Stopping nut before harvest?

[Hyakutak]

I've read a lot of discussion about stopping nutrients 1-2 weeks before harvest & flushing. Do any of you have experience with this?

I don't want my buds to taste bad, but this looks more like stoner science to me. This is an interesting read on RIU.

[QuantumMechanic]

I flush my all-perlite inorganic Hempy buckets for 2 weeks with RO water and Clearex. I test the runoff and try to get less than 100 ppm (700 scale) coming out the first day. By the end of flush, about 20 ppm is all that comes out. I see the plants start to deteriorate after about 6 days. By 14 days, I need to keep a close eye on the bud leaves so that they won't yellow too far in.

I also keep the plants in the dark for 36 hours before the harvest and do the harvesting of plants in the dark.

I drop the nutrient level a bit for the last 2 weeks before the 2 week flush.

I don't use "perfumed" nutes. (Is there some reason CalMag+ needs perfume?)

In addition, I feel that if you burn your plants in flower at all, you are unlikely to have good tasting bud no matter what. The immobile nutes are stuck. So feed less than you think the plants need. When I first started growing, I thought that "feed em until they burn, then back it off a little" was the proper way. It ain't. This one took me a long, long time to learn. NO burnt leaf tips allowed!

All just the opinions of a picky guy that likes herb that's not too offensive tasting. I much prefer a smooth and bland herb to one that is just chock full of "tastes and flavors." The same goes for seeking a few extra trichomes at the expense of taste.

[unkle_psycho]

I think theres a lot of stoner science involved, and varying opinions, but perhaps thats just to show it's a topic that matters.

Your first concideration would seem to be your grow medium, each seems to get different recommendations.

A troll on RIU discussions was going on about how 'if you have to flush it means you already fucked up the nutrients". I traditionally grow in soil that I 'pre-fertilize' and in that context I agree. I rarely have to add much nutrients, and usually aim to have pretty yellow plants when I'm done.

Now I am just finishing a test with coco, and just following the advise on the (canna coco) bottle, every plant got burnt tips. I've been flushing a Herer for over a week and still no signs of loosing color. Smell seems to be back to mint/spice, which gives hope. Nitrogen toxicity does not begin with burnt tips though... first sign is that the new growth is as dark green as the established leaves. New growth during veg and stretch should always be a little lighter then the rest of the plant.

I was originally planning on flushing them all for a long time, but decided to use only water with the Herer. The others have been receiving a very mild mix, which should already be pulling down the EC, but not cause any deficiencies.

I think flushing is an important topic for people who use lots of commercial nutes, and follow nutritional advise beyond their eye's and experience. I'm doing one more coco plant just to show myself it can be done right, ignoring the bottle recommendations and keeping ec low. It does not look like it will yield any less.

[H0m3B0Y]

This is only my opinion, and it seems I'm in the minority with this one, but I don't think flushing the plants does them any good. That said, I've yet to do a side-by-side double blind taste test of flushed vs. non-flushed plant to be able to say conclusively if I can tell the difference.

But from biological point of view, the plant does not "store" nutes. Especially cannabis, since it just grows as fast as it can, produce flowers and hope for seeds and then die off. It uptakes as much nutes as it can use and more (that "more" will result in burnt plant since osmotic balance is off). Flushing the plant shouldn't have any significant effect. But again, I've not done a proper test to conclude that.

Flushing sounds kind of like foliar feeding or adding molases to the nutes/growth medium. Plant only uptake gases through leaves, and spraying salts (==nutes) on the leaves just seems silly. And adding molases... well, plants are _the_ organisms that produce sugars. No animal can do that, we have to kill plants to get sugars. Why would you feed sugar to an organism that produces it? It's like giving humans CO2 to breathe.... or giving O2 enriched air to a plant. Just seems silly.

Again, only my opinion, and not a very popular one.

[unkle_psycho]

I thought the melassis was for the bacteria in the ground.

I read conversations on flushing, and I'm pretty sure many experienced growers see value in it. Hydro growers say they see a big effect in a few days, I don't see one despite flushing my herer for a week now. Smell did return to normal, from the reek that over fertilization caused, so thats a sure positive.

And surely the plant takes up the NPK and a host of other stuff, cannabis is a bio-accumulator. Can be used to clean toxic land or even nuclear contamination. Won't get that shit out with a simple flush though.

But I never practiced it in my soil grows (i'm basicly trying coco for the first time), so I only know what I'm observing at the moment.

[Capt. Saicin]

Flushing sounds kind of like foliar feeding or adding molases to the nutes/growth medium. Plant only uptake gases through leaves, and spraying salts (==nutes) on the leaves just seems silly.

