A critical look at preharvest flushing

Im a fruit and vegetable grower. Fruit and vegetables are a huge industry, many peoples livelyhoods depend on and have depended on for countless generations on harvesting the best possible quality fruit and vegetables for market. I am unaware of any fruit and vegetable growers who ever have or who do currently espouse starving the plants of nutrients before harvest. If I suggested such a thing I would be laughed at and asked what I was smoking. And justifiably so. Cannabis can be argued as a fruiting or vegetable producing plant, either way it makes no difference. Flushing is just an old hippies myth, just like harvesting your crop under a full moon. If it floats your boat , do it. But dont try and pretend to any logical thinking adult that it has any science or logic to it. Ive asked the fairies who live in the bottom of my garden and they agree.
 
Foster420 said:
I don't know bout all that but, I flushed my plants yesterday morning. And woke up today to seriously fattened up buds.
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what are your EC run off levels? what week in flower are you? did you take in account flushing doesn't occur overnight? so what you say makes little logical sense, maybe you hadd issues with salt build up. since Root pressure results when solutes accumulate to a greater concentration in root xylem than other root tissues. the plants stop taking in water, this happens because most people dont get that osmosis wich is the main way plants take up water (transpiration - the movement of water through a plant, is still not really understood) but first rule of osmosis is salts never pass through a semi permeable membrane.. cold simply be you freed her from wasting ATP to take in nutrients, as plants can actually force intake against the osmosis balance and so force.
 
Captain goodvibes said:
Im a fruit and vegetable grower. Fruit and vegetables are a huge industry, many peoples livelyhoods depend on and have depended on for countless generations on harvesting the best possible quality fruit and vegetables for market. I am unaware of any fruit and vegetable growers who ever have or who do currently espouse starving the plants of nutrients before harvest. If I suggested such a thing I would be laughed at and asked what I was smoking. And justifiably so. Cannabis can be argued as a fruiting or vegetable producing plant, either way it makes no difference. Flushing is just an old hippies myth, just like harvesting your crop under a full moon. If it floats your boat , do it. But dont try and pretend to any logical thinking adult that it has any science or logic to it. Ive asked the fairies who live in the bottom of my garden and they agree.
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i asked someone with a master in biology, he also looked at me and made me repeat myself 3 times because he couldnt have understood that right, his argument is that starving her forces her to use atp to fix your mistake, atp she could use to grow or fatten up, if the smoothness comes from residual carbohydrates and sugars ten it SORT of makes sense to do it, but this is the only thing i can come up with, but then youd want to do it by hang drying id think
 
Smokin Moose said:
Pre harvest flushing is a controversial topic. Flushing is supposed to improve taste of the final bud by either giving only pure water, clearing solutions or extensive flushing for the last 7-14 days of flowering. While many growers claim a positive effect, others deny any positive influence or even suggest reduced yield and quality.

The theory of pre harvest flushing is to remove nutrients from the grow medium/root zone. A lack of nutrients creates a deficiency, forcing the plant to translocate and use up its internal nutrient compounds.

Nutrient fundamentals and uptake:

The nutrient uptake process is explained in this faq.

A good read about plant nutrition can be found here.

Until recently it was common thought that all nutrients are absorbed by plant roots as ions of mineral elements. However in newer studies more and more evidence emerged that additionally plant roots are capable of taking up complex organic molecules like amino acids directly thus bypassing the mineralization process.

The major nutrient uptake processes are:

1) Active transport mechanism into root hairs (the plant has to put energy in it, ATP driven) which is selective to some degree. This is one way the plant (being immobile) can adjust to the environment.

2) Passive transport (diffusion) through symplast to endodermis.

‘chemical’ ferted plants need to be flushed should be taken with a grain of salt. Organic and synthetic ferted plants take up mineral ions alike, probably to a different degree though. Many influences play key roles in the taste and flavor of the final bud, like the nutrition balance and strength throughout the entire life cycle of the plant, the drying and curing process and other environmental conditions.

3) Active transport mechanism of organic molecules into root hairs via endocytosis.


Here is a simplified overview of nutrient functions:

Nitrogen is needed to build chlorophyll, amino acids, and proteins. Phosphorus is necessary for photosynthesis and other growth processes. Potassium is utilized to form sugar and starch and to activate enzymes. Magnesium also plays a role in activating enzymes and is part of chlorophyll. Calcium is used during cell growth and division and is part of the cell wall. Sulfur is part of amino acids and proteins.

