The Flowering Phase of the Marijuana Plant Once the marijuana plant has reached 12" height, or the height of your choice, it is time to start the flowering phase. The plant will begin to pre flower, then it will fully flower. The 24/0 light cycle is changed at this time. This can be changed to a straight 12/12 cycle, or it can be set at 14/10 and slowly adjusted until the 12/12 cycle is reached. Some growers will take the light steadily back to a 10/14 schedule, or even as far back as an 8/16. This depends on each growers preference. Pre flowering usually begins in the 4th week of vegetation. Preflowering can only be detected by magnification. At the 4th node down the stem, you should be able to see the tiny pear -shaped node which identifies the female, along with the two tiny pistils. Occasionally the pistils will not develop for several days into pre -flowering. Make sure you know whether your plant is male or female before you decide to pull it. Full flowering begins 1 to 2 weeks after changing the light schedule. In a matter of days, most or all of the nodes on the marijuana plant will be covered in white pistils. These will begin to develop into flowers, which will reach their maturity in 6 to 8 weeks` time. The buds will also develop at these same nodes. They will be covered with white crystals, and near maturity the trichromes may be seen. These start out as clear and white and turn amber or darker as the tiny white pistils turn red or dark. When you see these changes beginning to occur, pay close attention to your plant, because harvest time is near. The buds may be harvested when the trichromes or white, or you may wait until they darken. Often some buds will be ready while the trichromes in others are still developing the right colors. If this should happen, if you can, then cut the ripened buds and leave the rest to develop for a week or two longer. This will ensure a maximum yield.