Climate Zones for growing Plants
Unfortunately, there is not one single global standard for the Climate Zones for growing plants. However, similar systems exist in other regions and they can be mapped. Therefore Always makes sure that you check the zone correctly for your country and the plants, due to the different standards, when on this site the climate zone is referred to, you must double check.
- US: USDA Hardiness Zones Map [Link to Map]
- Europe: The Royal Horticultural Society (RHS) in the United Kingdom provides a hardiness zone map. [Link to Map]
- Australia: The Australian National Botanic Gardens offers a map for Australian climates. [Link to Map]
- Worldwide: The Köppen climate classification system categorizes climates globally, although it’s not directly tied to plant hardiness.
| Climate Zone System | Description | Equivalent Systems |
|---|---|---|
| USDA Hardiness Zones | Based on average annual extreme minimum winter temperature. | – RHS Climate Zones: Roughly equivalent, but RHS provides finer distinctions. – ANBG Zones: Not directly equivalent. |
| RHS Climate Zones | Based on absolute minimum winter temperatures. There are nine hardiness zone ratings. | – USDA Hardiness Zones: RHS zones align with USDA zones, but RHS provides more precise ratings. – ANBG Zones: Corresponding ANBG zones for Australian climates. |
| ANBG Zones | Developed by the Australian National Botanic Gardens. | – RHS Climate Zones: Not directly equivalent. – USDA Hardiness Zones: Not directly equivalent. |
| Köppen Climate Classification | Based on temperature and precipitation patterns. | – RHS Climate Zones: Not directly equivalent. – USDA Hardiness Zones: Not directly equivalent. – ANBG Zones: Not directly equivalent. |
More Resource links:
- Wikipedia: Hardening zones
USDA Hardiness Zone Mapping table for global use
On this website we refer extensively to the USDA climate zones, but as the system is globally applicable, as well as this website, we have made an easy to apply table which will help you to assess and determin the zone that best fit for you. In any case, always consult your local garden shop to assess the suitability of the plans in your area, as there area more factors (such as rainfall, sun and maximum temperature) that determine whether the plants would suit in your garden.
| USDA Hardiness Zone | Average Annual Extreme Minimum Temperature (°F) | Average Annual Extreme Minimum Temperature (°C) |
|---|---|---|
| Zone 1 | Below -50 | Below -45.6 |
| Zone 2 | -50 to -40 | -45.6 to -40.0 |
| Zone 3 | -40 to -30 | -40.0 to -34.4 |
| Zone 4 | -30 to -20 | -34.4 to -28.9 |
| Zone 5 | -20 to -10 | -28.9 to -23.3 |
| Zone 6 | -10 to 0 | -23.3 to -17.8 |
| Zone 7 | 0 to 10 | -17.8 to -12.2 |
| Zone 8 | 10 to 20 | -12.2 to -6.7 |
| Zone 9 | 20 to 30 | -6.7 to -1.1 |
| Zone 10 | 30 to 40 | -1.1 to 4.4 |
| Zone 11 | Above 40 | Above 4.4 |
Understanding USDA Plant Hardiness Zones
The USDA plant hardiness zones were originally established for the United States, but are now widely used for other countries. The hardiness zones are based on the concept of the average winter minimum temperatures. The lower the number, the colder the winter climate in that area.
The USDA plant hardiness map is a valuable tool created and updated by the U.S. Department of Agriculture. Its purpose is to divide North America into distinct zones based on minimum average annual temperatures. Each zone represents a range of temperatures, allowing gardeners to make informed decisions about which plants will thrive in their local environment.
Here are the key points about USDA hardiness zones
- Temperature-Based Division:
- The map divides North America into eleven zones, numbered from 1 (coldest) to 11 (warmest).
- Each zone represents a ten-degree difference in minimum average annual temperature.
- Zones are further divided into “a” and “b” segments, each representing a five-degree difference.
- For example, Zone 4 covers minimum temperatures between -30°F to -20°F (-34°C to -29°C), while Zone 4a represents -30°F to -25°F (-34°C to -32°C), and Zone 4b represents -25°F to -20°F (-32°C to -29°C).
- Hardiness and Plant Survival:
- Hardiness refers to how well a plant can withstand cold temperatures.
- Gardeners use these zones to select perennials, trees, and shrubs that are most likely to survive local winters.
- Annuals, which complete their life cycle in one season, are less affected by hardiness zones.
- Limitations and Other Factors:
- While USDA zones are helpful, they don’t account for other critical factors:
- Freeze dates: When the last frost occurs in spring and the first frost in fall.
- Freeze-thaw cycles: The impact of rapid temperature changes.
- Snow cover: How snow insulates plants.
- Precipitation and elevation.
- In the western U.S., consider using the Sunset climate zones, which incorporate additional factors beyond just minimum temperatures.
- While USDA zones are helpful, they don’t account for other critical factors:
- Microclimates and Your Garden:
- Even within your own garden, there may be microclimates influenced by factors like sun exposure, wind, and soil type.
- Use USDA or Sunset zones as a guide, but always observe your specific conditions for the best gardening success.