The sidewalks of my neighborhood are filled with stacks of cedar planking from fences blown over in hurricane Ike. Being a cheap fellow, I hauled a bunch of them home to make some more raised bed/square foot gardening boxes. I made the assumption that cedar wood fencing ISN'T treated with anti-rotting agents but now I'm second guessing myself. Are cedar fence planks chemically treated or are they safe to make gardens?

How about the 2x4's? I assumed they ARE treated pine and I shouldn't use them on the inside of raise beds.

Thanks,
-Blast