The History of Hybrids: How Breeding And Selection Led to Modern Marijuana

By Joe Bender, Cannabis Crop Solutions, LLC

Cannabis growers are always searching for the next remarkable strain. The countless flavors and multitude of effects combine to create endless possibilities. In the last 60 years, breeders have capitalized on the diversity of cannabis more than ever before, crossing strains from around the globe.

Today, as cannabis laws become more tolerant in North America and elsewhere, breeding is becoming easier than ever before, which is reflected by the number of strains available through seed distributors. As you browse a seed catalog and contemplate which strains to buy, you might ask yourself, “Where did all of these strains come from?” The story is complicated for many modern strains, which are often hybrids of hybrids. But the key building blocks of many strains are a relatively few, very important breeding projects and landraces.

Understanding the history of the modern hybrid has value beyond musing about cannabis lore. Familiarity with strain lineage can help guide seed or clone purchases. Commercial growers and dispensaries benefit from diverse strain collections, which are attractive to customers with various needs, so knowing how to select a wide spectrum of flavors and effects is a useful skill. Growers should also understand the environmental requirements for their strains and which cultural practices might work best for each one, and these factors are heavily influenced by lineage. Furthermore, breeding for strain diversity and quality in the future will require thoughtful selection, and will be benefited by knowledge of strains of the past.

Cannabis’s Taxing Taxonomy

There are several distinct types of cannabis. Although taxonomists have often disagreed on how to classify Cannabis, suffice it to say that four widely recognized types are sativa, indica, afghanica and ruderalis. Preeminent ethnobotanist Richard Evans Schultes interestingly noted that although “zealous taxonomists” are often determined to precisely compartmentalize plants, their plastic nature and adaptive ability to interbreed between seemingly separate genera or species implies that “plants were not made to be cataloged and classified,” and that in cases like the identification of Cannabis, “a historical perspective is imperative.” Weighing in these considerations, I will delineate Cannabis plant types in as useful a way as possible.

Sativas grow as tall as 20 feet, have smooth, hollow stems with longer internodes than their counterparts, and produce achenes that are partially exposed (achenes are the dry fruits of some plants such as sunflowers, which are commonly called seeds, but are in fact fruits containing a single seed). C. sativa leaves are relatively large, with long, lance-shaped leaflets. Sativa flower clusters are somewhat indeterminate, meaning the plants continue to grow new flowers above the old ones for a lengthy period, with equatorial strains flowering for as long as five months. Although not isolated to the tropics, sativa plants are adapted to warmer latitudes, where day length varies little throughout the year and warm conditions allow for continual development.

Indica plants are shorter in stature than sativas, sometimes growing to 10 feet in height, and have a more determinate flowering habit. They have smooth, dense, nearly solid stems, and their leaflets are smaller than sativa or afghanica types. Curiously, C. indica has rather narrow, pointy leaflets.

Adapted to a mountainous, cold climate, and bred for hashish production, afghanica plants are short, stout and potent, and have nearly solid stems. Afghani marijuana is usually referred to as indica; however, in 1926 Nikolai Vavilov described afghanica as a distinct type. Following his description, some growers have continued to separate afghanica due to its shorter stature (less than six feet tall), ribbed stems, wider and longer leaflets, characteristically long petioles, denser buds, faster flowering time and more sedative high than typical indica strains. When most cannabis users refer to indica, they are thinking of plants with Afghani heritage. Bear in mind that while India has cold mountains to the north, it also has tropical climates to the south; this large environmental variation could help explain the morphological differences that create the need to partition afghanica from indica.

First classified in 1924, ruderalis plants are believed to have originated in Western Russia, Western Siberia and Central Asia. C. Ruderalis is typically less than two feet tall, may be unbranched, has smooth, hollow stems and small, wide leaflets, and readily sheds mature achenes, which possess a characteristic, fleshy abscission layer at their base. Most famously, ruderalis is regarded as the source of auto-flowering genetics in cannabis. Auto-flowering strains don’t require short days (less than 12 hours) to flower, as do most cannabis strains; regardless of light cycle, they start to flower as soon as they reach maturity, which is within a few weeks after germination.

Landraces: The Root of All Good

When farmers allow natural pollination and collect the seeds of their crops, then plant them the following year and repeat this process over time, heirloom varieties are developed. This was standard practice until the modern era. Heirloom varieties are somewhat the result of natural selection. Environmental pressures such as rainfall amounts, temperatures, humidity levels and hours of sunlight per day, along with biological pressures such as pathogens and herbivorous animals, determine the viability of individual plants in their environment. Plants with characteristics that allow them to best cope with these pressures will on average produce more pollen and seeds than lesser-fit plants. Therefore, heirloom varieties are well-adapted to their local conditions. When farmers trade heirloom seeds regionally, and continue the process of collecting seeds for subsequent crops, landraces are developed. Within a landrace, plants share common characteristics, but also maintain a level of genetic diversity. Cannabis landraces are the foundation of modern hybrids. Notable examples of landraces include Afghani, Durban Poison, Jamaican, Colombian Gold, Panama Red and Thai.

