cannabis phenotype

Basic Cannabis Knowledge: Genotype and Phenotype

Many growers tend to misuse the words genotype and phenotype when talking about cannabis. Let’s clear the smoke around this issue and resolve all the unnecessary confusion.


There’s a point in the life of every grower when suddenly questions arise. Most of the time, this moment of confusion comes right after completing the first couple of grows, and at the latest, when the same strain is repeatedly grown using the identical set-up.

Why in the world does every single cannabis plant grown from seed look slightly different?

When these or similar questions remain unanswered, a logical reaction for a rookie grower would be to switch to another breeder. The more experienced cultivators know that this phenomenon, meaning variations among different plants of the same strain, is natural and won’t get any better by changing the seed supplier. We have to keep in mind that seeds are products of living organisms and the outcome of a natural breeding process, hence unique as any person, animal or plant on earth. Although it’s tempting to characterize all the things around us, we’re quick to reach limitations when dealing with nature.


Every living organism is the result of evolution that works by the same basic principle. The genotype or genetic code carries all the genetic information regarding growth, appearance, and all the characteristics we can later observe. It’s crucial to understand that a genotype or genetic code is not something that is set in stone but rather defines a certain range of possibilities. It mainly depends on the environment the organism lives in what specific bits and pieces of the genotype will be activated. The interaction between genotype and environment results in a phenotype, meaning the physical expression of certain genes the environment triggered.

genotype (G) + environment (E) + genotype and environment interactions (GE) = phenotype (P)


Let’s examine a cannabis related example to get a better idea. You purchase seeds from a reputable breeder and intend to grow a purple strain. Instead of growing all plants in your indoor grow tent, you’ll decide on moving half of your plants outdoors. Besides the fact that no plant seems to be identical to one another, you’ll notice that the plants in your outdoor garden are much richer in purple colours compared to the ones in your indoor grow tent. Although the genotype carries the information to produce purple hues, it’s the environment, and in this particular case, the temperatures of the environment, that allow two different physical expressions (phenotypes) from seemingly the same genetic code (genotype).


We got the idea that the environment is the determining factor influencing a genotype to express different phenotypes, but this doesn’t answer the initial question why every cannabis plant grown from seed appears to be slightly different, even when it’s grown in a constant environment of an indoor grow room.

How can a strain possibly express different phenotypes when the environment doesn’t change?

Well, it’s maybe an inconvenient truth, but every single cannabis seed has its unique genotype. Many growers assume that seeds from the same cannabis strain share an identical genetic code and understandingly expect homogeneous growth. Unfortunately, this is a common misassumption. There are lots of people using the term phenotype to describe the variations of plants they get from the same strain grown from seed. In fact, and what they usually don’t know, they’re talking about different genotypes. It’s not only the environment that determines phenotypic expression, but logically also the genotype itself.

When you purchase seeds of a certain strain, you’ll receive “family members” of this strain that share a large percentage of genetics with thousands of (inbred) siblings, yet they’re not identical twins. The genotype is usually very close to identical, but there are still differences, comparable to fraternal twins if you will. That’s the main reason why every cannabis plant grown from seed expresses slight variations regarding characteristics like plant height, yield, flavour, etc. – the genotype of seeds is usually not identical.


If you want to take homogeneity to the next level, you have two different options. The first option is to germinate more seeds as you intend to grow, and simply select the ones that express the desired traits at an early stage. But if you’re aiming for maximum efficiency and consistency, your best option is to select a mother plant to take clones from. These clones copy the genotype of the mother plant 1:1 and you’ll continuously end up with the same phenotype assuming a constant environment. Let’s say you grow one of these identical clones using a hydro set-up, and one in organic soil. This varying environment might result in different phenotypes of the same genotype.

Why is every single cannabis plant grown from seed slightly different? Read this blog on genotypes and phenotypes for a comprehensible explanation.

Cannabis Plant Phenotypes And Pheno Hunting Explained

The cannabis plant has evolved over thousands of years and can express an extensive range of aromas, colours, growth patterns, flowering times, yields, cannabinoid profiles and effects when consumed. Cannabis seeds contain some of this variety, making each individual cannabis plant slightly different. These different varieties within strains are called phenotypes. By growing many seeds, a grower can look for a specific male or female phenotype and keep their favourite version of a strain.

