Flushing debate

[Aqua Man]

For sure, my input 2 weeks out from harvest is 1.5ec, runoff will be 1.6-1.8 ec.

For my last 3 water only feedings the runoff will drop to like 1.2- 1.0 - 0.8.. So there is absolutely still nutrients in the soil. There has to be residual nutes in any media which has a CEC unless you use a flushing agent. I never actually flush all the nutrients out.

I'm in hydro completely different but that would seem high feeding to me my last week feed is about 300ppm. I use a 500ppm scale so EC would be .6

That's why I feel hydro needs no flush just feed adjustment

 

[Aqua Man]

For sure, my input 2 weeks out from harvest is 1.5ec, runoff will be 1.6-1.8 ec.

For my last 3 water only feedings the runoff will drop to like 1.2- 1.0 - 0.8.. So there is absolutely still nutrients in the soil. There has to be residual nutes in any media which has a CEC unless you use a flushing agent. I never actually flush all the nutrients out.

I think we are on the same page saying the same thing. If you are bringing your feed down to those levels by flushing I can absolutely see it being beneficial. It's not so much starving the plants as it is making sure they are not uptaking excess.

 

[MIMedGrower]

For sure, my input 2 weeks out from harvest is 1.5ec, runoff will be 1.6-1.8 ec.

For my last 3 water only feedings the runoff will drop to like 1.2- 1.0 - 0.8.. So there is absolutely still nutrients in the soil. There has to be residual nutes in any media which has a CEC unless you use a flushing agent. I never actually flush all the nutrients out.

For comparison i like to be (depending on specific plant needs) closer to 1.2 ec two weeks from harvest. And never get up to 1.8.

 

[Dirtbag]

I'm in hydro completely different but that would seem high feeding to me my last week feed is about 300ppm. I use a 500ppm scale so EC would be .6

That's why I feel hydro needs no flush just feed adjustment

I also use a feed-feed-water program with my peat based mix. 1.5ec/750 ppm is as high as I go, and usually only for weeks 2-6 of flower.

Hydro defo uses less.. When I grew coco I fed 300-400ppm with excellent results.

 

[Dirtbag]

For comparison i like to be (depending on specific plant needs) closer to 1.2 ec two weeks from harvest. And never get up to 1.8.

Yeah I never feed 1.8. Most I ever feed is about 1.5, but runoff usually comes out a couple points higher.

1.2 is a happy place too though. I have done that as well and just fed every watering instead of feed feed water. Many ways to skin a cat.

 

[Aqua Man]

I also use a feed-feed-water program with my peat based mix. 1.5ec/750 ppm is as high as I go, and usually only for weeks 2-6 of flower.

Hydro defo uses less.. When I grew coco I fed 300-400ppm with excellent results.

Lol I was just posting and had to delete since you answered it. I was going to say it's interesting how in hydro I find I need less nutes compared to you soil guys. Maybe organics? Availability? I really feel you soil guys have a big advantage on the microbes

 

[Dirtbag]

Lol I was just posting and had to delete since you answered it. I was going to say it's interesting how in hydro I find I need less nutes compared to you soil guys. Maybe organics? Availability? I really feel you soil guys have a big advantage on the microbes

Hydro uses less because of the Instant availability of every chelated nutrient in the solution. No CEC in rockwool/clay pellets so the media wont hoard nutrients either.

 

[MIMedGrower]

Lol I was just posting and had to delete since you answered it. I was going to say it's interesting how in hydro I find I need less nutes compared to you soil guys. Maybe organics? Availability? I really feel you soil guys have a big advantage on the microbes

Hydro is direct to the roots. Should be much less needed. I hear aero needs even less.

 

[MIMedGrower]

@Dirtbag beat me to it.

 

[Dirtbag]

Yup, and the roots are always in contact with a balanced nutrient, all day every day. With soil you feed it once and the plant uses up what you've added over the course of several days so you have to feed enough to get by.

 

[Migrower]

I'm curious if you were using pure blend pro for these experiments? I have a pet theory that pbp being organic has much less of a detrimental effect feeding up to the end compared to feeding a standard mineral based nutrient. In fact it might even require it.
I will say, feeding floranova right to the end was no bueno.

I’m currently using gh floranova series.+ I am curious as to what week you stop using the bloom. And do you use koolbloom dry at the end or have you tried it.?

