I will absolutely go contact my local nursery's for mix. A few have already gotten back to me and have nothing for raised beds. I am waiting for one in particular that offers bulk mulch, local made compost, soil conditioner and more. I'm most hopeful that they have one. If they don't, I'll look more into making one. It does seem like with a bottomless one, it doesn't have to be anything super specific.solid7 said:Coco is great for seed starting, so nothing wasted. You can literally plant seeds in pure coco for seed starts. And, as if the coco wasn't forgiving enough, the depth of the solo cups make it almost impossible to overwater. You really don't need to bottom water coco, though, and I'd absolutely recommend against it, for seedlings. If you are, in any way, going to be able to overwater coco, that's how you'd be able to accomplish it. Plus, it can/does grow mold, being constantly saturated. I've seen it, done it, and am absolutely not ambivalent about recommending against bottom watering seed starts in coco.
If your raised bed is open on the bottom, you've got the closest thing that there is to growing in earth. There will be no problems with drainage - providing that you aren't sitting on top of some impermeable substrate. You get all the advantages of an in-ground garden, but with localized premium grow media. Your plan for filling them sounds fine, but definitely go find nursery mix. I put all sorts of rotten wood and things in my beds. I don't think you need to go too crazy with multiple ingredients if you find that nursery mix. It's going to break down just fine, and any good nursery mix will already have a fairly significant amount of partially/fully composted material.
If you don't like the idea of companion/layered planting, consider mulching with yard waste. I do that so often in another section of my garden, that I'm considering buying a quality shredder this year, and never sending anything to the landfill again.
I did have a question about size. I was thinking about a 4x8 or two depending on how bulk the medium ends up being. But how tall? I saw people say taller is better, but I assume that mostly means for closed bottom raised beds. Would 8-12" work for a bottomless?