The O.G. Kush on the left has much more leaf than the one on the right. Looking through sites like Leafly, you can see that every plant grown from seed is unique.

A Good Example

A phenotype is a collection of traits that cause a cannabis plant to be different from the others. You may be growing a strain from seed that is a hybrid of two other strains. Crosses like this often end up with different phenotypes that look more like one parent than the other.

This is the same variation that causes children to look more like their mother or father. When growing cannabis seeds you may notice vast differences between the seedlings after a few weeks. Strains with little to no variation are often described as “stable” strains.

We’ll take any excuse to use cute animal pictures, but this is a good example. The kittens in this litter are all from the same parents, but still look different: they all have different phenotypes! You could say that this “strain” of cats is not very stable.

In most early hybrids, some plants are taller and have leaves that are more sativa in appearance, while others might take more after their indica parent. You may also be able to notice a difference in aroma between plants from the same batch of cannabis seeds.

Hunting Phenotypes With Cannabis Seeds

One exciting part of cannabis cultivation is what is called pheno finding or pheno hunting. This simply means you are looking for the best individuals within a group of plants from the same strain. The “best phenotype” is completely dependant on what you want as a grower, and can depend on any trait you think is important.

Desired traits are often not expressed by a cannabis plant until they start flowering, so clones are usually taken before any of these traits show. Clones should be carefully labeled, so that they can be grown out or discarded later. If you are looking to breed shorter plants for example, you would only keep the clones of your shorter cannabis plants. Generally however, selection revolves around growth speed, yield and resistance. Once you know what you’re looking for, you will know immediately which of the plants you will not want to keep. These “runts” are usually the smallest in size and production or the ones that have no significant aroma.

Most of the desired traits are only clear during flowering, but growth rate can be seen from day one. In this test we discarded the cannabis plant on the top right early, as it was lagging behind too much.

Many seed banks and professional breeders will hunt phenotypes from up to a thousand seeds and eventually work their way through selection until they have one or two phenotypes they are happy with. This extensive and laborious process has to take place to make sure only the best genetics make their way to growers.

Important For Breeding New Strains Of Cannabis Seeds

If a breeder did not take the time to find the strongest and best phenotypes around, then new strains may not be as potent or productive as they could be. When using regular cannabis seeds over feminised cannabis seeds, a grower can expect much more diversity. Besides having female and male cannabis plants, the plants will display a wider range of characteristics from the original parental lineage. This is because regular cannabis seeds are bred using two parents, whereas feminized seeds are often bred from only one hermaphrodite parent.

Pheno hunting is always based on selection criteria that the grower or breeder decides are important. Like we mentioned, these criteria often include aroma, growth rate, potency and yield. You can always add more criteria as you go along. It might simply come down to the final yield when potency is similar between plants. When working with a wider range of phenotypes the differences can be much larger.

This picture contains two test reports of the same strain that show the cannabinoid and terpene content. Even though our strains are stabilized over several generations and considered highly stable, you’ll still see differences between plants.

Different phenos can also cause a different experience, like a narcotic indica high with an earthy after taste, or a citrus tasting sativa buzz. Practical differences are also important, as selecting different phenotypes can also be the difference between a cannabis plant that flowers in 8 weeks or one that flowers in 10.

Breeders work with large numbers of different phenotypes, as it allows a lineage of cannabis to really evolve. Many crosses are made to combine the best properties of different strains. Our Gold Bar Kush for example was created to combine the citrus tones of Orange Bud with the taste and effect of our Medical Kush. Crossing the two strains is easy enough, the challenge lies in selecting a phenotype that combines all the best properties of both strains. Every time a cross is made, you end up with a range of different phenotypes to choose from. Once a desired phenotype is found, a breeder has to stabilize this line through inbreeding.

The ability to create new flavours, different effects, change flowering times and growth forms and increase resistances is what makes breeding and pheno hunting an amazing process.

