Exotic Tropical Plants - Zone hardiness map page

This system of Plant Hardiness Zones was originally developed by the US Department of Agriculture and applied to Northern America only, but it has been extended to other parts of the world. The coldest zone is Zone 1, which is a subarctic climate such as central Canada or Siberia; the warmest zone is Zone 12, which covers the tropics along the equator. Zones 1-6 (the very cold zones) do not occur in Australia.

Where a plant is described as being suitable for a range (eg Zones 9 – 11), the lower zone indicates the coldest area where the plant is likely to survive through an average winter. This minimum zone is probably not where the plant will grow best, however, but it means that it should survive through the winters. Because the zones refers to minimum temperatures, a plant given Zone 9 (for example), will grow perfectly well in Zone 10, but Zone 8 will be too cold. Plants grown in higher zones than recommended might grow well, but they are likely to behave differently.

Zones are not the end of the story in selecting plant types – water requirements, drought hardiness, humidity etc are all factors in what a plant needs to grow well. A plant may grow perfectly happily out of its ‘Zone’ if you give it the right microclimate.

Many people have also suggested that the above map is a bit conservative, and that temperatures in their areas are higher than noted on this map. For that reason, you should also have a look at the alternate map (from this page: http://www.anbg.gov.au/gardens/research/hort.research/zones.html) - this map is particularly designed for Australia - you should probably use both maps together as a guide to determine whether a particular plant is right for your area.

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