Flowers: Selection

Gardens & Landscapes March 26, 2008 Print Friendly and PDF

Flowers | Selection | General Requirements and Maintenance | Annuals | Perennials | Bulbs | Problems

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Flower Life Cycles

Selecting plants for a particular situation is often dependent on how long the plant lives. Have you ever been asked this question or wondered: Which needs planting every year, an annual or perennial?

This chart shows the difference between annual, biennial, and perennial life cycles.
This chart shows the difference between annual, biennial, and perennial life cycles.

You can answer this question by understanding life cycles. Flowers are divided into three life cycle categories: annual, biennial, and perennial.

See the following for more information on how the life cycles differ:

Climate Conditions

One of the most critical factors in selecting flowering plants for your garden is to ensure that they are well-suited to their environment. Knowing your hardiness zone is one way to help ensure that the odds of overwintering a biennial or perennial will be successful. Similarly, knowing your heat zone helps ensure that your annuals, biennials, and perennials can tolerate summer or year-round heat. Hardiness and heat zone maps are useful in the flower selection process, but they are not a be-all-end-all criteria for determining whether a flower will survive in its environment. Other factors, such as rainfall distribution, humidity, soil characteristics, water availability, and duration and intensity of light help determine if your plants are well suited for their environment.

Hardiness Map

USDA hardiness zone map
USDA hardiness zone map


  • The National Arboretum's USDA Hardiness Zone Map (U.S. National Arboretum) was released in 1990. Note that finding a suitable plant is not just dependent on the hardiness zone map. See what the National Arboretum has to say about choosing a suitable plant in relation to stress factors, new plant management systems, and artificial environments.

A few years ago, a new hardiness map was released. It was not approved by the USDA. It was controversial because it showed us in warmer zones, reflective of the past few years. Another draft is in the works that will be based on more years' data. Extension and the USDA continue to make recommendations using the older 1990 map.

Heat Zone Map


  • The AHS Plant Heat Zone Map (American Horticultural Society) helps you understand how to apply its recommendations. Notice that factors other than heat can apply stress to plants and skew the heat zone rating. The AHS Plant Heat Zone ratings assume that adequate water is supplied to the roots of the plant at all times.

Find Your Heat Zone:

  • Use the Heat Zone Finder (American Horticultural Society) to find the rating for your local zip code.

Garden Design

For some, the design process is the most rewarding part of gardening; for others it can be a daunting task. Garden design with annuals and perennials is an art and a science. Visit and review the following to learn about the design process:

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.