What is the Difference Between an Annual, Biennial and Perennial Plant?

Plants that lose their leaves for the winter are deciduous while those plants which retain leaves are called evergreen. Most evergreens will eventually lose their leaved, but not all in the same season or at the same time. This is the case with most pines which normally drop needles that are three to five years old.

Annual plants are those plants which complete their live cycle ( seed to seed) in one growing season. Most bedding plants are annuals. Perennial plants are plants which grow year after year, often taking many years to mature.
When a subtropical perennial, such as a tomato or coleus, is grown in colder regions it cannot survive a cold winter and dies. Under these conditions a perennial plant is forced to grow as an annual.

A biennial plant normally completes its live cycle in two growing seasons. During the first year it grows the aboveground foliage while storing food reserves in the root or stem. Many times the over wintering form of the plant is called a rosette which is a low growing cluster of leaves around a short stem. During the second growing season, the biennial uses its reserves to flower. After the first growing season, the cold winter provides the plant with a trigger mechanism necessary for this plant to bolt or send up a seed stalk the second season. Celery and parsnip are examples of biennials. Many weeds and vegetables are biennials. Even though dandelions form rosettes for over wintering, they are a perennial since they live over several years.

Unlike the annuals and biennials, perennials do not necessarily die after flowering. The century plant is one of the exceptions. Combinations of the three categories occur. Asparagus, rhubarb and many bulb crops are examples of herbaceous perennials in which the above ground parts are killed each year, however the roots remain alive to provide new shoots each spring. Boysenberries, raspberries and other cane fruits have perennial root systems with biennial shoots.

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