When growing or breeding cannabis, knowing the basics of phenotypes and genotypes is important for anyone interested in understanding why two plants from the same batch of seeds can still look and act very differently. The answer comes down to the plant’s genetic information (genotype) and how it shows up when influenced by the environment (phenotype). In this guide, we’ll break down these simple but key ideas to help you see what shapes every cannabis plant, from its look to its chemical makeup.
What Are Cannabis Genetics?
Cannabis genetics is the study of how a cannabis plant’s traits and features are passed on. Like all living things, cannabis has a unique set of genes that decides everything from how it looks and grows to its smell, flavor, and cannabinoid levels. This genetic code makes each cannabis strain what it is today.
Cannabis genetics is not just a theory; it’s the practical science driving the entire industry. By knowing these traits, cannabis breeders and growers can purposely create new or improved types by breeding, working to get certain characteristics that meet various preferences and needs.
How Do Genetics Affect Cannabis Growing?
Genetics are the basic instructions for how a cannabis plant can turn out. They decide everything the plant is capable of-like how strong it can get, how much it can produce, how well it can deal with bugs and disease, and even the flavors and smells that make each strain unique. If you’re growing cannabis, you need to know this because it helps you pick the right seeds or clones and gives you an idea of what to expect as you grow your plants.
If you don’t know your plant’s genetics, it’s like guessing in the dark. For example, a strain with genes for high THC will likely be stronger than one bred for CBD, even if you treat them both the same way. Genetics set the limits; the growing environment then allows those possibilities to come through-or not.
Cannabis Types: Species, Subspecies, and Hybrids
Cannabis plants go back thousands of years, starting with original “landrace” strains. These grew wild and adapted themselves to specific regions over time. Indicas, with their short, sturdy builds and fat leaves, did well in cooler mountains (30 to 50 degrees latitude). Sativas, by contrast, grew tall and spindly in hot, tropical areas closer to the equator (around 30 degrees latitude).
Starting in the 1970s and 80s, more growers moved indoors and began mixing these different types, leading to today’s many hybrids. Breeders cross Indicas and Sativas to get plants with combined, more appealing traits. For instance, Blue Dream is a mix of Blueberry (Indica) and Haze (Sativa). Nowadays, there are many strains to choose from, with different looks, effects, flavors, and growth habits. Some people miss the older, original genetics, but some breeders still try to bring these classic strains back because they see their value.
Genotypes: The Plant’s Genetic Instructions
The genotype is the “instruction manual” hidden inside the plant’s DNA. This is what decides what a cannabis plant might be like-even if you can’t see all these qualities just by looking at it.
What Is a Genotype?
A genotype is the total of all the genes inside a plant-its full genetic code. This code comes from the plant’s parents and decides all the things the plant could be, like size, shape, yield, leaf and flower structure, colors, and cannabinoid or terpene makeup.
But a genotype isn’t a strict rulebook. It just lays out what’s possible. The actual results depend on how the plant grows-in other words, the environment chooses which of those possibilities show up. Still, genotype always marks the outer limits of what the plant can do.
How Do Genotypes Shape a Cannabis Plant?
The genotype spells out everything a plant can be. It tells the plant whether it can make lots of THC or CBD, if it’s likely to resist certain bugs, how tall it can grow, and what the leaves and flowers will look like.
Breeders count on genotypes when trying to create new strains or pass certain traits down. By picking plants that have the right genotype, breeders can improve strength, yield, taste, and keep those traits steady in future generations. The environment decides how much of the genotype comes out, but the genotype is the source of what’s possible.
Genotype vs. Chemotype: What’s the Difference?
The genotype is all of a plant’s genes. The chemotype is about the chemicals it actually makes, like cannabinoids and terpenes. A plant’s genotype might let it create many different chemicals, but the chemotype shows exactly which ones and in what amounts.
For example, a plant may be able to make both THC and CBD (genotype), but you won’t know the actual amounts until you see what it produces (chemotype). Cannabis is often grouped like this:
| Chemotype | Main Chemicals |
|---|---|
| 1 | High THC, low CBD |
| 2 | Roughly equal THC and CBD |
| 3 | High CBD, low THC |
The difference matters, especially as breeders try to control not just the look or size of the plant, but also its strength and the way it affects people.
Phenotypes: What You See and Smell
The phenotype is what you can notice about a plant-its height, color, leaf shape, bud structure, and even smell and taste. Phenotype doesn’t just cover the look; it also covers growth style, development, and chemistry.
What Is a Phenotype?
