5 Surefire Ways to Increase THC in Home-Grown Marijuana

Let’s face it. At the end of each grow, you’re really interested in THC. Yes, it’s great if the buds taste good and have a dank, earthy, diesel odor. But even if they’re a bit raggedy or don’t smell so nice, as long as they rock your socks off when you smoke them you’re probably not complaining. So let’s take a look at a few tricks you can use when growing marijuana indoors or out to boost THC levels.

Here are 6 proven ways you can increase the THC content in a single grow cycle:

Important Note! Many of these techniques talk about boosting resin on your buds. Please keep in mind that lots of resin doesn’t necessarily mean lots of THC. However, if you are growing a strain that is genetically predisposed to produce lots of THC and the plant is healthy, increasing resin content will usually cause a correlating increase in THC content.

1. Start Out with the Right Strain

This may seem obvious… but genetics are hugely important when it comes to cannabinoid profiles. Resin production is largely determined by genes, so if you want tons of THC in your buds start with seeds or clones for a strain that is genetically inclined to produce a potent harvest.

Here’s a few strains to try:

Girl Scout Cookies from The Cookie Family

With THC levels testing at upwards of 28%, this hybrid strain packs a punch. Even the weakest buds tested came in at 17% THC, which is more than enough to knock the day’s cares away. The high is nice and balanced. There is a euphoric mental high often described as blissful, and a deep, relaxing body stone that melts away tension.

Critical Neville Haze from Delicious Seeds

Critical Neville Haze clocks in with THC levels at 23.5%. Another hybrid strain, the smoke starts out intensely cerebral with an invigorating high. It takes a while for the Indica effects to kick in, but when they do you get a pleasant buzzing body stone without losing the clear-headed high.

Strawberry Cough

While the THC content of Strawberry Cough is typically reported between 15-18%, a few buds tested at the 2015 High Times Cannabis Cup contained over 28% THC. That means the genetic possibility is there… you just have to bring it out in the grow room. Read on for tips to do just that!

2. Decrease CO₂ During the Ripening Phase

At the end of flowering the buds “ripen”. This is when they begin to produce resin, full of cannabinoids (like THC), terpenes and flavonoids, in earnest. Lower CO₂ at this stage causes plants produce extra ethylene. Ethylene is a hormone which is essential to many ripening processes, including stimulation of the resin glands.

By dropping CO₂ and thus increasing ethylene production encourage the plant to put all of its remaining energy into resin secretion.

3. Decrease Temperature During the Ripening Phase

At the same time you decrease the CO₂ in the grow room, try dropping the temperature down 10-15°F. Cooler temperatures simulate fall and the impending winter. The plant sees this as a signal that the first frosts are coming, and rushes to finish flowering before it is killed by freezing temperatures. It puts all of its remaining energy into producing resin and improving the cannabinoid and terpene content of the resin already produced. This technique can also improve the aroma of your buds.

4. Add UV Light to your Flowering Grow Room

You have probably heard that adding UV light during flowering results in higher THC levels. To understand why this works, we need to look at a little cannabis history:

Where did the strains with the highest THC levels evolve? Think about it for a minute…

That’s right. We’re talking equatorial Sativas and Indicas from high altitude regions like the mountains of the Hindu Kush.

What do these two regions have in common? High light intensity and a large amount of UV light in the natural spectrum compared to other regions. A Swiss study of clones grown at different altitudes suggests that higher altitudes do indeed produce higher THC content. The image below shows the latitudes that naturally grow marijuana with high THC. This is also where UV light is the most intense.

Why does this work? Well, THC-heavy resin is a protective coating that defends both plant and seed from the damaging effects of powerful UV light or ultra-intense light. Cannabis evolved higher resin and THC content to protect itself from harsh light conditions.

Armed with this knowledge, you can apply it to your grow room. Try increasing light intensity during flowering, or add UV light to your set-up.

5. Make Your Plants Thirsty

Decreasing humidity levels and watering less during flowering will also cause a protective response. Dry conditions simulate drought. In times of drought, cannabis plants produce extra resin to coat the delicate flowers and seeds. This is a strategy to seal in moisture and prevent damage from lack of water. By letting your plants dry out somewhat during flowering, you will create a drought stress that boosts THC content.

6. Companion Planting

I know. The title says “5 Surefire Ways to Increase THC”. This last one is not so surefire, so we didn’t include it in the title count. It is a logical idea that should work, but there seems to be very few people who have tried it yet, so we can’t say for certain.

Here’s the premise: in nature plants work together. Many vegetable gardeners take advantage of this with “companion planting”, the practice of placing certain plants near one another to improve production. Legumes like clover or peas put nitrogen in the soil to feed nearby plants. Chamomile pulls up minerals from deep in the earth. Marigold repels nasty pests while bee balm attracts pollinators, and so on.

So how can companion planting with marijuana to improve THC content? Some plants have been shown to increase essential oil content in neighboring plants. Stinging nettle is a good example. Many growers have speculated that planting stinging nettle alongside cannabis plants may boost resin production.

If you’ve tried this technique, please let us know how it worked out in the comments below!

Make Your Next Harvest the Most Potent One Yet

Of all these tricks for boosting THC in marijuana, the first is both the hardest and the most important. It is essential to start with a high genetic inclination to produce tons of THC. If you aren’t sure where to purchase quality seeds with great genetics, check out our list of reputable seed banks.

Once you have good seeds from a potent strain, your next job is to grow healthy plants. All of the tricks in the world won’t help you if your plants are diseased, stunted or damaged. Follow good basic marijuana growing protocols to ensure a healthy crop.

Once you have healthy flowering plants you can give some of these techniques a try. Just remember that there is no quick gimmick to a great harvest, as nothing can replace hard work in the grow room.

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