Petunias generally tolerate cold temperatures down to about 39°F (4°C) without significant damage, but they are not frost-hardy and can be damaged or killed by freezing temperatures at 32°F (0°C) or below
. Some varieties like Wave® petunias can tolerate slightly lower temperatures, down to about 35°F (2°C)
. In practical terms, petunias can survive brief exposures to temperatures in the upper 20s°F (around -2 to -3°C) if they have gradually acclimated to cooler weather in the fall, but sustained or hard freezes will kill them
. A new frost-hardy variety called Petunia ‘Below Zero’ reportedly tolerates temperatures as low as 14°F (-10°C), but this type is not widely available yet
. For most gardeners, petunias are grown as annuals because they cannot survive typical winter frosts in many climates. In USDA zones 9 to 11, where winters are mild, petunias can be grown as perennials and may survive year- round with proper care
. To protect petunias from cold snaps, covering them with fabric (not plastic) or moving potted plants to sheltered locations can help extend their life during cool weather
Summary:
- Tolerate down to about 39°F (4°C) without damage
- Damaged at 32°F (0°C) and killed by hard freezes
- Some varieties tolerate down to 35°F (2°C)
- Rare frost-hardy variety tolerates down to 14°F (-10°C)
- Best grown as annuals outside USDA zones 9-11
- Protection methods can extend cold tolerance slightly
