How To Choose The Best Cannabis Seeds Based On THC Levels And Genetics

A line of brown, healthy cannabis seeds
October 01, 2020

The world’s best cannabis horticulturists stress the importance of providing the best environmental conditions for marijuana plants to flourish in. Sometimes, though, there are plants that underperform even when given the utmost care. In that case, the problem may be due to poor genetics. That is why the seed selection process is as essential as nurturing plants throughout their life cycle and post-processing the harvested sinsemilla buds. The next time you want to grow high-THC strains, you also have to consider the quality and reliability of the seeds (or source of clones).


Cannabis not only produces psychoactive effects, but it is also highly medicinal. Among the many compounds found in the plant, one that is notoriously popular is THC.

What is THC?

Cannabis contains more than 400 active compounds. So far, scientists and researchers have isolated and identified 61 active compounds collectively called cannabinoids. Of note is Δ9-THC, which is mainly responsible for the associated psychoactive effects such as euphoric cerebral and physically relaxing high.

Δ9-THC affects behavior and cognition through agonist actions at CB1 receptors. Moreover, it can alter perception, intensify sensory experiences, and alleviate neuropathic pains. During the mid-19th century, western medicines included resins and leaves used to treat insomnia, anxiety, rheumatic disorders, migraines, and strychnine poisoning. In modern times, its medicinal benefits also include controlling nausea and vomiting induced by chemotherapy, treating waste syndrome in AIDS patients and glaucoma by reducing ocular pressure.

Note: THC, contrary to popular perception, is not the only compound that exerts psychoactive effects. Some of the other cannabinoids might also have similar properties. Most of these, though, are rarely studied.

Why Does THC Matter?

THC has shown immense potential in treating glaucoma, muscle spasticity, low appetite, and insomnia. Furthermore, it could help alleviate pain, anxiety, and nausea. However, it is also the one cannabinoid that has taken all the flak from legal standpoints. Cannabis-derived products that contain 0.3% THC or more, for example, fall under Schedule I drugs. These are substances and chemicals with no accepted medical use and have a high potential for abuse. Among the other drugs in this category are:

  • Heroin
  • Lysergic acid diethylamide (LSD)
  • 3,4-methylenedioxymethamphetamine (ecstasy)
  • Methaqualone
  • Peyote

Although many states have legalized cannabis for medicinal use (some also allow recreational use), it remains prohibited at the federal level. That may change as new evidence from the scientific community comes to light, affirming the therapeutic benefits of THC.

Seed Genetics

A reputable seed bank would only start producing seeds after stabilizing a mother plant. Moreover, after harvesting the seeds, they would also inspect them for signs of problems. These are to ensure that you receive the highest quality seeds. You could say the same thing for clones, too. Ideally, the cuts should come from a donor that exhibits the best traits, including flavors, fragrance, effects, and potency.

Apart from the quality of seeds (and clones), choosing the right strain is of utmost importance. With hundreds to choose from, you are bound to find dozens providing similar highs and effects. Unlike merely buying dried buds or other derivatives, you have the growth pattern when growing marijuana at home. If the conditions of your grow are not perfect or even ideal, then you should choose a cannabis strain that is hardy and easy to grow.

The foundation of healthy growth starts with the quality and reliability of seeds and clones. If they are inferior, to begin with, you can expect them to be problematic throughout their growth cycle. Even if these plants were to survive, the quality of the buds would be less than satisfactory. On the other hand, choosing the best genetics (strain and seed/clone) ensures that the plants can potentially attain their full potential – much to your delight.

Which Cannabis Species Should You Choose?

Mainly, there are two types of cannabis species. For energetic, euphoric cerebral high, choose Sativa. If you prefer to chill and relax, then pick an Indica strain. Most seeds you can obtain today are hybrids – a combination of the two species. They could be evenly balanced or exhibit dominance on either mental or physical effects.

Sativa strains are usually tall and thin. They take a longer time to mature, with a flowering period ranging from 10 to 12 weeks. Some could even take up to 16 weeks. For example, Purple Thai takes up to 13 weeks to reach full maturity after switching to 12/12 light cycle. One advantage of having a long life cycle is that these plants tend to produce high yields.

Indica strains, on the other hand, do not require as much vertical space as Sativa due to their compact, bushy nature. Although their yields are not as generous, the buds can be as potent, but the effects are more physically relaxing. Both Afghan and the Hindu Kush are two such strains that can melt away tensions, thus inducing a profound mind and body relaxation.

Most of the strains you can find are photoperiods in that they rely on light cycles. You have three choices:

  • Regular seeds (50/50 male to female ratio)
  • Feminized seeds (100% female)
  • Fast version seeds (100% female, quicker flowering time than regular or feminized seeds)

Among all seed types, feminized seeds dominate the market. Largely because they are convenient to grow, and there is no need to deal with males. Another class of seeds, auto-flowers, are becoming increasingly popular with homegrowers. From germination to harvest, they take anywhere from 7 to 9 weeks. Besides the rapid growth cycle, most of the autos are also feminized.

Browsing the seed catalog of seed banks like Homegrown Cannabis Co., it can be confusing, considering it has more than 400 in-house genetics. One way to narrow down the selection is to decide on either Sativa or Indica, based on the desired effects. You can further simplify the process by adding more criteria to filter the search results.

On which type of seeds to choose would depend on individual preference. Feminized seeds are by far the most popular type. If you need a male plant to fertilize females and produce seeds, then opt for regular seeds. Plants grown from fast version seeds have similar vegging time as other photoperiod seeds, but they flower around two weeks faster. Finally, for less patient growers, choosing to grow autoflower seeds is the best way to go.

How to Inspect Cannabis Seed Quality?

A line of healthy cannabis seeds
Healthy cannabis seeds are dark brown with a lighter brown or black pattern

You cannot determine gender or the reliability of the genetics by visually inspecting cannabis seeds. What you can surmise is their suitability. To do that, you need to know what a fresh, healthy seed looks like and how they appear if otherwise.

Before germinating seeds, inspect each one by looking at these three things:

  • Color– A healthy seed has a dark color with a tan, brown, or black pattern. If it has a green or light shade, then discard.
  • Pattern– You cannot identify a strain by looking at the markings on a seed. Sativa seeds, though, usually are small with one shade and no discernible pattern. Indica seeds, on the other hand, are typically larger and have stripes.
  • Hardness– A hard shell is an indicator of good quality. Avoid the ones that feel softer compared to others.

How to Preserve Good Seeds?

What should you do with excess seeds, the ones you are not germinating? You should store them for future use, but you also have to preserve them. You can store and preserve seeds for up to 10 years if you preserve them correctly. All you need to do is ensure that they are in a cool, dark, and dry place. Avoid temperatures that are too cold or too hot, and exposure to light or its quality can degrade.

Seeds and Genetics Are Important

Good genetics not only begins with the selection of strain. You also need to consider other factors – the seed bank and the quality of seeds offered. Even if the plants grew under the best environment and received optimal care, they may not attain their full potential if they started as poor-quality seeds. They may be weak, vulnerable to diseases, and unable to tolerate moderate stress.

By exercising due diligence, you could avoid problematic plants by buying the seeds only from a reputable supplier. More importantly, you could visually inspect them before germinating. By observing the colors, patterns, and testing their hardness, you could determine the most viable seeds. These are the plans that have the highest potential to thrive and deliver the highest potency and yields.