Flush or not to Flush?

Oh Canada!

Oh Canada!

Well-Known Member
I've been growing since legalization in Canada Feb 18 2018.
I was always under the impression that flushing was necessary. People have recently been telling me not to flush and keep feeding the entire way to harvest.
I have heard not flushing would reslut in the weed not burning properly producing black ash. Im sure there are many other reasons to flush but is there any reason not to flush?
 
curious2garden

curious2garden

Well-Known Mod
Staff member
The biggest reason not to flush is because it's for the substrate not the plant. The roots are a semi-permeable membrane that essentially allows one way nutrient flow. So once it's in the plant you are merely starving the plant at the time the plant is doing it's final bulk. It does nothing for you but reduce your yield.

As for burning nicely that's what the longer, slower dry phase is for. The plant continues to metabolize the chlorophyll and other molecules out of the plant. This is known from studies on Burley Tobacco.

If you're in hydro or feeding a salt based nutrient then it's wise to give your substrate a good rinse thereby reducing retained salts and reducing chance of burning your plant. Especially if you're like me and not all that careful about feed amounts. That is what flushing is for, correcting your substrate, not your plant.
I hope that helps, best of luck on your grow.
 
shnkrmn

shnkrmn

Well-Known Member
Oh Canada! said:
I've been growing since legalization in Canada Feb 18 2018.
I was always under the impression that flushing was necessary. People have recently been telling me not to flush and keep feeding the entire way to harvest.
I have heard not flushing would reslut in the weed not burning properly producing black ash. Im sure there are many other reasons to flush but is there any reason not to flush?
Click to expand...
Just ask yourself what other agricultural practice involves a ripening stage that includes depriving the plants of essential nutrients. I don't flush ripening tomatoes before I pick them, for example. Cannabis is nothing special, just another plant.
 
PopAndSonGrows

PopAndSonGrows

Well-Known Member
I'm a coco grower & I actually went back to doing a 3 to 5-day flush prior to harvest, but mostly just for my own peace of mind, and it saves me a few days of using nutrients. Another thing, I skip the last day of watering at all, just before harvest, so that the pots are much lighter and easier to move.

I don't necessarily recommend a flush, BUT, I do advise a tapering-down of nutrients toward the end of flower.
 
Oh Canada!

Oh Canada!

Well-Known Member
curious2garden said:
The biggest reason not to flush is because it's for the substrate not the plant. The roots are a semi-permeable membrane that essentially allows one way nutrient flow. So once it's in the plant you are merely starving the plant at the time the plant is doing it's final bulk. It does nothing for you but reduce your yield.

As for burning nicely that's what the longer, slower dry phase is for. The plant continues to metabolize the chlorophyll and other molecules out of the plant. This is known from studies on Burley Tobacco.

If you're in hydro or feeding a salt based nutrient then it's wise to give your substrate a good rinse thereby reducing retained salts and reducing chance of burning your plant. Especially if you're like me and not all that careful about feed amounts. That is what flushing is for, correcting your substrate, not your plant.
I hope that helps, best of luck on your grow.
Click to expand...
Really informative, thanks
 
MadBret

MadBret

Member
shnkrmn said:
Just ask yourself what other agricultural practice involves a ripening stage that includes depriving the plants of essential nutrients. I don't flush ripening tomatoes before I pick them, for example. Cannabis is nothing special, just another plant.
Click to expand...
Vegetables that we eat should be chocked full of nutrients. But we don't smoke tomatoes. I don't think flushing at the end is a bad practice, personally but to each there own. If you can grow smooth smoking weed with a nice white ash without flushing, more power to you. I'm now curious if tobacco crops are fed all the way to the end. Hmmm...
 
curious2garden

curious2garden

Well-Known Mod
Staff member
MadBret said:
Vegetables that we eat should be chocked full of nutrients. But we don't smoke tomatoes. I don't think flushing at the end is a bad practice, personally but to each there own. If you can grow smooth smoking weed with a nice white ash without flushing, more power to you. I'm now curious if tobacco crops are fed all the way to the end. Hmmm...
Click to expand...
Tell me how you flush plants in soil? They are much akin to tomatoes also grown in soil, nutrients aren't your enemy, retained chlorophyll is.
 
shnkrmn

shnkrmn

Well-Known Member
MadBret said:
Vegetables that we eat should be chocked full of nutrients. But we don't smoke tomatoes. I don't think flushing at the end is a bad practice, personally but to each there own. If you can grow smooth smoking weed with a nice white ash without flushing, more power to you. I'm now curious if tobacco crops are fed all the way to the end. Hmmm...
Click to expand...
Let us know what you discover. The increase and diffusion of knowledge is what we are here for.
 
