Is Pre-harvest Flushing A Myth?

[Monster762]

I think flushing does help but the quick 1 week deal don’t do much.
Has to actually have time to do something. You need to strip the soil then the plant takes up nothing nutrient wise from the soil Then it uses its reserves to survive n try to reproduce. It’s another form of low stress actually.
Common sense though says it does work.
If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )
also you can just stop all uptake from the ground other ways but you don’t want to kill the plant doing it.you want it to force the ripening.
On other end strip of soil takes a minute.
I use flushing agent cause I bought a bottle in my beginning. I use full strength n let it sit in the soil for most of a day or a day. They say 6 hrs then rinse. Then I flush til my runoff is clear ( or damn close)
Then I feed nothing but water n molasses for a few days. Then clean water only til chop. I don’t time flush as 2 weeks. I just start the porcess when I see swell slow on buds n know it’ll be soon. Usually I start my flush with the actual flush at about 6-1/2 weeks in 8 week strain. I run clean water til the plant shows me it’s clean. Faded with colors and heightened smell of all things. It will get stupid loud about a week into flush then louder every day. Then it’ll just fade. That’s my chop point. 1-1/2 to 3 weeks water at end. I still check trichs They can change quick in flush.

 

[Monster762]

I think flushing does help but the quick 1 week deal don’t do much.
Has to actually have time to do something. You need to strip the soil then the plant takes up nothing nutrient wise from the soil Then it uses its reserves to survive n try to reproduce. It’s another form of low stress actually.
Common sense though says it does work.
If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )
also you can just stop all uptake from the ground other ways but you don’t want to kill the plant doing it.you want it to force the ripening.
On other end strip of soil takes a minute.
I use flushing agent cause I bought a bottle in my beginning. I use full strength n let it sit in the soil for most of a day or a day. They say 6 hrs then rinse. Then I flush til my runoff is clear ( or damn close)
Then I feed nothing but water n molasses for a few days. Then clean water only til chop. I don’t time flush as 2 weeks. I just start the porcess when I see swell slow on buds n know it’ll be soon. Usually I start my flush with the actual flush at about 6-1/2 weeks in 8 week strain. I run clean water til the plant shows me it’s clean. Faded with colors and heightened smell of all things. It will get stupid loud about a week into flush then louder every day. Then it’ll just fade. That’s my chop point. 1-1/2 to 3 weeks water at end. I still check trichs They can change quick in flush.

Oh n maybe it’s just the 5 strains I’ve run but swell always hits weeks 4-7 never at the end. No last minute gains none of that n I’ve pushed nutes longer to see this ( final swell) . Ended up with 10 wk bitter ass Amber trich plant with green leaves. No strain I’ve ran n I can list like 5-6 gains a single gram at the end. Weight is on by week 7 on all my 8-10 wk strains. period then it’s just trichs ripening. Now I’m no pro. No # plants in my tent but its consistent. And fire.

 

[Kot]

Flushing might be good for soil grow or for people who overfeed. I am in coco and if I give more than 400 PPM to my girls they burn. So if I was to flush then they would have no food. Flushing doesn't do anything, the drying and curing process and how you do it will determine how the smoke will be.

I don't like the idea of starving my plants in the last 10 days or so when they get on weight and make THC. Anyway they will get the needed nutrients, either from the feeding you give them either trough the stored nutrients in the leaves. But I think they have to work harder to get the nutrients from the leaves, which also will be damaged and photosyntheses will be hurt.

 

[Glow]

I think flushing does help but the quick 1 week deal don’t do much.
Has to actually have time to do something. You need to strip the soil then the plant takes up nothing nutrient wise from the soil Then it uses its reserves to survive n try to reproduce. It’s another form of low stress actually.
Common sense though says it does work.
If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )
also you can just stop all uptake from the ground other ways but you don’t want to kill the plant doing it.you want it to force the ripening.
On other end strip of soil takes a minute.
I use flushing agent cause I bought a bottle in my beginning. I use full strength n let it sit in the soil for most of a day or a day. They say 6 hrs then rinse. Then I flush til my runoff is clear ( or damn close)
Then I feed nothing but water n molasses for a few days. Then clean water only til chop. I don’t time flush as 2 weeks. I just start the porcess when I see swell slow on buds n know it’ll be soon. Usually I start my flush with the actual flush at about 6-1/2 weeks in 8 week strain. I run clean water til the plant shows me it’s clean. Faded with colors and heightened smell of all things. It will get stupid loud about a week into flush then louder every day. Then it’ll just fade. That’s my chop point. 1-1/2 to 3 weeks water at end. I still check trichs They can change quick in flush.

