It is counted among the earliest cultivated crops. In prehistory, when cannabis transitioned from a wild plant to a desirable one for humans, it flourished in certain regions. The two original species utilized early on were Cannabis sativa and Cannabis indica. Sativa is tall, leaves long, with smaller flowers held on top and a thin, shorter growing season. Indica is a shorter, wider plant, the leaves far more broad with flowering all along the stems. Indica is more adaptable to long-term residential cultivation due to its size-to-flower ratio.

Because species are known to naturally cross-pollinate in nature, virtually all pot grown today descends from one or the other. Or, in the case of hybrids, both.

Cannabis was among the first plants to be improved by selection. This is the process of choosing and planting seed of the best plants to concentrate certain characteristics. Ancient farmer landrace strains are the heirloom roots of modern breeding. They are the foundation of modern strains and hybrids based on the gene pool of these two relatively different species.

These heirloom strains from India, Mexico, Morocco and Southeast Asia stabilized in the cultures of origin for reliable seed cultivation. Early breeders in 1960s America sought to obtain the most isolated seed sources from these genesis areas as stock for hybridization. The more adulterated the culture though, the more adulterated the cannabis gene pool. Today, these original plants are hard to find and treasured breeding stock, when they are found by plant hunters in the field.

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Some of the original strains, considered phenotypes, have interesting stories that explain their value to the big picture. Each have been sculpted genetically for many characteristics, from disease resistance to flower size, potency or fiber quality. Amateur breeders first used the original strains in America to develop new hybrids. Modern breeders still seek these old-school named varieties for more pristine, undiluted original gene pools.

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Because each of these original strains are now coming together in the budding agriculture of cannabis cultivation, breeding is occurring at an even faster rate. Many hybrids are seedless and thus can only be propagated by cloning. When a great plant is selected and named, this is the only way to create a genetically identical plant. Cloning can occur with most propagation methods such as layering, or on a mammoth scale with microscopic tissue culture of plants. By and large, most of the major strains sold today are hybrids. Those listed as I/S mean characteristics of Cannabis indica dominate and vice versa, but this is highly subjective. Some dispensaries sell live clone seedlings and seeds of named varieties for those who wish to grow at home.

Cannabis breeding is still in its infancy compared to other homegrown vegetables or herbs. Yet like vegetables, it has yet to come into the garden. Once commercial growers pick it up as a garden plant, all the breeding will pay off in easy-to-grow hybrids and traditional heirlooms from around the world, and right around the corner.

Southeast Asian strains were discovered during the Vietnam War, and to this day are the most potent. Adapted to a frost-free climate, plants there may become perennial. This makes them difficult to flower in other climate zones, so they are bred with short season, strong flowering Hindu Kush for greater adaptability. Those returning from the war brought these strains to California, where amateur breeding was flourishing.

In Colombia, cannabis grown in the highlands for centuries was a time-honored local art. These strains are adapted to a year-round equatorial climate without defined seasons. Drug traffickers smuggled this seed in quality commercial-grade marijuana to the states. This became the most widely available seed for breeding new strains for indoor cultivation, and Colombian genes can be found in many.

From the Hindu Kush Mountain Range of Afghanistan and Pakistan is a strain originating at 10,000 feet in elevation. It was discovered growing in village gardens where the growing season is very short. Thus, this is a valuable short season strain easily grown in mountain communities.

Indian ganja is said to be the medicinal cannabis of the 19th century Materia medica. The best quality plants were found among selective breeding by indigenous farmers. Centuries of selection for quality and productivity (12-foot plants) yields strains that attract commercial breeders seeking a greater yield per plant.