Maybe someone out there can help me out with this. I was walking along a main thoroughfare towards the Bird’s Nest Stadium in Beijing and came across on the grass verge a construction consisting of tubs of what I believe may be sweet potato plants craftily arranged on a metal framework in the general shape of a Christmas tree. Here it is below (click on it to enlarge).Can somebody explain the point? Is this vegetative cone merely decorative, or do the plants have symbolic value? Are they in fact sweet potatoes?