In descending order, by date published.
Cannabis sativa is a summer annual plant that is strongly photoperiod-sensitive (flowers according to day length/photoperiod; not physiological maturity). It is mostly dioecious in that male and female flowers occur on separate plants (i.e. there are both male plants and female plants). However, there are also several monoecious commercial varieties (male and female flower parts on the same plant). Different plant parts are harvested for specific purposes, and modern day hemp may be produced for one or more purposes. Depending on the harvestable component of interest, (i.e. fiber, grain or cannabinoids) male plants and/or pollen might be vitally necessary or completely unwanted.