The Cannabis Life Cycle

THE PLANT

From seed to harvest, an annual cannabis plant passes through four stages, germination, seedling, vegetative growth and flowering, and light is the switch between them. Knowing the stages explains why timing, and daylight, control everything a grower does.

Germination and seedling

A viable seed cracks open in warm, moist conditions and pushes out a root and its first pair of round seed-leaves (cotyledons). Over the next two to three weeks the seedling grows its first true, serrated leaves and establishes roots. It is fragile and needs gentle light and humidity.

Vegetative growth

With strong light (typically 18 hours a day indoors) the plant enters the vegetative stage: fast growth of stems, branches and fan leaves, building the frame that will later carry flowers. There are no flowers yet, and the plant is sexually immature.

Growers hold plants here as long as they want more size, then trigger flowering by changing the light.

Flowering

Cannabis is usually photoperiod-dependent: it starts flowering when nights get longer, which indoors means switching to about 12 hours of darkness. Autoflowering (ruderalis-derived) plants ignore this and flower by age.

Over roughly 7 to 12 weeks the female plant develops colas, the pistils mature, and the trichomes fill with resin. Harvest timing is judged by watching the trichomes.

The stages at a glance

Why the cycle matters

Every practical decision, when to train the plant, when to flip the lights, when to harvest, is a decision about where you are in this cycle. It also explains why an outdoor plant flowers in autumn as the days shorten.

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