To Flush or not to Flush

Flushing has been a debate for a long time. If you google “Flushing Cannabis” the very first Websites says “Flushing is free and easy technique that may improve the quality and smoothness of your cannabis buds before harvest.” …but is that true?

Do I flush?
Is flushing the right choice for my garden?
Will flushing help my grow to a cleaner smoke?

These might be some of the questions you might have. To answer these questions, we must first understand what flushing is, and where did the term come from.

FLUSHING - to flush, the act of cleansing a plants roots of nutrients and contaminants by giving the plant large amounts of water (usually equal to 3 times the volume of soil the plant is in).

The term Flushing came to be when a soil grower used the wrong nutrients, and instead of throwing the soil, this idea came to be.

From the same website aforementioned above, they go on to myths of growing and say this:

***However, flushing does not “leach out” nutrients/minerals that are already in the buds. While your plant can use up extra stored nutrients in the leaves of the plant, this does not remove a “chemical” taste from your buds if you’ve provided too many nutrients throughout the flowering stage.

Many people believe that flushing with plain water takes nutrients (and thus bad taste) out of the buds, in a sense, returning them to their ‘natural flavor’. Unfortunately, this just isn’t the case.

When it comes to ensuring good taste and smell of your cannabis plants, an ounce of prevention is worth a pound of cure. Instead of relying on the flush to prevent extra nutrients from being stored in your buds, it’s better to avoid ever giving the plant more nutrients than it can use in the first place. That means keeping nutrient levels as low as you can throughout the grow while preventing nutrient deficiencies.***

I personally don’t believe in Flushing at all, unless used for its original purpose of cleaning out wrong nutrients from the soil.

(By YarraSparra)
I will list some points that not only challenge the absurd impracticality and illogicality of this myth, but point out how the pseudoscience behind it is fundamentally flawed (as is all pseudoscience) and can be countered by what is known about basic plant biology.

  1. Robbing plants of essential nutrients at any stage of their life cycle is NOT beneficial for growth. I challenge anyone to provide a single peer reviewed paper from a reputable journal that provides evidence suggesting otherwise.

  2. If this was practical, wouldn’t you expect all big agricultural hydroponic growers adopt the same practice?

  3. Plants take minerals into their tissues, from their roots via the treachery elements; i.e. xylem. Once these minerals are in the plant, they are there to stay, the plant does not expel them, unless it’s through senescence-driven abscission of leaf petioles. From the treachery elements nutrients are translocated into the phloem - the plant’s ‘blood supply’ - after being integrated into various biomolecules, or are used for various metabolic functions. Where is the logic in thinking the plant ‘uses’ these up in that last week of flushing, in order to avoid smoking them? All the N P K Fe Mg Ca etc. is still there.

  4. For arguments sake say we counter the last point by suggesting these minerals in their ‘raw form’ will taste ‘hasher’ or ‘nastier’ in the form of pyrolytic breakdown products (formed when weed is burned) than artifacts of larger biomolecules of which these minerals/macro nutrients are now a part of, for example phosphorylated PO43-. Even if this was the case it still doesn’t correlate with the myth, as the transports steam in the treachery elements is measured in minutes not a week. i.e. a PO43- molecule does not wait around in these vessels for a week before subsequent translocation and modification.

  5. If there was any truth to this myth, then plants grown in soil would always taste worse than plants grown in hydro. Why? Because obviously soil is not an inert medium you can flush for a week. And a plant CANNOT distinguish between a PO43- molecule that comes from soil from that of a PO43- molecule that comes from hydro solution (which also debunks another myth, but we’ll leave that one).

  6. Are there studies that have conducted double blind trials to investigate if flushed weed tastes any ‘sweeter’ than unflushed weed. Again, need peer reviewed papers. And doesn’t have to be weed, can be strawberries or any other type of fruit.

  7. What is the proposed mechanism to support this myth, and how is it consistent with fundamental plant biology.

  8. How does starving the plant of food in the last week increase thc production in the trichome? Papers?

  9. Given, under certain conditions stressed plants upregulate certain defence compounds, but they will almost certainly produce less inflorescence weight per watt of light. Growth is always retarded under stress - not promoted. Nutrient starvation is a form of stress. Looking for peer reviewed papers that suggest otherwise.

