Unfortunately the flowers didn't last long. My mailbox gets direct sunlight and I didn't water them enough.
So I started looking for mailbox garden ideas. A friend told me about their neighbor who had a large pot that their mailbox post was in. I decided to try it for my mail box.
I purchased a large (22"+) wine barrel that I cut a small hole in the base. This was so I could put it over my mailbox post, since my post was cemented in the ground. I had to remove the cross post and my mail box in order to position the pot. This was fairly easy since we had screwed the posts together.
I filled the bottom of the pot with gravel to help with drainage, and I also filled in around the pot with gravel to fend off weeds.
I am very pleased with the end result! I'm hoping that the potting soil (and the pot) will help keep more moisture for the plants. My mailbox is now one of a kind!