Yes, I'm playing devils advocate here to see what growers views are.

You've just though given a commonly held opinion (arguable myth, which is what I am questioning) about flushing in that by running water only for X period of time the plant uses up stored nutrients. This BTW from a scientific perspective cannot happen and that's why I put up the research that supports this. So firstly growers need to understand that once nutrients are stored in the plant tissue these nutrients can't be flushed away by starving the plant. What though can feasibly happen is that mobile nutrients (i.e. N, P, K, and Mg) may move directly to the flowers (when the plant is put under nutrient stress) where they are most needed which really - based on the theory of flushing - is undesirable because these nutrients are then present in the combustible product. Therefore, flushing’ will mainly speed up senescence and induce nutrient relocation. P, K, and Mg are most useful in photosynthetic and reproductive tissues; therefore, they will be translocated to the younger leaves and flowering tips (otherwise called buds) and not the other way round as we hoped for! Only N will potentially be redistributed to the roots in a vain attempt to increase root mass and hopefully acquire more nutrients. Concomitantly, a part of the stored sugars is also made available to the roots to support their growth. But a reduction in soluble nitrogen species (mostly amino acids and derivatives) results in a compensatory accumulation of carbohydrates in the upper plant parts; these are nearly as unwelcome in the final product as proteins. This means, flushing will at best reduce nitrogen but possibly affect carbohydrate distribution in a negative way.

Organically bound nitrogen but also free nitrate as well as free and bound phosphates decompose when burnt, resulting to a good part in undesirable products. Phosphate, though can only be reduced by limiting its application early enough. Only nitrogen-containing proteins and amino acids which not only glow badly but also stink like burnt hair could be potentially reduced by prolonged flushing.

Other organic molecules such as carbohydrates, not comprised in a mineral analysis (as per the research paper cited), consist mostly of insoluble structural constituents like cellulose fibres and soluble sugars and starch. These fibres are the main reason why dried plants can be smoked whereas the latter two are undesirable and result in dark smoke and a ‘charred’ smell.

Bottom line is, instead of quantifying inorganic minerals, it would be better to determine organic and therefore combustible substances like soluble and total nitrogen as well as soluble sugars and starch.

You make a good point here with "If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )"

Technically you sort of have this right. Towards the end of the crop cycle photosynthesis drastically slows and cell division becomes about nil. Therefore, the plant nutrient requirements are about nil (no cell division = no nutrients required to power cell division) so feeding a plant nutrients during this point of the crop cycle is pointless and no growth benefits will be obtained. The study I linked to showed this so if nothing else growers can save on input costs (the cost of the nutrient) by simply running water in the last 10 - 14 days of the crop cycle.

Flushing is a subject that fascinates me because 1) its value is hotly debated 2) it is potentially the greatest most persevering myth in the grow scene 3) the arguments flushing proponents use to support flushing are often highly scientifically flawed.

BTW, what flushing agent do you use? Most of these flushing agents are simply citric acid or citric acid and glucose. I personally have never understood why growers use them. I've of course read the marketing hype used to flog them but frankly for the most part this is science defying dribble (alien tech).


Glow

 

[Monster762]

I’m in coco and can litterally throw the full strength 3 part plus bloom booster carbs and calmag all in one feed.every day No burn.chit like syrup. Molasses too. So mostly that’s dependent on the ladies. These ones take it all. Some are finniky and wont really want anything. ( like my blueberry crosses)
I get your point on making em work harder for nutes but look at every other aspect. When you make plant work it produces better. Think of it. Training cropping blasting with light to build trich for defenses splitting stalks extra dark to stress it.

Theses stresses are part of what hieghtens the numbers all around. Potency and weight.

Yes, I'm playing devils advocate here to see what growers views are.

