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Cold damage

Also known as Chilling injury, Frost damage

DiseaseHarmful
Fig leaves killed by frost: limp and blackened Photo: Famartin · CC BY-SA 4.0

In short

Cold damage covers chilling injury, which harms tropical and subtropical plants at temperatures above freezing, and frost injury below freezing. Most tropical foliage plants can be damaged below about 10 °C (50 °F). Symptoms show within hours to a few days and range from water-soaked patches to blackened, collapsed leaves.

How it looks

Chilling first shows on the youngest leaves as yellowing, water-soaked or translucent patches and wilting; later the tissue darkens and leaves drop. Leaves and shoots can turn purplish-red or black. In Dieffenbachia, severe chilling makes the stem base reddish-brown and water-soaked before it collapses. Frost turns soft growth black and limp. Symptoms may keep developing for up to a week.

Signs

Sudden leaf drop after a cold night or cold draught; water-soaked patches that turn dark; blackened leaves or shoots; collapsed stems.

What favours it

Temperatures below about 10 °C (50 °F) for sensitive tropical plants (UF/IFAS describes chilling between just above freezing and about 15 °C); cold draughts near windows and doors; unheated porches; watering with cold water. Damage depends on the species and cultivar, how cold it gets and for how long: brief exposure may be survived, long exposure causes irreversible injury.

Prevention

  • Keep tropical plants above about 10 °C (50 °F) and away from cold draughts near windows and doors.
  • Outdoors, cover tender plants overnight with cloth (not plastic) on cold nights and water dry soil at least three days before a cold spell.
  • Choose chilling-tolerant species or cultivars for cooler spots.

Treatment

Start with the first step and move down only if the problem persists.

  1. Move the plant to a warm spot away from draughts.
  2. Wait a week or so before judging the damage, as symptoms keep developing.
  3. Trim clearly dead leaves and stems once live and dead tissue can be told apart.
  4. Water sparingly and do not fertilise until new growth resumes; discard plants with collapsed, rotting stem bases.

Pros and cons

Cons

  • Damaged tissue does not recover.
  • Chilled tissue decays easily and can invite rots.

Look-alikes

Bacterial soft rot
Soft rot spreads from a spot, smells foul and keeps advancing; chilling damage appears all at once after cold and then stops.
Overwatering
Waterlogging yellows lower leaves over weeks; cold damage appears suddenly and hits young leaves first.
Bacterial leaf spot
Bacterial spots have yellow halos and spread between plants over time.

Affected plants

Tropical and subtropical plants such as Dieffenbachia, African violet, banana, mango, avocado and tomato. Cultivar tolerance varies widely.

Sources

  1. EP530: Chilling Injury in Tropical Foliage Plants: III. Dieffenbachia — UF/IFAS
  2. Chilling Injury — UC Statewide IPM Program
  3. Diagnose Indoor Plant Problems — University of Maryland Extension
  4. Houseplant Diseases & Disorders — Clemson HGIC
  5. How to help a poorly houseplant — RHS

Written in our own words from these sources. Check a product label before using any treatment.