I used concrete blocks, they're very sturdy and you can get flat blocks for the top row so you can sit or kneel right on it. A frame for screen or row cover works great on the blocks too.

I would use cedar wood if it was me, and certainly dont use any treated wood. You might check out the DIY network on the web and see what suggestions they have.

If you want to use wood I'd go with the cedar or the composite decking material that looks like wood but is actually a plastic. If you're willing to replace the wood in a few years, you can use untreated lumber. That's what my garden is made of. I'm going to use cinder blocks for the next one, though. It's easier for me to work with.

My raised veggie beds are made with cinder blocks, and I love them. I leave the holes upright, fill with potting soil and plant my zinnias and marigolds in them.

Thank you! I never even thought of cinder blocks and I've already got some of those around.