To start off I'd like to say I think that flushing to "increase thc" or benefit the plant at all besides preventing nute burn or improving taste Isnt needed. Flushing to improve taste may not even be needed with some strains or some grows depending on nutrient reserves in the plant itself.
I'd like to see some peer reviewed articles on this subject myself to clear things up for me and anyone interested, but it seems there aren't many if any at all.
I've smoked bud from the exact same crop/strain, most plants were flushed and a few were not, there was an EXTREME difference in the way the weed burned and finished. But it's all speculative and could have been just a fluke accident or other factors may have been involved.
Some of you are saying it's just plain wrong and is bad science, or people just don't understand. You say things like "flowers are not nutrient sinks" and "the plant uses the nutrients it has available"(nanogadget). If it were that easy we would never have problems growing, there would be no problems with "hot spots", or "nutrient burn" because after all a plant only takes what it needs correct? No it's not......high nutrient levels are not typical in nature, so when nutrients are encountered, all are welcome. In fact, at certain pHs, plants can uptake lethal nutrient concentrations. But this is also speculative, if you feed only what's needed (may be hard to dial in), flushing is probably not needed to improve smoke or taste.
I've read flushing causes nutrients, especially nitrogen, to be moved into the buds to support growth. So although growers aim to remove nitrogen from the buds by flushing, the plant concentrates nutrients in the buds from other places in the plant. These nutrient concentrations are less than if the plant were nourished during the flush week, but concentrating less in the plant biomass is entirely different than removing nutrients from the biomass.
You can't know exactly how much of each nutrient is optimal for every strain without testing, it's just not possible. Also claiming that saying salts build up on roots is bad science.... is just plain nonsense, or even non-science (land of the lost..lol) don't take offense please....It's plain and simple, when using synthetic nutrients in ALL VARIETIES of mediums, there can be some salt build up. Not always but sometimes. This is a known fact. IF! this becomes a problem It can be helped by flushing your medium with a decent amount of water (and even a flushing agent to help break down salts). Some people say up to 3x more than pot size I just go about the same as pot size, 5 gal water to 5 gal pot.
I also read in this thread that people are saying flushing is bad and suffocates the roots, that just sounds like plan bs to me as well, I've seen roots do just fine submerged in water for awhile and I've never even heard of a plant reacting badly to flushing (of course unless you don't understand overwatering and you do that as well). In fact I just flushed two plants with 5 gallons of water each 2 weeks into bud, they didn't even skip a beat, plenty of growth over the next few days. (They will be fed again when they dry completely)
I can provide picture proof if needed of the plants before and after, but who cares really? I don't lol. Another thing is when you burn a bowl and it leaves behind a black ash plug and doesn't burn all the way/leave white ash, I'd say either there's something left in your product that could essentially be "flushed" out before cropping, or it's just by chance that it taste like crap, pops and cracks and doesn't burn correctly, who knows really there are tons of variables.
I say if you grow some smoke that don't burn right maybe try flushing the last week to help lower nutrient concentrations, it seems like that's where people get confused is in the term itself, "flushing" isn't flushing at all, more like an intentional starving of nitrogen to lower concentrations in the biomass and then later in the buds (which have stem and leaves in them by the way) in a last attempt to improve flavor in case of high n levels.
To each his own though correct? I've smoked good bud that wasn't flushed but I've never smoked flushed bud that didn't burn correctly. I think some strains are better at keeping n levels low close to harvest than others and that causes arguments that aren't needed. The only bad thing I've ever seen from a flush is that it takes an extra week! I'm all for it though as long as I feel it makes my crop taste better.
But who knows maybe I'm wrong cause I'm just a nOOB!
Sorry for the long reply. I was bored. I'm not a scientist, I'm not trying to prove anyone wrong just speculating. Have a good day guys.
What a subject though. Both sides have good points.