An annual plant is a plant that completes its life cycle, from germination to the production of seed, within one year, and then dies. Summer annuals germinate during spring or early summer and mature by autumn of the same year. Winter annuals germinate during the autumn and mature during the spring or summer of the following calendar year.
One seed-to-seed life cycle for an annual can occur in as little as a month in some species, though most last several months. Oilseed rapa can go from seed-to-seed in about five weeks under a bank of fluorescent lamps. This style of growing is often used in classrooms for education. Many desert annuals are therophytes, because their seed-to-seed life cycle is only weeks and they spend most of the year as seeds to survive dry conditions.
In cultivation, many food plants are, or are grown as, annuals, including virtually all domesticated grains. Some perennials and biennials are grown in gardens as annuals for convenience, particularly if they are not considered cold hardy for the local climate. Carrot, celery and parsley are true biennials that are usually grown as annual crops for their edible roots, petioles and leaves, respectively. Tomato, sweet potato and bell pepper are tender perennials usually grown as annuals. Ornamental perennials commonly grown as annuals are impatiens, wax begonia, snapdragon, Pelargonium, coleus and petunia. Examples of true annuals include corn, wheat, rice, lettuce, peas, watermelon, beans, zinnia and marigold.