Is this OUR shale? Surely not the future for our shale - "biting the dirt"!! Although it is hard to find and expensive when you do!!


Expanded shale is like "Vermiculite plus"--it is, as I understand it, "popcorned" shale rock.
Please realize that vermiculite is expanded, or "popcorned", mica. Mica is naturally a rock made of many fine layers--all fragile and glassy (silica rock is, basically, glass--so you have whisper-thin layers of glass puffed out, mostly apart). When expanded, mica forms a very fragile accordian shape that holds a lot of moisture--and usually some air. The air is needed to keep roots from drowning--they have to breathe, too! Alas, mica breaks down quickly into tiny blobs that can form a gray mass of blech -- say, if used at the bottom of a container. Even if the blobs are evenly distributed in your dirt-free soil mix, they still won't hold air anymore--and don't hold much water. Blobby mica is not a sterling aid to roots anymore. Solution? Add more vermiculite (at an annual cost), try another product/substance/method, or move to expanded shale.
Unlike mica (which expands into a fragile accordian shape to make vermiculite), shale starts as a roundish rock. Expanded shale retains a smooth rocky appearance--just larger. (Think of corn expanding into hominy--still a distinct shape, but bulkier.)
What is so wonderful about expanded shale? Expanded shale *always* retains 30% air. Even if you dump it into a bucket of water, the stuff still retains 30% air (in normal environmental conditions). This means your plants'
roots always have access to air, so they are pretty much drown-proofed. Texas A&M tested solid clay soil, in a ground-level bed, with moisture-sensitive plants. Solid clay soil slew the poor test plants rapidly (as anyone with clay soil already knew.....) The plants in the bed with expanded shale survived and *thrived*--that 30% air pocket content saved them. Naturally, the 70% water pocket content provides needed moisture to plants, even in challenging conditions like raised beds/containers in 110+ degree F summers. (Probably great for vacation survival for houseplants, too. Also for people with "blue thumbs" who overwater everything....)
Expanded shale is easy to use. It is useless to put a layer of expanded shale in the bottom of a container--just mix it evenly in the soil. The A&M experiment was 50% clay, 50% expanded shale. Your good compost/coir (or peat, or varied, aged compost only) soil mix will not need that much shale.
Unlike the water absorbing gels, expanded shale will never swell or shrink, so you don't have to worry about the soil (and plants) heaving up or collapsing.
I got mine at a fine plant nursery in Dallas, Texas called Northhaven Gardens. The brand name is TruGro Soil Conditioner.
Expanded shale weighs more like lava rock than vermiculite--and has the same ability as lava rock to remain intact for many years (centuries? millenia?) at a moderate initial investment.
Can you introduce expanded shale into your squarefooting program gradually (and spread the initial cost of 8-10 U.S. dollars for a bag the size of a large sack of compost/hummus/soil)? Yes. I think you could gradually mix expanded shale into your squares along with your new scoop of compost, each time you replant. An end result of 25-33 % expanded shale should be very beneficial to your squarefoot beds or containers, whether raised or in ground. I'm sure that even 1-15% would give a definite benefit to most gardens.
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