USDA hardiness zones
A hardiness zone is the average coldest winter temperature for an area — it tells you which perennials survive your winter. It only loosely predicts frost dates, so for a planting calendar use your state or your own frost dates.
| Zone | Winter low | Season | Character |
|---|---|---|---|
| Zone 1 | -60°F to -50°F | ~65 days | Extreme sub-arctic |
| Zone 2 | -50°F to -40°F | ~90 days | Sub-arctic |
| Zone 3 | -40°F to -30°F | ~120 days | Cold northern |
| Zone 4 | -30°F to -20°F | ~135 days | Cold |
| Zone 5 | -20°F to -10°F | ~160 days | Cool temperate |
| Zone 6 | -10°F to 0°F | ~185 days | Temperate |
| Zone 7 | 0°F to 10°F | ~200 days | Warm temperate |
| Zone 8 | 10°F to 20°F | ~230 days | Mild |
| Zone 9 | 20°F to 30°F | ~280 days | Warm |
| Zone 10 | 30°F to 40°F | ~330 days | Hot / near frost-free |
| Zone 11 | 40°F to 50°F | Year-round | Frost-free tropical |
| Zone 12 | 50°F to 60°F | Year-round | Tropical |
| Zone 13 | 60°F to 70°F | Year-round | Hot tropical |