How To Flush Cannabis Plants and The Benefits

01 Feb 2022

As a purveyor of the finest flavours on the planet, we passionately spend our adult lives in search of the best grown Cannabis flowers. A trip to Amsterdam, California or Barcelona can inspire you to go home and grow the best tasting crop ever. How a grower flushes their garden when flowering Cannabis plants will play a massive role in how well the dried flower tastes, smokes when burning and the overall experience. Below we breakdown all you need to know about flushing Cannabis and the benefits associated and some top tips.

What Does Flushing Cannabis Mean?

Most people only know how to flush a toilet, so as a grower you will be responsible for flushing your plants. Basically this term means using no more nutrients after a certain point of the flowering cycle. This is normally done over a 14 days period which starts during the final 2 weeks of the flowering period. The best way to understand how flushing works is to look at it from 2 different points.

  • Using plain water or an enzyme solution to flush Cannabis plants will allow the undissolved salts that have built up in the growing medium, and have accumulated around the root zone to wash away. If you are using organic or hydroponic nutrients, over the duration of the vegetative stage and flowering stage nutrients will have built up, so using plain water gives the undissolved salts an opportunity to finally dissolve.
  • The Cannabis plants are allowed to use up all of their internal reserves and in return, make one final push to really pack on the size, weights, resin, terpenes, and flavonoids. A good analogy is the same as a person fasting from food and all of the internal reserves they have will be used up accordingly. 

Seasonal Colours and Fading

If you have ever seen mature flowering Cannabis plants that have turned multicolored and thought it was down to genetics, then you may be mistaken. As Cannabis plants are flushed and push for the finish line, the array of colour pigment that is on display is a true wonder of Nature. You will know when the plants are getting closer to flushing as the fan leaves and smaller leaves will fade into yellow, purple, orange and red and pink in some cases. 


How To Flush Cannabis Plants and The Benefits
Fan leaves after harvesting a well flushed plant

Using Enzymes!

Enzymes are an excellent way to accelerate the flushing period and to allow a growing medium to be washed clean of salts for re-use if needed (coco-substrate). Some growers will use enzymes from the start to finish of their indoor grow, others will only use during flush and some will not use at all. Using multiple brands of enzymes and mixing them together into one solution is recommended and will ensure you have as many different organic enzymes working together. 

5 Signs of Unflushed Cannabis Flower

  1. The first sign is after you have rolled your joint, blunt,  prepared a bowl, or bong hit. As soon as you burn the dried flower the ash will become dark, black, and leave behind a chalky residue. Cleaning your ashtray, bong or pipe after smoking will reveal how unclean the flower truly was.
  2. The second sign is once you inhale, your mouth becomes filled with a harsh, hot, and spicy smoke that causes you to cough and leaves a very unpleasant aftertaste. It does not matter how good the strain was when it was flowering, the experience of smoking is foul and will be a burden to anyone who consumes it causing coughing fits. 
  3. The third is that the ember of a rolled joint will not burn like a traditional cigarette or joint, and will begin to side-burn and need to be patiently nursed with a lighter. An easy way to notice this is how the ash burns at a different rate and no matter how perfect your rolled joints are, they will all burn with a uneven tendency.
  4. The fourth sign is not only will the ember struggle to burn and every toke becomes hard work, you will also find that the joint constantly needs lighting. This can be unbelievably frustrating and defeats the purpose of relaxing and smoking a nice greasy joint. 
  5. The final sign to look out for is the aroma of the Cannabis flower when being burnt. Normally a well-grown flower when first lit will release an abundance of terpenes into the atmosphere reminiscent of entering an Amsterdam coffeeshop!. However, unflushed Cannabis will actually burn with an unpleasant chemical aroma that is somewhat a reflection of the taste also.
How To Flush Cannabis Plants and The Benefits
A plant in the final week of flush and fading.

What To Avoid When Flushing Cannabis

When growing Cannabis flushing should be a straightforward process, and is as simple as sticking to the same watering schedule as you normal, but making sure there are zero nutrients used. This means absolutely no more Nitrogen, Phosphorus, and Potassium. Below are some common mistakes an indoor grower can make when flowering Cannabis.

Over Watering: 

There are some growers who feel that giving the plants 10 times the amount of the pot size is a substantial flush, and will produce the cleanest plants possible. This old-school method can end up causing plants to become overwatered during the final few weeks and do more harm than good

Top Tip: If you have been feeding daily with a nutrient solution, simply stick to the same regime, however only use plain water. Do not increase the feeding frequency and over saturate the medium.

7-Day Flush:

When it comes to flushing Cannabis plants, some growers will work with a 7-10 day flushing period instead of the full 14. This does not mean the plants are not ready to harvest and won't smoke as clean as any Dutch coffeeshop flower, however beginner growers should get into the habit of a full 14 days and maybe longer in some scenarios.

Top Tip: The best way to know if your plants are fully done is to pay attention to the fade. When the leaves have become totally depleted of Nitrogen and many other nutrients and trace elements, then you can be totally confident they are perfect.

No Flush!:

Unfortunately number driven growers who are hell bent on the biggest yields, will neglect the flushing period. Under the naive impression the more nutrients the plants receive the bigger the buds will be is a guaranteed way to produce the worst-tasting crop imaginable. Especially if the Cannabis plants have been hammered with chemical nutrients and boosters until the final days. 

Top Tip: Make sure you do the tests and checks to see how well the dried flower burns when smoking, how often it needs relighting, the taste, aroma when burning and the quality of the ember and ash colour.