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USDA Zones and Plant Lists

Our plant descriptions take "a" and "b" sub-zones into account. If you want to play it absolutely safe, buy plants that are hardy to your zone, not just marginally hardy to the "b" subzone.

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USDA Zone 3

Average minimum temperature: -30 F to -40 F
Spring: April 15 - June 15
Average last frost date: May 1- 31
Average first frost date: September 1 - 30
Fall: August 15 - October 1

For the most part, USDA Zone 3 stretches along the U.S.-Canadian boundary. Winter temperatures plummet to -40 to -30 F, while summers are warm to hot. Away from the coast, the zone is subject to relatively dry conditions — in International Falls, average precipitation is slightly less than 23 inches, and in Sidney, Montana, 14 inches; closer to the coast, precipitation rises — Van Buren, Maine, 37.5 inches. Depending on the area, the growing season can be as short as two months or as long as four.

Although dormancy is long and plant roots freeze, the plants that are adaptable to the climate seem to come out of winters relatively unscathed. Redosier dogwood (Cornus sericea), American arborvitae (Thuja occidentalis), paper birch (Betula papyrifera), bunchberry dogwood (Cornus canadensis), Eastern larch (Larix laricina), bush cinquefoil (Potentilla fruticosa) and American cranberry bush (Viburnum trilobum) do well here. Hosta, daylily, bluestar, alyssum, blanket flower (Gaillardia), penstemon, garden phlox, creeping Jenny and coneflower are some of the many perennials that are hardy in this zone. Needled evergreens do well here, but the only broadleaf evergreens that make it in this climate are prostrate forms that are low enough to be covered by snow. Where summers are warm, cereal crops do very well, as do root crops and spinach.

The USDA hardiness zone map is based on average minimum winter temperatures, each zone representing a 10-degree difference from the ones above and below it. Each zone is further divided into "a" and "b" areas. The difference between each of these sub-zones is a matter of five degrees. The average minimum temperature in winter in Zone 3a is -35 to -40F. In Zone 3b, it's -30 to -35 F.

Sample Cities in USDA Zone 3a

International Falls, Minnesota
St. Michael, Alaska

Sample Cities in USDA Zone 3b

Tomahawk, Wisconsin
Sidney, Montana
Crosby, North Dakota

Plants for USDA Zone 3

Deciduous Shrubs
Deciduous Trees
Conifers
Perennials
Vines

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