Those of you set in your ways, each to their own and best of luck to you. Those who are willing to change their views in light of new evidence, or lack thereof, be ready for increased yields by feeding those hungry ladies right up until the second you chop.


I was already debating this technique, and now this just confirmed my thinking. I just picked green beans from my garden and ate them. Didn’t cook, rinse, or anything. I just gave them their nutrients two days ago. No flush ever done, nutes every week. They taste delicious to me. No different than they ever have. No different than a store. And after reading your post it only makes more sense to not flush, because why would no nutrients ever be a good thing for your plant. I get it. Awesome post @Aquaponic_Dumme, you’ve been making some very thought provoking threads lately and I’m loving it! Keep it up, and thanks!


I have grown a few plants outside when I was younger, before I ever read a thing about growing Marijuana, when I poured miracle grow on them ever couple days until frost would hit them. They were never top grade stuff, but never had a harsh, or chemical taste. So in that light, I would tend to agree with you.:beers:


I wish everything was this simple to prove or disprove (paranormal subjects implied)

-flower two clones
-flush one but not the other
-get back to us with your opinion


I have, and in my opinion there is no difference in taste. In fact I was thinking of doing it again with documentation & pictures. What I did notice is chlorosis in the leaves on the AK48 clone that was flushed.


Maybe then, a push of nutrients at the end of vegetation and the beginning of flowering, to lay a base to build on? To build bud structure and maybe boost thc production?
After that, return to a lower ppm to maintain?
Finally,the last few weeks, a minimum of nutes, but if there’s a supplement for taste, use that?

We have logic for plant growth, but logic isn’t always right…science is better…we need a test, @Paranorman has the idea, and a few eager participants…raise your hand if you want to volunteer.

I know there are studies, plants can use some nutrients more at certain times of growth…Those rates need to be determined.
It’s been pointed out to me the four stages of flowering, and increasing some nutes during particular weeks.


I’ll do a journal on this. Once I get my other two buckets up, I’ll flush one and not the other and compare taste. I’ll keep details and what not, and even do a blind test with friends and family.
But I’d love to see someone who’s mastered soil do this as well. @Aquaponic_Dumme said he’ll do one for is aquaponic system. I’ll do one for DWC, and someone else could do a soil. Or multiples would be great, get a bunch of results from numerous members on this subject.


One of the points I was making is that “Flushing” is a soil growing term. Flushing is to clean the soil of its nutrients. In DWC and Hydroponics, there is no soil. Basically, as a DWC grower, you’re just changing the nutrient enriched water, to pHed water, and starving the plants. It wouldn’t be called Flushing.

For the life of me, I don’t understand how growers confuse the Flushing term to something only done for chemical taste after harvest. I’ve looked and looked for this myths origins and can’t find it. If you know, please share.

As defined by google:

gerund or present participle: flushing
(of a person’s skin or face) become red and hot, typically as the result of illness or strong emotion.
“Mr. Cunningham flushed angrily”
synonyms: blush, redden, go pink, go red, go crimson, go scarlet, color (up) More
cleanse (something, especially a toilet) by causing large quantities of water to pass through it.
“flush the toilet”


I think the real debate is whether or not starving the plant of nutrients in its critical growth time (the last 2 weeks) will in fact have non-chemical tasting buds. In my experience, not cutting early, drying properly (preferably 7-11days), and curing properly, is where your taste comes from, and is just as important as the growing itself.


the words don’t matter, it’s all about that base, bout that base, bout that base… ‘In my experience, not cutting early, drying properly (preferably 7-11days), and curing properly, is where your taste comes from, and is just as important as the growing itself.’ @Aquaponic_Dumme

Robert’s ILGM nutes fertilize at low numbers ppm, under 1000
Advanced Nutrients numbers approach 2000 ppm

I tried both…ILGM’s were too expensive for my hydro, took too long to replenish…but they worked great…just I got a bump of 100 ppm for every 10 ml, and a bottle was 250 ml
AN’s nutes were cheaper and sold by Amazon, and they worked

both worked, one at double the ppm (and half the price)

just wondering about what’s left behind for comparison


What type of nutrients don’t really matter. Plants require certain nutrients to survive. These studies were done in the 1930’s Hoagland & Arnon. With the source being irrelevant, Premixes mix their nutrient lines based on this formula.

