Geranium Frostbite: Spraying Water Helps Only If Caught in Act

Geraniums left out in frost. Spray with water to save?

Science of Frost

Frost = ice crystals forming on surfaces via ice-nucleating bacteria (Pseudomonas syringae). Pure water supercools below 32°F without freezing—needs nucleus.

Spraying Water

• Works ONLY if done WHILE frost is forming (pre-dawn). Raises tissue temp, disrupts crystallization.
• Useless after damage—like water on burned house.

Geranium Hardiness

Pelargoniums hardy to 28°F if hardened off (weeks of cool nights). Sudden frost on unhardened plants kills.

Recovery Aids

• Harpin protein (Messenger): Accelerates tissue repair. Stock up—original maker bankrupt.
• Plant antifreeze experimental: Science Daily.

Prevention

Harden off gradually. Don't fertilize/water late season—disrupts antifreeze production.