Bulb-type plants can survive dormancy without nutrients or moisture. In this sense they are perennials. Some bulbs are planted once and last for years. Others last only a year or two. Nonhardy bulbs must be planted each spring, dug up in the fall and stored where they will not freeze.
Biennials produce only foliage and roots the first year.
The roots survive the first winter. During the second growing season, the biennial blooms, produces seeds and then dies. Biennials may reseed and appear to be perennial. Gardeners usually purchase biennials from nurseries, rather than grow them from seed. This avoids wasted space taken by biennials during their first, nonflowering year of growth.