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Cannabis Genotypes and Phenotypes: What Makes a Strain Unique?

April 14, 2014

Sometimes you find a cannabis strain so good, you can’t help but revisit the experience every time the opportunity presents itself. One day you might be surprised to discover a new batch of Blue Dream looks nothing like the one you last tried: what was once a spear-shaped flower now looks like a chunky bulb of crystal trichomes. It’s the same strain, so what’s with the variability?

Two things influence the structural formation of any given cannabis plant: genetics and environment. The plant’s genetic makeup, also called a genotype, acts as a blueprint for growth: it allows a spectrum of physical possibilities, but it is up to the environment to induce these characteristics. The physical expression of a genotype is referred to as a phenotype, which is simply defined as the traits that the environment pulls out from the plant’s genetic code. Everything from color, shape, smell, and resin production are affected by the environment.

This guide to cannabis genetics will carry you through the evolution of the cannabis plant, from its antique beginnings through today’s modern cultivation. By the end of it, you will understand that there are indeed defining characteristics for every strain, but each plant is as special as a snowflake as it uniquely expresses genes according to its garden environment.

The Earliest Cannabis Species

Cannabis is an ancient plant with roots all over the world. The earliest species are thought to have grown in the mountainous Hindu Kush region of Pakistan, while others later proliferated in tropical climates. These earliest varieties, called landrace strains, are considered the diamonds of cannabis genetics. Thousands of years of adaptation allowed these strains to express their very best traits for a specific geographical location. These areas are what breeders like DJ Short call “sweet spots.”

Our short, resin-heavy indicas populated latitudes between 30 to 50 degrees, whereas the tall, slow-growing sativas naturally homestead in equatorial regions around 30 degrees latitude. These diverse habitats conditioned a colorful array of cannabis varieties, each with its own long-standing history.

Cannabis in the Great Indoors

Cannabis breeding took a major turn beginning in the 1970s and 80s when federal anti-cannabis sentiments peaked, driving cultivation from the great outdoors to underground. Indoor gardens, raised by soil, electric lights, and hydroponic systems, produce a bulk of the cannabis seen in the market today. While there’s little doubt that masterfully grown strains have been cultivated indoors, experts will agree that the generic, unnatural environment can only bring out so much of the plant’s potential.

Narrowing diversity even further, growers during this time were primarily motivated by THC content and selectively chose this characteristic over other important chemical constituents like CBD.

In spite of this lost richness, we see great variability in the plant’s phenotypic expression: nutrients, temperature, the amount and angle of light, soil type, photoperiod length, time of harvest, and the distance between the plant and light source are among the many conditions that affect the plant’s characteristics. Certain conditions may coax sativa- or indica-like traits, so as much as we love categorizing strains here at Leafly, we have to acknowledge that a strain’s traits are not necessarily set in genetic stone.

The Age of Hybridization

Hand-in-hand with the indoor grow revolution came hybridized strains, an intermixing of global indigenous varieties. This is when the sativa met the indica, beginning an ever-branching tree of hybrid offspring. Growers admired indicas for their resin-coated buds and short flowering periods, both of which are coveted traits for commercial production.

(Amy Phung/Leafly)

If we think of indicas and sativas as falling on opposite ends of the genetic spectrum, it becomes possible to imagine the scope of phenotypic expression. Take Blue Dream for example: a cross between the indica Blueberry and sativa Haze, Blue Dream may reflect characteristics anywhere on the spectrum between its parents, depending on how it was raised. This is why we may sometimes see an indica-like phenotype of Blue Dream when we expect a sativa. That isn’t to say strains are unpredictable genetic wildcards; rather, we just shouldn’t be surprised when a strain does not fit perfectly within a categorical box. Again, it is possible to wheedle sativa or indica characteristics with specific conditions in a controlled garden.

