Biennials are plants that require two growing seasons to complete their lifecycle. The first year they usually produce only a rosette of foliage; they then bloom, set seed and die the second year. Some biennials may appear to have perennial characteristics because they self-sow and therefore reappear year after year. Many gardeners choose to purchase greenhouse-grown biennial plants rather than grow them from seed because the plants are in their second year and will bloom that season.
Some biennials need a cold period in order to stimulate flowering. Many of our herbs and vegetables such as parsley (Petroselinum); carrots (Daucus carota), and kale (Brassica) that are grown as annuals are actually biennials and would flower the second year if not harvested. In several cases, plant breeders have successfully propagated annual strains of long-time biennials such as hollyhock (Alcea species) and some foxgloves (Digitalis species). Biennials should be maintained in similar ways as annuals and perennials.
View the following link for a List of Biennials.
For more information on biennials and their requirements, visit the SULIS Plant Selection Program and sort by plant type 'biennial'. Another plant database that contains details about specific plants is Dave's Garden. Use the 'advanced search' and sort by the plant category 'biennial'.
For more on proper plant selection based on site and plant characteristics, see Plant Elements of Design plant selection database.
Click on any of the following headings and link to chapters that explain care and maintenance of herbaceous plants.
Mulching & Watering
Why Use Mulch?
Application of Mulch
Mulching for Weed Control
Mulching for Winter Protection
Mulching for Moisture Control
Watering Your Landscape
How to Determine the Frequency and Rate of Watering
Water Quality and its Effect on Plants
Nutrition, Fertilizers, and Compost
The Basics of Plant Nutrition and Fertilizers
Fertilizer: the Do's and Don'ts
Organic Fertilizers (FUTURE)
Inorganic Fertilizers (FUTURE)
Salt Tolerant Plants
Weed Identification and Lifecycles
Cultural Management Methods for Weed Control
Pruning for Weed Control (FUTURE)
Understanding Labels (FUTURE)
Alternatives to Chemical Herbicides (FUTURE)
Clemson University Cooperative Extension, online information, "Biennial Plants", Bob Spalding. December 1, 1997.
Meyer, Mary H., list of biennials, 2000 core course packet, HORT 1011, University of Minnesota.
Ohio State University, online information, "Biennials".
Dave's Garden; http://davesgarden.com/guides/pf/