Between the concrete slabs of big cities, wild plants spring up: butterfly tree, mugwort, senna... On the walls flourish tags: Escro, Odsu, Idiot, Ralers, Jerve... Stalked, eliminated, plants and signatures are always coming back to life. What if the tags reveal themselves to those who try to decipher them? Are they really so meaningless? Who are the taggers who walk our sleepy streets? On the borderline between questioning and fascination, "Mauvaises herbes" takes a mischievous, lucid look at the underground world of tagging in Brussels. Against a backdrop of urban poetry, the filmmakers at last reveal the vision of those involved in this movement, between urgency and artistic gesture.