The Life Cycle of a Biennial Plant

Written by elizabeth layne
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The Life Cycle of a Biennial Plant
Wait patiently for hollyhocks to bloom -- they're biennial. (Hemera Technologies/ Images)

Plants are classified as annual, biennial or perennial based on their life cycles. Knowing a plant's classification is helpful when establishing a garden. A plant that does not seem to be growing could just need a little bit more time.

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Biennial Plants

A biennial requires all or part of two years to complete its life cycle. During the first season, it produces vegetative structures, such as leaves. Following that, it needs a period of dormancy in winter. Then the plant produces flowers, fruit and seeds the following spring and summer, and dies in the fall. Swiss chard, carrots, beets, foxglove, hollyhock and sweet william are biennials.

The Life Cycle of a Biennial Plant
Carrots take two years to grow. (Carrots image by Alla Podkopaeva from


Sometimes biennials move from seed germination to seed production in only one growing season, according to Oregon State University. Known as "bolting," this occurs when extreme environmental conditions, such as drought or temperature variation, cause the plant to rapidly cycle through the equivalent of two growing seasons. Bolting can also occur when biennial plant starts are exposed to a cold spell before being planted outside.

Annuals and Perrennials

An annual completes its life cycle in one year, in which it starts, matures, blooms, produces seeds and dies. Perennial plants are those that live for more than two years. Perennials are divided into two categories: herbaceous and woody.

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