When to Flower

When to Flower. Indoors, growers force marijuana to flower at any time. Even seedlings will indicate sex and produce flowers given the right conditions. Marijuana flowers in response to the light cycle. Under natural conditions, the plant senses oncoming autumn by chemically measuring the uninterrupted dark period. Indoors, when the light regimen includes a dark period of 10-12 hours each day, the plant stops its vegetative growth cycle and starts growing reproductive organs, male and female flowers, which usually occur on separate plants. When light hits a leaf the tissue absorbs certain rays which it uses in photosynthesis. Those rays are unavailable to leaves below the top. 1000 watt HID lights penetrate only 12-18 inches of leaves depending on their size and quantity all from marijuana seeds.