Dokudami (どくだみ) is one of my favorite Tokyo weeds. It grows on cinder block walls and sidewalk cracks. Above is a large patch in front of my apartment building in May. The roughly 2 by 5 meter strip is a never changing display of flowers tended by the residents; its wildness contrasts with the clipped hedge on the other side of the entry path and heavily pruned trees in the parking lot.
Here are some other May flowers, including what is called in Japan “American jasmine.” The middle two plants I do not know the names. The last one is Datura, originally from Mexico.