Study on flushing

So they’re saying don’t flush now…

Rx Green Technologies evaluated the effects of different flushing times on chemical profile, flavor, and smoking characteristics in Cannabis flower.
Flushing periods of 14, 10, 7 and 0 days were imposed on Cherry Diesel.
No differences were detected between flush treatments for yield, potency, or terpenes.
Analysis of mineral content of leaves indicated small changes in content of iron and zinc.
Taste test panelists tended to prefer flower flushed for 0 days.


Saw this on reddit.
Posted this link There as well.

I havent read this entire document by any means. From what I understand though the main pints are as follows:
Plants go into senescence regardless of flushing or keep feeding. Therefore, feeding once the plant has started senescence is a waste of $$ and nutes.

Pages and pages of discussion about it on ICmag


Smoothness of the smoke increased with decreasing flushing time, although was not significantly different (Figure 4d). Thirty-six percent of testers rated the smoke from the zero-day flush flower as smooth whereas only 19.4% rated the 14-day flush flower as smooth. The 14-day flush had the highest percentage of harsh ratings (41.7%) compared to other samples. Panelists were asked for their flavor preferences before testing in order to determine whether personal preference would affect taste test results. Statistical analysis determined that personal preferences did not influence taste test outcomes (data not shown).



“ No differences were detected between flush treatments for yield, potency, or terpenes.”

Lol funny stuff, so science says why bother feeding the last 14 days since it wont change anything. Therefore feeding last 14 days is a waste of time, $, and nutes.

Yet “Taste test panelists tended to prefer flower flushed for 0 days.“
So the conclusion is to go against science and go with taste test results??

Makes zero sense.

Sounds like the study was funded by a nute company wanting people to use more unnecessary nutes.


Honestly don’t know what to make of it…

Even the old aquaponics system - running same clones perpetually. We did notice a difference and the last week I’d cut off the nutrients and run tap water (hard rocky mountain granite water) with no pH adjustment for the last week before cutting.

Ex wife could 100% tell which were and weren’t flushed (and no i never told her) and be 100% accurate.


I never feed for the last 2 weeks just straight water but very seldom do I have fade like most on here.
Most the time they turn yellow, which is telling me that there isn’t any nutes left in that bucket.


Im with this one here.
Who really are the people doing these studies ?
Probably the people putting out that bland greenery on the shelves.


Could you tell what differences she noticed?


Thank you, science!! I can now justify my laziness!!! Let it ride until chop chop!!


I have always found my unflushed always had almost a blk ash with joints ( I use elements good rice papers too)
Now the flushed was light gray not quit white, Think it could be the unflush was still a little wet
coming from a 62% Boveda pak jar?
I need to try drying the herb over night and roll it again and see.
The unflushed just tasted nasty to me most times, but now wondering if it could be to moisture contents.


The ash is to be white/grey, the darker the ash the more nutes are still in the plant


The secret to a good smooth bud is in the dry/cure.

Most hang for a few days then trim and jar for burping but I take up to 5 weeks to get my bud dry enough for jars then am burping for another few weeks to get it dry enough to smoke.

The smells are really nice in the jars. Never grassy smelling and just sweet sweet bud.

I just take the whole plant in it’s pot upstairs to my man cave and do my final trimming as I snip each cola off the plant. Buds go into doubled or tripled paper bags and then down into the cool basement.

For the first week I pour them out into a clean pan. Usually the drip pans for the pots. Gently break up the clumps and let air dry for an hour or so then back into the bags. If you weigh the bags and note the weight loss after 10 days or so I’ll jar them when a bag that started at around 120g wet is only losing a g/day. They can still form a big clump the first few days in the jars but that stops as they get drier.

I have a bunch of plastic tobacco cans that work great for this. Smooth walls all the way up so I can just dump the huge clump out into a pan without digging them out like with mason jars. Once ready to smoke they can go into mason jars for storage as they are all separate and easily pour out.

I never flush but will stop feeding a week or more before chopping in soilless and begin reducing ppm after week 6 or so in DWC but still be around 300ppm at the end.

Flushing agents do sweet fug all so don’t waste money on that shit. And carbs/sugars are for feeding the microherd and don’t really affect the final product other than you may get a better yield when growing in dirt mixes that has a healthy myco population.

Make sure they have lots of sulfur and Mg in late flowering for extra resin production and good old Epsom Salts does that well and cheaply.



For my ex, it was harsher… I didn’t notice any difference between the two myself. But she was one of those people who could tell if a child hid a sock under the couch in the living room from the kitchen while cooking :joy:


Thats also a myth/broscience as seen in the article I linked above.
They concluded that the bud had same content whether flushed or not.

Ash colour has more recently been linked to Moisture content.


I wonder if its not more enzymes and other products in the plant…

Like (hunting example) the difference between a wild deer that dropped on the spot vs one that ran for a km before dieing… They have vastly different tastes - yet chemically they’re the same.


Ya, I think there needs to be another study.
It’s incomplete and probably done by someone who don’t partake. LoL


Says who conducted the study right in the very first line.

I’m interested in the methodology used, so I’m reading it. So far, it doesn’t sound especially rigorous, but better than some I’ve seen.

Honestly, while I’d prefer a more rigorous study by people with no ties to the industry, it seems as if they at least tried to be somewhat more objective than most. I prefer tissue analysis to subjective anecdotes every single time. I wish this was an area with more active study.


This argument gets exhausting, if you understand the way a plants biology works you will understand that flushing does have benefits sometimes more then others depending on your growing methods and when you start to flush. If you have grown alot of herb and tried flushed vs unflushed you cant deny the difference. No black ash, no sparking, better cure with less time. Theoretical science vs real life observations are always frustrating. I took part in a long discussion somewhere else on this site about all of this and posted links to some good information on the subject.
Check out the to flush ot not to flush threads.
Here is one link that is food for though


As i undersrand in this instance; feeding last 2 weeks is not the same as flushing last 2 weeks.

I dunno :man_shrugging: about any of you… but I’m gonna stick to the knowledge that I’m learning here and keep flushing. From what I read -
Flushing helps a lot. I will be flushing my babies when they are ready.