High-THC strains have always been in demand, but especially so after the Cannabis Cup events pitted U.S. growers against each other, making it into a genuine, bona fide competition with machines doing the measuring.
At first, the Cannabis Cup was a relatively small competition in Amsterdam started in 1988, and was held there each November up until 2015. At that time, cannabis legalization started picking up steam in the United States, which pushed cannabis production in the U.S. to a whole new level.
Following the 2014 event, Cannabis Cup became the High Times Cannabis Cup, and it was announced that, in 2015, the event would be moved overseas to the U.S. Growers there quickly became some the biggest experts in growing cannabis—or maybe they already were, but were just hiding in the shadows because of the way the system was set up?
Either way, the first Cannabis Cup events in the U.S. started in the early 2010s, and ever since, each consecutive event has showcased the highest THC strains ever seen.
Whether or not they were, in fact, the highest THC strains or not may remain up for debate, as cases of false potency labeling have been occurring in the U.S.
However, it should be mentioned that all strains entered into the competition are tested on site, which means the potential to cheat the test is significantly reduced.
What is considered high THC?
If someone has ever talked, or better yet smoked, with one of the older people from his or her inner circle, he or she would have inevitably heard the, “in my time, cannabis was not this strong, and we still got high” story.
It’s oft said that the numbers cannabis growers were getting in the earlier days were mostly limited to 10 percent THC, although this wasn’t always the case.
In most cases, the reported numbers would often come from police departments, district attorney offices or similar authoritative agencies, meaning the number represented the potency of the cannabis they confiscated. Since “brick-weed” was one of the biggest problems during the war on drugs, and it was coming from Mexico, most of the cannabis that police confiscated was of low quality and almost always tested below 10 percent.
Today’s cannabis is much different, and that is, in part, due to the legalization in the U.S. Homegrown cannabis is more and more present, and products often leak from the dispensaries to the streets through the hands of their customers.
There are many different names for good cannabis today, so if someone says chronic, dro, sensimilla, dank, kush, skunk, haze or “that good good,” it’s clear that he or she is not looking to buy a bag of seedy Mexican brick-weed. So, with that change, the expectation of cannabis consumers in the U.S., and around the world, started changing. Good cannabis was in demand.
In just a couple years, over the course of the early 2010s, the rise of an “elitist” smoking society, if I may say so, was witnessed. Cannabis strains that tested for more than 20 percent THC were being grown left and right as legalization began and everything was now moving in the right direction. So, when someone says they are looking for high-THC strains, in today’s world, that means they’re looking for strains with over 18 percent THC.
Once again, keep in mind that the test results displayed on the packaging of the products displayed in dispensaries can be skewed and misleading. But why does this happen?
Well, since cannabis is just a plant, various parts of it are of different strength. Since this article is explaining only the highest THC strains, it will not take into account much of anything else, such as CBD levels, terpenes, genetics, etc., although these elements will be touched on in the list below. Note that some numbers cited are from the Washington state’s I-502 data, which is a state program for regulating cannabis in the state, while the remainder are from author’s experiences with cannabis across North America.
High-THC sativa strains
Sativa strains are generally known to be uplifting, high in THC, and they are very good for growing outside. They tend to be taller than indica plants, with long branches and thin leaves. Being used to all types of weather, they can be exposed to the elements without suffering ill effects.
Pure sativa strains (landraces) take long to flower. Because of their size, they can grow a lot and become quite difficult to maintain and harvest at the right time.
This article will also include a couple of sativa-dominant hybrids in the list, as hybrids usually tend to be more potent that pure strains.
This strain is a pure sativa that was made by crossing Thai and Mexican/Colombian genetics. With about 20 percent THC, which is pretty high for a pure sativa. Smoking some Destroyer will leave the user with a somewhat cerebral effect, but mostly uplifted and energetic.
One of the reasons why this strain was included in the list, aside from it’s high THC content, is because it grows faster than most Thai-crosses. It is mould-resistant, usually flowers in about eight to 12 weeks, has a sweet taste and gives off a very strong smell of lavender.
This strain got its name after the highest mountain in Africa. The name is very appropriate as this strain also has one of the highest THC contents of all sativa strains.
It is a landrace that was first grown on the mountain slopes of Tanzania. Just like with most sativas, this strain’s effects are primarily energetic and uplifting. It tastes of citrus fruit and spices, and its aroma is pleasant as well.
Kilimanjaro is one of the highest THC strains in Canada, as it is popular among users in Calgary, Toronto and several other bigger cities across the country. This strain was largely grown in Europe before coming to Canada and the U.S., and offers up to 20 percent THC.
