How To Use a Temperature Zone Map for your Garden

If you are serious about your home garden, there are various factors that need to be considered when you want to grow different kinds of plants and flowers. Each plant differs in its water needs, the type of soil it thrives on, and the fertilizer needed for optimal growth. In addition to this, another important factor is the temperature zone that is suited to each plant. There is an optimum temperature zone, which means a particular range of temperatures where a plant grows best

Therefore, for a gardener to know which plants to best cultivate in one's garden, you should make use of the temperature zone map called the hardiness zone map. Created in 1990, it bases its findings on the temperature readings from 1971 to 1984 in the United States, Mexico and Canada.

There is also a newer version posted by The Arborady Society which has newer temperature readings from 1990 to 2006. One can still use the older map, but recent climate changes may have changed temperatures around the globe, that plants are now growing in new areas.

According to The United States Department of Agriculture plant hardiness map, North America is divided into 11 hardiness zones from the coldest to the warmest temperature zones.  In between, there is a gradual increase in temperature across the continent, with some variations in some places. As expected, the higher the place, the colder the temperature.  

Coming back to your garden, all you have to do is to find out which zone your place falls in, based on the map. So, it is better to go for plants that will survive both the cold and warm extremes of your temperature zone.

In the Western parts of United States, another system created 40 years ago by the Sunset magazine is still being used. These are called sunset maps, which is a 24-zone climate system that covers 13 states in the west. This is much more accurate than USDA's temperature system because it takes more factors into consideration, like height of summer heat, crop season length, humidity present and the rain the location receives.

Those from outside North America who cannot find their temperature zone can try finding out the highest and lowest temperatures in their area and convert the readings using the chart given below, in both Celsius and Fahrenheit.

  1. Zone 1:    below -46 C        below -50 F
  2. Zone 2:    -46C to -40 C        -50 to -40 F
  3. Zone 3:    -40C to -34 C        -40 to -30 F
  4. Zone 4:    -34C to -29 C        -30 to -20 F
  5. Zone 5:    -29C to -23 C        -20 to -10 F
  6. Zone 6:    -23C to -18 C        -10 to 0 F
  7. Zone 7:    -18C to -12 C        0 to 10 F
  8. Zone 8:    -12C to -7 C        10 to 20 F
  9. Zone 9:    -7C   to -1 C        20 to 30 F
  10. Zone 10:     -1C  to   4 C        30 to 40 F
  11. Zone 11:     above 4 C             above 40 F

In summary, checking with a plant hardiness map is a safe way to ensure you are planting the right plants, flowers and crops. This will help increase the possibility that the time and effort spent on cultivating new plants will bear rich fruit or beautiful flowers.


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