Root zone temperature massively influences nutrient uptake and growth. Optimisation for maximum cannabis performance.
The temperature of the root zone is often overlooked, but is critical for optimal cannabis growth:
Optimal root zone temperatures:
Soil cultivation:
- Optimal: 18-22°C
- Acceptable: 16-24°C
- Critical: below 15°C or above 26°C
- Buffers temperature fluctuations
Hydro systems:
- Optimal: 18-20°C
- Acceptable: 16-22°C
- Critical: below 15°C or above 24°C
- Less tolerance than soil
Coco substrate:
- Optimal: 19-23°C
- Acceptable: 17-25°C
- Between soil and hydro
- Faster temperature reaction
Effects of incorrect temperatures:
Root zone too cold (24°C):
- Lack of oxygen in the water
- Risk of root rot
- Accelerated metabolism
- Increased water consumption
- Harmful bacteria multiply
Temperature measurement:
Soil thermometer:
- Digital with probe
- Measure at different depths
- Multiple measuring points
- Min/max memory useful
Infrared thermometer:
- Surface temperature
- Fast measurements
- Non-invasive
- For substrate surface
Continuous monitoring:
- Data logger with alarms
- Smartphone apps available
- Recognise trends
- Automation possible
Cool root zone:
Passive cooling:
- Insulate pots from hot surfaces
- Reflective pot covers
- Mulch for soil surface
- Shade for pots
Active cooling:
- Water-cooled reservoirs
- Chillers for hydro systems
- Ventilation around pots
- Air conditioning for grow room
Hydro-specific cooling:
- Aquarium chiller
- Frozen water bottles (temporary)
- Underground reservoir
- Minimise pump heat
Warm up root zone:
Heating mats:
- Place under pots
- Thermostat-controlled
- Even heat distribution
- Suitable for soil and coco
Water heater:
- Aquarium heater in reservoirs
- Thermostat important
- For DWC and other hydro systems
- Uniform temperature control
Optimise room heating:
- Often colder near the floor
- Direct warm air downwards
- Insulate cold floors
- Timing with light cycles
**Utilising temperature gradients
Natural variation:
- Warmer at the top, cooler at the bottom
- Roots prefer slightly cooler temperatures
- 2-4°C difference normal
- Avoid extremes
Seasonal adaptations:
- Winter: More heating needed
- Summer: Cooling more critical
- Transition periods: Intensify monitoring
- Outdoor: Ground insulation
Substrate-specific strategies:
Soil:
- Slower temperature changes
- Insulation through organic material
- Mulch helps with stabilisation
- Larger pots = more stability
Coco:
- Faster temperature response
- More frequent monitoring required
- Drainage affects temperature
- Irrigation temperature important
Hydro:
- Immediate temperature transfer
- Continuous control critical
- Chiller often essential
- Backup systems recommended
**Integration with climate control