Stand in front of a wall of flower jars and one thing jumps out: the big percentage. And nine times out of ten, the biggest number on the label isn't "THC" at all — it's THCA. It looks like it should be the headline potency figure, but in the jar it can't get you high on its own. That one quirk is the single most confusing thing about a Vermont cannabis label, and once it clicks, the rest of the numbers make sense. Here's what THCA is, what heat does to it, why it reads higher than the THC number right next to it, and which figure to actually shop by.

What is THCA?

THCA is tetrahydrocannabinolic acid — the raw, natural form of THC that the cannabis plant actually makes. Living and freshly harvested flower is loaded with THCA and contains very little active THC. It's an acid: the molecule carries an extra chemical group (a carboxyl group, the "A" in THCA) that THC doesn't have. That small structural difference matters, because THCA in its raw state doesn't fit the receptors that produce a high. Eat a nug of raw flower and you won't feel intoxicated from it — the THCA simply hasn't been converted yet.

So the plant doesn't really make THC directly. It makes THCA, and THC is what THCA becomes once it's heated. That's the whole trick of the label: the number you see is mostly the *potential*, sitting there in acid form, waiting for heat to unlock it.

How does THCA turn into THC?

Through a reaction called decarboxylation — "decarb" for short. When THCA is heated, that extra carboxyl group breaks off and floats away as carbon dioxide, and what's left behind is delta-9 THC, the intoxicating compound. You don't have to do anything special to trigger it; it happens automatically the moment heat is involved:

• Smoking or vaping — the flame or the vape's heating element decarboxylates the THCA on the spot, in real time, as you inhale. This is why raw flower doesn't get you high but smoked flower does.
• Cooking or making edibles — the flower is gently heated first (in an oven) to decarb it before it's infused into butter or oil. Skip that step and the edible won't do much. Our cannabutter guide walks through the temperatures.
• Time and light — a little THCA slowly converts on its own as flower ages, which is one reason storing it cool, dark, and sealed keeps it at its best.

The takeaway: THCA is the "before" and THC is the "after," and heat is the switch between them. The number on the jar is describing the before.

Why is the THCA number bigger than the THC number?

Pull up the lab report — the Certificate of Analysis (COA) — for a jar of flower and you'll typically see three related numbers: a big THCA figure, a very small delta-9 THC figure, and a Total THC figure. New shoppers assume the tiny delta-9 number is a mistake or a sign of weak flower. It isn't. Fresh, cured flower is *supposed* to read that way — almost all of the potency is still locked up as THCA that hasn't been heated yet.

So why doesn't the THCA number just equal the THC you'll get? Because the molecule literally weighs a little less after it decarbs. When that carboxyl group breaks off as carbon dioxide, the flower loses that mass. A gram of pure THCA can't turn into a gram of pure THC — some of the weight leaves as gas. Labs account for this with a fixed conversion factor, 0.877, which comes from the ratio of the two molecules' weights. The standard formula every lab uses is:

That's why the numbers line up the way they do: THCA is the biggest figure, delta-9 THC is tiny, and Total THC lands a bit below the THCA number — never above it. If a label shows THCA of, say, roughly a quarter of the flower's weight, the Total THC will read a touch lower, because that 0.877 haircut is baked in.

So which number should I compare between jars?

Total THC. It's the one figure that's apples-to-apples across products, because it already does the decarb math for you — it estimates what you'll actually get once the flower is heated. Comparing two jars by their raw THCA numbers, or by the tiny delta-9 numbers, can be misleading; comparing them by Total THC is honest.

That said — and we say this in almost every guide because it's true — the potency number is not the whole story. Two jars with the same Total THC can smell, taste, and land quite differently depending on their terpenes and minor cannabinoids. Chasing the single highest number is a common beginner move that often leads to a product you don't actually enjoy. Our guides to how to choose flower and the entourage effect dig into why the full label beats the big number.

