PS - It wasn’t my crappy weed. An old stoner friend of mine from our early 70s higher education at Kent State who now lives in mostly peaceful Portland, Anarchygon sent me some of his backyard clone grow. Good buzz but about as tasty as fermented lawn trimmings, with subtle notes of rotting leaves, day-old dog turds, and organic deer droppings.
Saw the often repeated line that post harvest processing, trimming, drying and curing is 50% of how your final buds, taste, smell, and look. Complete newbie me, they probably make some difference but I can just do those things okay but how I grow it mostly determines the final product 
Oh to be so ignorant! I eliminate any additional feedings during the last week if the plants look good but if I see the need for some nutrients in the last 2 weeks I’ll add it. I do use living soil so the plants can still uptake nutrients anyhow. Even when I used syn nutes at the start I feel I should have listened to good advice and focused on drying and curing properly rather than what I feel are very minor gains from flushing at best. My $.02.
When i grew outside, i usually flushed mine with molasses and water, let it soak good, once the trichomes were ready i cut it down.
The last one was a tree and some of the best smoke I’ve had and everybody that tried it said the same.
Not duplicated the results, it was a random seed that prob had good genetics.
It was the stickiest bud I’ve ever seen and was killer.
I tried to keep as much as i could but people were driving me nuts…
I still have that bag of seeds, doubt i could get the same but may try.
Those are pheno type, I’m doing autos now.
May have to try both in the bigger tent once i get it up and ready to go.
I run RDWC and have harvested with and without flush. Could not tell a difference. I don’t know about soil.
I grow hydroponically using General Hydroponics Flora Series and I started out flushing because that’s what I was told to do. I stopped flushing a few years ago and I never saw a difference. It might just be me, but I believe that improper drying and cure lead to harsh and crappy weed, NOT flushing.
I’m the same i do rdwc like the guy above and i use gh trio and I’ve never noticed a difference by flushing
Like many others, I have done soil and hydroponics. I do end up flushing the last couple of weeks. As someone mentioned before, if it doesn’t make a noticeable difference in the smoke reports, save your nutrients. I make up 30 gallons of nutrients at a time, so if I can save 6-8 totes full of nutrients in the last couple of weeks with no downside, why not? When was the last time that you either bought commercial stuff from a dispensary or even went to a friends house, and when you smoke it you say “ Hey, this doesn’t taste like you used nutrients up until harvest. Did you?” Just my thoughts.
I started out using GH trio, but switched to Jack’s a few years back. Less expensive and in my opinion better.
Flushing by way of running stripped water through the plant will eventually remove minerals from soil but it doesn’t remove it from plant material and the plants will not use up all of the minerals that are stored in it. This has been tested scientifically, published, and posted here, probably multipletimes. While there are certain arguments that could be made for reduction in elements remaining in harvested plant material, most non-volatile mineral elements that go into plants will not transfer through plants or evaporate to ever be completely removed.
When someone does something like flushing and makes a claim for or against it’s extremely difficult to call them a liar. But there’s so much additional context that could explain their conclusion. And nobody likes to be wrong on the internet.
How’s my argument of me just being cheap? Hope that I got points for that one
Most of us don’t believe in unnecessarily feeding our plants. It just takes having a little feel for timing the reduction in fertilizer properly.
This says it all and this dude ain’t a rookie
Flushing Cannabis: The Complete Science-Based Guide For Better Harvests In 2025

Jorge Cervantes
• Sep 5th 2025
• 0
CultivationGrowing

By Jorge Cervantes, Cannabis Cultivation Expert with 40+ Years Experience and Dr. Gary Yates, PhD, cultivation manager.
The most complete study on flushing cannabis: a comprehensive guide based on thorough research and data analysis.
Legal Disclaimer: This educational content is intended for adults 21+ in jurisdictions where cannabis cultivation is legally permitted. Always check your local laws before growing cannabis plants.
What Does Flushing Do For Cannabis?

