A Zone Primer

Hardiness zones refer to regions that share similar climates. Originally created by the United States Department of Agriculture, and available at their website, these maps use decades of weather information to get an idea of a specific area's climate.

These zones can let you know which plants will thrive where you live and which will struggle. Each zone is grouped by average lowest temperature in the winter. The plants that are rated to grow well in certain zones are based on the minimum temperature in which they can survive. It's not just about pretty blossoms in the summer, but also about making it through the winter for another pretty blossom next year.

Knowing what zone you live in is important to deciding what plants will thrive for you. The map splits the U.S., Canada and Mexico into eleven zones, each representing a ten degree spectrum. Zone 11 is the warmest zone, where the average low temperature remains above 40º F (4º C), and zone 1 is the coldest, with an average low below -50º F (-46º C).

Here are some plants that do well in each zone. Keep in mind that most of these plants do well in more than one climate zone.
Zone 1: evergreen trees and bushes
coldest temperature below -50º F (below -46º C)
Zone 2: green mound alpine currant
coldest temperature -50º to -40º F (-46º to -40º C)
Zone 3: bugloss
coldest temperature -40º to -30º F (-40º to -34º C)
Zone 4: primroses
coldest temperature -30º to -20º F (-34º to -29º C)
Zone 5: peonies
coldest temperature -20º to -10º F (-29º to -23º C)
Zone 6: many varieties of fern and roses
coldest temperature -10º to 0º F (-23º to -18º C)
Zone 7: ground master hosta
coldest temperature 0º to 10º F (-18º to -12º C)
Zone 8: cannas
coldest temperature 10º to 20º F (-12º to -7º C)
Zone 9: camellia and variegated hydrangea
coldest temperature 20º to 30º F (-7º to -1º C)
Zone 10: many varieties of azaleas
coldest temperature 30º to 40º F (-1º to 4º C)
Zone 11: many varieties of rhododendrons
coldest temperature above 40º F (4º C)

The zone hardiness ratings apply only to perennials, plants that live year after year, blooming every spring or summer. Annuals, which have a lifespan of one year, die out during the winter so the zone ratings don't apply.

The zone hardiness map is an extremely helpful tool when planning your garden or outdoor plantings, but it's not perfect. There are many factors—not just how cold it gets—that affect how plants grow. These include the type of soil, the amount of water it receives, how hot it gets, the humidity, the wind and how much sun it gets.

Knowing the different microclimates on your own property will help you find plants that will thrive under your care. Speak with other gardeners in your neighborhood and the folks at your local garden center if you have questions about what will thrive in your neighborhood. The zone hardiness map is a good tool, but definitely not the only one to use when deciding what to plant.

And when your flowers are in full bloom, cut some of them and bring them inside, to brighten the interior of your home as well. It's so satisfying when you can bring in the bright blossoms that came about from your hard work and knowledge of your climate. The zone maps help ensure that your garden will give you great results, year after year.