Clematis is a climbing perennial vine that features attractive, star-shaped blooms that span half an inch to 7 inches across. The colors of the blooms include white, red, pink, blue and purple. Install a trellis behind your mailbox and the clematis will grow up it, creating an eye-catching display.
The creeping variety of this perennial plant provides showy ground cover around your mailbox. The plant grows in mounds that reach 4 to 6 inches in height and spread about 2 feet wide. Large quantities of small, star-shaped flowers cover the plant in colors of red, blue, white and lavender.
For a punch of color that will last all summer long, plant petunias around your mailbox. There are several varieties of these annual flowers, all of which grow flowers that resemble trumpets and come in an array of colors, including white, red, magenta and deep purple. They either grow upright or spread out in a creeping form along the ground.
Another annual flower, marigolds are circular flowers that are characterized by several petals that grow on top of one another, creating what looks like a fluffy ball. They are orange and yellow in color and typically grow to be about a foot tall, though some varieties may reach 4 feet.