Zone 6 on the USDA Plant Hardiness Zone map, includes the upper south, mid-Atlantic and select parts of the inland west. Some examples are Kentucky, southern Missouri, northern Texas, western Pennsylvania or northeastern Arizona. Temperatures in zone 6 have a minimum low of -10 degrees Fahrenheit and do experience frost. When selecting annuals for this, or any area, plant after the last frost and select plants that are hardy enough to last into the fall.
Marigold (Tagetes) is a long-time gardener's favorite that is easy to grow and provides warm color to a garden. Marigolds can reach 4 feet tall and have compact flowers (sometimes several to a stalk) that range in color from yellows and oranges to browns. Plants will bloom from early summer to first frost and spent blooms should be pinched off to encourage growth. Plant in full sun and water regularly. These plants have a sturdy stem and make good cut flowers.
Vinca (Catharanthus roseus) has a look similar to impatiens (also a good zone 6 annual), but the leaves are glossier and longer and the blooms appear more vibrant. Vinca, which is also known as Madagascar periwinkle, is a low-growing shrub that flowers from spring to fall, thrives in sun to partial shade and requires little watering. Plant is available with blooms in pinks, purples, reds and white that last into the fall. This plant self-sows and may survive the winters, though in zone 6, it is treated as a annual.
Popular in all zones, zinnia (Zinnia) has a vibrant, round flower that can last into early fall. Zinnia leaves are long and narrow and flowers are available in orange, pinks, reds, yellows, purples, greens and white, and some varieties have bi-color blooms. Zinnias can grow to 3 feet tall, though the popular Augustifolia tops out at about 1 foot. Plant in full sun and keep moist throughout the growing season, with the exception of the Grandiflora variety, which is nearly drought-tolerant and is a perennial in some zones.