• Professor Sprout

Cannabis Grow Guide PART 1: What Causes Weed to Have Black Ash?

Updated: Apr 24


Settling the Cannabis Black vs White Ash Debate Once and For All


Does this scenario sound familiar? You’ve got your grow space dialled in. Humidity and temperature levels are on point, every square inch of your canopy is bathed in high intensity lumens, air is being scrubbed and replenished on regular intervals, you’re feeding the highest quality nutrients money can buy and your plants are ripening fast without any sign of deficiency, pest, or disease.


Come harvest time you’re chopping down giant, resin soaked colas that glitter and sparkle enticingly. You spend hours hand trimming and carefully slow drying the buds to a perfect 60% humidity before delicately placing in glass jars in a cool, dark space to cure. You revisit them daily to burp the jars and watch as your flowers slowly fade from raw green into golden nuggets of perfectly cured cannabis perfection.


Then that much awaited day comes, many months after first sprouting those magic beans, to sample your harvest. You crack open the jar and are greeted by an intoxicating perfume of sweet skunkiness. Selecting a nice fat bud you break it down and roll it up in your favourite paper, taking a dry toke to taste the unique flavours of this special strain you’ve spent months slaving over.


You spark your lighter and put flame to the end of your precisely rolled joint to begin the transmutation of herb into higher consciousness and…


Fuck! The dreaded black ash!


Not only that but the damn thing won’t stay lit; burning out almost immediately after taking a puff. It cracks and pops when you take a draw, leaving an acrid taste lingering on your tongue, and why the hell do your lungs suddenly feel congested and heavy? And is that a headache you feel starting? This is hardly the experience you were hoping for.


Unfortunately this is an extremely common occurrence, and if you’re a cannabis connoisseur and grower it can be one of the most frustrating and disheartening scenarios that you’ll encounter. And encounter it you will, my friend.


So what to do? If you’re anything like Professor Sprout, you’ll head to the interwebs in search of some knowledge. But you’ll be sorely disappointed. The discourse on this topic is fraught with an abundance of ‘bro-science’.


“Your buds are just too wet, dude. Dry that shit out and it will burn white”


“You need to flush homie, black ash is just built up nutrients”


“Don’t use molasses in your fertilizer, it makes your buds burn black”


“You need to cure longer. Curing is what makes the buds burn nice and clean”


“Don’t foliar spray man, it builds up on the buds and makes them taste like shit”


“Go organic and you’ll never have black ash again, fuck synthetics”


Every one of these statements is incorrect. I know from experience and a lot of trial and error.

I’ve been growing cannabis for over a decade and in that time I’ve grown grown weed that produces the whitest and cleanest ash you’ve ever seen and some of the blackest, tar like ash that absolutely refused to stay lit and made me nearly cough my lungs out. I did everything they told me on the forums with completely inconsistent results. I flushed, I went organic, I eliminated foliar spraying, I perfected my drying and curing process, and I completely eschewed all pesticides, fungicides and chemicals of any kind.

I still got some plants that burned white, some that burned black, and many in between.


I decided enough was enough. Somebody needed to step up and do a proper experiment to get to the bottom of this issue once and for all, and I guess it was going to have to be me.


Professor Sprout’s Great Black Ash Experiment


With cannabis prohibition stifling almost all scientific investigation into cannabis growing techniques I knew I would need to look elsewhere to solve this dreaded black ash problem. So I turned to the tobacco industry.


Gasp! I know, awful right?


It’s common knowledge that cigarette tobacco is bathed in chemicals that make it burn better and smoother, and as a organic grower there is just no way in hell I was willing to go down that road. But tobacco grown for high quality cigar production is a different story. It is largely unadulterated and you can even find organic cigars if you look hard enough.


As someone who enjoys a nice cigar from time to time, I’ve noticed that ash colour varies considerably between brands and growing regions. Some cigars produce a bright white ash, others a darker more salt and pepper ash. Only very poor quality cheap cigars produce a black, tarry ash.


A top shelf cigar will produce a nice column of ash that holds together firmly, burns clean and evenly, produces a very pleasant aroma, and doesn’t need to be constantly re-lit. Obviously tobacco farmers who produce the highest quality leaf destined for cigar production know what they’re doing. They wouldn’t leave something as important as burn quality to trial and error.


So I researched all I could about tobacco farming in order to gain some understanding of the variables that dictate ash quality in cigars. I combined this information with the anecdotal information provided by years of bro-science online and designed an experiment that would hopefully get to the bottom of this quagmire.


In the next series of posts I will provide you with the results of my experiment and all the knowledge that you will need in order to grow cannabis that burns clean and smooth with a beautiful white ash, every single time.


Stay tuned folks!


-Professor Sprout


Read Part 2

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