 

[Dirtbag]

I’m currently using gh floranova series.+ I am curious as to what week you stop using the bloom. And do you use koolbloom dry at the end or have you tried it.?

I stop feeding about 10-14 days before I chop. And I have used dry koolbloom before yeah. It seems to speed up senescence a bit but have stopped using it. I prefer the finished flavour of the pot without it. Might have been my imagination but I feel the koolbloom changed the flavour a bit. This was a long time ago mind you.

 

[Jimster]

Hello farmers I have a question for you. Lately I have been seeing many growers say they don't flush their plants towards the end of harvest and say that flushing is nothing but "bro science".

I personally have always flushed and found great results but a lot of these newer growers are swearing by not flushing and claiming it doesn't do anything to better the taste / final smoke quality. I'm not of this mentality at all but would love to hear what everyone around here thinks.

I have never used a flush, but then again, I don't pour nearly as much fertilizers into the Promix medium that I use. I have great results from my base medium recipe that includes wood ashes and compost/manure, but I feed every 10-15 days on avg. At the end of the season, I cut back on the feedings and allow the plant to pull the remaining nutrients out of the soil. With my Sativa strains, the result is my fan leaves yellow and drop at the very end of flowering, sort of like trees in the fall. Flushing tries to accomplish the same general process, but it is sort of like a force flush/South Beach Diet … they get fed high doses then flush them out with water to take away any "chemical or nutrient" taste. It's a matter of preference and touch of Bro Science or Urban Legend. There is often a small grain of truth behind most legends, but most have turned into rumors. flushing, molasses, and a few other ideas might be used in some circumstances, but there are specific uses for some of these old wives tales and most make no change at all.

 

[Jimster]

Again I'm not so sure.. My buddies that run drip hydro in a big LP kept getting customer complaints about their pot not burning properly and black ash etc, and that was with 3 days of straight water at the end.
They ended up having to go with 5 days of plain water at the end to get a product that didnt draw complaints.

And they cure their buds carefully in a climate controlled curing chamber. Buds still burned black.

This is one of those interesting subjects that has Avid proponents on both sides but little real science behind it. All I can do is grow based on personal experiences. And on that I feel i get the best product by feeding (not flushing) plain water for the last 2-3 waterings.

In my experience, black ash and lousy burning is often a result of insect damage, especially white flies. The honeydew that seeps from the damaged areas contains sugars that don't burn well and leave a black ash. Perhaps some of the finishers have the same effect? I haven't seen anything that would cause a black ash unless the plant material was damaged or had something on it. Sugar turns to carbon when burned and this is probably why the lousy burn and black ash, but what would produce sugars on the plant, beyond the normal sugars found in all strains?

 

[OldManRiver]

I'm not a believer. Regardless of what some people believe their senses are telling them, it would be surprising to any biologist that flushing would have any effect. In the range of concentrations that can allow a healthy plant to exist, eg., the concentrations that good growers use and get vigorous plants with, there is no pathway out of the plant for nutrient chemicals. None. The pathways and mechanisms that transport nitrogen, phosphorus, and potassium across the root boundary are very well understood, and they work one way, in. There is not a sufficient osmotic pressure inside the plant of these chemicals to make them go out through the root boundary at the concentrations that exist. There is no transport pathway down from the buds to the roots. The nutrients are not exhaled from the leaves. A study I quoted here earlier this year, peer reviewed, measured and found that flushing had -no- measurable effect on the concentrations of nutrients in the plant, which is unsurprising to anyone who has studied cell biology. None of what believers in flushing think is happening is physically possible, or in fact happening.

Think about it from an evolutionary standpoint. Why would any plant ever want or need, in a nutrient poor world, ever evolve a mechanism to get rid of nitrogen? There is no need or benefit.

So why do we think something is going to happen that the plant didn't evolve to do? I would no more expect it to grow ears.

I have many years of practical, consumer experience to back up this belief. But that's beside the point.

 

[Dirtbag]

I'm not a believer. Regardless of what some people believe their senses are telling them, it would be surprising to any biologist that flushing would have any effect. In the range of concentrations that can allow a healthy plant to exist, eg., the concentrations that good growers use and get vigorous plants with, there is no pathway out of the plant for nutrient chemicals. None. The pathways and mechanisms that transport nitrogen, phosphorus, and potassium across the root boundary are very well understood, and they work one way, in. There is not a sufficient osmotic pressure inside the plant of these chemicals to make them go out through the root boundary at the concentrations that exist. There is no transport pathway down from the buds to the roots. The nutrients are not exhaled from the leaves. A study I quoted here earlier this year, peer reviewed, measured and found that flushing had -no- measurable effect on the concentrations of nutrients in the plant, which is unsurprising to anyone who has studied cell biology. None of what believers in flushing think is happening is physically possible, or in fact happening.

