The Vegetative Stage: Building the Framework for Yield

The vegetative stage begins when the seedling has established its root system and begins producing true leaves — typically 1–2 weeks after germination — and ends when you change the light schedule to 12/12 to trigger flowering. During this phase, the plant's entire focus is on structural growth: roots, stems, leaves, and the development of the branching pattern on which flowers will eventually form.

LIGHT REQUIREMENTS IN VEG

Photoperiod plants in vegetative growth require more than 12–13 hours of continuous darkness to remain in the vegetative phase. Standard practice is an 18/6 schedule (18 hours of light, 6 hours of dark), though some growers use 20/4 or even 24/0. The longer the light period, the faster the vegetative growth. 18/6 is the most common compromise between growth speed and electricity costs, and also allows for more consistent temperature cycles.

TEMPERATURE AND HUMIDITY

During vegetative growth: daytime temperature 22–28°C, nighttime 18–24°C. Humidity 50–70% — higher humidity during veg allows leaves to absorb moisture through their surfaces, supporting vigorous growth. Ensure good air circulation to prevent the high-humidity microenvironments that encourage mould.

VEGETATIVE DURATION

How long you keep plants in vegetative growth determines their final size and yield potential. Most indoor grows veg for 4–8 weeks before switching to flower. Smaller plants (4 weeks veg) produce faster harvests with lower yields; larger plants (8+ weeks) produce higher yields but require more space. A useful rule of thumb: plants will approximately double in size during the first 2 weeks of flowering (the "stretch"), so plan your vegetative size accordingly for your available height.

TRAINING DURING VEG

The vegetative phase is the optimal time for all training interventions. LST can begin when the plant has 3–5 nodes; topping is performed at any point during vigorous vegetative growth. Allow sufficient recovery time between training events and ensure the plant is healthy before introducing any stress.