Re: Seeking advice on a frog and plant rack build
I'd paint it as well. I never had any luck staining pine, even after using wood conditioner; pine takes stain poorly (blotchy) and won't stain the same as the (oak?) plywood.
If you paint, you can fill the gaps first, if you like. Paint will cover the fastener heads, too -- might be best to sink those flush before finishing.
I think I could turn and live with animals, they are so placid and self-contain'd.