How high will they grow?

I've been fascinated by the size of the sunflowers that were planted by the Health Literacy Missouri staff in tiny (for the size of the plants) snippets of ground at the Terrace Building on Euclid. These giants definitely like the real estate.
In the alley around the corner, I've also been watching this charming little volunteer marigold which seems very happy in quite inhospitable soil. The saying "bloom where you're planted," or at least, "wherever the wind takes you," definitely rings true where nature is concerned.