You've just though given a commonly held opinion (arguable myth, which is what I am questioning) about flushing in that by running water only for X period of time the plant uses up stored nutrients. This BTW from a scientific perspective cannot happen and that's why I put up the research that supports this. So firstly growers need to understand that once nutrients are stored in the plant tissue these nutrients can't be flushed away by starving the plant. What though can feasibly happen is that mobile nutrients (i.e. N, P, K, and Mg) may move directly to the flowers (when the plant is put under nutrient stress) where they are most needed which really - based on the theory of flushing - is undesirable because these nutrients are then present in the combustible product. Therefore, flushing’ will mainly speed up senescence and induce nutrient relocation. P, K, and Mg are most useful in photosynthetic and reproductive tissues; therefore, they will be translocated to the younger leaves and flowering tips (otherwise called buds) and not the other way round as we hoped for! Only N will potentially be redistributed to the roots in a vain attempt to increase root mass and hopefully acquire more nutrients. Concomitantly, a part of the stored sugars is also made available to the roots to support their growth. But a reduction in soluble nitrogen species (mostly amino acids and derivatives) results in a compensatory accumulation of carbohydrates in the upper plant parts; these are nearly as unwelcome in the final product as proteins. This means, flushing will at best reduce nitrogen but possibly affect carbohydrate distribution in a negative way.

Organically bound nitrogen but also free nitrate as well as free and bound phosphates decompose when burnt, resulting to a good part in undesirable products. Phosphate, though can only be reduced by limiting its application early enough. Only nitrogen-containing proteins and amino acids which not only glow badly but also stink like burnt hair could be potentially reduced by prolonged flushing.

Other organic molecules such as carbohydrates, not comprised in a mineral analysis (as per the research paper cited), consist mostly of insoluble structural constituents like cellulose fibres and soluble sugars and starch. These fibres are the main reason why dried plants can be smoked whereas the latter two are undesirable and result in dark smoke and a ‘charred’ smell.

Bottom line is, instead of quantifying inorganic minerals, it would be better to determine organic and therefore combustible substances like soluble and total nitrogen as well as soluble sugars and starch.

You make a good point here with "If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )"

Technically you sort of have this right. Towards the end of the crop cycle photosynthesis drastically slows and cell division becomes about nil. Therefore, the plant nutrient requirements are about nil (no cell division = no nutrients required to power cell division) so feeding a plant nutrients during this point of the crop cycle is pointless and no growth benefits will be obtained. The study I linked to showed this so if nothing else growers can save on input costs (the cost of the nutrient) by simply running water in the last 10 - 14 days of the crop cycle.

Flushing is a subject that fascinates me because 1) its value is hotly debated 2) it is potentially the greatest most persevering myth in the grow scene 3) the arguments flushing proponents use to support flushing are often highly scientifically flawed.

BTW, what flushing agent do you use? Most of these flushing agents are simply citric acid or citric acid and glucose. I personally have never understood why growers use them. I've of course read the marketing hype used to flog them but frankly for the most part this is science defying dribble (alien tech).


Glow

i bought flawless finish when I started to go with my AN nutes. Just wanted a simple program. It’s chelated mag and iron or something ( I’ll have to check bottle) but water soluble and somehow clings to stuff in soil and leaches it out to be rinsed easy. ( supposedly). I. Leave it in at least twice as long as they say n runoff comes out dark. I run til mostly clear then no nutes. Within a week fade happens n colors fly. Smell gets better. Actually smell gets better as your flushing the water through.

Idk the science to it all but it seems to help me fade and the senescence your were saying. It does help the trichs ripen quicker.

 

[Glow]

I’m in coco and can litterally throw the full strength 3 part plus bloom booster carbs and calmag all in one feed.every day No burn.chit like syrup. Molasses too. So mostly that’s dependent on the ladies. These ones take it all. Some are finniky and wont really want anything. ( like my blueberry crosses)
I get your point on making em work harder for nutes but look at every other aspect. When you make plant work it produces better. Think of it. Training cropping blasting with light to build trich for defenses splitting stalks extra dark to stress it.

