Depicted below in my customary varied films perspective (Hipstamatic on iPAD) is the newest piece from Banksy, located on Staple Street in Tribeca. Here is a stencil of the Twin Towers with what appears to be a Dahlia sticking out of it. The dahlia seems to represent the first explosion on 09/11/01, plus flowers generally symbolize hope. From a website on flowers and meanings, it says this about the dahlia:
Dahlia’s are spicy flowers, and their meanings range from a sign of warning, to change, to travel, to even a portent of betrayal. The varied symbolic meanings of the dahlia make this flower a wild card.