Techniques exist, however, to figure out the sex of a plant fairly early in its growth cycle. One of the easiest methods is to take a cutting of the growing plant and induce the rooting clone to flower to show sex. The donor plant continues to grow in its vegetative state while the flowering cutting reveals the parent's gender.
Plants grown indoors under lights spend the first stage of their lives receiving 18 to 24 hours of light per day. This vegetative period, simulating summertime, allows seedlings to establish the healthy roots, branches and foliar growth necessary for higher yields down the road. Some growers vegetate plants for more than a month in order to grow huge bushes in large containers. Sea of Green growers limit this vegetative time to just a week or less, but compensate by growing more plants and spacing them closer together. Either way, the plant will continue to grow in its vegetative state until it is triggered to flower.
The flowering process for both males and females begins when plants are exposed to compete darkness for 12 or more continuous hours per day. Indoors, the photoperiod is controlled by the grower, who sets the timer for a 12-hour on/12-hour off daily lighting schedule; outdoors, the sun's diminishing rays in early autumn force cannabis to bloom.
Flowers will begin to indicate themselves after a week or two into the flowering cycle. indicas will show sex sooner than sativas, so be patient with the longer-flowering varieties.