So you grow your plants „like everybody else does”... by planting them in soil, and then pouring shitloads of fertilisers, so you can flush them out when the time comes. But have you ever thought, that what you're doing is absolutely crazy? Well, it is for reasons that are plenty!
It's hard to say when „flushing is necesssary for the smoothest bud” thing came about, but it definitely rose in popularity with indoor/hydro boom of the early 90s, when warehouse operations around the world started churning out tonnes of middling quality bud, while outdoor operations came to a halt (well, not really, but they were diminished).
The thing is, that hydro and soil growing are two very different animals, and they have very little in common, so using hydro methods in soil is like crossbreeding an elephant and an eagle. No way it'll work! EVER!
Another problem is, that cannabis growers can't even agree on what flushing is, and how it works! So let's check the looney bin to see if we can find any logic or anything that is based on indisputable facts for that matter.
First version of flushing that you usually bump on when browsing through different threads is that flushing is giving pure water for 2-3 last weeks of flowering, which gives you a smoother bud. Now what is smooth for one smoker is totally unacceptable for another one, and comes down to one thing: the palate!
Logically, effects of this type of flushing, can only be assessed by the smoker with his subjective take. There's no scientific way to settle if it gives a really smooth smoke or not!
However, the problems with this practice remain, and they have much more to do with theory behind it or lack thereof. First of all, flushing in the world of cannabis growing has nothing in common with what flushing really is, which is defined in Soil Remediation and Plants as:
An in situ chemical method of soil remediation. It involves the extraction of heavy metals via a fluid injected into the contaminated soil. The extraction fluid is pumped to the surface, which brings along the absorbed contaminants with itself.
The extraction fluid is made by the liquefaction of various gases such as propane, carbon dioxide and butane. Soil flushing works on all types of soil pollutants, usually in combination with other techniques.
As confronted with this definition, cannabis growers rarely use proper flushing, cause they really don't need to, so when they use the term they WRONGLY DEFINE a process of simple watering... which is what we do with every other plant on this planet! There's nothing mystical about it, and you obviously can't go wrong with giving pure water.
What is really mind-boggling is that, when growers talk about watering – as no flushing is really involved here – they also go out on a limb claiming pure water forces the plant to use leftover nutrients in soil, so they purge or cleanse, and some go completely trippin' by saying that plants „sweat” the nutrients or put them back in soil!
Now that's like saying you can dodge gravity and start flying by only eating bread with peanut butter for two weeks... there's no consequence in this chain of thought as false presumption is muddling the water.
To be exact, expecting different effects from the same practice – watering – in different stages of plant's growth, that NEVER changes its basic biochemical functions, is a double fallacy! It also goes 100% against botanical knowledge, that we've acquired for the last 300 years, and it ignores absolutely everything we know about plants' metabolism.
And though cannabis is undoubtedly a unique and fascinating plant, IT IS STILL JUST A PLANT, SO EVERYTHING THAT APPLIES TO ALL THE OTHER PLANTS ALSO APPLIES TO CANNABIS!
One of these things that we know FOR CERTAIN – and you may accept it or not, but you really SHOULD – is that plants release ONLY products of photosynthesis during their life cycle. These are oxygen, exudates, which are carbon molecules used to feed beneficial bacteria and fungi, and volatile compounds (terpenoids, flavonoids).
THE FACT IS, that once nutrients uptaken by the roots have been absorbed by xylem/phloem, and got sent to various parts of the plant, or integrated into complex, biochemical pathways, they'll never be released back during plant's life. And the only way of putting them back in soil is to compost the whole plant, which is how cycle of nutrients works in nature!
So it begs to highlight, that NO MATTER HOW MUCH WATER YOU GIVE, THERE'S NO WAY FOR THE PLANT TO GO IN REVERSE! NO FUCKIN' WAY! NUTRIENTS STAY IN BUDS, LEAVES, STEMS AND ROOTS TILL THE PLANT IS ALIVE! GET OVER IT!
Some growers fortunately possess minimum of botanical knowledge, and they know they shouldn't expect magic, where magic won't work. However with „purging myth” comes another one pervading every discussion about „flushing”. It's removing salt buildup in soil with water.
The obvious question that we should pose to ourselves here is, why do we use so much salts, that we need to flush them out? Wouldn't it be just easier to use fewer, so we don't have to flush (Occam's razor comes to help)? Well, that's what organic growers do indeed. They use very few salts in their grow – FYI: there are also organic salts – so they rarely have any problems, and they never flush.
But let's address the plants, that are on mad feeding schedules with synthetic nutrients added almost on a daily basis. Is there gonna be a salt buildup? Most definitely we'll see it eventually as potash, phosphate and ammonia salts (ammonium chloride, ammonium sulfate) – so much abused by commercial growers – will start taking over the soil.
The problem is that even when we try to leach them by using rapid stream of water, which is another way cannabis growers define flushing (I know people using flushing tables for this reason), most of them will stick to soil particles or rather peat particles due to their high CEC! And sphagnum peat is the medium, which cannabis growers use as their staple!
Unfortunately for the growers, the only nutrients, that can be easily flushed away with water are mobile, anionic ones: nitrates and sulphur. And they are both crucial for cannabis in all stages of development, which is why growers, who leach nutes, often get heavy deficiencies in late flowering! Another myth, that automatically comes with it as a bias reinforcement, is that they're necessary!
Cations, which have postive charge, don't easily flow away with percolating water, except if percentage of soluble ones is higher than CEC, which leads to unlatching of weakly binding ones and being carried them down the stream of water, which has a neutral charge, so it takes both cations and anions.
Unfortunately again, potash and phosphate salts are very strongly binding ones, so those that escape fastest are cations of calcium and magnesium, which frequently lose competiton with abovementioned, especially when base saturation is low.
Sadly, both calcium and magnesium are central to quality of cannabis (terpene and THC production) and to final yield (they raise specific gravity), which means by trying to leach salts you not only get nothing in return, but you lower your potential yield, destroy microlife and put your plants in a state of shock!
And here we finally get to the right question, is there a way out of this? Yes, you can go organic, start working with low concentration of nutrients, weak salts, building your soil microlife, caring more about your plants' health, and you'll never have to flush again in your life! I personally never did!
There's really no other way to achieve high quality, nutrient dense or #higbrix cannabis, which I wish everybody was able to compare their current produce too! But if you wanna keep flushing, it's your choice... I'm not here to force you to do anything.
My only wish is that even if you wanna follow the flock and stick to flushing, you get a better understanding of how soil works, and stop spreading inaccurate or outrightly deranged info, that makes a circus out of cannabis growing.
Photo credits (from the top): Sunset Sherbet grown by Purple Gun Rack, Slurricane grown by Care Staker, Platinum Gorilla grown by Stage, Acapulco Gold nugs grown by Curly Beaver. All pics courtesy of 420magazine
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