A plant rated USDA zone X survives in zone X and warmer. Your zone number should be at or above the plant's rating to grow it outdoors.
The USDA bands
| Band | Temperature range | Description |
|---|---|---|
| Zone 1 | down to −45.6 °C | Sub-arctic — winter lows below −45 °C |
| Zone 2 | −45.6 °C to −40 °C | Severe continental cold |
| Zone 3 | −40 °C to −34.4 °C | Very cold winters |
| Zone 4 | −34.4 °C to −28.9 °C | Cold winters, short growing season |
| Zone 5 | −28.9 °C to −23.3 °C | Cold continental winters |
| Zone 6 | −23.3 °C to −17.8 °C | Moderately cold winters |
| Zone 7 | −17.8 °C to −12.2 °C | Mild cold winters |
| Zone 8 | −12.2 °C to −6.7 °C | Mild winters with light freezes |
| Zone 9 | −6.7 °C to −1.1 °C | Light frost only |
| Zone 10 | −1.1 °C to 4.4 °C | Near frost-free |
| Zone 11 | 4.4 °C to 10 °C | Frost-free, warm winters |
| Zone 12 | 10 °C to 15.6 °C | Tropical |
| Zone 13 | 15.6 °C and warmer | Hot tropical |
How USDA compares to the other systems
Hardiness scales do not translate one-to-one, because each was built for a different climate and reads in a different direction. Compare the USDA scale with the other three:
- RHS hardiness rating (United Kingdom) – plant needs at least this level of cold tolerance.
- Canadian plant hardiness zone (Canada) – plant tolerates down to this zone.
- Australian (ANBG) zone (Australia) – plant tolerates down to this zone.
Example plants rated in the USDA system
- Bog myrtle (Sweet gale) Myrica gale – Zone 1–6
- Apothecary’s rose Rosa gallica ‘Officinalis’ – Zone 3–8
- Hairy vetch Vicia villosa – Zone 3–9
- Solomon's seal Polygonatum biflorum – Zone 3–8
- European beech Fagus sylvatica – Zone 4–7
- Roundleaf serviceberry Amelanchier rotundifolia – Zone 4–8
- Cretan mountain mint Clinopodium nepeta – Zone 5–9
- Wisteria Wisteria sinensis – Zone 5–9
- Fuchsia Fuchsia magellanica – Zone 7–10
- Common agapanthus Agapanthus praecox – Zone 8–11
- Tanner’s sumac (Sicilian sumac) Rhus coriaria – Zone 8–10
- Grevillea ‘Robyn Gordon’ Grevillea ‘Robyn Gordon’ – Zone 9–11
- Silver tree Leucadendron argenteum – Zone 9–10
- Yellow mangosteen Garcinia xanthochymus – Zone 10–12