Flushing cannabis is one of the most debated topics in cannabis cultivation. After four decades of growing cannabis plants across five continents, I’ve seen countless growers argue about whether flushing cannabis plants actually works. Flushing is a common practice among cannabis cultivators, especially when using mineral fertilizers or inert substrates, as it is believed to improve the quality of the harvest.
Flushing cannabis means giving your plants only plain water during the final weeks of the flowering stage. No nutrients, no fertilizers—just pH-adjusted water. The goal is to allow the plant to use up all the nutrients stored in its tissues before harvest. Many growers believe this “washes” nutrients out of cannabis buds, creating smoother, better-tasting cannabis by removing extra nutrients that could negatively affect taste and quality.
Flushing is also believed to prevent nutrient buildup in the growing medium, which can impact plant health and bud quality.
The Traditional Case For Flushing Cannabis Plants

Why Growers Have Always Flushed
For decades, cannabis growers have sworn by flushing cannabis plants before harvest. The conventional wisdom suggests that flushing removes excess nutrients from cannabis buds, resulting in smoother smoke and better flavor profiles. This belief has been passed down through generations of cultivators who observed visual improvements in their plants during the flushing process.
Traditional growers report several benefits from flushing cannabis plants:
The plant begins breaking down chlorophyll in its fan leaves. This creates the “fade” that many growers love to see. Yellow, purple, and orange colors appear as the plant redirects energy to the cannabis buds. Growers often monitor when leaves have turned yellow as a sign that the plant is nearing harvest.
Many experienced cultivators believe flushing improves the final smoking experience by removing harsh chemical tastes associated with synthetic nutrients. The theory suggests that excess minerals stored in plant tissues create harsh, unpleasant smoke when combusted.
Commercial growers often flush to achieve visual consistency in their products. The autumn-like colors that develop during flushing create an appealing appearance that consumers associate with high-quality cannabis.
How Traditional Flushing Works

The conventional approach to flushing cannabis involves stopping all nutrient inputs during the final 7-14 days before harvest. Growers provide only pH-adjusted water, believing this forces the plant to consume stored nutrients from its tissues.
During this process, fan leaves typically turn yellow as the plant supposedly uses up nitrogen reserves. Purple and orange colors may appear as other nutrients are depleted. These visual changes have long been considered signs of successful flushing.
Traditional growers time their flush based on trichome development and overall plant appearance. Many also check the condition of all the leaves, including sugar and fan leaves, to ensure they are not yellowing or showing signs of overripe buds before starting the flush. When trichomes show mostly cloudy with some amber coloration, many cultivators begin their flushing period to coincide with the final ripening phase.
Enzyme Use During Cannabis Flushing
Breaking Down Undissolved Salts With Enzymes
Some growers use enzymes during flushing to break down undissolved salts in the growing medium. These specialized enzyme products work by converting accumulated mineral salts and organic residues into forms that are more easily flushed from the root zone. When synthetic nutrients build up over time, they can create salt deposits that interfere with water and nutrient uptake, even during the flushing process. Enzyme additives contain specific proteins that catalyze the breakdown of these salt accumulations, helping to clear the growing medium more effectively than plain water alone.
The science behind enzyme flushing involves enzymatic hydrolysis, where enzymes break the molecular bonds in accumulated salts and organic compounds. This process can be particularly beneficial in hydroponic systems and soilless growing mediums like coco coir, where salt buildup is more common than in living soil systems. By using enzyme products during the final flush, growers can ensure that their plants have access to clean water without the interference of residual nutrients or salt deposits that might affect the natural senescence process.
However, it’s important to note that enzyme use during flushing should complement, not replace, proper feeding practices throughout the growing cycle. The most effective approach is to prevent excessive salt buildup by maintaining appropriate nutrient concentrations and regular monitoring of electrical conductivity (EC) levels in your growing medium. When enzymes are used during flushing, they should be applied according to manufacturer instructions, typically at reduced concentrations since the goal is to clean the medium rather than feed the plant. This technique can be especially valuable for growers who have experienced nutrient lockout or salt accumulation issues in previous grows, helping to ensure a cleaner transition to the final harvest phase.
Recent Scientific Studies Challenge Flushing Myths
The Rx Green Technologies Study: What The Research Really Shows
Recent research from Rx Green Technologies and other scientific studies on Cannabis sativa L. reveal surprising findings about flushing cannabis. The Rx Green Technologies research remains the most comprehensive scientific study on flushing cannabis plants. They tested different flushing times—specifically 0, seven days, 10, and 14 days—using Cherry Diesel plants in controlled conditions.
Data collected from this study revealed surprising results. Flushed and unflushed plants showed no meaningful differences in:
•THC content in the final product
•Terpene content and flavor profiles
•Mineral content in dried cannabis buds
•Overall quality ratings from expert panels
The blind taste test results were particularly interesting. In the Rx Green Technologies study, professional evaluators showed no consistent preference between flushed and unflushed cannabis, with some panels slightly favoring unflushed samples. This contradicts the common belief that flushing cannabis consistently improves the smoking experience.
The Real Science Behind Flushing Cannabis Plants

