The USDA has updated their plant hardiness zones which resulted in most zones going up 1/2 – one zone. However, Canada’s plant hardiness zones are due for a review this year which will likely result in a change.
What Is the Difference Between Canada & USA’s Zones?
The americans use one factor to determine their zones. That factor is the lowest extreme temperature. Canada uses seven factors over 30 years to determine our map.
These factors that make up Canada’s growing zones:
- minimum winter temperatures,
- length of the frost-free period,
- summer rainfall,
- maximum temperatures,
- snow cover,
- January rainfall
- maximum wind speed.
USDA Grow Zones Are Equal To Canadian Grow Zones
There is a single variable map for Canada that looks the the lowest extreme temperature. This allows us Canadians to compare ourselves to our favourite US gardeners.
US Equivalent to Canadian Plant Zones
Below is a list of both US & Canada areas that fall under the same zone using the single factor of the minimum extreme temperature.
Zone 3 US & Canada using single factor (Light & Dark Salmon)
- Northern parts of Montana
- Northern parts of North Dakota
- Northern parts of Minnesota
- Northern parts of Wisconsin
- Northern parts of Wyoming
- Northern parts of New York
- Northern parts of Maine
- Fort Nelson
- Edmonton
- Saskatoon
- Regina
- Churchhill
- Winnipeg
- Brandon
- Kenora
- Chisaibi
Zone 4 US & Canada Using Single Factor (Purple & Dark Blue)
- Southern Parts of Montana,
- Southern Parts of Wyoming,
- Southern Parts of North Dakota,
- Southern Parts of South Dakota,
- Southern Parts of Minnesota,
- Southern Parts of Wisconsin,
- Northern Parts of New York,
- Northern Parts of Vermont,
- Northern Parts of New Hampshire,
- Northern Parts of Maine
- Prince George
- Calgary
- Sault Saint Marie
- Montreal
- Ottawa
- Fredericton
Zone 5 US & Canada Using Single Factor (Light Blue & Teal)
- Minnesota,
- Iowa,
- Nebraska,
- Areas of Wisconsin
- Areas of Montana,
- Areas of Wyoming,
- Northern California,
- Oregon,
- Washington,
- Idaho,
- Colorado,
- Nevada,
- Areas of Alaska
Zone 6 US & Canada Using Single Factor (Dark & Light Green)
- St. John’s
- Halifax
- Portions of the Okonogin
- Lower Portion on Ontario below Toronto
- New York,
- New Jersey,
- Pennsylvania,
- West Virginia
- North Carolina,
- Maryland,
- District of Columbia
Zone 8 US & Canada Using Single Factor (Yellows)
- Victoria
- Vancouver
- Areas of California
- Texas,
- Louisiana,
- Mississippi,
- Alabama,
- Georgia,
- Carolinas,
- Coast of Virginia.
Why Garden Zones Do Not Matter
Garden zones lack on of the most crucial factors gardeners rely on and that is first and last frost dates. The last frost date in particular is an indicator for when annual plants can go outside in your areas. Your zone at most is going to give you an indication of what perenials can be planted in your area.
What Are Canada’s Plant Zones Changing To?
Canada’s plant hardiness zones are getting reassest this year but unfortunately there is no estimated release date. The messaging from Agriculture & Agri Food Canada is that the zones are unlikely change much. The east can expect to drop 1/2 to 1 zone, while the west coast is likely to go up or stay the same.
The post Canada’s Growing Zones Are Changing 2024 appeared first on Gardening In Canada.
