# Vermiculite



## Marc (Feb 20, 2011)

Today I was browsing around to find a store that sells coarse perlite to use in a potting mix. I couldn't find anything bigger then 3.6mm. However I found a site that sold big bags of vermiculite with a size up to 6 or 7mm.

I was wondering if this product can be used in the same way as perlite? I did some searching on this site. But the only thing I found was using it in "mud" mix for orchids.


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## gonewild (Feb 20, 2011)

Marc said:


> Today I was browsing around to find a store that sells coarse perlite to use in a potting mix. I couldn't find anything bigger then 3.6mm. However I found a site that sold big bags of vermiculite with a size up to 6 or 7mm.
> 
> I was wondering if this product can be used in the same way as perlite? I did some searching on this site. But the only thing I found was using it in "mud" mix for orchids.



No. vermiculite is completely different from perlite. It soaks up water and also smashes with little pressure.

Try finding coarse perlite at hydroponic grow shops. The weed growers like the coasre grade.


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## Shiva (Feb 20, 2011)

Perlite absorbs water but it keeps the mix open for air. Vermiculite also absorbs water but it compacts the mix. For orchids, it will suffocate the roots to death. Not good!


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## Marc (Feb 20, 2011)

Shiva said:


> Perlite absorbs water but it keeps the mix open for air. Vermiculite also absorbs water but it compacts the mix. For orchids, it will suffocate the roots to death. Not good!



Thanks for the heads up 

I've vound various stores selling perlite. But none of them mentions the size of the perlite. The bark I normally use is quite coarse so I would prefer to find a source that sells perlite that is at least bigger then 5mm.

Or do the experts here say that using fine perlite in a coarse bark mix is ok?

I'm scared it will flush out and collect at the bottom of the pot.


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## likespaphs (Feb 20, 2011)

it is sometimes listed as "sponge rock"


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## Marc (Feb 20, 2011)

I've found a site that sells it, even has a picture on the site of the bag they sell it in. On the bag it says "Coarse"  So my guess is that's the one I want to have.


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## Shiva (Feb 20, 2011)

Perlite comes in two or three sizes. The larger the bark, the larger the size of perlite recommended because large bark is associated with large plants like vandas or cattleyas who really need a lot of air at the roots. So smaller perlite should be used with smaller bark. Perlite can be bought just about anywhere on the Internet and since it's very light, the shipping cost shouldn't be that expansive. One way to learn more about anything is to use Google. I use Google all the time to find all kinds of stuff and check out orchid seller reputations.


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## gonewild (Feb 20, 2011)

Marc said:


> Thanks for the heads up
> 
> I've vound various stores selling perlite. But none of them mentions the size of the perlite. The bark I normally use is quite coarse so I would prefer to find a source that sells perlite that is at least bigger then 5mm.
> 
> ...



Perlite won't flush down and out the bottom of the pot. If anything it will float up. Once it is in the mix of bark it should stay in place because of the sharp and rough edges.

It really does not matter what size it is in comparison to the bark size... that would all depend on why you are mixing it with bark in the first place.

There is not right or wrong... get what ever size you can find and try it.


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## Mathias (Feb 20, 2011)

Marc said:


> I've found a site that sells it, even has a picture on the site of the bag they sell it in. On the bag it says "Coarse"  So my guess is that's the one I want to have.



Let me know if you find really coarse perlite here in Europe. I have found it difficult to find this product over here.


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## Eric Muehlbauer (Feb 20, 2011)

Ray has about the best quality Spongerock that I have seen in years.


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## Marc (Feb 21, 2011)

Eric Muehlbauer said:


> Ray has about the best quality Spongerock that I have seen in years.



I take it that the Ray you speak about is somewere in the U.S.? If so the info doesn't help me because I live on another continent. 

Still usefull for our readers from the U.S. and / or Canada.



Mathias said:


> Let me know if you find really coarse perlite here in Europe. I have found it difficult to find this product over here.



Will do, I'll either buy it from a Growshop which we have plenty of in our country, or I'll try to aquire through my fathers network of orchid breeders etc.


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## Ricky (Feb 21, 2011)

Mathias said:


> Let me know if you find really coarse perlite here in Europe. I have found it difficult to find this product over here.



Yes, impossible to get it here in Germany too.


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## Bolero (Feb 22, 2011)

I haven't seen vermiculite used on its own but I do know of some growers who use a mixture of coarse perlite and vermiculite with their Cattleya's. They highly recommend it.


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## Marc (Feb 22, 2011)

@ Mathias and Ricky, and perhaps the rest.

What would be considered coarse for perlite? The sizes I allready stated as in +3.6mm? Can someone specify a size in mm's to indicate what is considered to be coarse perlite so I can ask it when I send a mail to a company?


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## gonewild (Feb 22, 2011)

I don't know the measurement but what I see here in the gro stores is about 10-12mm.


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## Mathias (Feb 22, 2011)

Marc said:


> @ Mathias and Ricky, and perhaps the rest.
> 
> What would be considered coarse for perlite? The sizes I allready stated as in +3.6mm? Can someone specify a size in mm's to indicate what is considered to be coarse perlite so I can ask it when I send a mail to a company?



I have been searching for what is called "Sponge rock" in the US, which is perlite but a larger grade (called grade #3 or #4). From what I know it is around 10-13 mm in size, sometimes ever larger. 

I actually found sponge rock in the UK (http://orchidaccessories.co.uk/catalog/index.php?cPath=32), but I have tried several times to get the vendor to ship to Sweden without success. Seems he only ship within the UK.


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## gonewild (Feb 22, 2011)

Since you can't find perlite how about pumice?
I much prefer pumice rather than perlite.


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## Marc (Feb 22, 2011)

I've found some suppliers for horiculture, I'm trying to contact them to see if they sell it to me. Lot's of big suppliers over here refuse to sell to normal consumers.


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## Mathias (Feb 22, 2011)

gonewild said:


> Since you can't find perlite how about pumice?
> I much prefer pumice rather than perlite.



Yes, pumice is readily available. Some German nurseries, for example Röllke, have it where it is called bimsstein. Can be found in grades up to 20-30 mm. 

As pumice is porous, isn't there a risk of accumulating salts?


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## gonewild (Feb 22, 2011)

Perlite is porous.

In fact perlite is more porous than pumice. Perlite will soak up water to the point of saturation where pumice won't. Pumice has closed holes that trap air.

Pumice is much better than perlite for growing media but lost position in the horticulture industry because it is heavier than perlite and costs more to transport. 

It is easy to purchase perlite here in California but very difficult to find pumice. 

Pumice won't risk salt accumulation any more than any other part of your media mix.

Use pumice....forget perlite.


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## Marc (Feb 26, 2011)

Bought a bag of 100 liters last friday. 

It was the coarsest class they had available 1 - 7.5mm.

I left it at my parrents place because they have more room then I do/ Going there tomorrow to fill a bucket. Probably will run it through a sieve to get the fine stuff out.

Will let you know how the stuff looks when I get it out of the bag.


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