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David Rhodes

David has been working in the cannabis industry for the past 17 years with experience working overseas in Amsterdam as a budtender for 5 years! Learn More About David!

Essentially, the act of flushing carries with it benefits. When you flush cannabis, it strips away the accumulation of nutrients from the plant’s roots and soil, hence enabling other suppressed nutrients to re-emerge. Consequently, your plant capitalizes on the nutrient richness present in the soil which aids in its proper growth.

Nutrient buildup can cause burning out and excess absorption, leading to plant defects. Timing is also an important factor to consider when flushing weed plants. When you flush too early and often, you can reach away too many nutrients and leave the soil bare. As a result, the plant can stop developing and may die off. Leaves may be discolored or yellowed with stunted stems. 

When To Flush Cannabis? (Feminized and Autoflowers)

You should flush cannabis two weeks before you plan on harvesting. So if it’s an 8-week flowering strain, then you should flush 6-weeks after flowering has begun and when the trichomes turn to an off-white color.

Is Flushing Cannabis Beneficial?

It is often argued that flushing weed is not useful. Some growers may not see the benefits that come with flushing. While others believe it is important to improve the quality of weed plants. Some growers doubt the effectiveness of flushing due to the following reasons:

  • Flushing lowers soil nutrient content, thus, can slow down weed plant growth.
  • Flushing larger plant bags may be challenging. Insufficient nutrients may not go around for all individual plants.
  • There is little research that backs up the effectiveness of flushing.
  • Induced nutrient deficiency, or flushing,  may not be one of the factors that trigger trichome production.  Weed plants need energy and nutrients to produce trichomes, thus flushing is questionable.

These reasons may be valid, but only when flushing is not done properly. When the process is done with time, at the last flowering stages, then you give your cannabis a reset before you harvest and can help get rid of mold, and correct nutrient deficiencies such as nitrogen, magnesium, or potassium!

Basic Facts to Know About Flushing Cannabis

All the different flushing methods you may come across target one thing: to remove nutrients for high yield. Leaving some nutrients in the soil can help the plant to utilize other nutrients and salts that have not been available to the plant. The weed plants can store these nutrients in their original form, just like fats are stored in the animal body for later use. 

All nutrients have to be dissolved in water to be assimilated. To start flushing, ensure to use cool water, and lower the pH. This will prevent the leaching of essential nutrients, as with warmer water. 

An important tool to have when flushing is a working pH meter. The PH-200 is ideal to use for pH testing. Also, EV and TDS meters see nutrient meters that read nutrient levels and solutions. They also help to indicate the nature of nutrients when pH levels fall out of the suggested range. Extreme pH levels can cause nutrients to precipitate in solution and prevent them from being assimilated.

Factors To Consider When Flushing Cannabis


The acidity and alkalinity of the soil are important when flushing. This is because nutrient solubility relies on optimum pH. When pH is too low or high, it can cause nutrients to become precipitated and ineffective. The optimum pH for flushing is almost neutral, around 5.7-6.1 pH. At this point, the nutrients are almost neutral and remain in the solution firm.

Water Temperature

When water is warm or lukewarm, nutrients can dissolve faster. As a result, more nutrients can be easily reached out of the soil system. This defeats the purpose of flushing, as only a few nutrients need to be leached. Avoid using warm water. Instead, use cooler water with a temperature of 24°C or 74°F.

How To Flush Cannabis

Check Water’s pH Levels

Check the pH level of the water you want to use for flushing. This will help you know if the current water pH is appropriate for weed plants. The optimum water pH for soil-grown weed is between 6.1 and 6.9. Also, make sure to check the pH of the soil.

Check Water’s Temperature

Next, check the temperature of the water. Make sure that the temperature does not exceed 25°C. You can also check out the temperature of the soil. If it is warmer, then you can lower the room temperature.

Measure Your Total Dissolved Solution

Total dissolved solids in the soil should be checked or tested using a TDS reader or meter. This will give you prior knowledge of the number of nutrients available in the soil.

Pour Water Over Cannabis Plant To Flush The Plant

Ensure that you get the flushing time right. Flushing should be done two weeks before you harvest weed plants. When the time comes, water the plants at the scheduled time for watering. Make sure it’s plain water. Do not add any supplements or nutrients to the soil. Also, ensure excess water is drained properly.

Repeat After Waiting For 15 Minutes

5. Repeat the same process 15 minutes later.

Measure pH Of Soil

After flushing, use the pH meter to ensure that the pH levels are optimum. Also, check for the total number of dissolved solids using a working TDS meter or reader. If you find lower levels, then the flushing process may have been successful.

Examine Cannabis Plant Days After Flushing

Days after flushing, closely examine the state of the plants. Look out for yellowing or any other temporary defects. The weed plant may lose its color after some time, but this is normal. However, it is important to observe the leaves close to the buds. Make sure to harvest the red plants before the bud leaves yellow out. If you allow all the leaves to turn yellow, the buds may begin to decay as the plants have matured already.

Final Thoughts On Flushing Cannabis Plants

Flushing may hasten the maturation process of your weed plants. You will notice the gradual change in the color of the leaves after flushing. When this happens, it shows that the plants are ready to be harvested. 

It is advised to flush the plants after they have undergone natural or artificial transpiration. This can occur in the early hours of the morning or late hours of the evening. Transpiration expels excess water from the leaves and flushing after this prevents too much water from accumulating in the plants.

About David Rhodes

David has been working in the cannabis industry for the past 17 years with experience working overseas in Amsterdam as a budtender for 5 years! His goal is to help you with your cannabis grow! Learn More About David!

David Rhodes