Should flushing be done?
- Thread starter validnasi
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Fuzzy Duck
Well-Known Member
Flushing at what stage of growth & for what reason ?
Emilya Green
Well-Known Member
If salt and nutes have built up in your soil to the point that you are seeing deficiencies and lockouts, a 3x the container size flush can oftentimes fix the problem. If you have used strong nutes all through a grow, a 3x flush around week 6, as you are going into final bud swell, can help clear the soil so that the buds can have full uptake of water and finishing nutes, right up to the end of the grow.
If you are referring to the process of starving your plants at the end, giving them nothing but water for a week or two, as a flush... you are misusing the term. This starvation diet is how people grew pot in the 70's, because they didn't know any better. Now we know there is no rational reason for starving the plants at the point in the grow where they need more nutes than any other time.
If you are referring to the process of starving your plants at the end, giving them nothing but water for a week or two, as a flush... you are misusing the term. This starvation diet is how people grew pot in the 70's, because they didn't know any better. Now we know there is no rational reason for starving the plants at the point in the grow where they need more nutes than any other time.
Flushing when using salt based nutrients is essential to prevent lock out from the medium being salt filled.Flushing before harvest is personal choice.Science now shows that flushing plants just before harvest only stunts growth and does not remove anything from the plant or buds.Cannabis is an accumulator which means what ever it takes up stays in the plant and cannot be flushed out.
Emilya Green
Well-Known Member
I want to clarify this "stunting the plant" thing, because it is confusing people to think that flushes cause stunting. They do not, a flush is simply a very complete watering. At the end however, when the plant is finishing out the buds, every day that they can get more nutes into that bud to help it finish out is important, vital even... but we still follow the water/nutes/water/nutes pattern right up to the end. The reason we do this is so that on the nute pass we give full strength nutes, of which only about half of it is able to be taken up into the plant. We follow that with a pH adjusted water pass, so that we reactivate the nutes left over on the first pass, so that they can now be lifted up into the plant. If instead, we flushed to wash out those extra nutes, we would leave the plant at the most critical time, with no nutes in the system, and for that cycle, the plant needs to go on cruise control (stunting) until the next nute pass. Is it a stunting you could see or measure? no. But it is a 1-3 day period where you could have supplied nutes for extra growth, but didn't. Ok sure, stunting it is.... but immeasurable it also is.
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- #6
sorry just to clarify, i'm talking flush before harvest
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- #7
how do you spot salt build up.
also, i've been meaning to reuse soil as it's quite expensive here. payed 30 euro for a bag of terra canna professional. quite a bit when everything starts to add up.
should the soil be flushed before being reused? if so, how?
any other tips to reuse soil? or just clean it and throw it in the pot?
Emilya Green
Well-Known Member
you can't always visually "spot" a salt buildup. What you can see is what the plants are doing and learn to read deficiencies and lockouts so that you can recognize when there is a problem. If suddenly without explanation problems arise, when there has been no changes in feeding that had been working fine, a lot of times that indicates a buildup of something in the soil, usually salt.
I am a big fan of reusing soil... I got about 7 years out of my last batch that now is starting to wear out. If you regularly flush the debris out of your soil, including some of the organics that break down and turn the soil acidic (which is probably what I need to do myself) you should be able to use a good soil for years. I like the FoxFarm Ocean Forest as a good base soil because of its large sized organics that take a long long time to break down. It probably is a good idea to flush the soil before reusing it by running 3x the container size through it. I think I will do this before trying to pack it down into a container so that the initial flush doesn't super compact the soil for a new plant to have to break through. These are good points to consider... thank you for taking me here.
In soil flushing wont get rid if what everyone is saying it does.
Do I need to post the facts and the science AGAIN?
Water extra going down the stretch.
2 reasons - plants got larger and are using more water to build flowers
I don't have a 2nd reason. Just water dont put a label on it.
Are we tossing the excess water that we get at run off and where are we putting that water?
Food for thought.
Do I need to post the facts and the science AGAIN?
Water extra going down the stretch.
2 reasons - plants got larger and are using more water to build flowers
I don't have a 2nd reason. Just water dont put a label on it.
Are we tossing the excess water that we get at run off and where are we putting that water?
Food for thought.
Flushing will not flush what the medium is holding but it will wash away salt that has built up and is in crystalline form out side of the medium.Like what crusts up on the holes and outside of bags.
There's science that says water wont have any effect on any of that built up nutrients.
Ever try and wash it off a plastic container. Yeah that. There's a molecular bond that happens it wont rinse off with plain water. Hard to get it off scrubbing with soap and hot water. Basically has to be removed with friction.
Ever try and wash it off a plastic container. Yeah that. There's a molecular bond that happens it wont rinse off with plain water. Hard to get it off scrubbing with soap and hot water. Basically has to be removed with friction.
Fuzzy Duck
Well-Known Member
Ye that might be lime scale if your water source is from alkaline bed rock under ground water supple etc etc etc
Some times with soil grows & using salt based nutrients you can get a white crust of salts on top layer of the soil just some thing to watch out for !
