The vegetative phase lays the foundation for high yields. Light, nutrients and training for explosive development.
The vegetative phase largely determines the final size and structure of cannabis plants:
Vegetative phase basics:
Duration of the vegetative phase:
- Photoperiod varieties: 4-8 weeks
- Depending on the desired plant size
- Indoor usually shorter than outdoor
- Strain-specific differences
- Take space restrictions into account
Physiological processes:
- Intensive cell division and elongation
- Build-up of leaf mass for photosynthesis
- Development of the root system
- Stem and branch thickening
- Energy storage for the flowering phase
Optimal light conditions:
Vegetative light cycles:
- 18/6 standard (18h light, 6h darkness)
- 20/4 for accelerated growth
- 24/0 possible but energy-intensive
- Constant cycles important
- Timer precision required
Light intensity:
- PPFD 400-600 µmol/m²/s optimal
- DLI 25-40 mol/m²/day
- Gradually increase from 300 to 600
- Avoid light burn
- Uniform illumination
Spectrum for vegetative growth:
- Blue-emphasised spectrum (400-500nm)
- Promotes compact, bushy growth
- Full spectrum LEDs optimal
- 6500K colour temperature with CFL
- UV-A additive for stress resistance
Nutrient management vegetative:
NPK ratio vegetative:
- Nitrogen-emphasised (3-1-2 or 2-1-1)
- High N values for leaf growth
- Moderate P and K values
- Calcium and magnesium important
- Do not neglect micronutrients
Feeding schedule vegetative:
- Week 1-2: EC 0.8-1.0
- Week 3-4: EC 1.0-1.4
- Week 5+: EC 1.4-1.8
- pH 6.0-6.5 (soil) / 5.5-6.0 (hydro)
- Regular flushing every 2-3 weeks
Organic fertilisation vegetative:
- Nitrogen-rich organic fertilisers
- Blood meal, fish emulsion
- Compost tea weekly
- Kelp meal for trace elements
- Molasses for soil microbes
Environmental optimisation:
Vegetative temperature:
- Day: 22-26°C optimal
- Night: 18-22°C
- Temperature difference should not exceed 10°C
- Aim for constant values
- Air circulation for homogeneity
Humidity vegetative:
- 60-70% RH optimal
- Higher values than in flowering
- Good air circulation nevertheless important
- VPD 0.8-1.2 kPa
- Gradual reduction during flowering
Training in vegetative phase:
LST (Low Stress Training):
- Continuous gentle bending
- Promote horizontal spread
- More light for all shoots
- Daily small adjustments
- Prepare structure for SCROG
Topping and FIM:
- Possible after 4-6 nodes
- At least 2 weeks before flowering change
- Doubles number of main shoots
- Requires recovery time
- Only for healthy plants
Defoliation:
- Selective removal of large leaves
- Improved air circulation
- More light for lower areas
- No more than 20% at a time
- allow 1-2 weeks recovery
Growth monitoring:
Development indicators:
- Daily height increase
- New nodes formation
- Leaf size and colour
- Stem thickening
- General vigour
Recognise problems early:
- Discolouration or spots
- Growth arrest
- Pest infestation
- Nutrient deficiencies or excess