Cheerful and reliable September blooms:
Rudbeckia (Black-eyed Susan) zones: 3-9
One of the easiest perennials to grow, and there is something universally cheerful about a huge stand of these daisy-like yellow flowers. Plant in full sun.
Despite anything you may have heard, Black-eyed Susans are NOT deer resistant. But they do naturalize if given the chance, so two or three plants can become a large stand over time. Once they reach a certain critical mass, any deer damage tends to remain on the edges, not diminishing the effect of the whole clump.
Until your Rudbeckia reaches such a critical mass, protect them with deer repellent, such as Deer Defeat.