Theses stresses are part of what hieghtens the numbers all around. Potency and weight.

i bought flawless finish when I started to go with my AN nutes. Just wanted a simple program. It’s chelated mag and iron or something ( I’ll have to check bottle) but water soluble and somehow clings to stuff in soil and leaches it out to be rinsed easy. ( supposedly). I. Leave it in at least twice as long as they say n runoff comes out dark. I run til mostly clear then no nutes. Within a week fade happens n colors fly. Smell gets better. Actually smell gets better as your flushing the water through.

Idk the science to it all but it seems to help me fade and the senescence your were saying. It does help the trichs ripen quicker.

Yes technically by not providing a plant with nutrients this could feasibly speed up senescence (ripening).

BTW, just so we are clear I am a grower and a smoker of about 35 + years. The thing is I myself flush (run water only for about 7 - 10 days) but more importantly what I also do is taper off nutrients after the swell phase when growth begins to slow. This reduces the accumulation of nutrients in the tissue when compared to luxury feeding higher levels of nutrients than the plant requires to achieve genetic potential. While I absolutely know that one cannot remove stored nutrients from the plant tissue through flushing my theory is that the benefits of flushing are relative to what might be occurring at an organic (not inorganic mineral) level.

 

[Monster762]

Yes technically by not providing a plant with nutrients this could feasibly speed up senescence (ripening).

BTW, just so we are clear I am a grower and a smoker of about 35 + years. The thing is I myself flush (run water only for about 7 - 10 days) but more importantly what I also do is taper off nutrients after the swell phase when growth begins to slow. This reduces the accumulation of nutrients in the tissue when compared to luxury feeding higher levels of nutrients than the plant requires to achieve genetic potential. While I absolutely know that one cannot remove stored nutrients from the plant tissue through flushing my theory is that the benefits of flushing are relative to what might be occurring at an organic (not inorganic mineral) level.

Yeah I usually run 1/2 strength max through the cycle. a 1 liter 3 part last like 4 runs. But this run in this coco mix they’re demanding. 1/2 strength they yellow up quick.

 

[Smokefree]

Your CORRECT!

 

[Monster762]

Yes, I'm playing devils advocate here to see what growers views are.

You've just though given a commonly held opinion (arguable myth, which is what I am questioning) about flushing in that by running water only for X period of time the plant uses up stored nutrients. This BTW from a scientific perspective cannot happen and that's why I put up the research that supports this. So firstly growers need to understand that once nutrients are stored in the plant tissue these nutrients can't be flushed away by starving the plant. What though can feasibly happen is that mobile nutrients (i.e. N, P, K, and Mg) may move directly to the flowers (when the plant is put under nutrient stress) where they are most needed which really - based on the theory of flushing - is undesirable because these nutrients are then present in the combustible product. Therefore, flushing’ will mainly speed up senescence and induce nutrient relocation. P, K, and Mg are most useful in photosynthetic and reproductive tissues; therefore, they will be translocated to the younger leaves and flowering tips (otherwise called buds) and not the other way round as we hoped for! Only N will potentially be redistributed to the roots in a vain attempt to increase root mass and hopefully acquire more nutrients. Concomitantly, a part of the stored sugars is also made available to the roots to support their growth. But a reduction in soluble nitrogen species (mostly amino acids and derivatives) results in a compensatory accumulation of carbohydrates in the upper plant parts; these are nearly as unwelcome in the final product as proteins. This means, flushing will at best reduce nitrogen but possibly affect carbohydrate distribution in a negative way.

Organically bound nitrogen but also free nitrate as well as free and bound phosphates decompose when burnt, resulting to a good part in undesirable products. Phosphate, though can only be reduced by limiting its application early enough. Only nitrogen-containing proteins and amino acids which not only glow badly but also stink like burnt hair could be potentially reduced by prolonged flushing.

Other organic molecules such as carbohydrates, not comprised in a mineral analysis (as per the research paper cited), consist mostly of insoluble structural constituents like cellulose fibres and soluble sugars and starch. These fibres are the main reason why dried plants can be smoked whereas the latter two are undesirable and result in dark smoke and a ‘charred’ smell.

Bottom line is, instead of quantifying inorganic minerals, it would be better to determine organic and therefore combustible substances like soluble and total nitrogen as well as soluble sugars and starch.

