glossary Advice

Q. What is an evergreen plant?

A plant that retains its leaves all year round.

Q. What is a deciduous plant?

A plant that annually sheds its leaves.

Q. What is a perennial plant?

A perennial plant or perennial (Latin per, through, annus, year) is a plant that lives for more than two years. Herbaceous perennials are plants that do not form woody tissue and the term perennial more commonly describes these plants, since woody plants (i.e., trees and shrubs) are always perennials. Perennials that flower and fruit only once and then die are termed monocarpic (semelparous). However, most perennials are polycarpic, flowering over many seasons in their lifetime.

In warmer and more clement climates, perennials grow continuously. In seasonal climates, their growth is limited to the growing season. For example, in temperate regions a perennial plant may grow and bloom during the warm part of the year, with the foliage dying back in the winter. These plants are deciduous perennials. Regrowth is from existing stem tissue. In many parts of the world, seasonality is expressed as wet and dry periods rather than warm and cold periods. In some species, perennials retain their foliage all year round; these are evergreen perennials.

Perennial plants dominate most natural ecosystems. For example, grasses and most forbs on the prairie are perennials. Perennial plants are usually better competitors than annual plants, especially under stable, resource-poor conditions. This is due to the development of larger root systems which can access water and soil nutrients deeper in the soil and to earlier emergence in the spring.

Perennials can be grouped by hardiness. For example, varieties that flourish in Nebraska may not survive a Nebraska winter. In the United States, the Department of Agriculture publishes a hardiness map, using average minimum temperature ranges to form a zone numbering system. The higher the zone number, the less hardy the plant. For example, a zone 8 perennial, suited to a minimum temperature range of 10 to 20 degrees F, will not survive a normal zone 4 winter, which has a minimum temperature range of -30 to -20 degrees F.

Q. What is a biennial plant?

A Biennial plant is a plant that takes between twelve and twenty-four months to complete its lifecycle. In the first year the plant grows leaves and stems (vegetative structures) and then it enters a period of dormancy over the colder months. The next spring/summer it produces fruit, flowers and seeds, and then dies.

Under extreme climatic conditions a biennial plant may 'bolt' through the separate stages of its lifecycle in a very short period of time (eg. 3 or 4 months instead of 2 years). This is quite common in vegetable or flower seedlings which were exposed to cold conditions before they were planted in the ground. This behaviour leads to many normally biennial plants being treated as annuals in some areas.

From a gardener's persepective, a plant's status as annual or perennial often varies based on location. For example, a perennial plant in a warm place might easily be grown as an annual plant in somewhere colder. This is because climatic conditions play a large role in determining the length of a plant's life-cycle. If a normally biennial plant is grown in extremely harsh conditions it is likely to be treated as an annual because it will not survive the winter cold. Conversely, an annual grown under extremely favourable conditions may have such a highly successful propagation rate that it gives the appearance of being bi- or perennial.

Q. What is an annual plant?

An annual plant is a plant that usually germinates, flowers and dies in one year.

Annuals are often used in gardens to provide splashes of color, as they tend to produce more flowers than perennials. Some perennials and biennials are grown in gardens as annuals for convenience, particularly if they are not considered hardy for the local climate. Also, many food plants are, or are grown as, annuals, including most domesticated grains.

The life-cycle of an annual can occur in a period as short as two or three months in some species, though most last a bit longer. Vegetables grown in apartment container gardens can last up to two years, if they are maintained indoors during the winter months.

Examples of annual plants include peas, Indian Blanket, Lemon Mint, and Baby's Breath.