Biennial

While most plants are either annuals or perennials, a select few can claim biennial status.


Biennial plants take two years to complete their lifecycle from seed to flower and fruit, before dying. Not to be mistaken with biannual, which happens twice each year, biennial plants spread their growth and development out over two years, often taking advantage of a cooler dormant period.

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During their first year of life, biennial plants focus their energies on growing vegetative structures, such as stems, leaves and roots. Very often, biennial plants are low growing, with a rosette shape, but not always. As temperatures drop, these plants enter a dormant period of vernalization that is necessary for them to flower the next spring. Some biennial plants, such as lettuce, spinach, and fennel, generally are not considered edible after they have gone to seed. Other biennial plants include radish, parsley, leeks, Black-eyed Susan, and carrots.


Unusual temperature changes can trick biennial plants into suddenly going to seed during their first year. This is called bolting. It may make the plant too woody or bitter to enjoy eating, but it has now become a source of seeds for next year’s crop. 


Note: I generally let my lettuce go to seed (pictured) after harvesting as much as I can get from each plant. The result is that I now have lettuce popping up all over my yard, to be grown where it is or transplanted to a raised bed.