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High THC seeds in Canada
Cannabis strains listed at 25% THC or more, from a Quebec seed bank. Over 80 high-THC strains in feminized and autoflower versions.
25% THC and up
Every strain in this category is listed at 25% THC or more.
Over 75 strains
Feminized and autoflower genetics.
Genetics set the ceiling
Your growing conditions decide how close a plant gets to its listed THC level.
Free seeds, every order
Orders over $200 also ship free across Canada and to the USA.
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Eleven Roses Fast Version Feminized Cannabis Seeds
5 Seeds by Pack
$38.50 USD $55.00 USD Add to Cart
High THC seeds: common questions
What counts as a high THC strain?
This category lists strains with an expected THC level of 25% or more. Each strain's page shows its listed level.
Will my plants reach the listed THC level?
The listed level is what the genetics can reach. Light, nutrition, harvest timing and curing all affect the final result.
Do you ship high THC seeds across Canada?
Yes. Quebec Cannabis Seeds ships from Quebec across Canada and to the USA. Orders over $200 ship free, and every order includes free seeds.
Does a higher THC percentage mean a better strain
Not necessarily. Potency is one attribute among several. Terpenes shape the flavour and the character of the effect, and many people find a 20% strain more usable than a 30% one. The highest number is not automatically the best choice.
Are high THC strains harder to grow
Often, yes. Strains bred for a headline THC figure tend to be fussier about feeding, humidity and harvest timing. If it is your first grow, an easier strain in the 15 to 20% range usually produces a better result.
Will a beginner get the listed THC percentage
Rarely on a first attempt. The figure on a listing reflects a well grown plant under good conditions, tested on its best material. Light, feeding, harvest timing and which part of the plant you use all move the real number.
How is THC percentage measured
By laboratory analysis of dried flower, reported as a percentage of dry weight. Results vary between labs, between harvests and between plants grown from the same packet of seeds.
Do high THC strains yield less
Not as a rule. Yield and potency are separate traits that breeders select for independently. Some of the strongest modern strains are also heavy producers.
Is there a maximum THC level cannabis can reach
In practice the ceiling sits around the low thirties for flower. Claims far above that usually refer to concentrates rather than to the plant itself.
Grower guides
- Harvest timing: reading trichomes — how to pick the day that decides your final potency
- White Widow strain review — flavour, effects and a full growing guide for the classic
- What does indica do to you? — what a strong indica actually feels like, and for how long
Read more about high THC seeds
Marijuana Seeds with THC over 25%
In this exclusive category, discover marijuana seeds that deliver mind-blowing THC levels exceeding 25%. These expertly bred cultivars are designed to produce intense and long-lasting highs, perfect for connoisseurs seeking an elevated cannabis experience. With every plant, you can expect dense, resinous buds bursting with rich terpene profiles, offering a symphony of flavors ranging from zesty citrus to spicy earthiness.
Successfully growing these high-THC strains requires more attention to detail, as they often demand precise environmental conditions, balanced nutrient regimens, and adequate ventilation. However, the reward is well worth the effort. With proper care and advanced techniques like topping or low-stress training, you can optimize yields while preserving the full potency of your harvest.
Because these strains pack an extra punch, moderation is key. Beginners should proceed slowly to avoid overwhelming effects, while seasoned enthusiasts can enjoy a remarkable sense of relaxation, creativity, or euphoria. Whether you’re cultivating indoors or outdoors, our collection of marijuana seeds with THC over 25% caters to both personal consumption and those aiming for top-tier quality in their harvest. Embark on this potent journey, and elevate your cultivation experience by exploring the fascinating world of ultra-high THC cannabis seeds. Next-level potency undoubtedly awaits.
About AlphaType Genetics
Who is AlphaType?
AlphaType is a cannabis genetics company that develops F1 hybrid cultivars through a data-driven breeding program. AlphaType maintains Alexandria, a biobank of more than 1,500 coded, open-source cultivars, and uses statistical clustering and cultivar-variance analysis to identify superior genetics before they become new F1 hybrids. AlphaType operates out of Seattle (Washington, USA), Basel (Switzerland) and Bogotá (Colombia). Some of the genetics in this collection were bred specifically for QCS: QCS selects the parent genetics and the traits it is looking for, and AlphaType carries out the breeding to those specifications. Learn more directly from AlphaType
A note on this collection
AlphaType refreshes its own genetics lineup every year, and some of what's listed here was bred to QCS's own specifications rather than pulled straight from AlphaType's general catalog. So some strains may no longer appear (or may never have appeared) in AlphaType's public lineup even though the seeds themselves are unchanged and available here while supplies last.
Frequently Asked Questions about AlphaType
What is AlphaType?
AlphaType is a cannabis genetics company that develops F1 hybrid cultivars using a biobank-based, data-driven breeding program rather than traditional selection alone.
Where is AlphaType based?
AlphaType lists operations in Seattle, Washington (USA), Basel (Switzerland) and Bogotá, Colombia.
How does AlphaType develop its genetics?
AlphaType maintains a biobank called Alexandria, with data from over 1,500 coded, open-source cultivars, and applies statistical clustering and cultivar-variance analysis to identify superior candidates for its F1 hybrids.
Are the strains on this page AlphaType's current lineup?
Not necessarily. AlphaType changes its own menu of genetics every year, so some strains QCS carries here may no longer be part of AlphaType's current catalog, even though the seeds remain available from QCS while supplies last.
Does AlphaType publish lab testing or COAs for its genetics?
AlphaType's own materials describe a scientific, data-driven selection process (the Alexandria biobank and statistical clustering), but we have not found a published certificate of analysis (COA) tied to individual cultivars. We do not present specific potency numbers as AlphaType-certified lab results.
Where can I see THC/CBD, flowering time and yield for a strain?
Each product listed on this page shows its own typical genetics, cannabinoid range, flowering time and yield, as reported by QCS based on grow data for that specific strain.
Is AlphaType affiliated with Quebec Cannabis Seeds?
No. QCS is an independent, Quebec-based seed bank. AlphaType is one of the outside genetics sources QCS carries seeds from; it is not owned by or formally affiliated with QCS.
Does QCS choose which genetics AlphaType breeds for this collection?
Yes, for some of the strains here. QCS selects the parent genetics and the traits it wants, and AlphaType carries out the breeding to those specifications, rather than QCS simply reselling whatever is on AlphaType's general public menu.
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