Cannabis sativa and cannbis indica in nature are photo-period plants meaning they require a change in the daily light cycle to initiate flowering. The length of the period of darkness in each 24-hour light cycle needs to be 12-hours long or longer before flowering will begin. Cannabis ruderalis does not require a photo-period change. Instead they are genetically 'timed' to begin to flower after a certain number of growing days have passed regardless of length of periods of light and dark.i see weed strains online that have automatic in them, what does this mean?