Cannabis plants are sensitive to temperature changes, especially during the flowering phase. Temperatures that are too low can affect growth, cannabinoid production, flavor, and yield. It's crucial for growers to understand how cold affects plants and what measures can be taken to minimize negative effects.
- Ideal temperature during flowering
Daytime temperature: 22–28°C
Night temperature: 18–22°C
A difference of 5–10°C between day and night is acceptable and can even promote colour development.
Temperatures outside these ranges can cause stress and delay flowering.
- Effects of too cold temperatures
Growth retardation
Cold nights (<15°C) slow down metabolism and photosynthesis.
Plants grow slower and buds develop less quickly.
Color changes
Some indica and sativa strains develop purple, blue, or reddish hues in cooler nights.
This may be appealing, but it is often a stress response.
Decreased cannabinoid production
THC and CBD production may decrease if metabolism is too low due to cold.
Moisture problems and mold
Cold, damp nights promote botrytis (bud rot) and other fungi.
- Differences between races
Indica varieties: more resistant to cold, can handle slight temperature fluctuations.
Sativa varieties: more sensitive to cold nights; growth and yield may decrease significantly.
Hybrids: Depending on genetics, cold can enhance the effects on color and aroma or delay flowering.
- Measures for cold flowering conditions
Indoor growing: Use heating, insulation, and a thermostat to keep nighttime temperatures stable.
Outdoor cultivation: protect plants with greenhouses, cloths or foil on cold nights.
Ventilation and air circulation: prevents condensation and mould formation despite cold nights.
Monitoring: Check temperature and relative humidity regularly.
- Positive effects of light cold
Color development: purple and red tones can become more intense.
Stress-driven aromas: Some terpene profiles are amplified.
Important: Mild stress can be aesthetically and aromatically beneficial, but too much cold is always harmful.