MadBret

MadBret

Member
curious2garden said:
Tell me how you flush plants in soil? They are much akin to tomatoes also grown in soil, nutrients aren't your enemy, retained chlorophyll is.
Click to expand...
I've always just flushed for a week or two with plain water. Probably not ideal but my smoke burns clean and smokes smooth. The fact that I use smaller buckets than most folks to grow outdoor led me to believe that the flush was easier to accomplish than if I was in the ground or using huge containers. I also have used about 1/4 strength nutrients in the past to flush when I had a lockout problem. I believe that was a recommendation from gh, though it's been quite a while since I've used their products.
 
PopAndSonGrows

PopAndSonGrows

Well-Known Member
shnkrmn said:
Just ask yourself what other agricultural practice involves a ripening stage that includes depriving the plants of essential nutrients. I don't flush ripening tomatoes before I pick them, for example. Cannabis is nothing special, just another plant.
Click to expand...
I somewhat disagree. ALL plants are special and, if you want the absolute best quality product, you can't treat your weed like potatoes or tomatoes. Would you feed your cat dog food? --they're both animals/pets, why not? (in a pinch, I've actually done that, lol!!) But, i do agree that flushing isn't done anywhere agriculturally, so although cannabis may be special, it ain't THAT special, lol. Tobacco doesn't get flushed (one could argue tobacco isn't flower matter though).
 
curious2garden

curious2garden

Well-Known Mod
Staff member
MadBret said:
I've always just flushed for a week or two with plain water. Probably not ideal but my smoke burns clean and smokes smooth. The fact that I use smaller buckets than most folks to grow outdoor led me to believe that the flush was easier to accomplish than if I was in the ground or using huge containers. I also have used about 1/4 strength nutrients in the past to flush when I had a lockout problem. I believe that was a recommendation from gh, though it's been quite a while since I've used their products.
Click to expand...
I've used GH since 1996 and I've never seen that recommendation. Anyway they are your plants and if you like the results you get flushing you should flush. We all pay to play so do it how you want to. There are a million ways to skin a cat and they end up just as skinned :) So whatever way you do it, just drop that seed and grow it!

PopAndSonGrows said:
I somewhat disagree. ALL plants are special and, if you want the absolute best quality product, you can't treat your weed like potatoes or tomatoes. Would you feed your cat dog food? --they're both animals/pets, why not? (in a pinch, I've actually done that, lol!!) But, i do agree that flushing isn't done anywhere agriculturally, so although cannabis may be special, it ain't THAT special, lol. Tobacco doesn't get flushed (one could argue tobacco isn't flower matter though).
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I think you could make an argument about parallels being closer akin to tobacco in terms of harvesting not growing. But honestly I don't think it matters. If they are your plants do what you want. I was just sharing my answer to the the OP's question, "...but is there any reason not to flush?" and my logic. But I'm great with anyone doing as they wish.

The only time I expect to have a say is if I subsidize your grow. Then some expectations of shared control is reasonable. Otherwise, do as you will as it harm none; smoke pot and enjoy your life.
 
shnkrmn

shnkrmn

Well-Known Member
One point about tobacco to remember is after it is ripened and harvested it is dried slowly in dark, ventilated barns, i.e. cured. It's a big part of the classic sales pitch: Never a bite in a bowl, I protect my voice with Luckies, Craven A, for your throats sake. It had to be pure Virginia tobacco though, lol. Don't get me started on Turkish tobacco, I may never quit! LOL. It all burns with a pure grey white ash whatever country it's from. I used to buy Pak cigs to mix with hash, Wills were preferred because K2 had lumber in it lol.
 
