Cannabis strains
Cannabis strains are either pure or hybrid varieties of Cannabis, typically of C. sativa, C. indica and C. ruderalis. Varieties are developed to intensify specific characteristics of the plant, or to differentiate the strain for the purposes of marketing or to make it more effective as a drug. Variety names are typically chosen by their growers, and often reflect properties of the plant such as taste, color, smell, or the origin of the variety. Cannabis strains commonly refer to those varieties with recreational and medicinal use. These varieties have been cultivated to contain a high percentage of cannabinoids. Several varieties of Cannabis, known as hemp, have a very low cannabinoid content, and are instead grown for their fiber and seed.
The two species of the Cannabis genus that are most commonly grown are Cannabis indica and Cannabis sativa. A third species, Cannabis ruderalis is very short and produces only trace amounts of tetrahydrocannabinol (THC), and thus is not commonly grown for industrial, recreational or medicinal use. However, because Cannabis ruderalis flowers independently of the photoperiod and according to age, it has been used to breed autoflowering strains.
Pure sativas are relatively tall (reaching as high as 4.5 meters), with long internodes and branches, and large, narrow-bladed leaves. Pure indica varieties are shorter and bushier, have wider leaflets. They are often favored by indoor growers for their size. Sativas bloom later than indicas, often taking a month or two longer to mature. The subjective effects of sativas and indicas are said to differ, but the ratio of tetrahydrocannabinol (THC) to cannabidiol (CBD) in most named drug varieties of both types is similar (averaging about 200:1). Unlike most commercially developed strains, indica landraces exhibit plants with varying THC/CBD ratios. Avidekel, a medical marijuana strain developed in Israel, has a very low content of THC but a high content of CBD, limiting its recreational value but maximizing medical effect.
...
Wikipedia