A real bed, eh? A couple pillows and a night stand might be appropriate, KennyP.

I don't know about the concrete/soil question. Just wanted to comment on the elm.

My garden for nearly 10 years was not too far from an elm; it wasn't a large tree and still isn't. Other than dryland alfalfa in the field on the other side of the elm, there wasn't much around the tree but some grass and knapweed that was kept mowed. The irrigated garden was about 150 feet away. That was the only irrigated ground within about 300 feet to a lawn.

You guessed it. By about the 6th or 7th year, I began to find the elm roots along that one edge of the garden, 150 feet from the tree.

Steve

You could do the concrete, but it likely would need perforated drain pipes and stuff to manage the moisture. You could toss in a few handfuls of worms to keep the soil 'alive'.

If you used the dirt, find some of that woven, polypropylene weed barrier that allows water movement, and lay down a couple layers, then fill the raised bed. That should keep the tree roots out for a few years, anyway. But that weed barrier is tricky - the new stuff is a lot more impermeable than the older stuff.