I don't use science to blind people when common sense should prevail... just saying
Flushing is the act of leaching, slight bit of terminology to understand first before ranting on about science.
No rant bro. I've ranted on thus subject many times tho so I know the science.
Wanna go down that trail with me?
What exactly are we leaching with water run off?
Water has neither a negative nor a positive charge.
Nutrients be them soluble or not have anions and cations. As soon as they come into contact with soil particles there's a chemical process that takes place. Those anions and cations latch onto soil particles. That latching process is like a magnet positive atracts to negative. So the soil particles hold onto the nutrients in the soil via a chemical bond.
No amount of water will release that bond since it has no charge. Thats chemistry.
Yes you can get "some" leaching in sandy soil or soil with very low CEC (cation exchange capacity) but IN SOIL we don't have those conditions. Soil-less medium, yes you have that but we are talking soil here if I'm not mistaken.
About the only leachate you get will be some extra nitrogen even then the soil would have to be of very poor quality with little or no soil organic matter. Root cells can exchange those cations and anions but not water.
2 words to think about:
Diffusion
Cation exchange
To solve a problem with too much fertilizer (N) the best approach is to use less of it. Not to use excess and then try and remove it with water.
Flushing is a term that hydro farmers use to clean out there pipes and reservoirs. Somehow it morphed into cannabis grow culture. Its not a thing.
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- #14
alright thank you!you can't always visually "spot" a salt buildup. What you can see is what the plants are doing and learn to read deficiencies and lockouts so that you can recognize when there is a problem. If suddenly without explanation problems arise, when there has been no changes in feeding that had been working fine, a lot of times that indicates a buildup of something in the soil, usually salt.
I am a big fan of reusing soil... I got about 7 years out of my last batch that now is starting to wear out. If you regularly flush the debris out of your soil, including some of the organics that break down and turn the soil acidic (which is probably what I need to do myself) you should be able to use a good soil for years. I like the FoxFarm Ocean Forest as a good base soil because of its large sized organics that take a long long time to break down. It probably is a good idea to flush the soil before reusing it by running 3x the container size through it. I think I will do this before trying to pack it down into a container so that the initial flush doesn't super compact the soil for a new plant to have to break through. These are good points to consider... thank you for taking me here.
another thing about salt build up , can it happen with fresh soil, or does it happen only after the soil has been used for a while?
i know salt build up happens everywhere in potted plants. but can it happen even in the short life cycle of weed with new soil?
i'm glad i'll be able to re-use soil. another question. this soil pretty much has no nutrients (terra canna professional) it's i guess what people call a "light mix" does that mean i don't have to worry to add compost and other stuff to "revive" the soil? and i can just throw it back into a pot?
or would putting a some granural fertilizer help?
i hate people who say you can't reuse soil, i have plants in soil and they've been in those pots for 15+ years, and they still look healthy! ofc we're trying to maximize yield when it comes to weed.
but i don't see the issue with re-using it at least once or twice...
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- #15
well, what a surprise, conflicting opinions, like always when it comes to growing weed. it's so hard to choose sides sometimes
i'm guessing a flush wouldn't hurt, what bad will it do? i water until saturation anyways.
Depends on your goals. If you want to grow organically without salts/fertilizer it can be done. I mixed my current soil I'm in back in 2015. I'm still using it all year long indoors in containers.
Compost is key. You get your compost right it will sustain your plants for years with very little amendments.
Using fertilizer in containers I have no idea. With fertilizer use its important to know what your soil make up is so that you know how much to use so you dont get build up.
Compost is key. You get your compost right it will sustain your plants for years with very little amendments.
Using fertilizer in containers I have no idea. With fertilizer use its important to know what your soil make up is so that you know how much to use so you dont get build up.
well, what a surprise, conflicting opinions, like always when it comes to growing weed. it's so hard to choose sides sometimes
i'm guessing a flush wouldn't hurt, what bad will it do? i water until saturation anyways.
Yeah but its not my opinion. Its science.
My theory or opinion on why "flushing" seems to work is that folks get into a routine with watering. Use the same amount all the time but the plants requirements change specially during flowering. They are larger and are growing flowers so they need more water. Flush to the rescue, it works but its working for a different reason than what is thought. Plants just need more water down the stretch.
Fuzzy Duck
Well-Known Member
Yes science it plays it part but does the average person understand that ?
Cannabis growing has some really borked ideas about it, full stop !
It is a weed, just look at what some people try to grow it in... when you understand the technical term of weed from horticultural point of view ya understand, not that it is undesirable in my point of view !
Lets just say I've been involved with horticulture for 25 years at some point I looked after green house's & poly tunnels with up to 30 thousand of plants, just a small amount & not cannabis... same laws of science ah buddy they are all plants in my own personal experience...
Do you honestly expect that I PH corrected water & feed for 30k worth of plants over several different species... ya gotta be joking even tho some did require special care.
I find the less I do with the weeds the better they grow! I basically take pics after flip to harvest when I feel like it. Automated watering so I don't even have to do that. Make sure the lights are on when they are supposed to be. 
Fuzzy Duck
Well-Known Member
I'll take a look at grow journal if ya got up & running.
