Does white ash equal quality cannabis? Leafly asked the experts

We’re probably all familiar with the belief that cannabis flower burning to “white ash” indicates it was grown right or is otherwise good bud. Similarly, we likely all know the old-school belief that holding in a hit gets you higher (“if you cough you don’t get off”), which was disproved by research over 30 years ago.

So if the long-held belief that holding in hits gets you higher is not true, yet persists, what about white ash?

Is there something about bud that burns to white that makes it better than bud that burns to black?

Leafly reached out to a team of cannabis experts, researchers, growers, and patients to try and ascertain what truth is behind the beliefs around white ash.

Common white ash theories

Before turning to the experts, Leafly wanted to see what folks were saying on social media about the white vs. black ash debate.

We saw three main responses:

  • People who felt a growing step called “flushing” was the cause of white ash and a sign of good bud;
  • people who felt it was a measure of moisture in the bud (too moist bud = black ash);
  • and people critical of the entire premise.

“A properly grown bud flushed of nutrients with water for the last 10 days of growth will give you a white ash when the bowl is cashed,” said Jake Sassaman.

I used to think that was the case, but I have come to learn that it may not be indicative, actually, of residual salts, completed cure, or otherwise,” said Demetrius Daniels.

My layperson’s understanding is that this is a rough measure of remaining water content,” said Jay Reynolds.

For us old hippies, white ash is not a factor. Smoke to the last hit—as long as we can get high it’s good,” said Janet Benaquisto.

Some unflushed Supreme Diesel sungrown from 2020 burns to white ash and is super-tasty. (David Downs/Leafly)
Some unflushed Supreme Diesel sungrown from 2020 burns to white ash and is super tasty. How do you even flush sungrown? (David Downs/Leafly)

The Dank Diplomat and the star of Netflix’s Cooking on High, Ngaio Bealum, said, “I have noticed that white ash tends to indicate a better bud.”

Tappié Dufresne, a longtime cannabis patient and consultant who formerly worked at the historic early collective C.H.A.M.P., added, “White burning ash (from anything burning) indicates a clean combustion. You can think of campfires you might have watched. If the wood is green, it leaves a chunky charcoal.”

The ‘flushing’ controversy swirls

While there is some divide over what white ash signifies, there is pretty wide consensus around the importance of a weed grower’s common practice called “flushing.”

Hydroponic indoor growers “flush” the plant for the last 10 days before harvest by only feeding it water, instead of a nutrient mix.

Dufresne compared flushing cannabis with water to fasting for people, “It forces any stored nutrients to be used up by the plant and triggers a push to ripen.”

While Dufresne supports flushing, she also noted, “Even well-flushed flowers that are rushed through the drying and curing process will not burn perfectly.”

But what does the research on flushing say?

Flushing science is thin

Dr. Robert Flannery (Dr. Robb), an expert in cannabis biology, said, “There isn’t much research that supports this concept,” and pointed to a Master’s Thesis which found flushing “to be ineffective in removing any significant amount of nutrient from the bud.”

Dr. Robb is co-authoring The Cannabis Grower’s Handbook with Ed Rosenthal and Angela Bacca, which will be released this September and delves deep into flushing, how it is done, and if it actually does anything.

It specifically points to a lack of “double-blind studies that have been performed to test the efficacy of flushing,” but notes that despite that absence of research, “the overwhelming majority of cannabis growers flush.”

Josh Wurzer, the president and co-founder of SC Labs in California, said he personally “can taste a poor flush when smoking flowers.”

Why wet weed won’t burn white

While the majority of cannabis growers flush and it is a concern for some consumers, others wonder if black ash may be the result of too much water, rather than not enough.

Despite being able to taste the difference in flushed vs. not flushed flowers, Wurzer at SC Labs was clear that “black ash is a sign of incomplete combustion,” adding, “I’m not aware of a plausible explanation that a cause of poor combustion would be a poor flush.”

Wurzer listed the potential reasons for incomplete combustion, such as:

  • too much moisture in the flower (as is the case with a poor dry and cure);
  • a poorly rolled joint;
  • or a really resinous flower.

Wurzer said taste, not ash color, is “probably a better indicator” of good bud.

Of bowls and black ash

White ash may not have as much to do with the bud itself, but how it is smoked, specifically, in a joint or a blunt.

SC Labs’ Wurzer explained the science behind joints burning more:

“Joints/blunts also heat the material that is about to be burned, vaporizing both the resin and moisture in that part of the bud, which means that two of the major contributors to an inefficient combustion—and therefore black ash—are removed from the equation, or at least reduced before that part of the joint even combusts.”

 

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Additionally, Wurzer noted that “the airflow is much more optimized for an efficient combustion in a joint vs. a bong or bowl.”

That is why pipes tend to burn black while joints burn white.

It really comes down to if you like the smell, taste, and the high—not the ash, it seems.

White ash on its own is an insufficient proxy for quality; there’s too many other factors at play. (I mean, cigarettes burn pure white, and no one’s Instagramming their Camel Lights.)

So if it burns white and you like it—great! If it doesn’t—that can be OK, too.

What are your thoughts on the white vs. black ash debate? Leave us a comment and join the conversation.

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