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How to Select Seeds Based on Genetics & THC

Feb 18, 2020
Common Cannabis Questions

How to Select Seeds Based on Genetics and THC Content

Cannabis is well known for its effects when smoked. But, where does the high come from, and how can growers ensure their crop is as high quality as possible? It all begins with seed selection. You’ll need to have a firm understanding of how to cultivate cannabis and which genetic qualities are most desirable.

When you grow a great strain or have a good growing season, you’ll likely want to put away some seeds so it’s easier to duplicate that success in the future. In this guide, we’ll cover the essentials of selecting marijuana seeds based on THC content and genetics.

How to Select the Right Seeds for Cannabis Cultivation

When growing crops from seed, there are many methods from which to choose and several growth mediums to use. Though it’s easy to grow cannabis with regular soil, plenty of other options are available. We’ll cover them later, but for now, let’s look at some of the best seed types and selection methods.

Important Things to Remember About Seeds for Cultivation

Before we show you how to choose the best seeds for a great crop, we’ll provide some basic info on these seeds. Cannabis seeds develop within the female plant’s flowers that have been pollinated by male plants. The important thing to remember here is that, where cannabis cultivation is concerned, the goal is to end up with a crop full of female plants (as these are the only ones to grow the buds we all want.) Here are a few other things to keep in mind:

  • It’s crucial to use only feminized seeds. With regular (unfeminized) seeds, you’ll end up with 50% female seeds and 50% male seeds. However, only female plants produce flower. You can either go with the luck of the draw by buying regular seeds or you can buy previously feminized seeds, which we recommend for the best results.
  • Strain selection is important: Because of breeders and cultivators who have worked carefully for years, there are many different varieties and strains of cannabis. Before selecting seeds, be sure they contain the genetics you’re after.

Count on the experts at to help you choose the right seeds for your cultivation and collection goals.

How to Choose Cannabis Seeds

When it’s time to choose seeds, many are confused simply because they’ve never seen cannabis seeds in the past. There are three primary factors to consider when selecting seeds.

  • Color: a healthy, good cannabis seed should be dark in color with a tan, dark brown, or black pattern. Try to stay away from seeds that are green or light in color.
  • Pattern: an interesting thing about seeds is that the pattern on the outside can help you determine the strain. Indica seeds are usually larger and striped, while Sativa seeds are smaller and single-colored with no discernible pattern.
  • Hardness: The final major factor to consider is the hardness of a seed. The harder a seed’s shell, the higher the quality. Stay away from softer seeds when choosing strains for cultivation.

Different Cannabis Strains

Now, let us look at a few different genetic varieties so you’ll have a better idea of which seeds to plant. A strain of cannabis contains a genetic blueprint (genotype) with certain traits (phenotypes) that are encouraged to develop when exposed to specific certain environmental variables, a process that defines one plant’s characteristics (like THC percentage) from another. All plants are Cannabis Sativa variants, and here we’ll look at the four main genetic varieties:

  • Cannabis Sativa: These plants are usually thin and tall. They take longer to mature, but they produce a greater yield in comparison to Indica-dominant plants. The high from a Sativa strain is very energetic and tends to inspire creative thinking.
  • Cannabis Indica: This marijuana strain typically yields bushy, short plants that mature earlier than Sativa varieties. However, overall yields are smaller, and you’ll get a restful, relaxing, and somewhat lethargic high.
  • Ruderalis or auto-flower: An auto-flowering cannabis plant is often crossed with Ruderalis genetics, which allows for faster growth cycles with reduced dependency on strict light schedules. These plants aren’t as potent as Sativa and Indica varieties, but they’re often crossed with other strains to increase their THC levels.
  • Hybrids: If several strains are crossed, a hybrid is the result. With hybrid cannabis strains, one strain is always dominant, i.e. Sativa-dominant hybrid. However, the type of high and the psychoactive experience you’ll get will be different from that of either parent strain alone.

What is THC And Why Does it Matter?

THC, which is shorthand for Delta-9 tetrahydrocannabinol, is the chemical structure (phytocannabinoid) in cannabis that provides the high you get when you smoke, vape, or consume an edible. The term is somewhat misleading, though. Certain kinds of THC, such as Delta-8 tetrahydrocannabinol, are somewhat different from Delta-9 tetrahydrocannabinol. Furthermore, THC isn’t the only phytocannabinoid that bonds to your body’s endocannabinoid system to produce feelings of being high.

Other phytocannabinoids also contribute to those amazing feelings. Phytocannabinoids encompass every THC variant, and they are the psychoactive ingredients that provide the high you want. Cannabis typically contains anywhere from one to six percent Delta-9 THC, as well as numerous other chemicals. Most of these additional compounds are activated through decarboxylation.

One of the trickiest things about cannabis is that it’s hard to find the right combination of phytocannabinoids for the best high. Even scientists, with their years of research and expertise, can’t find the perfect combo. Why is this the case? In part, because each person is different, meaning the high can’t be externally quantified; it can only be described by the individual. This makes it hard to prove correlations between chemical combinations and high strength or type.

