Posted: 17/10/2017 at 20:33
If the pot is 18 inches, the railings will be about 3 feet so we are looking for:
something which is over 2 ft tall and flowers all summer.
Not sure if Cosmos would do well in a pot but that is one. The bigger dahlias might be another. Catmint also flowers all summer. And I had flowers on my penstemons for months.