How to Flush Cannabis?

Flushing cannabis is a critical aspect in its growing stages. Growers who desire to obtain excellent buds do flush their plants weeks prior to the harvest date. But, this process might be tricky for newbies. In this article, we will discover drenching your cannabis growth, as well as the many aspects that come with it.

How to Flush Cannabis?

What is cannabis flushing?

The act of flushing a plant entails intentionally removing any nutrients from the soil with simple water. Commonly, a considerable amount of water passes through the soil and draining away. Any minerals and nutrients in the soil are carried away by the water over time, leaving it completely pure.

Flushing is the process of removing all nutrients from a cannabis plant and replacing them with only water. The procedure of washing the marijuana plant occurs typically during the plant’s final transition period, just before harvest.

When you stop giving the plant more nutrients, it has to use the nutrients it has saved throughout its final week of growth. Suppose a marijuana plant has an excessive amount of nutrients stored in its plant material; these nutrients can damage the flavor and general quality of the plant.

Subscribe to Weed-Smart

Subscribe to our newsletter and stay updated.

We use Sendinblue as our marketing platform. By Clicking below to submit this form, you acknowledge that the information you provided will be transferred to Sendinblue for processing in accordance with their terms of use

Why should I flush my cannabis plants?

Some growers may understand flushing from a negative perspective, but it helps the marijuana plant produce great buds.

Why would you wish to deplete the soil’s mineral content? Isn’t this affecting your crop? It has a significant impact on your harvest. When the nutrients in the soil are removed, your cannabis plant will use up any residual nutrients in the plant. It resembles the human body in many ways. We consume a large amount of food, and what we do not use gets stored as fat. In times when food is short, the body taps into its fat reserves for energy.

The main goal of flushing is to improve your marijuana’s taste. Most in marijuana products, there is typically a "chemical" flavor, which suggests there were too many nutrients at harvest. A possible explanation is that the grower didn’t flush or didn’t flush effectively. If you wash, though, you will just be left with the pure taste of marijuana along with smoother smoke.

Flushing is not just for the harvest season. The approach also applies to remove extra nutrients from the soil during the vegetative phase. Nutrients keep your plant healthy and maintain maximum harvests, but too many might lead to nutrient lockout, a condition in which plants cannot access nutrients. To better understand the different nutrient deficiencies for cannabis, read this article.

Salt accumulation and improper pH levels can also lead to nutrient lockup. The remedy for such a situation is by simply rinsing the plants with plain water. The fluids force nutrients out of the soil and wash away the accumulation, allowing roots to absorb nutrients once more quickly.

When should I flush my cannabis plants?

Critical to cannabis flushing is its timing. Flushing typically begins two weeks before harvest. If the plant has an eight-week flowering phase, you conduct flushing six weeks after the flowering stage begins. To determine when your cannabis is likely to be ready for harvest, examine the trichomes on your plant closely.

If the tiny trichomes start to change color from clear to cloudy and milky, it’s a good indicator that the plant is ready for flushing. After two weeks, the bulk of the trichomes should have fully transformed to the right color for harvest.

Plants with predominantly clear trichomes and a few milky and white trichomes are too early to harvest, but they’re ideal for flushing. Consider this: two weeks after the significant flush, you want the majority of the trichomes to have changed color. This method cannot be easy, especially for rookie growers, but it is something to consider.

What water quality should I achieve in flushing cannabis?

When discussing water quality and distinguishing between water types, it’s crucial to understand the word pH, or potential hydrogen, which is used to evaluate the acidity and alkalinity of any given fluid. pH uses a scale of 0 (most acidic) to 14 (most basic) (most alkaline) for its measurement.

Cannabis enjoys water in the 6-7 pH range, ideal for nutrient uptake, depending on the grow medium you are using.

Parts per million, or ppm, is another crucial concept to understand. Because most water isn’t pure H2O, ppm provides a precise measurement of the pollutants present in a given water source. This test determines whether or not there are any dissolved solids in the water.

We can refer to different categories to classify water contaminants:

  1. Chemical – chlorine, magnesium, calcium, salts, and nitrogen
  2. Physical – rocks, sand, sediment, and organic metal
  3. Biological – bacteria, mycotoxins, viruses, and parasites
  4. Radiological – cesium, and uranium

Many water sources include pollutants by nature. Biological contaminants such as bacteria and parasites can be found in streams, ponds, and lakes.

Other water sources, such as treated municipal or tap water, are frequently treated with chlorine, calcium, and magnesium to eliminate the likelihood of biological growth.

How do I flush my cannabis plants?

Flushing your marijuana plants entails more than just watering them. It should, in fact, not feature any water blasting at all. Instead, water your marijuana plants with pH-neutral water while you would regularly feed them.

Fill the soil to the brim with as much freshwater as it can take. Allow for a few minutes for all of the nutrients to be absorbed. Then flood the soil once again to flush everything away from the plant. If you’re using pots indoors, pay attention to the color of the water draining from the bottom of the container. It will be soiled and filthy in appearance.

A TDS (total dissolved solids) meter will be helpful in the above situation. If you collect and measure the TDS of the "drained off" water, you’ll find that it’s around 1300ppm, which is relatively high. It’s critical to maintain flushing the plant until the value falls below 50ppm or until it’s near matching the TDS of the freshwater you’re using in flushing. If you are thinking of purchasing a TDS meter, I recommend this one from

The color of the draining water will lighten, giving it a cleaner appearance. You want to remove as many dissolved minerals from the plant as possible.

How do I flush my hydroponics cannabis?

Flushing also applies to cannabis plants grown via the hydroponics system. If you are new to hydroponics growing, I suggest you read this relevant article.

Below is a step-by-step procedure for flushing cannabis in a hydroponics system.

  1. Drain the nutrient reservoir using the method that is best suitable for your system. You may pour the old liquid into your outdoor garden, trees, or bushes to augment their nutrients.
  2. Remove any sediment or algae that may have accumulated in the nutrient reservoir. If necessary, scrape algae off the sides of the tank using a plastic scraper before rinsing everything out.
  3. Pump plain water through the system after filling the tank. To make the procedure go faster and more effectively, use an optional flushing agent. This flushing agent is a bestseller that can help you in flushing your cannabis growth. Before starting the pump, read the instructions on the agent’s label to figure out how much to add to the water.
  4. Replace the flush water with plain water, with or without the flushing agent, as directed on the label. Test the pH of the water and, if necessary, use drops from a pH adjusting kit to bring the pH of the new water to around 6.0. Set the system to its customary operation and leave it running for 24 hours.
  5. Refill the system with a new nutrition solution after discarding the flush water. Start the system and let it operate normally until the nutrient solution needs to be changed again, usually in one to two weeks.

Was this helpful?