geronimo wrote:
For square foot gardening, I was thinking it might be cheaper to use
landscaping timbers that have two flat sides, drill holes near the
ends with two of them stacked, and then drive 1 in. EMT conduit into
the holes to fix them into position---- like I have seen done with
raised flowerbeds. Untreated wood would probably rot in a short time.

It depends on the timber. You can get untreated timber that will last 40
years or more in contact with the soil. Talk to you local timber merchant
to what is available in your area and the price. OTOH you can use concrete
blocks and other building materials that will last in contact with the soil.


But what about growing veggies? What are the chances that toxins could
get into the vegetables from the lumber if it's treated? Has someone
actually tested to see if arsenic leaches out and gets taken into the
plants?

I believe such tests have been done but I don't have a link. This is a
hot-button issue and all I can say is you should do your own research and be
comfortable with the risks you take (or don't take) based on solid
information and expert opinion. Such information and opinion may or may not
be available here.

David