soil boxes--what type of wood?
My old plywood 1x2x3 soil boxes for greenhouse gardening through the winter are starting to decay badly. I want to build new ones and I'm looking for recommendations about materials. I'd like something rot-resistant, nontoxic (or anyway not likely to release toxins into the soil--know this cuts out pressure treated, don't know abut plywood) and as cleanable as possible . Any suggestions would be greatly appreciated.
To be clear, these aren't frames set on top of the soil, they're complete boxes with wood bottoms with drainage holes.