Product code: Plant stand 15" x 15" square, plant caddy, plant buying stand, unfinished or painted , can hold up to 320 lbs
I will use four 2" swivel casters that are rated at 80lbs each, so your caddy will be able to safely hold a tree/plant and pot buying that can weigh 320lbs.
I will build it as a " composite caddy", joining two solid 8" spruce boards together as one panel about 14.5x14.5.
I will laminate on top of that a piece of 1/4 red mahogany plywood. The total thickness will be 1" thick. I will then wrap a piece of decorative molding around the edges for beauty, and it will also increase the strength. I will then attach the casters. I will then putty and sand entire caddy ready for paint.