Plants also require trace elements, which include boron, chlorine, copper, iron, manganese, sodium, zinc, molybdenum, nickel, cobalt, and silicon.

Copper, iron, and manganese are used in photosynthesis. Molybdenum, nickel, and cobalt are necessary for the movement of nitrogen in the plant. Boron is important for reproduction, while chlorine stimulates root growth and development. Sodium benefits the movement of water within the plant and zinc is neeeded for enzymes and used in auxins (organic plant hormones). Finally, silicon helps to build tough cell walls for better heat and drought tolerance.


You can get an idea from this how closely all the essential elements are involved in the many metabolic processes within the plant, often relying on each other.

Nutrient movement and mobility inside the plant:

Besides endocytosis, there are two major pathways inside the plant, the xylem and the phloem. When water and minerals are absorbed by plant roots, these substances must be transported up to the plant's stems and leaves for photosynthesis and further metabolic processes. This upward transport happens in the xylem. While the xylem is able to transport organic compounds, the phloem is much more adapted to do so.

The organic compounds thus originating in the leaves have to be moved throughout the plant, upwards and downwards, to where they are needed. This transport happens in the phloem. Compounds that are moving through the phloem are mostly:
Sugars as sugary saps, organic nitrogen compounds (amino acids and amides, ureides and legumes), hormones and proteins.

Not all nutrient compounds are moveable within the plant.

1) N, P, K, Mg and S are considered mobile: they can move up and down the plant in both xylem and phloem.
Deficiency appears on old leaves first.

2) Ca, Fe, Zn, Mo, B, Cu, Mn are considered immobile: they only move up the plant in the xylem.
Deficiency appears on new leaves first.

Storage organelles:
Salts and organic metabolites can be stored in storage organelles. The most important storage organelle is the vacuole, which can contribute up to 90% of the cell volume. The majority of compounds found in the vacuole are sugars, polysaccharides, organic acids and proteins though.

Translocation:
Now that the basics are explained, we can take a look at the translocation process. It should be already clear that only mobile elements can be translocated through the phloem. Immobile elements cant be translocated and are not more available to the plant for further metabolic processes and new plant growth.

Since flushing (in theory) induces a nutrient deficiency in the rootzone, the translocation process aids in the plants survival. Translocation is transportation of assimilates through the phloem from source (a net exporter of assimilate) to sink (a net importer of assimilate). Sources are mostly mature fan leaves and sinks are mostly apical meristems, lateral meristem, fruit, seed and developing leaves etc.

You can see this by the yellowing and later dying of the mature fan leaves from the second day on after flushing started. Developing leaves, bud leaves and calyxes don’t serve as sources, they are sinks. Changes in those plant parts are due to the deficient immobile elements which start to indicate on new growth first.

Unfortunately, several metabolic processes are unable to take place anymore since other elements needed are no longer available (the immobile ones). This includes processes where nitrogen and phosphorus, which have likely the most impact on taste, are involved.

For example nitrogen: usually plants use nitrogen to form plant proteins. Enzyme systems rapidly reduce nitrate-N (NO3-) to compounds that are used to build amino-nitrogen which is the basis for amino acids. Amino acids are building blocks for proteins, most of them are plant enzymes responsible for all the chemical changes important for plant growth.

Sulfur and calcium among others have major roles in production and activating of proteins, thereby decreasing nitrate within the plant. Excess nitrate within the plant may result from unbalanced nutrition rather than an excess of nitrogen.
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first off let me say that plants, are not like animals, that follow a certain sets of rules we understaand. like cellular resipration or ketosis etc etc but plants are still quite a mystery

no plant keeps a SINK. secondly, half of this info is semi correct. calcium is actually most important for nitrogen uptake. the truth of how plants uptake nutrients aren't known, we assume its due to water tension cohesin drawing water through and the nutirents must be ions or they won't pass the cell wall. also plants cannibalism the leaves that have the lowest photosynthetic efficiency first, IE the closest to a sink. older leaves. plants also can simply use active transport of which they have 2 different variations. every time you force a plant to use active transport your slowly her down.


so basically what im trying to say is, the mechanism's involved here are not as well understood as you seem to think., . we know of alot of cool things plants do, like their roots have all the photoreceptors as the leaves but not the photosynthetic ones. means roots see light. took HPA to work this out. also why are nutrients suddnely more available when provided in a super fine mist? like 5x sometimes. oh also plants can have anywhere from 1-8 chromosome pairs. we dont truly understand them at all. or the mechanisms that they use to achieve their results. like, no one has beyond a shadow of a doubt explained how a plant can draw water up as high as a giant redwood when you account for gravity, the maths says it's impossible. but then against, a plant only uses about 5% of the water it draws n, the other 95% are used (we thgink) to draw up more water against gravity)

plants vary greatly, theres some great research being done now but its all secret and aimed at reducing costs mostly.
 
