many food plants are, or are grown as, annuals, including most 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.