If you live around cities such as Anchorage, Alaska; Sherbrooke, Quebec; Ottawa, Ontario; Calgary, Alberta; Prince George, British Columbia; Butte, Montana; Bismarck, North Dakota; Casper, Wyoming; Minneapolis, Minnesota; Watertown, New York; Burlington, Vermont; Moscow, Russia; or Harbin, China; your plant hardiness zone is 4.
This means your average minimum winter temperatures are between -20°F and -30°F (-43.5 to -28.9 C).
Just remember, however, that on January 15th, 2009, as reported by Heather Adams, the temperature at the Bismarck Airport was -44°F, breaking the -36°F record set January 15, 1971.
Ideal Plants in Zone 4
According to PBS’s The Victory Garden, USDA plant hardiness zone 4 is ideally suited to plants of East Asian origin. The zone straddles the 45°N zone unless significantly impacted by water or elevation influences (e.g. Murmansk area of arctic Russia, 69° N; Anchorage, Alaska, 61° N).
The zone is restricted to the northern hemisphere because of its association with very cold and stormy interior continental type climates. Continental climates are not found in the Southern Hemisphere due to the absence of a land mass large enough and far enough away from the oceans and its currents to generate this effect.
What are Hardiness Zones?
Hardiness zones are defined geographic regions, most commonly based on USDA criteria, that support specific plants, flowers, and trees. They usually define a minimum range of temperature that a plant or tree can survive safely in that zone.
If possible it is advisable to consult other planting-related maps such as first and last frost dates, and heat zones.
Canada’s Zone Four Regions
In Canada USDA zone 4 dominates the southern interior of British Columbia, spots south-western Alberta, and crosses north-central Ontario from Thunder Bay to Ottawa and up the St. Lawrence River estuary into the Martime provinces.
Agriculture and Agri-Food Canada (AAFC) lists Peegee hydrangea (Hydrangea paniculata ‘Grandiflora’), Bouquet Blanc mock-orange (Philadelphus ‘Bouquet Blanc’), and Japanese yew (Taxus cuspidata) as shrubs indicative of this zone.
Zone Four Regions in the United States
The hardiest zone 4 takes a wide swath from below the Canadian border at Alberta, across the middle of Montana and the Dakotas, stretching from the Rockies to lower Wisconsin where it sweeps away from the cold of Lake Superior. Farther south it stretches as far down as Colorado in the west.
With the water influence of the oceans, the zone stretches into upper New England beyond Lake Ontario and along the southern and western shores of Alaska.
Russia, Kazakhstan and Hardiness Zone Four
A large portion of Russia west of the Urals in a belt running down through Moscow, lies under the influence of the Atlantic Ocean and within climatic Zone 4. In addition, severe winters determine a Zone 4 in the areas extending southeast below the south end of the Urals into Kazakhstan and toward Lake Balkhash near the northern Chinese border.
Zone Four Patterns in China
Plant hardiness zone 4 takes a wide 45°N swath from just above North Korea, through the city of Harbin and on to the Gobi Desert, before reaching the border with Kazakhstan. Due to the elevation influence of the Himalayas, a belt also forms farther south across northern Tibet at 35°N.
Plant Options for Gardeners
According to PBS’s The Victory Garden, the following plants grow well within hardiness zone 4:
- Amur River privet (Ligustrum amurense)
- Chinese juniper (Juniperus chinensis)
- Sugar maple (Acer saccharum)
- Panicle hydrangea (Hydrangea paniculata)
- Vanhouffe spirea (Spiraea x vanhouttei)
- Virginia creeper (Parthenocissus quinquefolia)
Asian Plants Thrive in Low Temperatures
The low temperatures experienced in zone 4 encourages gardeners to carefully consider what plants work best in their zone, while still allowing many Asian-origin plants and others to not only survive, but thrive.