Think about it from an evolutionary standpoint. Why would any plant ever want or need, in a nutrient poor world, ever evolve a mechanism to get rid of nitrogen? There is no need or benefit.

So why do we think something is going to happen that the plant didn't evolve to do? I would no more expect it to grow ears.

I have many years of practical, consumer experience to back up this belief. But that's beside the point.

I am actually a certified horticulturist with at least some background in cell biology, albeit I specialize in turf grass and I was last in school 20 years ago, besides the odd conference. I fully agree with most of what you are saying, although technically speaking roots do actually have exudates which CAN contain ions, but that's controlled by the plant, not flushing water over the roots.
But the idea behind feeding just water the last couple weeks Isnt to remove nutrients from the plant, it's to prevent putting surplus nutrients into the plant in the first place, so as not to end up with a plant that has senesced with an over abundance of unused nutrients and minerals in it.

This can be avoided by just feeding lighter near the end and tapering back, or in my case using peat based soil mix which has a fairly strong cation exchange capacity, just feeding water the last week or two. There is enough nutrients left in the soil and plant tissues to finish. And I have experienced bad burning cannabis numerous times. In the case of my LP buddies, there is no chance it was bugs. They grow in a Lab environment with very strict IPM protocols.

Now flushing to remove excess salts from the media, not the plant is a different thing, and absolutely has its place if needed.

 

[OldManRiver]

But the idea behind feeding just water the last couple weeks Isnt to remove nutrients from the plant, it's to prevent putting surplus nutrients into the plant in the first place, so as not to end up with a plant that has senesced with an over abundance of unused nutrients and minerals in it.

Implicit in your argument is the belief that surplus nutrients can in fact exist. I think when that happens, we see symptoms. Absent any symptoms, I suspect the plant has a balance of nutrients that the entire metabolism is designed to maintain within tolerance. That's what cells do. If the cells are healthy, if the plant is healthy, then the nutrient load must be normal, and the plant is going to try to maintain that, even if we flush.

I assert that the environment that good growers foster, never has such a surplus of nutrients in the plant. If you treat weed like tomatoes and corn, which I pretty much do, it grows like crazy, and there is no more need to flush my weed than to flush my tomatoes. Have done without for many moons, with lots of input that there is no negative effect on the weed.

 

[PlumberSoCal]

Implicit in your argument is the belief that surplus nutrients can in fact exist. I think when that happens, we see symptoms. Absent any symptoms, I suspect the plant has a balance of nutrients that the entire metabolism is designed to maintain within tolerance. That's what cells do. If the cells are healthy, if the plant is healthy, then the nutrient load must be normal, and the plant is going to try to maintain that, even if we flush.

I assert that the environment that good growers foster, never has such a surplus of nutrients in the plant. If you treat weed like tomatoes and corn, which I pretty much do, it grows like crazy, and there is no more need to flush my weed than to flush my tomatoes. Have done without for many moons, with lots of input that there is no negative effect on the weed.

Growing in the ground there really is no flush possible. I don't feed the last 2 weeks, sometimes a month just water, but by then it should have everything it needs in a healthy soil. Growing in confinded conditions like a pot may be different. I don't know, I hate growing in pots, never big enough and conditions can change quickly.

 

[RippedTorn]

If you dont believe in flushing your opinion is invalid. Taste buds are real. Nutes directly affecting smell flavor AND high is real. Cows dropping dead from ferts is real. Denying that you've observed reality says nothing about reality and lots about you.

 

[PlumberSoCal]

If you dont believe in flushing your opinion is invalid. Taste buds are real. Nutes directly affecting smell flavor AND high is real. Cows dropping dead from ferts is real. Denying that you've observed reality says nothing about reality and lots about you.

Wait, if someone doesn't believe like you then there opinion is invalid??? Sounds like politics today. Trying to flush a plant in clay soil would stress the plant as its roots sat in water for days. Dumb thing to do. I'll pass and enjoy my unflushed bud just fine.