Flushing is a term used to describe giving cannabis plants strictly water during the final stages of the flowering stage. If you are not familiar with flushing, there are several benefits associated with removing nutrients and allowing plants to flush out any reserve nutrients and undissolved salts from the root zone.
In this article, I will explain everything you need to know about flushing, including why it is important, when to flush, common mistakes to avoid when flushing, and the benefits of flushing to help you master the flushing stage and produce the best-tasting weed possible.
What is Flushing, and Why Is It Important?
The nutrients we feed our plants contain salts, and flushing is the process of removing those salts from the growing medium. Salts can accumulate over the vegetative and flowering stages and, if not properly washed out, can result in bad-tasting cannabis that struggles to burn when rolled in a joint and can oftentimes cause a harsh coughing sensation when smoking.
Flushing is necessary for two reasons. The first is that your plants receive a final push over the finishing line and can utilise all the reserve nutrients they may have. The other is to produce the smoothest and most enjoyable cannabis when smoking.
When Should You Flush Cannabis Plants?
That depends on the growing medium you are using and whether you are growing plants in soil, coco coir, or a hydroponic medium, such as rock wool. Typically, flushing should be done over a 14-day process or the final 2 weeks of the flowering cycle. Below is a breakdown of the different flushing protocols for soil and hydroponics.
Differences in timing for soil vs hydroponics
Many growers claim that flushing in the soil is unnecessary; however, when using liquid nutrients, flushing your plants with pH-adjusted water makes a significant difference in the smoothness of the smoking experience.
Growers who use coco coir typically flush for 14 days as well. When it comes to hydroponics, a 7-day flushing phase is normally sufficient, as the plants are growing in an inert medium that contains no nutrients.
How long does flushing take?
Soil and coco coir growers should make the flushing stage last for 2 weeks. I have flushed my plants for as long as 3 weeks before; however, 2 weeks will be the optimal time frame and will prevent the plants from fading. This occurs when the leaves of the plant shift in colour from green to an array of seasonal colours, including purple, pink, orange, and magenta.
How to Flush Cannabis Plants Step-by-Step
The art of flushing is to cut off your nutrients and replace them with water. Below is a step-by-step guide on how to flush your plants properly without the concern of overwatering or drowning the roots. Do not give the plants more or less than you have been doing when feeding with a nutrient solution, as consistency is key.
Step 1: Using the same volume of water as before, replace the nutrient solution with pH-adjusted water. (Between 6.0 - 6.8)
Step 2: Water your plants as usual and wait until you see runoff at the base of the pots.
Step 3: Wait until your plants are almost dry again before watering them.
Step 4: Repeat this process over 14 days, so in most cases, you may need to water every 48-72 hours.
Step 5: Allow the growing medium to dry before harvesting the plants.
Common Mistakes to Avoid When Flushing
I have seen many growers become overly enthusiastic about the flushing process over the years. Although flushing sounds straightforward, mistakes can still be made. Below is a breakdown of potential issues and recommendations for preventing them from occurring.
Overwatering
This issue occurs when a grower pours too much water through the pots, thinking that the more water, the better. When this happens, the growing medium becomes oversaturated, and the roots are deprived of the oxygen they need.
Flushing too early or too late
Flushing should be a consistent process that lasts for the final two weeks of the flowering stage. If you find that you need to leave your plants longer than expected to ripen and mature, you risk flushing too early. It is not a massive problem; however, providing your plants with as much nutrient solution as possible before the last two weeks is beneficial and will help boost yields and flower production.
Flushing your cannabis plants too late can be problematic and will result in a reduced flushing period, usually between 5-7 days. When growing in hydroponics, a week-long flush is sufficient. However, if using soil or coco coir, you increase the chances of harvesting weed that burns with black ash, creates a coughing sensation, and produces a taste that may be the most undesirable.
Incorrect pH levels and insufficient ventilation
If you have spent months carefully and meticulously watering and feeding your plants, then it makes no sense to overwater them in the end. A waterlogged growing medium not only takes longer to dry out, but the roots are also unable to breathe correctly.
Bacteria present in the soil can become acidic and even turn harmful to the plants. If the pH of your water is not within the safe zone of 6.0-6.8 for soil and 6.0 for coco coir, then your plants will suffer from nutrient lockout.
Benefits of Flushing
If you have ever smoked a joint that tasted incredible, was extremely smooth, had excellent flavour, and the ash was flush and white coloured, then this was a result of correctly flushed cannabis.
Then again, If you have smoked a joint and were coughing profusely, and the ash was charcoal black, and the joint needed constant lighting, then poorly flushed weed will have been the culprit. Below is an explanation of the benefits associated with flushing and what you should consider before your next harvest.
Improved taste and smoother smoke
We all love to smoke lip-licking flavours that have you rolling another joint before you have even finished the first one. Well-flushed cannabis produces the smoothest smoke possible, more prolific flavour profiles and the most enhanced smoking experience.
Removal of excess salts and nutrients
Have you ever emptied a plastic pot after harvesting and noticed a white, salty residue on the inside of the pot on the sides? This is the accumulation of excess salts that are stored within the nutrients. Flushing cannabis removes these salts and breaks down nutrients around the root zone.
Enhanced terpene and cannabinoid profile
I have known many growers who harvested some of the terpene-rich strains you can think of, only to end up with tasteless weed with little effect. Flushing is the difference maker between an enhanced terpene and cannabinoid profile or flower that has a flat, dull and lifeless taste and does not do much as far as potency is concerned.
FAQs
Do you need to flush cannabis?
Suppose you want to achieve the best-tasting cannabis that burns smoothly and has your friends complimenting you on how good a job you did this round, then the short answer is yes. If you think flushing is a waste of time and the plants need as many nutrients and boosters as possible during the final stages of their lifecycle, then you do not need to flush.
The proof will always be in the pudding, and it's better to have a small amount of great-tasting flushed weed over a large quantity of harsh, tasteless and low-potency buds, in my opinion.
Does flushing reduce your yield?
A study conducted by RX Technologies in the United States proved that flushing does not reduce yields. Logistically, why would you cut plants off from all that much-needed food during the final stages? Feeding nutrients does not increase yields, nor does it lower yields..
Can you only flush before your harvest?
It is a common practice to flush cannabis plants 2 weeks before your harvest date, regardless of whether you are growing a 7-week indica strain, a 12-week sativa or an auto-flowering cannabis plant. However, some growers prefer to flush their plants after a long vegetative period to help reduce the amount of salts in the growing medium.
Alternatively, flushing your plants when they have been over-fertilised or when the runoff EC levels are proving to be too high is an excellent way to help restore the balance and keep nutrient uptake, availability, and plant health optimal.
What about using enzymes to flush cannabis plants?
Water is a solvent that breaks down and washes away salt residue, but using enzymes is a great way to help accelerate the flushing process. Growers will often mix water with enzymes during the final 2 weeks of the flowering stage to help clean the roots even further and ensure they achieve a smooth taste and delicious buds.
