘hydroponics’ stores carry this mix regularly in the UK as their favourite plant must grow well in it. I’ll use it for the larger plants from now on. It isn’t expensive and the postage isn’t huge as the bags are so light,
David


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## abax (Nov 13, 2019)

Do you pre-soak the cubes before potting up? The
new growth is impressive.


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## monocotman (Nov 14, 2019)

No just use them straight from the bag. It’s much easier to pot up plants if the cubes are dry,
David


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## tomkalina (Nov 14, 2019)

What size is each individual cube; looks like the ones you're using for that adult Phrag. may be too large for seedlings? Also, what will you be using as fertilizer? Seems like you wouldn't need as much if there's no organic material in the mix.


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## monocotman (Nov 14, 2019)

Tom,
On average they are about an inch across, ok for large plants but not seedlings. I use the same fertiliser on everything I grow, akernes rain mix at about 180 microseiemens in rain water. Maybe drop it to 120 in the winter but everything gets the same, cattleyas in bark and phrags in rockwool.
David


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## tomkalina (Nov 14, 2019)

Thanks, David. Seems like 1/2 inch or so might be perfect for seedlings but not sure anyone sells them in the U.S. at that size. As far as your fertilizer, a near equivalent available here looks like Peter's 15-5-15 with Ca Mg fed at a rate of 115-120 ppm TDS (180 uS). - a non-urea formula.


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## monocotman (Nov 14, 2019)

I would have thought both sizes would be available for you. Jason Fischer swears by them. The rain mix is based on the old MSU formula although it has been tweaked. It was a revelation for me when I started to use it,
David


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## tomkalina (Nov 14, 2019)

I will check; it might be time for another mix experiment..........


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## richgarrison (Nov 15, 2019)

tomkalina said:


> I will check; it might be time for another mix experiment..........



Tom

from a local hydroponics store.... small stuff worked on a tiny plant... looking for picts


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## tomkalina (Nov 15, 2019)

Thanks, Rich - Does the bag contain any information regarding cube size or a unique part number? Looks like the cubes are about 3/4 inch square?


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## richgarrison (Nov 15, 2019)

thought i'd post this experience with Grodan...

i don't throw anything away that shows some sign of life...



potted up in straight grodan grow cubes watered with RO and peters orchid RO (basically MSU) - kept constantly wet 

sure it took a while but it certainly doesn't take up much space.. and who doesn't want another sedenii ;-)


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## richgarrison (Nov 15, 2019)

tomkalina said:


> Thanks, Rich - Does the bag contain any information regarding cube size or a unique part number? Looks like the cubes are about 3/4 inch square?


if you zoom in on the bottom part of hte bag photo, you can see a little section on "grow cubes vs. grow chunks"

also here's the website info

https://grodan101.com/products/grodan-stonewool/loose/grow-cubes

"Grow-Cubes are* small 1/4” cubes* of stone wool (stone wool). There are several advantages:


Grow-Cubes stack on top of each other leaving air space in between them this promotes root growth.
Each cube has four surfaces from which excess water can drain. This way, even if you water a lot, the Grow-Cubes will not get water logged.
You have less algae growth on the top than with the smooth surface Gro-Blocks™.
The Grow-Cubes are the driest of our products with properties of a 50/50 mix. (50% water/50% air)
Very easy to mix with any other potting mix.
Special advantages are achieved by mixing Grow-Cubes in with clay pellets. The Grow-Cubes will help spread the water in the container as well has keeping a water buffer in between the watering.
Lightweight; approx. 1/10 of the weight of a bag of potting soil.
"

the grow chunks section of the site doesn't tell you how big they are


We had a speaker from australia talk to us about their sarcochilus operation... He grows their sarchochilus for pot plants and grows them in fluffed rockwool with perlite... When they repot, they recycle the mix through a sterilizing station. 

I've started using it in mixes where i would have used sphagnum, for example in my coelogynes and dendrochilums.


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## richgarrison (Nov 15, 2019)

spaced...


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## tomkalina (Nov 15, 2019)

Thanks, Rich; We'll give these a try on a small scale and compare seedling growth rate to our regular mix.


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## monocotman (Nov 16, 2019)

These are what I use. The mini cubes came from eBay and the larger ones from Amazon.




Jason Fischer says he likes them because of the increased amount of air in the pot when using them. Maybe the chunks have even more than the mini cubes. It would be easy enough to check.
David


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## southernbelle (Nov 16, 2019)

I’ve grown my phrags in rock wool for the last 7 months. I use Jerry Fischer’s mix of 55% Grodan’s Grow Cubes (small ¼-½”), 35% sponge rock (or small grow stone), and 10% charcoal. My plants love it and have responded very well. I use clear plastic pots, so I do have algae, however you can see the root systems in the photos. Very pleased. I flush with plain r/o water about once a month, as the rock wool does hold onto salts, however that takes care of it.


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## tomkalina (Nov 22, 2019)

Are any of you who are using the mini-cubes for the smaller Phrags. sitting the pots in water, or just watering more frequently?


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## monocotman (Nov 22, 2019)

Mine always sit in water. Not much maybe 1cm maximum,
David


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## cnycharles (Nov 23, 2019)

When I had more of them and places to put, I used the mini cubes with small bark or Aussie bark, some diatomite charcoal and sponge rock in aircone pots, usually sitting in a little water. This was in upstate ny heated apartment
In general, I still place phrags that have mini cubes in the media in a little water


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## southernbelle (Nov 23, 2019)

tomkalina said:


> Are any of you who are using the mini-cubes for the smaller Phrags. sitting the pots in water, or just watering more frequently?


I water the plant you see (in a 5.5” pot) every 6 or 7 days. Maybe a day more now with less light and 74 degree days. When I see the mix dry at the top about ¾”. They are not sitting in water.


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## tomkalina (Nov 23, 2019)

Thanks all! I just put a very slow growing Phrag. sargentianum 'Really Red' (x self) seedling into Mini-Cubes w no other mix constituent, and placed the pot in 1" of rain water. Also put four Paph. species that have been struggling for years (!) into Mini-Cubes alone, but will water these weekly, w pots not sitting in water. Not going 'whole hog' into the Mini-Cubes, but just getting a feel for how the plants react.


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## richgarrison (Nov 23, 2019)

tomkalina said:


> Are any of you who are using the mini-cubes for the smaller Phrags. sitting the pots in water, or just watering more frequently?



that sedenii I posted a pict of gets water everyday..


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## richgarrison (Nov 24, 2019)

Relative to watering frequency... I always reach back to what many phrags are getting in situ . Where most are getting constant water via seeps in rock fissures. So '''watered'' vs "wet" or ''lushed' vs 'stagnant' becomes more the conversation. Ray has a lot to say about that. And empirical evidence in my greenhouse supports it well.


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