Because of hybridization, we have a virtually limitless selection of strains to choose from and even avid strain collectors will always have new hybrids to chase. Connoisseur-focused growers may mourn the loss of original cannabis genetics, but many still dedicate themselves to their resurrection. Not only would their revival make for a richer recreational market, ‘ancient’ strains could have a tremendous impact on cannabis as medicine. We hope that as political barriers fall over like dominoes, the horticultural art of cannabis cultivation will be able to bloom globally once again.

Image sources: Smokers High Life, Coleen WhitfieldThe Other Dan, Dave H

  • Marjorie Little

    I have some pot that smells like skunk. I have no idea what it is. Any clues?

    • Toddy Beaches

      Could be a variety of strains… most likely a sativa dominant strain. I believe the most common skunk phenotypes used in modern breeding are sativa dominant (more energetic). With the exception of Super Skunk, bred from Afghani, both indica’s (more relaxed). Does the weed have any distinct hairs? Lemon scent? Other characteristics to identify?

      • Marjorie Little

        No distinct hairs. Maybe a sweet lemon underscent. It’s quite oily and the buds are small.

        • Steven Runions

          Lemon haze maybe

    • The Spliff Potcast

      lol SO MANY possible answers, but mine are in the same ballpark. It could be a Skunk OG, or an Afghani of some sort. Both to me can swing either way. Only one real way to tell ;D

    • veracity
    • Emma Lou #2

      yeah. it is skunk.

      • Mike Lowe

        Just now read forum. Funny!


  • Mary Jane

    It’s funny how others often see smokers as dumb people who have an addiction problem, but really we are a bunch of diverse, creative, smart, and even “regular” people who are more than capable of writing beautiful things such as this by Bailey Rahn.

    • The Spliff Potcast

      historically peoples are often stereotyped in reverse to invalidate their achievements.

      But we ain’t gonna let it get us down 😀

    • Pat Ray Attic

      That old burnout stereotype has been perpetuated by dorks that want to let the world know they smoke weed, usually in school where everyone hasn’t been around it yet because of the stigma around drugs. Alot of my most productive and creative times have been with weed, not all.

    • corners

      I think there are a lot of smart people out there, they just dont have the time anymore to try something new and creative because of working pay check to pay check.

  • Ryan_Dyne

    I disagree with your definition of phenotype — but I’m just doing another go-around trying to get this straight.

    You say that it’s the result of cultural differences; I say it’s the resut of different genetics, due to the strain’s not being stable. That’s what happens when a strain remains heterozygous: different pairs of {dominant, recessive} genes will pair up during sexual … seed-making – and voila!: different phenotypes.

    Consider: Clones may display different characteristics given different growing conditionss.
    (as opposed to the same (roughly) under the same growth conditions)

    …whereas, seeds with the phenotypes built-in will be different regardless of the growing conditions

    • Vlad Sergeevich

      Always nice to hear an expert’s opinion on topics which most people haven’t even heard of! Thanks for sharing this.

    • Puckhead

      He stated “The physical expression of a genotype is referred to as a phenotype,
      which is simply defined as the traits that the environment pulls out
      from the plant’s genetic code. Everything from color, shape, smell, and resin production are affected by the environment.”
      So to be clear The term “phenotype” refers to the
      observable physical properties of an organism; these include the
      organism’s appearance, development, and behavior. An organism’s phenotype
      is determined by its genotype, which is the set of genes the organism
      carries, as well as by environmental influences upon these genes. Phenotypes even the built in ones will change according to the conditions. These conditions ultimately drive the expressions.

      • John Deininger

        I just wanted to +1 puckhead’s comment. As a chemist who teaches science, I must say he gave an excellent, concise, and understandable explanation. I just wanted to inject another element of genetic expression, epigenetics, into the discussion. It’s a relatively new field of study but one that is providing a deeper understanding of a very complex topic. To truly gain an understanding of hybridization, genetic manipulation, stabilization, etc. requires deep understanding of all things genetic.