A phenotype is the collection of visible traits in a cannabis plant. This includes:
- Plant height
- Shape of leaves
- Budding patterns
- Amount of resin
- Overall color
The name comes from a Greek word meaning “to show”-so it’s quite literally what the plant shows to us.
But phenotype isn’t only a matter of genes. It’s the result of both the plant’s genetics and its environment. This means that even plants with the same genes can turn out looking and acting differently if they’re grown in different conditions.
Why Do Plants with the Same Genotype Look Different?
This is one of the interesting things about cannabis: the same set of genes can give you very different results depending on where and how you grow the plant. For example, two clones from the same mother might behave in completely different ways if their light, temperature, or nutrition is different. One might grow short and bushy; another might grow tall and stretchy. Tiny changes-like a cooler spot that brings out purple colors-can create big differences in the final plant, even with identical genetics.
What Environmental Factors Change Cannabis Phenotypes?
These are some main things that affect how a plant’s genes “show up” as phenotype:
- Temperature: Cooler nights can make certain strains turn purple, if the genes for purple are there.
- Humidity: Changes how the plant takes up water and nutrients, affecting size and toughness.
- Lighting: How bright the light is, what type it is, and how long the plant gets it all matter for growth and chemical output.
- Soil or Growing Medium: Soil, coco, or hydroponics each allow different nutrients and microorganisms, changing taste, smell, and terpene profile.
- Nutrients and Fertilizers: The type and timing of feeding change the plant’s development and output.
- Watering: Both over- and under-watering can stress the plant or limit its traits.
- Training: Techniques like topping or LST (bending stems) redirect growth for bigger yields or different forms.
Even big, high-tech facilities struggle to keep environments exactly the same between crops, so small changes will always cause differences in how phenotypes show up.
Can One Strain Show Different Phenotypes?
Yes! Even in a single packet of hybrid cannabis seeds, you’ll see a variety of plants-some tall and slim like Sativas, some short and thick like Indicas, and some mixes. These differences show how both genes and the growing environment shape the result. No two seeds are the same, and no two growing spaces are the same, so each plant can turn out unique, even from stable seed lines.
How Genotype and Environment Combine to Make Phenotypes
The appearance of a cannabis plant comes from the mix of its genetic code and its environment. The basic “formula” is:
Phenotype = genotype + environment + how genotype and environment work together
This means your plant’s visible traits come from what’s possible genetically, filtered or pushed by its surroundings. Some genes will only show up in certain environments. A plant may have genes for purple color, but will only look purple in cool temperatures. This is why the same seed can grow into two very different looking (and smelling/tasting) plants depending on how and where it’s grown.
Examples of Phenotypic Variation
- If you grow half of a “purple” strain inside in warmth and half outside in cool air, likely only the outdoor ones will turn purple.
- Plants grown in rich, living soil might taste and smell better compared to those grown in plain synthetic mediums, because natural soil boosts more terpene production.
- Within a single seed batch from the same hybrid, you will get tall and skinny plants as well as short, bushy ones, all due to minor genetic or environmental shifts.
Common Myths about Phenotypes
- Not every seed from the same strain will make a plant that looks and grows the same. Even the best breeders can’t remove all differences.
- What happened in your last grow-what phenotypes showed up-won’t be exactly the same next time unless you control every detail of your environment.
- Each seed is more like a member of the same family than a copy, so don’t expect all your plants to be “twins.”
Dominant and Recessive Traits and Their Importance
Cannabis plants, like all organisms, inherit traits in pairs-one from each parent. Some traits are dominant and show up if you have even one copy of the gene; others are recessive and only show up if you have two copies, one from each parent.
How Do Dominant and Recessive Genes Work?
- Dominant traits: Show up even with just one copy of the gene.
- Recessive traits: Only show up when both gene copies are recessive.
Breeders use this knowledge to figure out what to cross to get certain outcomes (like more color, different leaf shapes, or higher THC levels) in future generations.
What Phenotypic Traits Do Breeders Usually Want?
Here are some traits breeders usually try to breed for:
- Strength: High THC or CBD levels for recreational or medical effects.
- Big Yields: Plants that produce more buds are better for commercial growers.
- Hardiness: Resistance to bugs, mold, temperature changes, and disease.
- Smell and Taste: Fruity, earthy, skunky, or citrus flavors and smells.
- Plant Structure: Short and stocky for indoor use, strong branching for outside.
- Resin:** More resin means stronger, better-tasting buds.
- Flowering Time: Faster flowering is good for quicker harvests.