How do I read a Vermont dispensary label and COA?

Every product on a licensed Vermont shelf is lab-tested, and the results are on the package or available as a COA. Here's what to look for, in order:

1. Total THC — the number to actually compare. It's your best estimate of potency after heating.
2. THCA and delta-9 THC — the two components behind that total. Expect a big THCA figure and a small delta-9 figure on fresh flower; that's normal.
3. CBD, and any minor cannabinoids — CBD, CBN, CBG and others. Even a little changes the character of a product, so they're worth a glance.
4. Terpenes — if the profile is listed, it's a map of the aroma and flavor. Two jars at the same Total THC can look completely different here.
5. Batch and lab details — the batch or lot number and the testing lab, so the numbers are traceable to a specific harvest.

If any of that is unfamiliar at the counter, just ask — that's what the staff is there for. Our questions to ask a budtender guide has good prompts, and you can browse the live menu before you visit us in downtown Burlington.

Isn't this the same "THCA flower" I've seen sold online?

No — and this is an important distinction. For a few years, smoke shops and websites have sold something marketed as "THCA flower" or "THCA hemp," pitched as federally legal because it technically tests under the delta-9 THC limit written into the 2018 federal Farm Bill. The catch is exactly the chemistry above: that flower is still packed with THCA, so the moment you light it, it decarbs into ordinary THC and gets you high — same as any other cannabis. It was a labeling loophole, not a different plant.

On a licensed Vermont dispensary label, "THCA" is not a product category or a loophole — it's just one line on the lab report for regular, tested adult-use cannabis, sitting right next to delta-9 THC and Total THC. Vermont has moved to pull intoxicating "hemp" products under the same regulator that oversees dispensary cannabis; we cover that in our guide to delta-8 and hemp THC under the Vermont Cannabis Control Board. The short version: at a licensed shop, the THCA number is information, not a marketing gimmick.

Does Vermont's 30% flower cap use THCA or Total THC?

Vermont limits the potency of adult-use cannabis flower to 30% THC (with a higher, separate ceiling for concentrates). That cap is measured as Total THC — the decarboxylated figure — because that's the number that reflects what the flower can actually deliver once it's heated. So when you see flower testing near that 30% line, it's the Total THC that's being held to the limit, not the raw THCA figure sitting above it.

This is another reason Total THC is the number that matters: it's the one Vermont regulates against. It keeps potency claims honest and comparable across every licensed jar in the state.

Which products does this apply to?

The THCA-versus-THC distinction shows up most clearly on whole flower and pre-rolls, where you're looking at the plant's natural cannabinoid mix on the label. It also applies to any product you heat yourself. The exact Vermont craft jars rotate, so rather than name specific strains, shop by format and read the Total THC on whatever's in:

• Whole flower — the clearest place to see a big THCA number, a small delta-9 number, and the Total THC that reconciles them.
• Pre-rolls — same flower, already ground and rolled; the label works the same way.
• Concentrates and vapes — many are made from extract and may already be partly or fully decarbed, so their labels can lean more toward active THC; see our concentrates guide for how those differ.
• Edibles — the flower is decarbed during production, so edibles are labeled in milligrams of THC per serving, not a THCA percentage.

You can see which Vermont growers are in stock on the live menu before you come, or ask a budtender to translate any label for you.

What Vermont rules apply when I shop?

The chemistry is the same everywhere; the rules are Vermont's. Cannabis here is adult-use for ages 21+, so bring a valid government-issued photo ID — no medical card needed. The menu price is the final, all-in price: Vermont's 14% cannabis excise tax and 6% sales tax are already included, so there's no math at the register. Public consumption isn't permitted anywhere in Vermont, so whatever you buy leaves the shop sealed and is for private use at home, and it can't legally cross state lines. Store it cool, dark, and sealed — both to protect the potency and to keep that THCA from slowly converting before you're ready — and well away from kids and pets.