Classic Breeding Products

In the 1960s and ’70s. the majority of the marijuana sold in the United States was grown outdoors. According to researchers, cannabis breeding in the United States for the purpose of producing high-THC strains that finished early enough for North American outdoor cultivation began in the early 1960s. Northern Mexican and Jamaican strains were quicker to finish flowering, but were moderate in potency. Breeders crossed (i.e., hybridized) these strains with more potent, longer-flowering Panamanian, Colombian and Thai strains, and then selectively inbred the hybrids to create the famous outdoor sativas of the 1970s, including Original Haze and Maui Wowie.

Inbreeding involves selecting male and female sibling plants exhibiting desirable characteristics, and pollinating the females using the males. With careful selection, inbreeding for several generations will produce a homogenized line, in which all of the plants exhibit the desired traits. Homogenized lines are referred to as “stabilized” or “true-breeding” because successive generations of inbreeding maintain the distinctive characteristics of the strain.

Skunk #1: Perhaps the most famous inbred line of all time is Skunk #1. During the mid- to late ’70s, traveling cannabis enthusiasts brought Afghani landrace strains to California. Breeders there found that afghanica plants hybridized well with the tall, lanky sativas that were popular at the time. A collective called Sacred Seeds emerged in the underground scene in Northern California and used inbreeding to stabilize a hybrid of Afghani, Colombian Gold and Acapulco Gold to create Skunk #1, which it offered to the public in its first seed catalog in 1981. Skunk #1 quickly became the most popular strain in California, thanks to its sweet flavor and soaring high. In 1982, California police shut down Sacred Seeds, but one of its breeders, Sam the Skunkman, managed to salvage the prized genetics.

In the 1980s, the relaxed cannabis laws of the Netherlands attracted growers and breeders and led to the creation of several Dutch seed companies, including the Seed Bank of Holland and the Super Sativa Seed Club. Fleeing California, Sam the Skunkman made the pilgrimage and brought his collection of Sacred strains, including Skunk #1. There, Sacred Seeds’ hard work came to further fruition in a new seed company, Cultivator’s Choice. This relocation of Californian genetics to uniquely weed-tolerant Holland was a monumental event for the future of cannabis. Breeding work flourished in Holland unhampered by the government, and a platform for shipping seeds worldwide was born. When the first High Times Cannabis Cup was held in Amsterdam in 1988, Skunk #1 by Cultivator’s Choice took first place.

Inbred since 1978, the homogenized, true-breeding nature of Skunk #1 makes it excellent for breeding new hybrids. When two true-breeding strains are crossed, the result is known as an F1 hybrid. F1 hybrids express traits of both parent lines in a uniform manner among individual plants. F1 hybrids also usually display “hybrid vigor,” meaning that the hybrid is more vigorous (better growth rate, yield, etc.) than the parent lines. Due to these factors of imparting uniformity and vigor in crosses, Skunk #1 is highly desirable for breeding, and it is now a progenitor of a great many strains, likely more than any other parental stock.

Owing to its combination of tropical sativa and Afghani traits, Skunk #1 is a high-yielding strain. Tropical sativas develop long, airy colas lacking density, which helps them dry after rainfall and resist mold in rainy climates.

Afghani plants have the opposite characteristics: small, nearly rock-hard colas, adapted to an arid environment with little pressure from Botrytis cinerea gray mold. Hybridizing these contrasting traits creates large colas, with a moderate, spongy density. This bud structure is wonderful for yields; however, Skunk #1 is prone to gray mold. If grown outdoors in humid areas of North America or Europe, Skunk #1 will continue flowering into fall’s mold-favoring conditions. Its slightly longer maturation period and hybrid bud structure also mean that its first flowers to develop are aging and surrounded by layers of younger flowers at harvest time, creating perfect conditions for Botrytis. For these reasons, Skunk #1 is best suited for growth indoors or in greenhouses, or outdoors in a Mediterranean climate. Strains with similarly structured hybrid buds, such as Serious Seeds’ AK-47 and T.H.Seeds’ S.A.G.E., also perform best in these environments.

