I would not consider letting PT wood anywhere near my garden and don’t use it elsewhere on our property either. The arsenic and other chenicals do leech our and eventually the wood does break down releasing the chemicals. There is a new type PT which the industry claims is safe but that is what they said about the original stuff. Alternatives stones, concrete blocks, logs, cedar or redwood, not creating raised beds at all.
I wouldn’t use treated wood. It’s been awhile since I investigated it, so I’m sure there are other group members better informed than I. What I remember is that the chemicals used to pressure treat the wood are toxic, and they can leach into the soil. There are several alternatives for framing beds, or raised beds. It kinda depends on your conditions. Right now I have a raised bed made out of straw bales. I started with the straw because it was free. I’m planning to frame the bales with untreated wood as the straw breaks down. It’s been an interesting experiment; don’t try straw unless you don’t mind yanking it’s sprouts on a daily basis! I also had a whole yard full of raised beds made out of concrete blocks when I moved here. They seemed to work just fine; I took them down and they now form the frame for my firewood. Straw and concrete are not too decorative, though; I know there are some more aesthetically pleasing alternatives out there.
Yup, this stuff will allow leaching of heavy metals into the soil, along with a bunch of nasty chemicals. If you live in the western US, use redwood. In other places I would use cement block for the base (ground contact) and lumber for the rest. Use an organic stain on the lumber and use a liner of some kind on the inside of the lumber. Only line one side of the lumber. It has to breath and dry out or it will rot prematurely. Cement leeches water out of the ground, so minimize contact with the cement blocks. I use metal plates on the corners of the box.
The treated boards really shouldn’t be used in a garden of food crops. The preservatives in the boards can slowly contaminate your soil and could be taken up through the roots of your garden plants. You could get sick if that happens. I have been gardening for some time now and have found that cider boards work pretty good and if you look around you can get them cheaper than the treated boards. The cider boards last a long time to. Lots of luck this coming growing year.