If you give your plants for example 12 hours light or less it will produce floral growth. Expose your cannabis plants coming from autoflowering seeds to the longest light cycle and they will grow as quickly as they can. The most growers use long light cycles to raise the young plants like seedlings and clones. If the cannabis plants get older they may threaten to grow to big for the garden space. This is where reducing the light cycle can come convenient. Controlling floral growth can be more difficult. To get the cannabis plants to flower the grower have to put his plants in the dark for 12 hours. After about 2 weeks of this dark cycle the cannabis plants begin to flower. During the floral period the plants are fickle and unforgiving for incorrectness. In the actually dark period the cannabis plants make a chemical,they named it phytochrome. Phytochrome is light-sensitive and is directly exterminated by exposure by light. Natural light is the first source most beginners use to grow cannabis plants.