Increasing Cannabis THC Levels – Potency

When it comes to growing cannabis, there are lots of different goals by different growers. Many growers are growing medical marijuana for medical-related purposes. Others are growing for their personal adult use. For many growers, including both medical marijuana and recreational cannabis growers, a common goal is to maximize the amount of THC and other cannabinoids produced when growing cannabis. Let’s take a look at a few tricks you can use when growing marijuana indoors or out to boost THC levels.

Why Increase Maximum THC Levels? 

  • Greater mental and psychoactive effects from the same amount of bud
  • Many medical marijuana growers desire high THC levels for the relief of nausea, certain types of pain, spasticity, certain symptoms of multiple sclerosis, etc.
  • Many of the things you do to increase THC levels will also increase your overall cannabis yields.

What increases THC levels and overall potency?

Strain & Individual Plant Genetics

This may seem obvious… but genetics are hugely important when it comes to cannabinoid profiles. Your plant genetics set the “upper limit” of how much THC and other cannabinoids your plant will ever be able to produce. So as a really rough example, let’s say your strain/plant genetics can only produce 15% THC at most. That means you may get less than 15% THC in your buds if you don’t grow the plant right, but no matter what you do you’ll never be able to increase it above 15%. Unfortunately there’s nothing you can do to beat genetics so start with good genes!

Harvest Time

Many cannabis growers don’t realizing they are actually harvesting their buds too early, dramatically reducing yields and potency! There is a 2-3 week period during the flowering stage when plants are “mature” and buds are at the highest levels of THC. At this point, the tiny resin glands (trichomes) on the buds have turned milky white, and most of the white hairs (pistils) on the buds have darkened and curled in.  If the plant is allowed to keep maturing, the cannabinoid profile continues to change. Buds harvested on the later side tend to produce more of a relaxed “body” effect, though the psychoactive effects of THC may be somewhat reduced. If you harvest earlier than this, the plant hasn’t reached its full potential. Sometimes early-harvested buds can produce a “speedy” effects, or give some people headaches (curing will help with this) so avoid harvesting early if you can!

Health & Care

In order to get your cannabis to produce the most potent buds possible, you need a robust, healthy cannabis plant with lots of bud sites getting direct light during the flowering stage. This means it’s important to avoid common plant health mistakes like overwatering,underwatering, heat stress, root problems, irregular light cycles and nutrient problems. Try to maintain balance and avoid environmental extremes.

  • 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, terpenes and flavonoids, in earnest. By dropping CO2 and thus increasing ethylene production encourage the plant to put all of its remaining energy into resin secretion.
  • Decrease Temperature During the Ripening Phase – 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.
  • Add UV Light to your Flowering Grow Room –  Although cannabis can grow in relatively low light conditions (it grows like a weed!), it will not produce significant amounts of bud without very bright light in the flowering stage. 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. 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. Try increasing light intensity during flowering, or add UV light to your set-up.

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.

Companion Planting

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.

Curing Process

Although there is no evidence that the curing process (jarring up buds after they’ve dried) increases THC levels directly, there is a lot of evidence that it increases the perceived potency of buds. Though not well understood, this may be because there are chemical changes that happen during the curing phase that “intensify” the effects of THC and other cannabinoids.

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.

[Updated, originally published 16.3. 2017]

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