Thai is one of those strains that is the dream of long-time growers, as it is one of the rare strains that grows huge, and still has up to 22 percent THC. Brought to the U.S. by the returning soldiers from the Vietnam War in the 70s and 80s,Thai usually has a strong, distinct fruity, citrus aroma. The flavour is somewhat different, though, as users report it tastes earthy and somewhat woody. It’s a bitter taste altogether, but a great high.
This strain will definitely keep a user uplifted and focused; just don’t smoke too much of it as the high is intense. Thai is popular across the U.S., although it is easily found only in Washington state and Portland. It also has a large presence throughout Canada.
Ghost Train Haze
Ghost Train Haze may be the most popular sativa-dominant hybrid out there, named by High Times as one of the Strongest Strains on Earth. A mix of Ghost OG and Neville’s Wreck, the strain’s genetics are 70 percent sativa and 30 percent indica, although it has been listed here because of its effects.
Ghost Train Haze represents the prototypical sativa profile, as it will provide a high that is energetic, uplifting and uplifting. If one is naturally creative, this strain will wake that up!
It once tested for 28 percent THC, which is probably the highest result a sativa has tested for, although this isn’t confirmed data.
Only when this strain is tasted will its indica presence be seen, as it gives off a bit of a kushy flavour, with just a hint of fruit.
A personal favourite, the Trainwreck strain is reminiscent of college and the times I smoked the strongest strain in my life. Trainwreck genetics go far back, as it was first made by crossing Mexican, Thai and Afghani, all known to be strong landraces.
While Mexican and Thai are pure sativas, Afghani is a pure indica. This mix is what gives the strain its potency, but also the reason why it kept its sativa-like effects.
Since it won a couple awards in the past, Trainwreck became hugely popular in all places across the U.S. and Canada. It is also loved among growers because it is easy to grow, and has a very high yield.
Honorary Mention: Sour Diesel
Sour Diesel has been a fan favourite for years, although it somewhat fell out of favour with the introduction of newer strains, especially easy-to-grow hybrids with similar effect.
Aside from that, Sour Diesel boasts an average testing of 19 percent THC, and is known for its thick colas that are notoriously hard to grow.
High-THC indica strains
Indica strains came all the way from Central Asia, and they tend to be somewhat different from the sativa strains in both effect and appearance. They tend to be much smaller and bushier than their counterparts, while their leaves are wider and thicker. They also smell a lot different than the sativa strains, which are almost always fruity in aroma and taste.
Indica strains historically grew in mountainous climates, which is why they are shorter and they can take cold weather rather well. They also have a much more pungent smell than sativas.
It goes without saying that indica strains are some of the highest THC strains in the world. Numerous purebreds and indica-potent strains tested for over 25 percent THC, which is unheard of in the world of high-THC sativa strains.
This strain was probably one of the “most-in-demand” strains of the early 2010s, as it won several awards at that time. One time, six of the largest testing labs in Washington State tested several strains for potency, Kosher Kush being one of these, and it consistently came in at over 21 percent THC.
Some results during the Cannabis Cup testing in 2010 and 2011, when it won Best Indica and Best Strain, respectively, came at a whopping 29 percent THC.
Kosher Kush is hugely popular on the West Coast, has a fair yield, flowers quickly and hits like a truck.
Another strain from the Kush family that is responsible for people craving record-setting levels of THC is Purple Kush. The strain is, by no means, the tastiest or the best smelling. It has a weird, almost peppery taste that doesn’t go away unless buds are cured extensively.
So, one might think, “Why is it the strain so loved among its peers?” Well, Purple Kush once tested for an astonishing 27 percent THC content. It was first bred in Oakland, for the exact purposes of entering and winning a competition.
Seeing how it’s crossed from Hindu Kush and Purple Afghani, expect that couch-locking high that leaves a user feeling blissful.
Starting to see a trend here? It’s not that we really like kushes—I mean we do, but that’s not the point—but they really are some of the highest THC strains.
Afghan Kush is an indica that has been popular for a while now, as it is the product of the Hindu Kush mountain range. This strain has been tested left and right, with various results from 16 percent to more than 25 percent THC content, so the percentage can’t really be pinpointed.
Afgahn Kush is very easy to grow both indoors and outside, as it is resistant to mould and mildew, and has huge yields compared to its size.
This strain is a close relative of the Afghan Kush, as they both come from the same mountain range. It is entirely possible that Hindu and Afghan Kush crossed paths at several points, which is why they are so much alike.
