Material for raised bed
 

I am thinking of using raised beds for my garden this year, I would like to
put several in before the start of the growing season. My question is what
to make them out of?

1. I could use untreated lumber, but then I need a way of preserving them.
Any thoughts or ideas on this? Are there non-toxic paints or stains I can
use?

2. I could use treated lumber, I think the newer kinds are arsenic free.
Are there chemicals in this kind of wood that may leech into the soil?

3. What about that artificial wood decking material that I see at Lowe's and
Home Depot? Would be expensive, but wouldn't last a long time?