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Climates and Microclimates
Climate, weather, site conditions and plant hardiness are key factors in how your garden or landscape will grow. In this page, learn more about:
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- How garden season length changes with your garden’s location.
- The placement of your garden affects the sunlight and exposure it receives.
- Other site conditions change how plants grow in your yard.
- What are plant hardiness zones, and how to find the one at your home.
- Plant hardiness information for other locations around the world, including North America, Canada, Europe, Australia, New Zealand, and South Africa.
Climate Considerations
Both your region’s climate and your site’s location will affect the flowers you can grow in your garden.
You’ve learned that flowering plants—annuals, biennials, perennials and bulbs—are sensitive to extremes of both cold and heat. We’ve even given you tools to use to help visualize and map your garden’s climate in our plant guides [see: Flower Facts and Bulb Basics].
Garden season length varies with the location of your landscape. Close to the equator, it’s nearly year-round. The farther one moves towards the poles, however, the number of days with ideal warmth and sunlight changes with the seasons and time of year.
Days are long during summer in the highest latitudes—far north toward the North Pole or far south towards the Antarctic. In winter, they are short or have no hours of daylight at all.
You’ll tailor your flower growing activities to these physical changes. You’ll also plan your flower plantings around temperature extremes, especially winters with freezing temperatures and very hot summer days.
Fortunately, most of the work has been done for you. Each plant’s preferred climate boil down to two labels: how hardy they are—what is the lowest temperature that kills them—and the plant hardiness zone limits they prefer.
For bulbs, you’ll require two further pieces of information. They are the season in which the bulbs flower and the season or seasons in which they are planted [see: Bulbs and Seasons of Bloom].
All of these important references are provided for each flowering plant included in our plant guides.
The only thing you must know is the plant hardiness zone of your garden, and that’s on the maps found here [see: Plant Hardiness Around the World, opposite].
Your Garden’s Climate
Every garden is unique. Ask the staff of your local garden center if they know of any general local conditions that make your site different from other areas in your hardiness zone.
Then take a very close look at your whole yard, but especially the areas of your landscape you want to plant with flowers [see: Understanding Garden Sites].
Here’s a quick overview of what you’ll be trying to find out.
You may be in a place that’s close to a large body of water. It may have prevailing winds that affect how plants will grow.
Some yards may receive more rain and greater amounts of snow than nearby lots. They may be on a hillside that either faces or is shaded from the sun.
Surrounding forests, buildings, and other factors also affect your flower garden.
Gardeners call these factors “microclimates.”
Pay very close attention to how your home and garden faces the sun. Plan to plant shade-loving plants where your structures or nearby trees cast shade. Reserve the sunniest areas of the landscape for plants than need maximum heat and long hours of light.
You’ll use these clues to help you choose flowering plants that love your microclimate and the different areas found within your yard.
U.S.D.A. Plant Hardiness Around the World
The United States Department of Agriculture (U.S.D.A.) divides North America and other areas of the world into 11 plant hardiness zones.
The U.S.D.A. Hardiness Zones, based on long-term extreme minimum annual temperatures, serve as a general guide to growing conditions.
Flowering plants of all species are rated by their breeders as to the zones for which they are best adapted—for example, zones 4–7—and these are usually listed on plant tags, container labels, and in plant references.
For your convenience, all the plants in our flowering plant guides have these plant hardiness zone ratings in the Hardiness tab of their care guides [see: Perennials and Bulbs].