Flushing your plants: what does it do?

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sticky is as sticky does
Okay, first let me clarify that what they mean by "flushing" in this article is, running water through your substrate until it has almost zero EC. So, REALLY flushing the soil of nutrients, to the greatest degree possible.

I don't do that! I know some people do, but it has always seemed excessive to me. What I do (and I think, what many others do), is simply STOP FEEDING. I do this about a week to ten days before harvest. I figure the substrate has enough accumulated nutrients, and adding more would be wasteful.

That said, the results detailed in this article are interesting and helpful. The bottom line is, flushing can be beneficial, but overdoing it results in reduced flower yields with less active ingredients.

https://www.cannabisbusinesstimes.com/article/cannabis-cultivation-flushing-research-yield/
 
Yes, Shov, I agree about that (over-abundance of nutes in the soil). That's why over the years I have used lighter feeds. I probably feed about 50% or less of what I once did. I am happy with the outcome.
 
I grow in coco. When I flush the plants at the end of flower, I flush the substrate until I get zero ppm runoff. Then I give plain water til harvest. Good or bad, I like the end result: clean smooth smoke, the ash is white, no Chem taste at all
 
The article was a bit disappointing to me...3 Phd's that seem to be focused on $$$, not quality. :(

What is it Uncle Ben always said?...flushing is for toilets. :p
His philosophy was that if you only give plants what they need, rather than what you want them to have, then "flushing" is unnecessary. The overall mantra of cannabis growers often seems to be...cram 'em full of every nutrient under the sun, to maximize yield. Problem is, what good is yield, if your product is crap? I took to heart the idea of only providing the plant with what it needs.

Some basic constructs I based my "flushing" around...
- For the most part, organic soils can not be "flushed", because the nutrient components of the soil are too large to be "flushed" out...so take great care in the amount of amendments added to the soil, so that it does not end up being too hot.
- Definition of "flushing". Too bad the world couldn't come to a consensus on this. My personal view is that "flushing" is what you do to remove excess salts from the substrate...and that eliminating nutrients from watering at the end of flower, is just that.
- Just because a plant might show signs of deficiency doesn't necessarily mean the substrate is deficient. Rather it is often lock-out caused by having added too much nutrients. The nutrients are there, but the plant is unable to access them.
- Just because you put it into the substrate doesn't mean the plant wants it. The plant will take up the elements it wants, and leave the rest behind. Over time, those salts left behind can build up and become problematic for the plant's ability to access what it wants.

All that being considered, what I found that worked best for me was to "flush" the substrate when putting plants into flower, and then again half way through flowering. This removed any excess salts from the medium, so that they would not become problematic later. Once I learned a strain's nutrient requirements, this became less necessary. At the end of that "flushing" process, I would water with a half strength mix so that the soil was not completely devoid of nutrients.

Then at the end of flowering, I would stop adding nutrients anywhere from one to two weeks, depending on how long the strain took to flower. For a 7 week indica, 7 days...for a 12+ week sativa, 14 days...for most 8 to 10 week hybrids, 10 days. This was not only for the plant to use up what's in the substrate, but what's already in the plant as well...because the goal is to not have any excess levels in the plant when you harvest. Done right, you get the smoothest smoking, cleanest burning outcome.

But that's just my opinion...everyone has to come to their own conclusions aboot what works best for them. :)
 
I play it by ears. Used to grow all organic and sometimes felt mix was still hot so I'd water well and often at the end. Other times just let them run dry.
have been using AN in the closet at less than recommended values and do not bother with their flush formula. Water only last week or two.
 
As a cabinet grower...there are two kinds of watering for me.
Top off watering where I try to water without having any drain out the bottom, and full watering which I do every few times where I pull the plant out of the cabinet into the bathtub to fully soak it with drainage.

This dynamic effects how much if any I need to flush at the end

If I went through a grow and every time watered until a good amount came out I wouldn't need to flush at all.
If I went through a whole grow just topping off the pot and never having a good amount drain out the bottom then I would likely need to for a few weeks.
 
The right answer is a very in depth explanation that I will give in my grow thread when I start it and give all the scientific evidence behind Fungal Repositories.
The short answer is this; flushing only takes nutrients out of your substrates. The synthetic fertilizers/chemicals don't flush out of the plant itself. Chemotherapy doesn't flush out of human or plant tissue...period.

I have spent the last 9 seasons developing and refining Fungal Repositories. It's a very simple technique that allows the plant it's optimal nutrients, health, pest resistance while helping greatly resistance to heat stresses.

My goal is to show natural plants grown to the utopia of they're needs will out perform any synthetic grown plants in cost, quality and quantity. I say this from the point of view from a medical grower. I haven't run my system on a corporate commercial level yet.

I may never grow on that scale, I do want all growers to know how to have STEROID results without the STEROIDS!
Peace farmerlion
 
As long as the plant is not overfed there really shouldn’t be any nutrient (or much) left in a substrate like coco (which I use) so flushing is not really necessary in the sense of using lots of water to saturate the substrate and flush all the remaining nutrients from it. I find that by feeding plain water it “flushes” the plant of nutrient by starving the roots and making it consume what is available to plant in the plant allowing it to fade and give harvest/fall colors and a cleaner more enjoyable smoke.
 
True Canna Genetics said:
As long as the plant is not overfed there really shouldn’t be any nutrient (or much) left in a substrate like coco (which I use) so flushing is not really necessary in the sense of using lots of water to saturate the substrate and flush all the remaining nutrients from it. I find that by feeding plain water it “flushes” the plant of nutrient by starving the roots and making it consume what is available to plant in the plant allowing it to fade and give harvest/fall colors and a cleaner more enjoyable smoke.
Click to expand...

That's how I learned as well. I worked at a 25yo co-op and they would not take any product unless it had a 3 week "flush". (Flush the way True Canna described it, as watering only plain water for the last 3 weeks of the plants life.)

...Some people might call me crazy for that, but it's tried and true imo.

I have seen research papers that say flushing doesn't make a difference, but in a blind smoke test imo you can tell.
 
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