From a gardener's perspective, a plant's status as annual, biennial, or perennial often varies based on location or purpose. Biennials grown for flowers, fruits, or seeds need to be grown for two years. Biennials that are grown for edible leaves or roots are grown as annuals, e.g. beets, Brussels sprouts, cabbage, carrots, celery, parsley, and Swiss chard. If a normally biennial plant is grown in extremely harsh conditions, it is likely to be treated as an annual because it will not survive the winter cold. Conversely, an annual grown under extremely favourable conditions may have highly successful seed propagation, giving it the appearance of being biennial or perennial. Some short-lived perennials may appear to be biennial rather than perennial. True biennials flower only once, while many perennials will flower every year once mature.