I have decided to make some raised planting boxes rather than go into the
earth, which here is a combination of sand dune sand and caliche. I believe
that some treated lumber would last the longest, or perhaps some railroad
ties. Maybe some old building beams if I can find them for a decent price.

Is there a danger of the chemicals leaching out from treated lumber or
railroad ties for garden beds? What if I put a liner? I intend on going to
the nursery, and getting a really good mix of soil delivered, or maybe just
getting some bales of peat moss, and some bags of soil and mixing. But I
don't want to do all the work and spend all the money if I am planting these
things in a toxic box.

TIA

Steve