What's in the bottom of your raised bed?

When I moved my beds I used two layers of cardboard under the bed over my lawn grass, then I covered my walkways also with two layers of cardboard then used woodchips down over the cardboard over my lawn grass, on the edges I only have a single layer and the only thing to come thru that is nut grass. The big reason I don't dig in my back yard is I have a large metal electrical box in the corner of my yard it could be a shocking experience, I know the wires are supposed to be buried deep But.  

I'm planing to use 2 layers of concrete block to make my raised bed. I have everything I need for my MM in the top 8" layer, but what should go in the bottom 8" as filler? I have heard/seen suggestions of recycling items - glass and plastic. Is that actually a good suggestion? What about sand? I like the cardboard and clippings suggestions posted in this thread but I don't have almost a yard worth of that stuff.

I would not put non-compostable things such as glass, plastic, or tin, in the bottom of the beds. And, sand would probably not be on my list either since it would allow the water to drain out too fast.  If you can get things such as free wood chips, straw, etc., those will slowly decompose and build good fungi-based soil.

All of my beds are 18" high, and I had to fill 12" in each of them so that there was only 6" left to fill with a good soil mixture.  Some of them are filled with topsoil that I bought from the local bulk mulch place, some are filled with wood to make them hugelkultur beds, and some are filled with excess garden soil that I had available. All of them have worked really well, and in all of them the soil or filler in the bottom has gotten richer and better with age - the earthworms have done a tremendous job of carrying nutrients up and down their tunnels.

With all of the beds, I placed a solid piece of half-inch hardware cloth on the ground, covered that with two layers of cardboard, and then put the raised bed on top and filled it. The half-inch hardware cloth is to keep the gophers and moles from burrowing into the bed, and the cardboard was to kill the grass and weeds in the ground so it would not grow into the bed.

Thanks, as always!

My beds are 36 inch deep brick built beds so are different to most folks .

A foot of sharp sand over the drainage hole in bottom of each bed , a foot of well rotted manure , then a foot of well made Mels mix .  Topped up with more Mel's mix three times by the time they had fully settled into quality productive beds .

I put about a foot of raked leaves in my legacy beds—they are a foot high.  After a year, that deflated; I added some peat and vermiculite (for volume) along with more compost.  Worked beautifully!  Still is!

The bottoms of my beds are lined with 1/4" hardware cloth, Mel's mix and gallons of sweat.

However, the bottoms of my beds are open to the dirt.

FGH, Generally recommended for tall, solid beds are washed sand for the lower part and 6-7" of Mel's Mix on the top.

  Just had a true thought that goes with this thread. " My feet are at the bottom of my raised bed " it's raised up on six times nine inch " Elephants Feet because I've got a bust up spine 

First, the beds are a foot deep to help retain moisture from excess sunlight.  Every year or every other year I remove the bottom half and re-stuff it with old llama manure and straw.  This also brings a nice worm community to the beds.  Then put 6 inches of Mel's mix back over the top.  I find this to be quite a potent mix.

LM,

I'm still looking for a new source of llama beans here in Central Oregon.  Not to mention mint compost.

Hi Donna, hope you find some.

Thanks, LM.

I've found a potential source of mint compost, but it's 2-hour, 45 minute trip from here, and being in a high-risk category or two, travel is pretty much out of the question for now.

I expect that I'll find a local source of llama beans eventually.  Meanwhile, I can't seem to make sufficient compost to feed my SFG properly.  Luckily, I have found a variety of composts that pretty much suffice.