The cannabis experience is different for every user, even among those who consume the same amount and the same strain as others. A blend of emotions such as paranoia, sleepiness, elation, euphoria, and lucidity may be felt by those ingesting similar strains in the same quantity.

The Crucial Nature of Genetics in Cannabis Seed Selection

The highest quality cannabis comes from strains with the right genes. We’ve all seen it: weed that tastes flavorful, smells great, and is potent. To grow the best crops, you’ll need to find strains with the right genetic makeup. However, it involves more than simply finding and purchasing top-quality seeds like those you’d find on There’s a considerable level of variation between seeds, even those within a single strain. The likelihood of a specific phenotype being expressed, such as high THC, depends on the variables present within the cultivation environment and the level of care exercised by the grower.

Unless you’ve already dealt with the mature plants from which your clones or seeds originated, cannabis cultivation is unpredictable. That’s why it’s important to clone or seed the best plants, because that helps to guarantee the next crop’s quality. People who have been cultivating marijuana for a few years usually have better crops. Why? They usually choose the best plants from one strain, keeping those seeds for the next season’s crop. They know the plants from which the seeds came, and with that knowledge, they become more able to provide the care their plants need.

Cultivating Your Selected Seeds

Though male cannabis plants aren’t valued by those who simply want to enjoy a smoke now and then, they’re still important for a very good reason. Male plants can pollinate female plants, diversifying a strain’s genetic makeup by offering new seeds. When you have a plant of each gender, put them close to one another and carefully shake the male plant. The shaking releases pollen, which falls onto the female plant and starts the reproductive process. Be sure to rotate the female plant so all parts are pollinated. Once a female plant has been pollinated, it will bear seeds within six weeks.

Preserving Good Seeds

After you’ve produced or purchased cannabis seeds and planted your crop, what should you do with the rest of the seeds? It’s advisable to store them, but it’s crucial to do it correctly. When properly stored, cannabis seeds can remain vital for 3 – 10 years. The main rules of seed storage are:

  • Keep seeds in a cool, dark place. Do not allow them to be exposed to sunlight.
  • Keep them dry.
  • Let your seeds stay at room temperature. If it’s too cold or too hot, your seeds may become damaged.


If you’ve been a cannabis enthusiast for any length of time, you’ve probably heard of sensimilla. You may, in fact, already know that it’s very high-quality cannabis, but you may not realize where the term originates. “Sensimilla” is Spanish for “without seeds,” and the word is used to describe female plants that mature without being pollinated. Outdoor cultivation of sensimilla is nearly impossible because female plants can be cross-pollinated from a mile or more away. Furthermore, there’s always the chance that plants could be mis-gendered, or that a grower could wait too long to segregate the plants by gender.

Why is it so important to prevent the pollination of female cannabis plants? When a plant is pollinated, it will use its energy to create seeds rather than buds. This process is a product of natural selection. Because plants that produce more seeds are more likely to reproduce, they tend to pass on those features. Though this is beneficial to the survival of the species, it’s not what we look for in consumable marijuana. Because sensimillas are never pollinated, they typically produce resinous buds in the absence of seeds.

Large-Scale Cannabis Production Through Genetic Selection

Though cannabis is the world’s only natural producer of THC, it’s not a very good industrial-scale producer. This psychoactive compound is usually found in the plant’s trichomes, which means that the leaves, stems, and stalk go to waste.

With careful selection and genetic engineering, breeders could provide better alternatives. Some biotech firms and researchers are striving to replace plants with microorganisms that have been engineered to synthesize THC, CBD, and other cannabinoids. Others want to accelerate the cannabis plant’s chemical synthesis by genetically modifying cells to make THC from root to tip, increasing overall yield.

In either case the goal is to create beneficial phytocannabinoids more efficiently, more cost-effectively, and more reliably than through conventional cultivation methods. With microbial synthesis and genetic engineering, it may be possible to produce large quantities of phytocannabinoids that are typically only present in trace amounts. Genetic selection and modification also allow breeders to engineer their plants for greater pest and stress resistance.

Why You Should Grow Your Crops from Carefully Selected Seeds

Though most indoor growers like to grow cannabis from cloned plants, it’s better to start from seeds for various reasons. One of the biggest reasons is that seeds can produce taproots, which anchor the plants firmly into the soil. Clones cannot create taproots, which means they’re not as efficient at nutrient absorption. Taproots dig into the soil to find nutrients and water, which is particularly important when growing outdoors.

There are more varieties of available seeds than clones, which is perfect for medical marijuana patients or anyone who wants to tailor a crop’s phytocannabinoid profile to suit their needs. An online seed bank like sells seeds from various breeders and can ship almost anywhere, but there’s always the risk of confiscation when products are sent through the mail. For those living in areas where cannabis cultivation is legal, the best bet is to buy seeds from a local or online seed bank.

In Closing

Genetics are the cornerstone of a successful cannabis crop. Whether you’re growing for recreational or personal use, the seeds you choose (and their genes) play a crucial role in the health, longevity, and yield of your plants. By choosing seeds with dominant, strong genes, you’re more likely to attain the yield you’re seeking, and you may even have some valuable seeds left over for next season. For help and advice on seed selection, count on the experts at We’ll do what it takes to get you growing!

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