You make a good point here with "If the nutrients are what causes harshness n I’ll flavors. Then why keep filling the plant with nutes ( if it’s days are numbered )"

Technically you sort of have this right. Towards the end of the crop cycle photosynthesis drastically slows and cell division becomes about nil. Therefore, the plant nutrient requirements are about nil (no cell division = no nutrients required to power cell division) so feeding a plant nutrients during this point of the crop cycle is pointless and no growth benefits will be obtained. The study I linked to showed this so if nothing else growers can save on input costs (the cost of the nutrient) by simply running water in the last 10 - 14 days of the crop cycle.

Flushing is a subject that fascinates me because 1) its value is hotly debated 2) it is potentially the greatest most persevering myth in the grow scene 3) the arguments flushing proponents use to support flushing are often highly scientifically flawed.

BTW, what flushing agent do you use? Most of these flushing agents are simply citric acid or citric acid and glucose. I personally have never understood why growers use them. I've of course read the marketing hype used to flog them but frankly for the most part this is science defying dribble (alien tech).


Glow

Oh I was wrong flawless finish is mag and sulfur not iron idk exactly what the claim is but supposedly works like a magnet to attract nutrients then carry them out

 

[Monster762]

Oh I was wrong flawless finish is mag and sulfur not iron idk exactly what the claim is but supposedly works like a magnet to attract nutrients then carry them out

Ok I didn’t take em upside down. Am I that stoned.

 

[Kot]

Ok I didn’t take em upside down. Am I that stoned.

This site sometimes makes that, no idea why. You can try to change the positions on your pics on your pc and upload them. I do it this way and it works.

 

[Glow]

lol. I won't comment other than to say that by adding salts (inorganic ions) to solution this sort of defeats the argued to be purpose of flushing yes? I expect there are non plant food ingredients such as citric acid perhaps. What does it smell like. Does it have a bit of an acrid smell?

 

[Kot]

Some info I've saved over the years about flushing. Though I don't use it because I do not need to.


"
If you want to ensure your coco is as neutral as possible in terms of nutrients you can extract it with a 1 g/L solution of calcium nitrate and then with 2g/L of tetrasodium EDTA. This will extract both macronutrients
that are exchangeable for Calcium and micro nutrients that can be extracted when using EDTA. The EDTA step is important as coco can hold a large amount of micro nutrients within it that can be exchanged
and used by the plant. If you want your nutrients to all come from solution you will need to remove these contributions from the media. After this you will then want to run plain water to remove
any excess Ca and EDTA and then run your full strength nutrient solution for a few days. This will strip the coco from ions and then it will equilibrate the cation exchange sites with your nutrient solution's composition."


"Plant Flusher contains a mixture of these 2 ingredients: EDTA tetrasodium salt and EDTA acid."

 

[Glow]

Some info I've saved over the years about flushing. Though I don't use it because I do not need to.


"
If you want to ensure your coco is as neutral as possible in terms of nutrients you can extract it with a 1 g/L solution of calcium nitrate and then with 2g/L of tetrasodium EDTA. This will extract both macronutrients
that are exchangeable for Calcium and micro nutrients that can be extracted when using EDTA. The EDTA step is important as coco can hold a large amount of micro nutrients within it that can be exchanged
and used by the plant. If you want your nutrients to all come from solution you will need to remove these contributions from the media. After this you will then want to run plain water to remove
any excess Ca and EDTA and then run your full strength nutrient solution for a few days. This will strip the coco from ions and then it will equilibrate the cation exchange sites with your nutrient solution's composition."


"Plant Flusher contains a mixture of these 2 ingredients: EDTA tetrasodium salt and EDTA acid."

Using EDTA (which is simply a chelator) is a horrible idea as EDTA is quite toxic and is uptaken by the plant where it remains unaltered. Also EDTA is shown to bind with heavy metals and thus if say there was cadmium in the substrate the application of EDTA could feasibly make these heavy metals available for plant uptake. Bit on this here

https://www.researchgate.net/public...toremediation_of_soil_and_composted_biosolids

 

[Glow]

BTW there is nothing really wrong with inhaling minerals such as calcium etc but heavy metals are another thing. For example, cadmium levels in the blood of cigarette smokers is shown to be about 4 times higher than non smokers.