Indica And Sativa Cannabis Plant Phenotypes

It is slightly more difficult to hunt phenos of indica dominant cannabis plants than finding diversity in hybrids or sativa dominant strains. Indica dominant plants are usually flower and easy to grow, so pheno hunting indica strains is often mostly geared towards improving flavour or effect. Indica plants obviously produce many different phenotypes, but some may only stand out once you smell them.

This picture gives a good impression of how different sativa and indica plants look in terms of leaf structure, branching and internode space.

The original UK Cheese for example, was created by pheno hunting based on aroma. UK Cheese was a phenotype of an Afghani Skunk that was selected for the dank creamy taste that is world famous today. Many Kush strains were developed through pheno hunting as well. Kush phenotypes are often selected based on their aroma, adding a little extra flavour to its unmistakable lemon fuel stench. Strains like our Purple Berry Kush for instance are the result of an extensive pheno hunt in which aroma and fragrance were more important than the final yield.

This picture is a simple overview of how you can develop new strains. First a cross is made between two parents, giving rise to a very variable offspring. These seeds are then grown out for the first round of selection, after which the best couple are selected. After a second round of selection, only the best phenotype is kept.

When hunting phenotypes in sativa strains, you will usually see several plants with a realistic flowering time of 13 weeks or more. While taste and smell is still very important, a lot of pheno hunting in sativa strains revolves around the flowering time. Old school haze heads usually don’t mind a logistically demanding strain or spending a few extra weeks growing marijuana. Commercial growers are usually looking to shorten the flowering time as much as possible for a fast turnover.

Hybrid Phenotypes

When growing hybrids you will come across more diversity in terms of phenotypes than with just indica or sativa cannabis seeds. A perfect example of this is K-Train, a cross between Train Wreck and O.G. Kush. When you grow this strain of cannabis, you will find some of the plants will be more O.G. Kush dominant in their size, the leaves, the smell and the stem size. You will notice that other plants are larger in size and grow thinner and lankier, taking more after their Train Wreck parent. When the plants transition to flowering, some plants will also stretch much more than others and the calyx to leaf ratio can be very different.

Different phenos also have differences in growth form: the tall lanky (sativa dominant) plant on the left and the short bushy (indica-dominant) one on the right are the same strain!

How To Find Different Phenotypes

  • Look at your plants from a distance and see which one stand out the most and has more of a presence than the others. Then inspect each cannabis plant closely and often and compare them to each other. This means getting hands on and up close to the leaves and stems, trichome production and colour patterns. You can be quite rough with the plants to see which ones can handle stress better or even super crop the main stem are early on to find out which one has the fastest recovery time.
  • Check the roots on a regular basis to check which plants are rooting more profusely and which have a stronger root ball. Some plants that look great up top may have a small root ball, while others may have a great root system despite being smaller in appearance.
  • Smell the plants by rubbing your fingers around the stems and the undersides of the leaves. A cannabis plant that gives off the most aroma and scent in an early stage will usually be the loudest one in the room by flowering time. Once you have buds growing you will find out for sure which individual cannabis plant has the best smell. Interesting differences can usually be seen the best during flowering, so this is the part where you may find something new.
  • Take clones from your plants and number them accordingly. This allows for you to make notes and when selection time comes, you will know exactly which clone corresponds with which final phenotype.
  • Our final tip is probably the most important one: select your strongest and most aromatic cannabis plants if you plan on keeping phenotypes around. Yield can always be worked on with growing techniques or breeding, but it is very difficult to recreate a specific flavour or aroma. When you have a cannabis plant with unique flavours that the internet forums go crazy for, you will know your selection process has paid off!

Final Thoughts On Pheno Hunting

We hope this article will help give you a better understanding of the process of pheno hunting and why it takes up most of a breeder’s time and space. Now you know what goes into making a new strain of cannabis seeds and why we’re so proud of the quality we’re able to offer. And whether we’ve inspired you to create your own brand new strain or given you a better idea of what to ask breeders, we wish you good luck growing cannabis!

The cannabis plant has evolved over thousands of years and can express an extensive range of aromas, colours, growth patterns, flowering times, yields,