Cannabis is a genus of flowering plants within the hemp family. A native of Asia, cannabis has been naturalized and cultivated worldwide over thousands of years. Traditionally, three major classes have been recognized: Cannabis sativa, Cannabis indica and Cannabis ruderalis. But cannabis is prolific and the case is made that these may simply be the most common of almost 700 variations of the genus.

Sativas originated in the world’s equatorial zones, growing up to 15-20 feet tall in the heat and light of the tropics. Shorter, larger-leafed indicas have adapted to grow at higher altitudes. Ruderalis is short, fibrous and has a remarkable range of uses from rope to cloth and nutriceuticals.

The cannabis leaf is iconic, with serrated leaflets radiating from the base in a distinctly palmate pattern recognized around the world. Cannabis is dioecious, having both male and female plants, although monoecious plants are not unusual. Until flowering, the sexes are differentiated by size and shape. The female is shorter and with thicker foliage, the male taller and sparsely leafed.

The flowers of cannabis develop as clusters or buds. The flowers of male plants are loose and hang from the plant. In females, flowers are dense, bristling with leaflets and upright in thick leaf clusters arrayed along the flowering limb. Cannabis produces psychotropic and therapeutic compounds in trichomes clustered on the flowers of the female plant. Male plants are staminate and produce pollen. Female plants are pistillate and produce seeds, which are fertilized by wind-driven pollen.

In the natural growth cycle, seeds germinate in the spring over the course of 3-7 days. A spindly embryonic stem topped by “seed leaves” emerges and grows to approximately 10 centimeters, or 4 inches. In the vegetative stage, the lengthening days of summer stimulate the plant to sprout leaves and limbs. As the season passes, the light signals of shorter days and longer lights cause the plant flower to begin the cycle again.