I tried to make this post on the container gardening forum, since I do container gardening; they referred me to this subforum, so that's why this is being posted here.

First I do container gardening; the soilless mixture I use is a combination of spaghnum peat moss, fine pine bark mulch, lime, and vermiculite.

I used this soil mixture last year, but I used perlite, because that's what was available. So I don't know what the best type of vermiculite to use is for container gardening, as I've never used it in my soil mixture before.

I make the soil mixture in large quantities, and it's just more economical to buy the ingredients for it in bulk. The biggest size bag available locally is 2 cubic feet, which isn't big enough. If I can find a place via the internet that has flat rate shipping and the product is a reasonable price, it will be cheaper for me to order it via the internet than buying it locally.

When I looked for vermiculite, I never realized there were so many different varieties; there is very coarse, coarse, medium, and fine with the size of the texture. My soil mixture calls for fine vermiculite, but it's cheaper to buy it in bulk via the internet with the coarse textured vermiculite, and medium grade vermiculite. I also found horticultural vermiculite, which is also supposed to be good for container gardening.

The main question I have is does it really matter how coarse the vermiculite is? Is how large/fine the texture of the vermiculite is affect drainage and soil aeration (as in if you use a large textured vermiculite as opposed to a fine textured vermiculite, will the soil drain poorly and have poor aeration because it's large textured, or vise versa)