interesting idea: plant box and belts . Hook together several belts to be large enough to go around if using real leather belts (from thrift store) . these "belts" look more like strap webbing and could be DIY made to size.
Unique DIY String Light Poles with Concrete Base. These DIY string light poles are extra sturdy and they look unlike any string light poles we’ve seen, with tree trunks taking the place of wooden or metal poles in the concrete bases.