BBS bagged Decomposed Granite (DG)

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jp29
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BBS bagged Decomposed Granite (DG)

Post by jp29 »

This Decomposed Granite (.5 cubic feet for $3.48) contains a lot of (clay?) dust which tends to migrate to the bottom of containers where it can form a drainage impeding "sludge". I washed it using a garden hose and a fine kitchen sieve to remove the dust which reduced the volume by almost one half.

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unwashed

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After washing

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Example of dried "dust sludge" - bottom layer stayed in pot

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With dust removed from inorganic component of a potting media
James
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DaveW
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Re: BBS bagged Decomposed Granite (DG)

Post by DaveW »

You can also get quarter inch to dust granite chips from builders merchants in the UK James. It is crushed granite waste from quarries I think and though granite dust is not clay being almost like cement powder it does act like yours if mainly used as the principle ingredient of the potting soil unless the dust is removed. If mixed with a soil based potting medium the dust is not so much a problem.

I guess it's a case of if you are using mineral mixes whatever you use you need to remove the dust. I have even had better rooting with soil based mixes if I have let them dry first before mixing then sieved the dust out using fly screen, which is about the equivalent of a flour sifter.

As you say, the problem is if your buying the ingredients you loose a considerable amount of what you have bought as dust, which can work out expensive if you have many plants to pot.
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Saxicola
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Re: BBS bagged Decomposed Granite (DG)

Post by Saxicola »

It may be nit picking but the dust is probably equivalent to sand, not clay. Sand varies from 2mm down to .05mm. Clay is .002mm or less. Loam is in the middle (.05-.002mm) size wise. Soil components act strangely in pots so I'm sure that dust can form a poorly draining sludge but in the ground or in a mix like Dave mentions it won't be a big problem. True clay soil would be a mess no matter what.
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iann
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Re: BBS bagged Decomposed Granite (DG)

Post by iann »

DG fines go down smaller than sand. Not quite clay, but far too fine to be good in a pot. Handy for packing into a solid pathway surface, OK for drainage in an open bed, but just clogs up a pot.
--ian
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