Scientific evidence from multiple studies shows that flushing cannabis plants affects the plant’s behavior, not its nutrient content. Cannabis plants don’t store excess nutrients in their buds like a warehouse. Essential nutrients become part of the plant’s structure—they can’t be “washed out” with plain water. This is basic plant biology that applies to all plants, not just cannabis.
When you flush plants, you’re not removing nutrients from the cannabis buds. Instead, you’re forcing the plant to use up nutrients stored in its leaves and stems. This process is called senescence—the natural aging that happens when plants prepare for winter. During senescence, the plant remobilizes nutrients from older tissues to support continued metabolic processes, but it doesn’t use up all nutrients stored in its tissues. Many nutrients, particularly immobile elements like calcium and iron, remain permanently incorporated into cellular structures.
The Rx Green Technologies study found no significant difference in mineral content between flushed and unflushed cannabis. Outcomes such as THC and terpene content were determined through objective analysis. This research included a blind taste test where professional panels actually preferred unflushed samples.
What The Study Means For Growers
The Rx Green Technologies findings don’t mean flushing is useless. Instead, they show that flushing works differently than most growers believe. The benefits aren’t from removing nutrients—they come from triggering natural plant responses.
Some growers still prefer flushing cannabis plants because they observe visual changes like improved colors and faster ripening. These effects are real, but they happen because of stress responses, not nutrient removal.
Commercial growers often use this research to make decisions about their cultivation practices. Some continue flushing for the visual benefits, while others focus on proper curing to achieve smooth, high-quality cannabis.
Excellent post @Dman1969
Thank you 
My Brother it’s a bit long winded but worth the read. It changed my whole outlook on flushing. 
Very interesting @Dman1969
“Flushing by way of running stripped water through the plant will eventually remove minerals from soil but it doesn’t remove it from plant material and the plants will not use up all of the minerals that are stored in it.”
“Scientific evidence from multiple studies shows that flushing cannabis plants affects the plant’s behavior, not its nutrient content. Cannabis plants don’t store excess nutrients in their buds like a warehouse. Essential nutrients become part of the plant’s structure—they can’t be “washed out” with plain water. This is basic plant biology that applies to all plants, not just cannabis.”
This makes feel dumb for even posing this tired old question - but the finding that suggests it does trigger plant responses is very interesting. Essentially creating a nutrient deficiency to trigger senescence - seems kinda plausible to me.
How do you feel about that @dbrn32?
@Olaf.ILGM Thank you it’s crazy that it doesn’t do what we think but does do something 
If I had to limit myself to a single source for info on all things cannabis, Jorge Cervantes is that source. When it comes to old school, new school, and everything in between, no one else comes close.
“it’s crazy that it doesn’t do what we think but does do something ”
That’s EXACTLY what my wifey says about me!
It’s a viable question and/or discussion because so many have no idea or will argue despite the evidence. If you take this to an individual level, I don’t care how each person wants to go about their grow. If they believe something to be valuable then by all means. But if it’s more of a discussion of best practices then I feel obligated to share at least what I believe to know.
The bit about triggering senescence could go either way too. Does this impact your grow in a positive fashion? I have always thought it to be perfectly fine to harvest healthy green plants when typical harvest criteria are met. But if there’s data stating otherwise it would be helpful.
After being in this roll for something like 7 years I notice one major point of contention with the practice of flushing plants. Newer growers often struggle to look at their plants and determine and estimated harvest date. If you suspect your plants are 1-2 weeks from harvest ready and start flushing when in reality plant is more like ~4 weeks out would probably put plants into state of deficiency prior to harvest window but feeding all the way up to harvest seems to have no ill effects.
Very good point too.
Ironically, the fade is one of the signs I rely on to indicate whether the plants are finishing, meaning senescence will have set in before I would even have a clue when to flush.