The stems remain compact and the leaves are low to the ground, often forming a rosette. Many biennials require a cold treatment, or vernalization before they will start to flower.
During the next spring or summer, the stem of the biennial plant grows very quickly, or "bolts". The plant then flowers, producing fruits and seeds before it finally dies.
Because of the longer wait til bloom time of these slow but sure bloomers,
many commercial growers propagate them and vernalize them, and sell them "ready to bloom" or even labeled as "annuals".
Examples of Biennials:
Sweet William Foxglove Hollyhock
Canterbury Bells Money Plant Forget-me-not