Northern Lights: Northern Lights is another classic strain, which has led to numerous, sensational breeding projects. Originating in the Pacific Northwest, Northern Lights is thought to be an inbred line of pure afghanica. It was introduced to the Dutch cannabis scene via the work of the late legend Nevil Schoenmakers, founder of the Seed Bank of Holland. Schoenmakers made various NL crosses and backcrosses, such as NL #5 x Haze, NL #5 x Skunk #1, Silver Pearl and Hash Plant xNL#1.

In 1991, Schoenmakers sold the Seed Bank of Holland to Sensi Seeds. Sensi Seeds currently offers a seed form of Northern Lights, which it created through extensive back-crossing of “three original Northern Lights variants.” Sensi Seeds describes the plants as having low odor and the cured buds as having a honey-musk, earthy, juniper scent.

Greenhouse Seed Co.’s Super Silver Haze, an outstanding Northern Lights hybrid, has the classic Haze taste, which is reminiscent of the smell of cedar wood, and has a truly psychedelic high, which is uplifting and enhances colors.

Blueberry: Blueberry by DJ Short is a stabilized, Afghani-sativa hybrid strain. It has varying tones of sweet berry flavor and a euphoric high. The scent is often like a blueberry pie, and the plants tend to have beautiful bluish-purple hues at harvest. It yields best when grown from seeds, but it can also provide ample harvests from clones. The clones must be well spaced to get plenty of light to their fan leaves, or they’ll yield poorly.

Like many other strains (such as AK-47), Blueberry mother plants tend to weakly flower when they’re left unpruned for too long. Frequent topping prevents this problem. Topping for maintenance and increased clone production exaggerates their already bushy Afghani structure. This creates a lot of shade around their pots, so prune lower branches conservatively to prevent infestations of fungus gnats, which prefer the shady conditions.

As an inbred line, Blueberry hybridizes exceptionally well with other inbred lines. Recognizing the quality and breeding compatibility of Blueberry, breeders have used it in countless hybrids, as evidenced by the number of “Blue” and “berry” names in the current seed catalogs.

Finding a ‘Golden Nugget’

No strain had impacted the cannabis world as significantly as Haze, Skunk #1 and Northern Lights—that is, until the advent of OG Kush. It has the strongest flavor of any cannabis variety I’ve ever tried. It’s hard to put a finger on, but once you know the Kush scent, you’ll never forget it. Not only does it have a strong flavor, its THC level can be higher than 25 percent, making it one of the strongest strains in the world.

Hybrids of OG Kush are now almost as ubiquitous in dispensaries and seed catalogs as the famous strains of the past are. One very successful hybrid of OG Kush is Girl Scout Cookies (OG Kush x Durban Poison), which packs a punch and has flavor to boot.

An interesting aspect of OG Kush is its combination of narrow branch angles and long internodes. The plants have a fairly stretchy, unique appearance, which in veg will not strike experienced growers as looking particularly healthy. Although the narrow crotches are unfavorable for branch strength, the overall result of the strain’s morphology is that a lot of light reaches the bottom of the canopy, so the plants tend to produce top quality even at the base of branches. This allows for tighter plant spacing than other strains, which, when judiciously paired with proper veg timing, could improve yields without sacrificing quality. If grown outdoors, however, you’ll need to protect OG Kush from the wind, which could easily split branches off of the main stem.

Hemp

In recent years, enthusiasm for cannabidiol (CBD) has grown exponentially. CBD provides anxiolytic, antiepileptic and anti-inflammatory effects. CBD is commonly extracted from seed-hemp plants, which are bred to have big buds that yield lots of seeds. These plants tend to have a significant resin content, but must not contain more than 0.3 percent THC to be considered hemp. Instead of a high-THC percentage, the resin of hemp is high in CBD. Fiber hemp differs from seed hemp in that it is grown closely spaced to promote stretching and long internodes, using tall strains that are high in fiber and generally low in flower yield. Dual-purpose hemp varieties exist, but they are less desirable for either seed or fiber production than specialized types.

Breeders have developed marijuana strains that produce both THC and CBD. The most famous strain of this type is Cannatonic from Resin Seeds. The best examples of Cannatonic have a ridiculously strong grapefruit scent and a 1:1 ratio of THC to CBD, creating a very relaxing effect.

Knowledge of cannabis history is crucial for predicting the future of the plant. Understanding the origins of modern hybrids can also help growers use their resources as effectively as possible, by guiding them in assembling a diverse strain menu and in choosing strain-specific cultural practices.

With improved legal status and a greater public interest than ever before, cannabis is set for a new wave of breeding success stories. The future may bring a revival of breeding for the outdoors, and as rules against shipping loosen, regional specialty strains could develop, as were once common. Undoubtedly, indoor, outdoor and greenhouse cultivation will continue to evolve, aided by technology, research and a never-before-seen availability of strains.

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Originally published in the October, 2019 issue of High Times magazine. Subscribe right here.