Organic Gardening in an Urban Setting

Plant Hardiness Zones

 Any time you decide to add a new type of vegetable or other plant to your garden it is a good

 idea to check out it's hardiness or suitability for your growing area and climate. All commercially grown plants as well as all commercially produced seeds have this information on the packaging or on a small tag inserted into the plants pot.

This is of particular interest for urban gardeners who live in high rise buildings. For every 3 stories you rise in elevation above the third floor your hardiness zone decreases by 1. 

There are 9 zones in Canada and 11 in the States.

These zones are based on the minimum temperature any given area will reach at the coldest part of their growing season. As this information is so prevalent here in North America and is presented in most plant databases scattered around the web that I'll show you how to determine yours no matter where you reside world wide. 

You can roughly translate the USDA hardiness zones by finding out how low your area's temperatures can reach, and then use the chart below to find your corresponding zone.

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

 Useful maps showing these zones are available for:

Canada here at the Department of Natural Resources

the States  here at the United States National Arboretum.