Hindu Kush has really good genetics because it had to get used to growing high up in the mountains. This is why, as a strain, it is known for its many trichomes and resistances to the elements.
Recent testing has shown that Hindu Kush can go as high as 23 percent THC content, although, traditionally, it tested anywhere between 15 percent and 20 percent, so the latest results might be skewed.
Seeing how most indica strains are at least part-kush, it was only adequate to round out the indica list with another kush. This strain isn’t a pure indica like the others on this list, but an indica-dominant cross with all the traits of indicas.
Critical Kush is a new strain that came as a result of crossing OG Kush with Critical Mass, both known to be heavy-hitters.
Tests keep coming positive for THC contents of up to 20 percent to 25 percent, which is to be expected from such a potent strain. It gives a strong, long-lasting, calming buzz that promotes a relaxed feeling for hours.
Aside from being potent, Critical Kush is also somewhat easy to grow and has massive yields that come from very thick buds.
Honourary mention: Grandaddy Purple
Grandaddy Purple is one the most popular pure-indica strains. It has a somewhat grape and berry flavour, which is where it gets the second part of its name.
If grown and dried properly, this strain can also have beautiful purple strands and hairs. It is very easy to grow and grows best in ground indoors.
American Grandaddy Purple tested for over 20 percent THC content several times, and several times just below, so the average came at a decent 17.5 percent.
High-THC hybrid strains
Hybrid strains are crosses that aren’t too dominant in any of the two standard types—indica and sativa. They are really the best of both worlds, as breeders try as hard as they can to make these new strains offer a combination of the best genetics their parents have to offer.
No matter how much you love the cerebral high-THC indica strains offer, or the uplifting and energetic high that sativas provide, you will definitely fall in love with the hybrids once tried.
Original Glue or Gorilla Glue #4
This award-winning, mind-numbing strain has been taking over the world of cannabis for the last few years. It was made several years ago for the exact purposes of winning the Cannabis Cup, which it did.
Gorilla Glue #4, or Original Glue as it is now known due to some legal dispute with regard to its name, has been tested several times and, each time, it came at over 20 percent THC content.
This strain became hugely popular in California some 20-plus years ago, right around the time Dr. Dre dropped “The Chronic” album. It is an indica-dominant strain that regularly tests between 20 percent and 25 percent THC content.
OG kush has a plethora of tastes, so the earthy and piney aromas are likely to quickly spread around the house and backyard.
There are many different phenotypes of OG Kush, which means that its genetics are incredibly strong and in demand for growing.
Girl Scout Cookies
This is another strain that became almost exclusively grown in California. It is a mix of OG Kush and Durban Poison, thus it’s strong genetics and high-THC contents.
As with OG kush, there are several different types of the GSC strain that register different levels of THC. However, in Washington State’s test date, Girl Scout Cookies came at a decent 19 percent THC content. Other results showed a bigger presence of THC, even up to 25 percent to 28 percent.
It has the looks of an indica strain, but its effects are more similar to a sativa as it leaves users happy, uplifted and energetic—just like girl scouts trying to sell cookies door to door.
Wappa is a 60 percent indica-dominant hybrid, which is perfectly balanced in its effects. Its aroma is very fruity and sweet, and the smell is very potent and citrusy.
In the past, Wappa tested for THC levels ranging from 18 percent to 19 percent on average, until the U.S. growers got their hands on it. Washington state’s I-502 data shows that Wappa came in second in THC levels, only behind Ghost OG.
Wappa is relatively easy to find across the U.S. and Canada. It has a very big presence in Europe as well, even in countries that haven’t legalized cannabis because it flowers quickly and has impressive yields.
This strain got its name after one of the most iconic Marvel characters ever—The Amazing Hulk, or rather the genius scientist who became the Hulk.
Not to say that this strain will turn one’s skin green and make one rage, but it’s safe to say that Bruce Banner himself would be impressed with this strain if he was a real person.
Washington state’s results show Bruce Banner consistently tested for over 24 percent THC content, making it one of the top three strains with high-THC content, only behind Ghost OG and Wappa.
Its genetics come from OG Kush and Strawberry Diesel, making it a perfect mix of sativa and indica genes. Bruce Banner strain has a very fruity aroma and an uplifting, energetic high.
Honourary Mention: Ghost OG
As mentioned, according to Washington state’s data, Ghost OG came in first with the highest THC content. It consistently came in at over 28 percent, which is unheard of.