Just found this very interesting read about flushing and it will probably blow your minds. It blew mine!! It’s worth the read I promise 
Flushing Cannabis: The Complete Science-Based Guide For Better Harvests In 2025
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Sep 5th 2025
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Cultivation
Growing
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.