Foliar feeding is definitely a thing, though! It does work and is mostly used to correct deficiency of nutrients. It's real fast since the nutrients will be absorbed directly by the leaves.
PDF discussing Foliar Feeding

As for flushing:
There are movable and immovable Nutrients.
Movable (N,P,K, Mg, Cl, Mo, Zn) are ready to be redistributed in the plant as needed, mostly to new growth.
So during flushing old leaves will start to yellow and their nutes will be distributed to new sugarleaves/buds. You will want to get the timing right so that the Buds are ready when they have used up all the nutrients coming from the leaves and have yellowed themselves. Chlorophyll is what gives weed it's harsh smoke, hence you cure it so the chlorophyll breaks down somewhat. If the leaves/buds are yellowing that chlorophyll has started to degrade already and stored nutrients are at the lowest point.
That's the theory afaik. Don't grow weed so don't know if it actually matters tastewise after curing. Maybe growers use it to decrease curing time, or for marketing/aesthetics?

[sdfoster22]

Yes, molasses is for organic growing. You feed the bacteria sugars. They eat the sugars, and produce the nutrients for the plant. You are not really feeding the plant sugars, you are creating a more active environment organically. If your not organic, it doesn't really do anything.

[Smokesmcghee]

From what I've read and in my experience, you don't need to flush unless your seeing an issue. Stopping nutes means slowing growth doesn't it? Don't we want the buds to mature up to the point we harvest? I know the general stoner bro science is that if you have the plant eat its own leaves, then your left with a "smoother" smoke and that cutting lights for more than 24 hours before harvest will pack the trichomes but it seems counter intuitive to give the plants stress at the very end of the grow and slowing down the process of what the plant does.

If you have excess salt buildup from your nutes, then maybe you want to leech or "flush" your grow medium of some of that built up extra salt which could have led to a plant issue. However flushing for the sake of flushing and cutting nutes seems counter intuitive.

I also believe the nutrient seller's feeding charts are recommending too high of a feed but I guess its also your water source that also plays a part in this consideration of how much to use. For example Coco Canna's feeding chart recommended 14 ml/g of both parts A and B for the feed schedule in Flower however I saw tip burn going past 12 ml/g and so it was obvious that this tip burn meant I can cut back on the nutrients and so I stuck 9 ml per gallon and the tip burning issue was solved.

I ran my first grow in Coco Coir with Coco Canna A + B. I never flushed and did not have any perlite in the medium and did not have an issue with taste, harsh smoke, or lacking in potency after doing a proper week or more of drying and a good cure in jars. If you smoke your bud right when you finish drying, it may be a harsh smoke, but with a good cure in a jar with burping, the buds dry out slower and improves on its qualities. This is from personal experience. I had white widow that smoked a little harsh and led to a racy head high but as the bud cured more and more, those effects were lessened and white widow became my preferred smoke when at first it made me feel a little anxious.

[unkle_psycho]

Yeah I've been running another test with canna coco. Don't really know about gallons, but the recommended is 4ml per litre (quart). In the previous round I did the recommended 4ml of A+B, this time I mostly stayed at 1.5ml, went up to 2ml for the last week before PK, then back down to 1.5ml. The plant looks about as healthy as one could hope for, but way too dark for my taste... Starting week 7 she don't need to look like a prom queen.

I don't know if I'll bother to try canna again, but keep the nutes at 1-1.5ml/ litre? Perhaps the substances I'm using to add micro elements are making things more available to the plants, because I never went above 1.2 ec, mostly around 0.6-0.8ec. Next time I'll probably go with something else.

In soil I definatly learned to fertilize in a way that allows plants to yellow up because I find it improves taste. All over the industry, and even in science there seems to be a concensus that fertilizing increases yield and reduces quality. Most culinary herbs are also spoiled by over-fertilization, some being very sensitive. With weed there is a certain nasty smell that comes with very high nutes, and my Jack just got it, and lost it with a 3 week flush. Curing will further improve the situation.

I never put a plant in a day of darkness before cutting, but I do tend to time my harvests for full moons and cut in the night. I read that terpene levels rise every night and fall through the day.

Curing is very important though, I'm hoping to build myself some type of curing device that keeps stable humidity while dropping temperature over a long period.

[Smokesmcghee]

I do believe that flushing or leaching your soil could benefit at the end of flower to leach or flush out the extra nitrogen from your soil. I also believe it helps with salt build up on hydro and coco but I wouldn't do a week long flush with coco or hydro due to those mediums being inert and and having nothing to feed the plants after a single flush.

I'd flush with no nutes the day before harvest with coco if I were to flush or leach out the nutrients since the coco won't retain it as much as soil would.