This is one of several related articles about cannabis. This article deals with the biology of the genus Cannabis. Cannabis is about marijuana, hashish and related drugs. Hemp is about cultivation for non-drug uses, and the non-drug uses themselves. Cannabis is a genus of flowering plant that includes one or more species. The plant is believed to have originated in the mountainous regions just north-west of the Himalayas in India , though it could also have come from Northern Africa . It is also known as hemp , although this term usually refers to varieties of cannabis cultivated for non-drug use. As a drug it usually comes in the form of dried flowers ( marijuana ), resin ( hashish ), or various extracts collectively referred to as hash oil .

The genus Cannabis was formerly placed with nettles in the family Urticaceae or with mulberries in the family Moraceae, but is now considered along with hops (Humulus sp.) to belong to the family Cannabaceae. All strains of Cannabis can interbreed, and produce fertile offspring, which means all known Cannabis plants satisfy one criterion for a single species type called (Cannabis sativa L.) The current Cannabis species model is classed as:

Cannabis gigantea hort. -> Cannabis sativa L. subsp. sativa
Cannabis indica Lam. s -> Cannabis sativa L. subsp. indica (Lam.) E. Small & Cronquist
Cannabis indica Lam. var. kafiristanica Vavilov -> Cannabis sativa L. subsp. indica (Lam.) E.Small & Cronquist var. kafiristanica (Vavilov) E.Small & Cronquist
Cannabis ruderalis Janisch. -> Cannabis sativa L. subsp. spontanea Serebr.
Cannabis sativa L. f. ruderalis (Janisch.) Chu -> Cannabis sativa L. subsp. spontanea Serebr.
Cannabis sativa L. subsp. indica (Lam.) E. Small & Cronquist
Cannabis sativa L. subsp. indica (Lam.) E.Small & Cronquist var. indica -> Cannabis sativa L. subsp. indica (Lam.) E. Small & Cronquist
Cannabis sativa L. subsp. indica (Lam.) E.Small & Cronquist var. kafiristanica (Vavilov) E.Small & Cronquist
Cannabis sativa L. subsp. ruderalis Janisch. -> Cannabis sativa L. subsp. spontanea Serebr.
Cannabis sativa L. subsp. sativa
Cannabis sativa L. subsp. sativa var. spontanea Vavilov -> Cannabis sativa L. subsp. spontanea Serebr.
Cannabis sativa L. subsp. spontanea Serebrjakova -> Cannabis sativa L. subsp. spontanea Serebr.
Cannabis sativa L. var. afghanica hort. -> ?
Cannabis sativa L. var. indica Lam. -> Cannabis sativa L. subsp. indica (Lam.) E. Small & Cronquist
Cannabis sativa L. var. kafiristanica ( Vavilov ) E.Small & A.Cronquist -> Cannabis sativa L. subsp. indica (Lam.) E.Small & Cronquist var. kafiristanica (Vavilov) E.Small & Cronquist
Cannabis sativa L. var. spontanea Vavilov -> Cannabis sativa L. subsp. spontanea Serebr.

Cannabis has shown three distinct landrace "land-race" known as Cannabis sativa, Cannabis indica and Cannabis ruderalis that are geographically isolated. Botanists, especially cannabis specialists, breeders and seed breeders, often refer to these three cannabis landrace as separate species or subspecies types. Whether the different strains of Cannabis constitute a single species (Cannabis sativa L.) or multiple species has been a contentious issue for well over two centuries.

It is traditionally (albeit contentiously) divided into at least five subspecies, indica/sativa, pure indica, pure sativa, mostly sativa and mostly indica, each found as a cultivar and a wild variety. Cannabis sativa male plants show evidence of selection for traits that enhance fiber production and seed-oil for fuel but the female plant produce seeds for food and flower buds that can be used as a psychoactive substance because it has higher levels of the psychoactive delta-9-tetrahydrocannabinol (THC), whereas Cannabis indica was primarily selected for drug production and has relatively higher levels of cannabidiol (CBD) and Cannabinol (CBN) than THC.

Some Cannabis sativa seedsBotanists Richard E. Schultes and Loran Anderson also conducted taxonomic studies of Cannabis, and concluded that sufficient evidence exists to support recognition of three species, Cannabis sativa, Cannabis indica Lam., and Cannabis ruderalis. According to their species descriptions, C. sativa is tall and laxly branched with relatively narrow leaflets, Cannabis indica is shorter, conical in shape, and has relatively wide leaflets, and Cannabis ruderalis is short, branchless, and grows wild in central Asia. This concept was embraced by cannabis afficionados who commonly distinguish narrow-leafed "sativa" drug strains from wide-leafed "indica" drug strains.

A recent study of genetic variation in Cannabis supports recognition of C. sativa and C. indica as separate species, although the existence of a third species, C. ruderalis, is less certain. This study assigned hemp (fiber/seed) landraces and feral populations from Europe, central Asia, and Asia Minor to C. sativa. Cannabis indica includes both narrow-leafed drug NLD and wide-leafed drug WLD strains, as well as southern and eastern Asian hemp strains and feral Himalayan populations.

In 2005 a DNA study of the variation in Cannabis according to the DNA in their mitochondria and chloroplasts was conducted. The results showed three distinct "races" of cannabis, including the newly discovered Cannabis rasta. In central Asia the THC-rich indica predominated, while in western Europe sativa was more common. In India, south-east Asia, Africa, Mexico and Jamaica the rasta variant predominated. It looks similar to the sativa subspecies, but generally contains higher levels of THC.

Some authors now refer to C. indica as the subspecies Cannabis sativa subsp. indica and C. ruderalis as the variety Cannabis sativa var. ruderalis reflecting the fact they may not be distinct enough to be classified as separate species. Several other botanical names have also been applied.

There may be political pressures to maintain that "all" Cannabis is designated Cannabis sativa L. for the purposes of avoiding challenges to current laws in various countries.
Cannabis is used as a food plant by the larvae of some Lepidoptera species including Ghost Moth and The Nutmeg.