What Zone Am I In?
We all know that plants are dynamic, living things, and because we understand so much about our own plants (we carry out trials around the world) we appreciate the subtle differences regarding their growth and habit.
Which is why it’s worthwhile visiting the section of our site which gives you local information – which plants are available; when it’s best to plant, prune and feed them; tips and so on. It’s all here to help you enjoy them more.
When looking at plants, you will find that they are labeled with descriptions such as "hardy to Zone 5" or "hardy in Zones 7-10". This description is a guide to the minimum temperature range that the plant can survive in given normal conditions.
The United States Department of Agriculture displays a map of zones for the United States on the National Arboretum (USNA) website. This is the basis used to classify plant hardiness in the USA. The address of the USNA website is www.usna.usda.gov/Hardzone/ushzmap.html should you require further information.
The climate of the United States is broken down into 11 different zones, with each zone representing an "average annual minimum temperature" range. This means that the zones are describing the lowest temperature that has been recorded by the US Department of Agriculture in winter for that region. The zone descriptions are given on plants to provide a guide to determine the cold hardiness of plants for your region.
For example, a plant label may state that the plant is "Hardy to Zone 5". This means that on average the lowest temperature the plant is likely to survive is -20°F (-28.8°C). However, the plant should survive anything higher than these temperatures.
You should keep in mind that the zoning does not take into account other factors that could affect your plant’s survival, such as rainfall, sunlight, shelter or the level of care it receives.
To assist you, we have included the United States National Arboretum table which breaks down the temperature range for each zone. NB. The temperatures outlined below are minimum temperature ranges for each zone.
| Zone | Fahrenheit | Celsius |
|---|---|---|
| 1 | Below -50ºF |
Below -45.5ºC |
| 2 | -50º to -40ºF | -45.5º to -40.0ºC |
| 3 | -40º to -30ºF | -39.9º to -37.2ºC |
| 4 | -30º to -20ºF | -37.1º to -28.9ºC |
| 5 | -20º to -10ºF | -28.8º to -23.4ºC |
| 6 | -10º to 0ºF | -23.3º to -17.8ºC |
| 7 | 0º to 10ºF | -17.7º to -12.3ºC |
| 8 | 10º to 20ºF | -12.2º to -6.7ºC |
| 9 | 20º to 30ºF | -6.6º to -1.2ºC |
| 10 | 30º to 40ºF | -1.1º to 4.4ºC |
| 11 | Above 40ºF | Above 4.5ºC |
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