While I now this isn't really "container gardening" I did not see any other subject area to ask this question. In the past, there has been a lot of discussion regarding treated vs. nontreated wood for raised beds. Is it safe/healthy/acceptable to use treated lumber for raised beds if I am not planting root crops? And if I do plant root crops, can I use treated wood on the lower section closest to the ground then regular lumber in the top 12" or so? Any advice will be great.
The chemicals used to treat wood used in landscaping have changed in the last few years. I believe arsenic was the main bad guy, but is not the case any longer.
Still, you're right that treated wood shouldn't be used for beds where you grow edible food plants, nor for childrens' play areas.
If you are planning to live there a while, and want to use treated lumber for an ornamental bed only, it's probably going to be okay. IF the wood is greenish, it's probably a copper based treatment which may alter your soil chemistry too much, which could in turn hurt your plants.
To my mind the real problem comes when you leave that property and the new owners have kids who play there, or they plant food plants in those beds thinking that no one would dare use treated lumber... Think about that, and if you are comfortable with your plans and willing to take a chance on possibly losing plants, then do it.
I'm all for doing whatever makes sense for us within reason. Heck, I inherited some beds with old railroad ties, and I sure didn't rip them out.