With that said, most nutrient companies like AN suggest overfeeding for a norm. This leads to you buying more, more frequently. It’s business 101. The more you use, the more you buy.

I don’t know what’s in ILGM’s nutrient mix, and have never used it.

PPM’s are not universal. Some mixes have higher amounts of compounds then others, but should still fall within the averages of Hoaglands Solution for larger fruiting plants.
N 210 ppm
K 235 ppm
Ca 200 ppm
P 31 ppm
S 64 ppm
Mg 48 ppm
B 0.5 ppm
Fe 1 to 5 ppm
Mn 0.5 ppm
Zn 0.05 ppm
Cu 0.02 ppm
Mo 0.01 ppm

Notice silica is missing…

I use my own mix that’s very close to this.


Now how many people grow beans in their garden with the same doses of nutrients we force feed our plants to get those huge nugs and dense buds and do you burn vegtables and inhale the smoke from them? Your stomach is full of acids and can digest almost anything your lungs and throat are a bit more sensitive many things that seem tasteless and harmless when vaporized are actually not. I have seen and tasted buds witch were under flushed can’t keep the joints lit harsh and hard on the throat and lungs and they burn super dark ashes. On the other spectrum a nicely flushed bud burns even and clean stays lit and is far smoother smoke


White ash = low humidity, not low chemicals (cured improperly). I fail to see a link in feeding schedule and white ash. …Another one of the myths

For example, cigarettes have a ton of chemical additives and still burn white ash.
If youve been smoking ash that’s black & harsh, it’s because it was dried wrong and probably not cured.


I’ve addressed this topic numerous times over the last couple of years.

For the most part, what @Donaldj said is correct.

Happy growing,



This is not entirely correct.

Properly “flushed” and cured weed will burn easily and not burn out, and will have the resulting white ash, even at the proper stored high humidity of around 65%.



For the most part the chemicals they add to tobacco are meant to make it burn faster and more evenly I am not saying people need to rinse soil if there is no huge build up simply that changing to straight ph’d water for last week or 2 can be helpful.

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Maybe I should have been more clear. I agree with you up to a point. I’ve always understood 62% was the proper RH to cure and store cannabis in. Where we differ is the flushing.

My main point to this thead is the term “flushing” being defined by the growing community as an act to clean out the chemical, harsh taste to bud, that’s being smoked. In fact, that is NOT the definition. As aforementioned, “flushing” is the cleansing of soil, and is completely separate for the act of starving the plant.

“Starving your plant” for the clean, smooth, smoke is a different topic. I don’t mind debating it as I don’t agree with it either, but its not “Flushing”, even though the flushing technique is used to accomplish doing it.


Be as it may, cigarettes contain:
Acetone – found in nail polish remover
Acetic Acid – an ingredient in hair dye
Ammonia – a common household cleaner
Arsenic – used in rat poison
Benzene – found in rubber cement
Butane – used in lighter fluid
Cadmium – active component in battery acid
Carbon Monoxide – released in car exhaust fumes
Formaldehyde – embalming fluid
Hexamine – found in barbecue lighter fluid
Lead – used in batteries
Naphthalene – an ingredient in mothballs
Methanol – a main component in rocket fuel
Nicotine – used as insecticide
Tar – material for paving roads
Toluene - used to manufacture paint

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Depending on preference and other factors, the proper RH for curing can be as low as about 55%, to as high as 65%.

I did say…[quote=“MacGyverStoner, post:16, topic:6432”]
stored high humidity of around 65%

I also did say the term is a misnomer, and not only that, I also said an actual flush is not necessarily needed…



And yes, the term originated with flushing soil for [quote=“MacGyverStoner, post:20, topic:6432”]
extreme pH problems, nutrient mineral salt toxicity build ups, and general over fertilization.



Although I don’t agree with starving you plants, ever, I want to thank you from clearing it up on where you stand on the issue. Up to this point, I haven’t has time to read all those threads yet. Again, thanks for your input.