Annual flowers complete their life cycle in one growing season. They grow, mature, bloom, produce seeds and die back in one year. Different climates blur the lines between annuals and tender perennials. Cold winter weather kills tender perennials and the only choice is to grow them as annuals. Occasionally annuals will survive extremely mild winters and grow as a long-lived annual.
Calliopsis (Coreopsis tinctoria) is a fast growing annual reaching 36 inches in height. Clusters of narrow green leaves spread out to 12 inches wide. Yellow petals surround maroon centers on daisy-like flowers. Calliopsis blossoms from mid-summer until frost.
China aster (Callistephus chinensis) is a tender annual with many narrow petals on the flower head. They reach 12 to 24 inches in height and loom over 12- to 18-inch clusters of narrow green leaves. China asters bloom in late summer until first fall frost in white, cream, pink, red, purple or blue colors.
Common sunflower (Helianthus annuus) is a hardy flower growing 2 to 8 feet tall. Large flower heads are produced on top of thick stalks surrounded by heart-shaped leaves. In midsummer the daisy-like flowers appear with yellow, bronze, red or orange petals. Seeds soon develop in the center as the flower expands.
Forget-me-nots (Myosotis sylvatica) grow in dense clusters of narrow, lance-shaped leaves that spread 8 to 10 inches. Flower stalks grow 12 to 18 inches tall with sky blue blossoms with white or yellow centers in mid spring. Forget-me-nots will continue blooming until July.
Nemesia (Nemesia strumosa) produces clusters of trumpet-shaped blossoms that are 12 to 24 inches high. Summer color includes white, pink, red, orange, yellow, lilac and light blue. Nemesia is a cool-weather annual that will stop blooming when exposed to hot temperatures. To revitalize the nemesia in hot weather, prune the plant back halfway and water well.
Rose moss (Portulaca grandiflora) is a low growing annual reaching only 6 inches in height. It forms a 6- to 8-inch mat of succulent needle-like leaves. Flowers with ruffled edges bloom in early summer until fall in white, pink, red, orange, yellow and magenta shades. The blossoms close in the late afternoon and on cloudy days, but they reopen at the first touch of a morning sunbeam.
Sweet alyssum (Lobularia maritime) forms masses of tiny white blossoms that grow 4 to 8 inches tall. Individual plants spread to 10 to 12 inches wide. Sweet alyssum begins blooming near the beginning of summer and stops at the first fall frost. It will stop temporarily flowering during the hottest part of the summer, but will start again once cooler weather appears.