Annual plants are those that germinate, grow, bloom, set seeds and die within one growing season. For many gardeners, the growing season starts in spring and ends with a killing frost in autumn. Even in tropical areas where there is no frost, annual plants still die after they produce seeds after flowering. Common annual plants include garden flowers, but many vegetables and pesky garden weeds and grasses are also annuals since they grow rapidly and die after producing seeds.
While many grasses come back year after year from their roots, lots of grasses are annuals. In a lawn, often tufted, fast-growing clumps of ryegrass or bluegrass grow, flowering and seeding and then dying within a couple months. Cereal grains are grasses, too, and are planted by farmers in spring and then naturally ripen and die by fall in time for harvest. Annual grain grasses include corn, sorghum, millet, wheat, barley, oats and rye.
Visit a garden center in early spring and you'll likely find a display of seed packets for an array of garden flowers. These annual flowers are sown after danger of frost ends in spring and then flower for our delight. Often the flowers ripen and reveal their seeds, which can be collected and then sown next spring. Common examples of annual garden flowers include sunflower, cosmos, zinnia, cockscomb, alyssum and marigolds.
While we don't marvel at the flowers of vegetables, many grow quickly and indeed are annual plants. Root crops that complete their life cycles within one growing season include radish and potato, although their roots may sprout new growth next spring if the winter soil isn't frozen. Other annuals include tropical vines like watermelon, cucumber, pumpkin, squash and cantaloupe. Cabbage, tomato, sweet pea, lettuce, spinach, dill, bean and sweet corn also are annual crops.