Biennials are those flowers which complete their life cycle over the course of two growing seasons. They produce foliage, and sometimes stems, during their first year of growth and then flowers during the second. Once this cycle is complete, they die. Biennials include the long time cottage garden favorites; hollyhock, foxglove, and sweet William.
Fertilizing during the first growing season will help biennials develop healthy foliage. At the end of the first season cut back the top foliage to the crown as you would a perennial. In colder climates covering biennials with salt marsh hay or bark to helps protect them from severe cold and ice. If, however, the plants are not hardy enough to survive a cold winter, they may be removed from the garden and over wintered in a coldframe. They can be replanted in the garden the following spring. Care for them as you would an annual.
After the biennial’s fist season of growth, it goes dormant for the winter. During this time, its root system stores the starches and sugars it requires. The following spring, it reemerges and produces stunning flowers. As a way for some biennials to ensure their species survival, they produce an abundance of seeds. Some of the most proficient seed producers are money plant (Lunaria annua), Forget-Me-Not (Myosotis sylvatica) and Pansy (Viola spp.).
Biennials have the ability to reseed itself so even though the original plant dies after two years, its seeds will often sprout and take its place, starting the two season cycle all over again. These new plants which sprout up throughout the garden can be transplanted to more appropriate spots if needed.
Some flowers which are considered biennials, such as sweet William, forget-me-not, and wallflower, are actually perennials. These particular plants begin their decline after the second season and become less showy each year.
When to Sow Biennials
Biennial seeds are generally planted in late spring or early summer. They can be sown in rows or broadcast throughout the garden. Biennials can also be sown in midsummer in order to force the plant to produce fall foliage and to bloom the early the following year.
In moderate climates, biennials are planted as seeds in late summer or fall. The emerging biennial plants will go dormant to survive the winter and flower the following season.
An alternative to starting biennials indoors is to buy biennial seedlings in their second year, then raising them as you would an annual.
Tip: Become familiar with the biennials you’ll be planting. Some gardeners accidentally pull out the first year’s foliage growth mistaking it for a weed. Give young plants a boost by thinning them as needed and mulching with compost. Transplant only in the first year of growth, not the second.