  • Doğa Can Yaman

    I love so called the landrace strains because those were what we smoked in the past. I live in Turkey and in my country we don’t call it cannabis or marihuana the public knows it as “indian hemp” and we used to have big fields full of male and female plants. When we bought it from the seller it always came with seeds and you can’t believe how nice it tastes and gives you a full mental piece.
    Over the years I have travelled abroad and smoked bunch of other stuff the feminized seeds I mean or the strains with a lot of thc. And I growed many of the known strains at the same time to compare with the natural seeds I find from my country. I observed them and my conclusion is local seeds are the best and im against all of this seed companies. They are not aware that they don’t do it in the right way. Most of the europeans and americans don’t know the feeling of that mental peace that ı talked about or if you give them a weed with seeds they will say no it’s bad it’s less thc and bla bla.

    People should think wisely on this subject and change their criterias to examine this plant. It’s not all about thc or cbd or the other ones that they couldn’t find yet. The highness the plany gives is not only about the bigger buds or stickyness or whatever. The most important thing is if the humans interacted with this plant or not. This is the question. Because no science can beat a plant, and its relationship with its own environment.

    We do not need to understand this plant we can’t do it. It has been around for thousands of years.
    we shouldn’t dare to modificate it simply because we don’t have the information of thousands of years of evolution and breeders are not aware of the value of adaptation.
    I hope some people get what I meant. fuck blue dream tangerine whatever white fuck or any other strain. They are all weak and soo new! Don’t forget what makes a plant or an organism is its history of evoulution in the real world under the real conditions.

    growing indoor is just a silly habit. and all the science behind is not real.

    • John Deininger

      Very anti science. I always find comments like these funny, particularly considering the medium being used to make the comments.

      Besides, the approach of these hybridizers is to mimic what occurs in nature. If we were to wait for evolution to produce these adaptations you speak of it would take thousands upon thousands of years to produce stable, useful, genetic changes to the genotype. By controlled breeding, these desirable traits can be identified and stabilized much faster. This is how agriculture has worked since its inception very, very long ago. Every plant that we consume has been genetically modified through selective breeding and other, so called, “natural” manipulation.

      So if you want to stick with “landrace” strains, more power to you…but many (most even, in certain areas where cultivation and use was much more prevalent), even of these strains, have been modified by humans, either directly or indirectly. Humans have been cultivating cannabis for thousands of years and by simply identifying and cultivating desirable plants they began an approach to breeding that one could properly call “scientific”, although they probably didn’t have a term for it back then.
      See, the point of science is not to “beat” nature, but to learn from it. I would love to have you in my Philosophy of Science class. It seems you have some erroneous beliefs about it which would classify your comments about science as a “straw man argument”.

      Oh…and humans are part of the “real world”. We are also, not the only species to manipulate “nature” as part of an evolved survival mechanism.

  • Buddy Bee Anthony

    Marijuana has to be in the proper environment to flourish. They need a loving grower just like a child needs a certain environment,good soil, a particular provenance in their family to flourish and grow.. Oh never mind… What I really want to know is why junk food tastes so good when doing Pot and when I’m clean, ,I’m less creative but several pounds lighter…It’s a trade off for me.

  • John Deininger

    A recent archeological/anthropological dig uncovered what is the earliest evidence of cannabis used for psychoactive purposes. The residue found, which was burned in a closed chamber (probably during sacred rituals) filling the air with smoke. Was that of a high THC strain (they say that cannabis is “stronger” now, but that’s clearly not true. This false “fact” probably stems from the fact that most of the cannabis (black market) consumed in the past was predominantly leaves, stems, seeds, and maybe a bit of the flower.

    Anyway, this evidence of psychoactive use was in China (I forgethe region but it can’t be hard to find. The article I read was recent). The estimated age puts the use at about 2500 years ago. They will find older examples eventually but finding testable residue from that far back is rare.