Biennial Plants: Definition, Examples & Quiz

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Taught by

Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

All plants need time to grow and reproduce. The amount of time they require depends on the type of plant. In this lesson we will learn about biennial plants.

We also recommend watching Seasonal Growth Cycles: Perennial, Annual and Biennial Plants and Nonvascular Plants: Examples, Definition & Characteristics

Definition of Biennial Plants

All plants need time to grow and successfully reproduce. They also need light to undergo the process of photosynthesis. Biennial plants require two years to complete their life cycle. Typically, in the first year the plants grow roots, stems, and leaves during the spring and summer months. As fall and winter occur the plants enter a period of dormancy. When spring arrives again the plants continue their growth and flower in order to reproduce. This allows then to fully complete their life cycle in two years.

Examples of Biennial Plants

Do you like to have onions on your burgers? If so you are enjoying part of a biennial plant. Onions require two years to fully grow and flower. They are planted in the spring of the year where the onion itself will begin to mature underground and the stem of the plant grows aboveground. In the fall and winter of the year the plant goes into a dormant period. The following year the plant will flower and reproduce. The onions that we commonly eat are harvested during the first year and the plant is killed rather than being allowed to go to its second year. However, in the wild and in order to fully cultivate them they require two years.

Onions are biennial plants.
An image of onions.

Foxgloves are popular plants sold in greenhouses today. Wild foxgloves are biennial plants. They grow from a bud in their first year and produce stems and leaves. In the fall of the year the leaves and stem die back. During the second year the plants continue to grow and produce beautiful flowers. While horticulturists have produced a variety of foxgloves that can do everything in one year the original wild varieties are biennial.

This wild foxglove is a biennial plant.
An image of a foxglove plant.

Hollyhocks are plants with beautiful purple and pink flowers. They grow from seeds that have fallen to the ground. In the first year of their life they establish roots and a small stem. In the second year they grow to maturity and produce their magnificent flowers.

Hollyhocks like this are biennials that require two years to complete their lives.
A picture of a holllyhock plant.

Summary of Biennial Plants

Biennial plants are any plants that require two years to grow, flower, and reproduce. There are a variety of biennial plants. Many of them are extremely successful in the landscaping industry.

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