Raised bed sides, paint, finish, or nothing?
With the rain finally giving us (New Hampshire) a break I am getting ready to finish building my raised bed sqft garden. I'm contructing the beds out of untreated 2x10's and douglas fir posts. I know these are going to rot, but I have some concerns about pressure treated (the new stuff is safer, but I would like it to be out for a bit longer before planting veggies right next to it). Anyhow, I have read here about untreated lasting a number of years before replacement. My question is, would finishing the bed sides and posts (the design has corner posts in it) with exterior house paint pose a danger as far as anyone here knows? Will it leach anything into the soil? My aim here is to try and get a little more life out of the beds, given the time it is taking to make them, and I think I might like the appearance. Also, same question, with regards to exterior polyurethane.
My concerns for both of these are breakdown in the soil into something the plants can take up and then I will end up eating. Anyone have an opinion on this. I've tried searching the forums before, but most posts seem to be about what to make the bed out of (PT lumber, untreated, concrete block, etc) as opposed to putting a finish on untreated lumber(with the exception of boiled linseed oil).
Thanks in advance!