Tried to build a raised garden bed in my Denver backyard last spring and learned why you don't use untreated pine for the frame | DIY Gone Wrong - Rigidtalk
Been there with the cheap pine. My old garden bed rotted out in like two years, total waste of time. Had to replace the whole thing, which cost more in the long run. Now I just save up for the pressure-treated stuff. It hurts the wallet upfront but saves so much hassle.