Relaxed

Relaxed

Well-Known Member
I use organic. usually last nut added couple weeks from chop. Water a few times normal without nuts before chop has always ended well. flush as in drownding them with water flush like if you nut burned a plant-no Id never recommend. IF not organic get other recommends. good luck
 
Thundercat

Thundercat

Well-Known Member
Been a while since I shared in one of these threads so I figured I would.

Until the last few years flushing always referred to "running large amounts (3x the container volume was often recommended) through your medium to remove nutrients, some people even suggested doing it multiple times. That is still the definition when talking about fixing a nutrient issue or salt buildup. However in the last 5ish, maybe 7 years some people have tried to change the definition to avoid flushing debates, or because as they learned the science and realized that pouring massive amounts of water through your medium wasn't helpful but they still had to justify their cognitive dissonance. Flushing is not the same as watering with plain water or watering with lighter nutrients.

Since I typed this all out already I might as well make my stance clear on the subject. I've done multiple side-by-sides with clones in the same environment where flushing was the only difference. I've mostly grown in hydro, but have done some soil runs as well, and I have grown well over a thousand plants at this point of many different genetics. I understand the process of how plants uptake and USE nutrients to grow. I don't flush plants at harvest, it's pointless. There have also been material analysis tests done that prove there is no significant difference in the molecular make up of flushed plants vs unflushed plants.

Flushing is only used for correcting a severe nutrient issue in the medium. Flushing a plant can absolutely damage the root system and stress the plant delaying growth so it should only be done if really necessary.

Tapering feed down at the end and watering according to the plants needs won't hurt anything at all, and promotes a healthy plant all the way to harvest. Using only water the actual last week or 2 won't hurt, but that's not flushing that's just called watering. The other issue is many many many growers(even experienced ones) don't seem to understand when the plant is actually in those last 2 weeks. In which case if you cut out nutrients too early you will loose out on something in the end, either yield or quality depending on the situation.

Grow your garden however you want to, its your garden :). But the best buds come from healthy plants that are grown until they are fully ripe and then dried properly to ensure a quality smoke.
 
Oh Canada!

Oh Canada!

Well-Known Member
Thundercat said:
Been a while since I shared in one of these threads so I figured I would.

Until the last few years flushing always referred to "running large amounts (3x the container volume was often recommended) through your medium to remove nutrients, some people even suggested doing it multiple times. That is still the definition when talking about fixing a nutrient issue or salt buildup. However in the last 5ish, maybe 7 years some people have tried to change the definition to avoid flushing debates, or because as they learned the science and realized that pouring massive amounts of water through your medium wasn't helpful but they still had to justify their cognitive dissonance. Flushing is not the same as watering with plain water or watering with lighter nutrients.

Since I typed this all out already I might as well make my stance clear on the subject. I've done multiple side-by-sides with clones in the same environment where flushing was the only difference. I've mostly grown in hydro, but have done some soil runs as well, and I have grown well over a thousand plants at this point of many different genetics. I understand the process of how plants uptake and USE nutrients to grow. I don't flush plants at harvest, it's pointless. There have also been material analysis tests done that prove there is no significant difference in the molecular make up of flushed plants vs unflushed plants.

Flushing is only used for correcting a severe nutrient issue in the medium. Flushing a plant can absolutely damage the root system and stress the plant delaying growth so it should only be done if really necessary.

Tapering feed down at the end and watering according to the plants needs won't hurt anything at all, and promotes a healthy plant all the way to harvest. Using only water the actual last week or 2 won't hurt, but that's not flushing that's just called watering. The other issue is many many many growers(even experienced ones) don't seem to understand when the plant is actually in those last 2 weeks. In which case if you cut out nutrients too early you will loose out on something in the end, either yield or quality depending on the situation.

Grow your garden however you want to, its your garden :). But the best buds come from healthy plants that are grown until they are fully ripe and then dried properly to ensure a quality smoke.
Click to expand...
Amazing thankyou for that detailed explanation. I will continue as is going forward.
 
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