Captain goodvibes said:
Im a fruit and vegetable grower. Fruit and vegetables are a huge industry, many peoples livelyhoods depend on and have depended on for countless generations on harvesting the best possible quality fruit and vegetables for market. I am unaware of any fruit and vegetable growers who ever have or who do currently espouse starving the plants of nutrients before harvest. If I suggested such a thing I would be laughed at and asked what I was smoking. And justifiably so. Cannabis can be argued as a fruiting or vegetable producing plant, either way it makes no difference. Flushing is just an old hippies myth, just like harvesting your crop under a full moon. If it floats your boat , do it. But dont try and pretend to any logical thinking adult that it has any science or logic to it. Ive asked the fairies who live in the bottom of my garden and they agree.
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You're a shitty fruit and vegatable grower then.

You internet dumbasses are an embarrassment to Cannabis. It is well known amongst the industry that elevated NPK levels ate detrimental to oil content, sugar content and overall shelf life of nearly all crops.

Every one of these pathetic forums is stupider than the last. The internet cults of sub-schwagg growing. Enjoy your 1500ppm trash you left wing morans.
 
You arent a very good weed grower if you are giving elevated NPK to your plants while they are flowering. Which was not my claim anyway. And the abuse is unneccassary and childish.
 
DirtBro said:
You're a shitty fruit and vegatable grower then.

You internet dumbasses are an embarrassment to Cannabis. It is well known amongst the industry that elevated NPK levels ate detrimental to oil content, sugar content and overall shelf life of nearly all crops.

Every one of these pathetic forums is stupider than the last. The internet cults of sub-schwagg growing. Enjoy your 1500ppm trash you left wing morans.
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You are a shitty person.... Infinity! I win!!!!!!
 
DirtBro said:
You're a shitty fruit and vegatable grower then.

You internet dumbasses are an embarrassment to Cannabis. It is well known amongst the industry that elevated NPK levels ate detrimental to oil content, sugar content and overall shelf life of nearly all crops.

Every one of these pathetic forums is stupider than the last. The internet cults of sub-schwagg growing. Enjoy your 1500ppm trash you left wing morans.
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Oh wow
I really don't like you BUDDY
I feel I want to punch you after that comment, I'm guessing your board and fell like picking on a small person
Well I'm a big brother and I feel I need to protect my crew from insects like you
So
We all cant be keyboard warrior's like you and know everything about cannabis, and be absolutely full of s#@t
We are hear to learn from each other

And instead of making negative comments, why not share your knowledge and help others
That's why we are here to ask questions and learn
Anyway have fun trolling people looking for help
 
I probably brought this on , i was a bit of a smart arse with my post and Dirt Bro might have been having a bad day. So yes, I agree, lets just relax. We can agree to disagree.
 
Firestone said:
If you can find a mid-70's copy of Ed Rosenthal's Marijuana Growers Guide,there are a couple of nice detailed methods laid out on how to dry leaf vs. bud. That book was worth it's weight in gold when it came out.

Well cured leaf can be a joy to smoke in a joint or bowl and you're not on the couch for the day afterwards. It's nice buzz for bs'ing and goofing around.

IMO,using food dehydrators as a drying method causes a lot of the harshness in today's weed. It retains a powerful buzz,but who wants to smoke something that uses a drying method that leaves the final product tasting like two day old hay?
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i think another grower named jorge cervantes may have covered it in his videos and books
 
Maybe to flush or not to flush has a lot to do with the method of growing; soil, coco, hydro, and the different types nutrients being used? Either way, I think it's personal choice, and there's no need to get so deep into it.

My experience has been to flush. I am a hydro grower and I use salts. My last crop, I did not get the chance to flush, The high is much cleaner now, tastes o.k., however,it won't stay lit, even though it's been dried and cured for over 6 months. I am about to do a 10-14 day flush..... on this crop.
 
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