After cannabis seeds germinate, the growth phase, also known as the vegetative phase, begins. This is the period in which the plant develops leaves, stems, and roots, and prepares for flowering. A healthy growth phase is crucial for strong plants and maximum yield.
- Duration of the growth phase
Indoor growing: 3–8 weeks, depending on desired plant size.
Outdoor cultivation: Variable, usually from spring to early summer before flowering begins.
Autoflowering strains: shorter growth phase, often 2–4 weeks.
Duration can be adjusted by light cycle and pruning, but the goal is always a healthy, well-developed plant before flowering.
- Characteristics of the growth phase
Rapid vegetative growth: stems and leaves develop quickly.
Large leaf surface area: ensures maximum photosynthesis and energy production.
Strong root development: crucial for water and nutrient uptake.
Increase in branches and nodes: preparation for future flowering points.
- Light and photoperiod
Photoperiod plants (photoperiod):
At least 18 hours of light and 6 hours of darkness per day during the vegetative phase.
Long light encourages vertical growth and strong branches.
Autoflowering plants:
Grow independently of light cycle, but benefit from 18–20 hours of light.
- Food and water
Macro nutrition: Nitrogen (N) is essential for leaf and stem development.
Micronutrients: magnesium, calcium and trace elements support photosynthesis and growth.
Water: Water regularly, but avoid overwatering; roots need oxygen.
pH: soil 6.0–6.8, coco/hydro 5.5–6.2 for optimal uptake.
- Pruning and training
Topping/FIM: stimulates branching and increases the number of buds.
Low-Stress Training (LST): Bending stems to improve light penetration.
Defoliation: Removes excess leaves to optimize air circulation and light distribution.
The goal is a healthy structure with many growing points for later flowering.
- Environmental factors
Temperature: 20–28°C ideal for vegetative growth.
Humidity: 50–70% to regulate evaporation and minimize stress.
Ventilation: Constant air circulation prevents mold and promotes strong stems.
- Common mistakes in the growth phase
Too little or too short light → slow growth and weak stems.
Over- or underwatering → root problems and growth retardation.
Nutrient deficiencies → yellowing, deformed leaves.
Insufficient training → lower yield and uneven buds.