- Color: Purple, pink, or red colors make the buds more attractive.
By breeding carefully, breeders hope to combine several great traits into new plants and keep them stable over generations.
Cannabis Breeding: Why and How?
Breeding cannabis means creating new plants by picking parents with specific traits and crossing them. It takes lots of patience, observation, and a good grasp of genetics to improve plants this way.
What Is Selective Breeding?
Selective breeding is when growers purposely choose parent plants with certain qualities-like smell, strength, or how well they resist disease-and breed them to make new plants that keep those qualities. This is different from random pollination, where you get more variety but less control over the details. Good breeders watch each generation, pick the best offspring, and then use those as parents next time.
What Is Pheno-hunting?
Pheno-hunting means planting a lot of seeds from the same parents and picking out the best individual plants-the ones that grow best, taste or smell the best, or have the highest yields. The grower then usually clones this “keeper” plant to make sure it can be reproduced exactly. This process can take several rounds of growing and careful checking to get it right.
What Do F1, F2, S1, and True F1 Mean?
- F1 (First Filial Generation): Offspring from crossing two different strains. These are often stronger and more uniform-this is called “hybrid vigor.”
- F2 (Second Filial Generation): Come from crossing two F1s. There’s more variety, so plants are less predictable in look and growth.
- S1 (Selfed): Made by “selfing” a plant; these seeds are more like the parent but less diverse, so plants are more uniform but can be less tough in varied environments.
- True F1: F1 seeds from crossing two highly-inbred, different parents. These give the most consistency in traits, like taste or strength, and are often considered the best for uniformity.
What Does Cloning Do for Phenotypes?
Cloning means cutting a piece from a “mother” plant and growing a new plant from it. This new plant is a genetic copy of the original. Growers use cloning to keep good traits going and get predictable results from plant to plant.
Does Cloning Make All Phenotypes the Same?
Clones have the exact same genes as the mother plant, so they’ll have the same potential. If you have a plant with fantastic smell, yield, or strength, cloning is the surest way to keep making more plants just like it.
But even clones can show differences if they’re grown in different spaces, with different temperatures or feeding schedules. The more similar the growing setup, the more alike the clones will be. But if two people in different locations both grow the same clone, their final buds may still turn out a bit different due to those differences in environment.
Chemotypes, THC/CBD Levels, and Genetics
Aside from looks, the chemicals in cannabis-THC, CBD, terpenes, and others-are extremely important. The kinds and amounts of chemicals the plant makes depend on both genetics and environment. The word “chemotype” is now widely used to sort cannabis by what it actually produces.
What Are Chemotypes?
A chemotype is a way of grouping cannabis by the major chemicals inside. Common groupings are:
- Chemotype 1: More THC than CBD; typically strong and psychoactive.
- Chemotype 2: THC and CBD are about equal; effects are more balanced.
- Chemotype 3: More CBD than THC; usually non-intoxicating, mainly used for health benefits.
In the future, there might be more types based on smaller cannabinoids or different terpenes.
How Do Genes Decide Cannabinoid Levels?
The plant’s genotype tells it how to make the enzymes that turn raw nutrients into THC, CBD, and other chemicals. Breeders use this knowledge to get plants with very specific chemical profiles.
Still, the growing environment changes how much of these chemicals will actually show up. For example, better light, more nutrients, or the right timing of harvest might give you higher THC or richer flavors, even with the same genetics.
Frequently Asked Questions
Is Every Cannabis Seed a Unique Phenotype?
Every seed has a unique set of genes, but if you grow a whole pack, not every plant will look completely different-especially from well-bred seeds. While each seed is not a “cloned twin,” they can be very similar. You’ll see a range of different phenotypes, rather than every one being totally unique.
Why Do Cannabis Plants from Different Areas Look and Act Differently?
Cannabis evolved over many years to survive in different places. Mountain plants became short and thick to handle colder air; tropical plants grew tall and thin for heat and humidity. The local climate, soil, and even daylight hours all shape which traits do best, creating the wide variety of looks and effects we have today.
How Do I Pick the Best Cannabis Genetics for Growing?
First, know your growing goals: High THC? Balanced CBD/THC? Unique flavors? Big yields? Tough plants?
Next, buy seeds from a reliable seed seller known for solid breeding practices. A good company will have lines that are mostly stable, so most of your seeds will give you similar plants. New growers should work on giving their plants the best possible growing environment first; then they can move on to advanced breeding or hunting for rare phenotypes if they want. Quality seeds and good growing conditions together give you the best results.