Enroll Now

News and Best Practices

Understanding Sample Testing, Part 3: Selecting Samples

September 28, 2016

In the first two parts of this series, we described sample testing with high-performance liquid chromatography (HPLC) and gas chromatography (GC) methods. Now that you understand the basics of lab testing, it’s critical to understand how sampling is done.

You’ve seen this already: You walk in to a rec store and find a strain that looks appealing. There’s a number next to it, such as “20% THC.” This is a measure of how much THC is in that product. But what does that mean, exactly?

If we say a bud is 20% THC, we’re saying that, by weight, 20% of that bud is made up of THC. That may sound like a lot (compared to most strains, it is), but consider that the bud should be relatively dry. The plant matter has weight but not as much weight as the oils and fats, which is where we find THC.

Bottom’s up

Now, here’s the kicker: Is that 20% value accurate? Well, no, it isn’t. And here’s why.

When any business reports its THC figures, assume those values were determined from just one part of the plant. If they’re clever, they would’ve selected buds from the bottom-most portion of the plant and submitted that to a lab. The lower sections of the plant are the oldest. Since those sprouted first, the buds have been producing THC longer than the top-most portions of the plant. On any given plant, the highest concentrations of THC are found near the bottom, even in plants that were hung upside-down during harvesting.

No state has strict requirements for accurate sampling or reporting. Some states, like Colorado, require separate tests for individual batches (a “batch” defined as any harvest that used specific chemicals in its cultivation). But where those buds get pulled for sampling isn’t monitored by the state or the lab. So that means the THC values we typically see on labels are the highest values available on that plant, and not necessarily the actual values in what was sold.

Toward more accuracy

How would we collect and report more accurate THC percentages?

First, we’d need to designate sections of the plant, such as “top,” “middle” and “bottom.” This might be designated by branch count or by a millimeter measurement from the top down. That means we’d conduct at least three sample tests based on how high (or low) on the plant from which we pulled our samples. We would report percentages only for those particular sections, even when those samples come from the same plant.

Second, we’d need to note from which batches we pulled these values. From a business perspective, sampling every plant in a harvest is impractical and expensive. From a statistical, scientific perspective, we don’t need to sample every single plant. We just need to sample a few from a single batch, then average those values.

Third, we’d require more open lab testing policies. In Colorado, one lab (The Good Lab) will test samples for consumers. Just about every other lab tests only for licensed businesses. Other states, such as Maine, also permit open testing but only at a specific, non-permanent location.

Accurate results help your business

Right now, we usually see the term “top shelf” reserved for the pricier buds. Any business can say a particular product is “top shelf” and sell it for whatever price they wish. If consumers really, really want those buds, they’ll pay for them.

Now, imagine we have a hot seller, such as Alien Rock Candy. Because this particular strain has an incredibly deep and complex terpene profile, we can charge more for it. It tastes really good, its buzz is legendary, and it smells amazing. But what if your customers can’t afford—or just aren’t willing—to pay a top shelf price for your Alien Rock Candy?

That’s where the lab values for THC, CBD or terpenes come in. If your results show that the top-most portion of your Alien Rock Candy batch has a lower THC (or terpene) potency than the bottom-most buds, you can charge less for the less potent buds while still charging top-shelf prices for the most potent ones. This way, your customers get more options and you, possibly, could generate more sales.

In the end, just remember that lab results currently serve as general guidelines rather than tried-and-true reports. Testing is necessary to ensure we’re dealing with safe products. But when it comes to potency values, there’s still a large gray area. We can anticipate that this system will change in the near future, especially as regulators and consumers grow more aware of these little nuances. You can always use these changes to your advantage and, as an entrepreneur, you should.


By Randy Robinson
Cannabis Cultivation Today articles are for informational purposes only and should not be considered legal guidance or advice on grow practices. You should contact an attorney or a qualified cultivation consultant for specific compliance and cultivation advice.
© 2016 CAN Performance Group, LLC. All rights reserved.

Subscribe to Cannabis Cultivation Today

* indicates required
Sign Up for Cannabis Cultivation Today

© 2019 CAN Performance Group, LLC. All rights reserved.