Climate Zones & Hardiness

A Hardiness Zone is a geographic standard based on the average annual extreme minimum winter temperature. Graded from Zone 1 (down to -50°F) to Zone 13 (tropical winters above 60°F), it indicates whether a perennial outdoor plant can survive the winter in your area.

Your climate zone is automatically identified based on your detected browser geolocation. Your current active zone appears as a badge (e.g., Zone 7b) in the top navigation header and sidebar.

Yes. By clicking the climate zone badge in the header or in your profile, you can select another zone from the list. This is helpful if your garden enjoys a distinct microclimate (such as a sheltered courtyard or south-facing brick wall).

No. Outdoor winter hardiness zones do not apply to indoor tropical houseplants living in climate-controlled indoor spaces (65°F–75°F year-round). For houseplants, indoor humidity, window exposure (North/South/East/West), and draft protection are the factors that matter.

Yes, they are directly related. The climate zone where you live, your climate zone, will change as the weather on Earth changes.

We know of 5 different scales: Canada, EGR, USDA; Sunset; and RHS.  Climate is a very large topic of great interest.  We do not attempt to keep up with the forefront of this climate science but strive to make plant-share.com as easy to use as possible!

Climate zones were independently created by different countries and for different purposes. For example, the US and Canada and Europe all developed their own scales using many factors. Farmers developed a separate scale for crops largely based on cold tolerance alone.  So far, there isn’t a universal scale for climate zone.

Climate Zone and Hardiness are very similar. Climate Zones rely on many variables whereas Hardiness depends primarily on cold tolerance.

Plants don’t move as humans do, but plants can adapt to growth conditions in many regions and climate zones across the world. Humans move plants around the world – as crops, ornamentals and houseplants – and because plants are highly adaptable, they can live in many of those new places.

Technically, you have only one. However, in practice, there are micro-environments or ‘climate pockets’ in every garden. For example, if you live in a cool climate like Seattle, you can grow better tomatoes (which prefer lots of heat) against a wall that gets warmed by the sun, typically a southern exposure.

As a rule, plants from other climate zones will not grow outside where you live. For example, banana trees will not grow outdoors in Antarctica!

• • • • World Climate Regions, by Deniz Karagulle, 2020
      • 2023 United States Department of Agriculture (USDA) Hardiness Zone Map
      • Royal Horticultural Society (RHS) hardiness rating - This article includes a table that cross-maps the 2012 RHS and USDA climate zones. 
      •  Gardenia Hardiness Zones of Europe 

We do this so that you know which plants from “Plants” will grow in your garden.

Seven factors determine climate zone: winter lows, summer highs, wind, humidity, elevation, length of growing season and timing and amount of rainfall.  

A climate zone is a number that summarizes the weather (i.e. the growing conditions) where you live. See a world map of the Earth’s climate zones here.