Whether Cannabis consists of a single species, Cannabis sativa L., or two or more closely related species is a contentious issue. According to botanists Small & Cronquist, the single species C. sativa is divisible into two subspecies, indica and sativa. Pure "sativas" are relatively tall (reaching as high as 4.5 meters), with long internodes and branches, and large, narrow-bladed leaves.
The so-called "indica" strains are shorter and bushier, have wider leaflets, and are often favored by indoor growers. "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 contrary to popular belief, the ratio of tetrahydrocannabinol (THC) to cannabidiol (CBD) in most named drug strains of both types is similar (averaging about 200:1).
Unlike most commercial drug strains, indica landraces often consist of a mixture of plants with varying THC/CBD ratios. The relatively high CBD to THC ratio typical of hashish produced in regions where these landraces are grown (e.g., Afghanistan and Pakistan) is useful for treating insomnia. In addition to "pure indica" and "pure sativa" strains, hybrids strains with varying ratios of these two types are common. For example, the White Widow hybrid is purported to have about 60% "indica," and 40% "sativa" genetics. These hybrid strains have combinations of traits derived from both parental types.