The best flowers are those that thrive in your area. Check to see what USDA hardiness zone you're in. It doesn't make sense to plant camellias, for example, if you live where the winters are very cold. The camellias won't make it through the first winter. Some flowers need a chilling period to bloom, such as lilacs. If you live where the winters are warm like Florida, lilacs aren't a good choice. Since annuals only live for one season, they're adaptable to most climates.
Zinnias grow from 6 inches high with flowers the size of a quarter (Thumbelina) to 3 feet high with flowers 4 inches across (ruffles). The stems are long and straight. They make a good cutting flower as well as for the garden. They prefer warm temperatures.
The happy faces of sunflowers brighten up any garden. The plants range from the dwarf variety at 3 feet tall to the giant variety 10 to 12 feet tall. Most grow between 5 to 7 feet tall. Sunflowers bloom in various shades of yellow and gold. There are a few burgundy colors as well.
Marigolds come in yellows, oranges and bicolor of burgundy and yellow. The plants have a distinct musky odor, which some people find unpleasant. The plants reach from 12 inches high for the French type to 24 inches for African marigolds. These flowers are good companion plants for the vegetable garden since they're thought to keep aphids and insects away.
If you have a shady spot, impatiens are the flowers for you. They bloom prolifically from late spring through fall. They don't like the heat and prefer a partially shaded spot. Colors include white, pinks and reds.
Cosmos grow from 24 inches to 48 inches tall with feathery leaves and five petaled daisy-like blossoms on long stems. They prefer warm weather and full sun. Most cosmos bloom in white, pinks and dark pink, although there are yellow and orange colors available.
Another full sun summer flower, Celosia looks like feathers in brilliant colors of red, orange, purple and hot pink. The leaves are edible and used as a foodstuff in Africa.
Nasturtiums are edible as well, both the leaves and the flowers, with a sharp peppery flavor. The plant grows easily from seeds. The seeds are about the size of peas. That makes them easy for children to plant. They sprout quickly and reliably especially if soaked overnight in warm water. Nasturtiums prefer cooler early spring weather.
The fragrance of sweet peas in full bloom scents an entire garden. The stems are short, no more than 6 inches, growing on a vine that reaches 6 feet tall. The seeds are slow to sprout and grow rather slowly. Once they start to bloom it's a nonstop show until the heat of summer hits.