Frost / chill injury identification & organic treatment
N/A — abiotic (cold temperature injury)
How to identify frost / chill injury
Ice formation inside plant cells (frost) or prolonged cold below a crop's tolerance (chilling, even above freezing for warm-season crops) ruptures cells and disrupts normal metabolism.
Symptoms
- Water-soaked, dark, collapsed tissue on leaves and stems after a frost event
- Blackened, wilted growth that does not recover, unlike transient wilting
- Chilling injury on warm-season crops (below about 50°F for extended periods) shows as dull, water-soaked patches, pitting, or failure to ripen properly without an actual freeze
- Whole plant collapse after a hard freeze
Host crops
Tomato, Pepper, Zucchini, Cucumber, Bush bean.
How it spreads
Not contagious; caused by temperature, not a pathogen, though frost-damaged tissue often invites secondary rot organisms.
Favorable conditions
Temperatures at or below 32°F for frost damage; sustained temperatures below about 50°F for chilling-sensitive warm-season crops like tomato, pepper, and cucurbits.
Progression
- Cold exposure (Frost event or extended chill) — Cell damage occurs, sometimes not visible until temperatures rise.
- Tissue collapse (Hours to a day after exposure) — Water-soaked, blackened tissue appears as damaged cells break down.
- Secondary rot (Following days if tissue stays wet) — Rot organisms can colonize dead tissue.
Organic treatment for frost / chill injury
- 1. Remove clearly dead tissue after damage is confirmed · low effort
Wait a day to see the full extent, then prune out blackened, collapsed tissue to reduce rot risk.
When: 1-2 days after a frost event
- 2. Protect remaining plants for future cold snaps · medium effort
Use row cover, cloches, or frost blankets ahead of forecast cold nights.
When: Ahead of any forecast frost/chill
Prevention
- Check local frost dates and don't set out warm-season transplants too early.
- Keep row cover or frost blankets on hand for surprise cold snaps.
- Choose a planting site away from low frost pockets.
Easy to confuse with
Late blight (blackened tissue but with fuzzy white sporulation and rapid spread, not a single overnight event), Herbicide injury.