Visiting Cologne yesterday, I spotted a wonderful modernist building near Barbarossaplatz that was surrounded by little balconies just for plants! The balconies appear to be too narrow for people to use, more like catwalks, and are well stocked by the residents with geraniums, potted trees and other thriving plants.
Fittingly, the business on the ground floor is a flower shop. I wondered if the storefront space had been intended as a flower shop from the very beginning, with the architect adding the plant-balconies to complement the business.
At any rate, the plants look just great.