Virtually all annuals grow easily from seed and add brilliant color to a summer garden. Hardy annuals are the easiest to grow, because mature plants drop seeds, sprouting new plants and providing color and foliage into late fall. Half-hardy annuals perform brilliantly during summer months, but die out when temperatures begin to drop.
Ageratum or Floss Flower
This half-hardy annual has long-lived flowers. Varieties include blue, pink and white. Dwarf varieties grow to 6 inches and are good for edging. Tall varieties grow to about 30 inches and can be used for cut flowers. The plants need full sun and well-drained soil. If you regularly deadhead spent flowers, they will bloom again.
Antirrhinum or Snapdragon
Snapdragon is a half-hardy annual that provides your summer garden with brilliant color. The snapdragon tall varieties grow up to 4 feet and can be used for cut flowers, intermediate varieties grow to 18 inches and dwarf varieties grow to about 12 inches and do well as edging or in container gardens. You can choose snapdragons in a wide variety of colors from yellow to deep red. Remove the flowers when they begin to fade to keep buds coming.
Impatiens or Busy Lizzie
Impatiens, sometimes called busy Lizzie, are half-hardy annuals that can be used in bedding, containers, hanging baskets and window boxes. They grow from 6 to 12 inches tall in a variety of colors. The plants will grow well in both full sun or moderate shade with well-drained soil. Take off dead flowers to keep plants blooming all summer long.
Limanthes or Poached Egg Flower
The cup-like flowers of this plant are white with yellow centers, giving it its unusual name. This hardy plant grows to 6 to 9 inches, produces masses of the white and yellow flowers all summer and into fall. Limanthes prefers full sun and moisture-retentive soil.
Dwarf varieties grow to 6 inches, while the "Dahlia Flower Mixed" variety of the zinnia grows up to 24 inches, making this half-hardy annual perfect for almost any summer garden. The plants love full sun and well-drained soil. Zinnias bloom from mid- to late summer and come in a variety of brilliant colors, including lavender, yellow, orange, gold, green, white, pink and red. The long stems make it a good cut flower.