 

[RippedTorn]

Anyone who says flushing is a myth is simply sabotaging other growers. There's no other explanation. Look at the last 6 months of TLC collective reviews and you could pin point which week Jungle Bros had problems and pulled early aka unflushed. A local producer switched from storganic coco to veg+bloom rockwool and all their customers noticed the flavor was shit. They now flush for 2 weeks and have customers again.

Unflushed bud is really obvious to most people who have smoked quality long enough. Flushing isn't pulling anything out of the plant, its keeping the plant from uptaking more, so nothing has to break down after chop, and the secondary metabolites can finish developing into their final form. Not only does unflushed weed taste bad, the effects lack depth. How hard is that to understand? It's reality. You smoke, and you experience reality. Nothing trumps reality.

Why do hydro growers say there bud is generically "harsh" until 'cured', where it becomes generically "smooth"? Chemical conversions are held back, which is why they can't describe the flavors in depth, and latent plant food still has to break down. Flushing is literally starting the cure at a time that makes more sense; on the vine.

I know I've seen calcium oxalate crystals in microscopic imagery posted to this very site, for those who need numeric and visual proof of what everyone with taste buds already knows.

 

[RippedTorn]

I don't like the idea of starving my plants in the last 10 days or so when they get on weight and make THC.

Which nutrient supports Thc production? Nitrogen? Potassium? Phosphorus? None of the above?

Most elevated thc %s from hydroponic grows are simply the reduction of other metabolites. 5% less sugars, esters, etc automatically turns 20% thc into 25% thc. Just thought I'd throw that out there before someone comes trying to defeat reality with numerics.

 

[Glow]

Anyone who says flushing is a myth is simply sabotaging other growers. There's no other explanation. Look at the last 6 months of TLC collective reviews and you could pin point which week Jungle Bros had problems and pulled early aka unflushed. A local producer switched from storganic coco to veg+bloom rockwool and all their customers noticed the flavor was shit. They now flush for 2 weeks and have customers again.

Unflushed bud is really obvious to most people who have smoked quality long enough. Flushing isn't pulling anything out of the plant, its keeping the plant from uptaking more, so nothing has to break down after chop, and the secondary metabolites can finish developing into their final form. Not only does unflushed weed taste bad, the effects lack depth. How hard is that to understand? It's reality. You smoke, and you experience reality. Nothing trumps reality.

Why do hydro growers say there bud is generically "harsh" until 'cured', where it becomes generically "smooth"? Chemical conversions are held back, which is why they can't describe the flavors in depth, and latent plant food still has to break down. Flushing is literally starting the cure at a time that makes more sense; on the vine.

I know I've seen calcium oxalate crystals in microscopic imagery posted to this very site, for those who need numeric and visual proof of what everyone with taste buds already knows.

No the myth is that you can flush nutrients (NPK etc) out of the plant once it is in the tissue. That my friend is an absolute and is scientifically proven. Definitely though flushing is imperative in hydroponically produced crops because most growers overfeed (luxury feed) and because cell division is about nil in the last two weeks you are simply wasting nutrients by supplying them to the plant anyway.

 

[Monster762]

No the myth is that you can flush nutrients (NPK etc) out of the plant once it is in the tissue. That my friend is an absolute and is scientifically proven. Definitely though flushing is imperative in hydroponically produced crops because most growers overfeed (luxury feed) and because cell division is about nil in the last two weeks you are simply wasting nutrients by supplying them to the plant anyway.

Yeah I think flush is to clean the soil so the plant can’t take up anything else there. Then goes to its reserves n eats stored nutes from leaves. So the plant itself is not flushed. It flushes itself eating the stored nutes.
but that’s where the “2 weeks flush”comes in. I usually strip the soil. Then water only n let the plant eat itself til it’s right.

Idk that’s just my take on it.

 

[Glow]

"Then goes to its reserves n eats stored nutes from leaves. So the plant itself is not flushed. It flushes itself eating the stored nutes. "

No this can't possibly happen and this also BTW has been scientifically proven in cannabis production through a recent study. That's the myth.

Synopsis of research here...

Note: "Flushing was found to be ineffective in removing any significant amount of nutrient from the bud."