water geven cannabis

All About Flushing Cannabis: How, When and Why

Any cannabis grower should know what flushing is. You should also understand how flushing is done and why the technique is used. Many growers use nutrients or other additives to improve growth of their weed crops. Plants never fully use 100% of the substances you add. As a result, certain compounds tend to accumulate in the plant tissue. Flushing at the right moment gets rid of all the excess chemicals, which will help improve taste and scent of your harvest. It’s not hard to do, but it can really boost your results. That’s why we discuss the hows, the whens and the whys of flushing cannabis below.

Why Start Flushing Cannabis?

There’s many things you can do to help a weed plants grow. Some techniques stimulate big and dense buds. Others promote better resistance to pests and fungi. Yield increase is another common reason to give cannabis plant a little something extra. Common additives and nutrients include nitrogen, phosphorus, and potassium. Although these (organic) chemicals aid growth, flushing cannabis is based on the idea of clearing out any leftover nutrients before harvesting. If you don’t flush, these chemicals can affect the taste and smell of your smoke.

That’s why you may decide to give your plants only pure water in the run-up to the harvest. Doing so forces the plant to use up all of the reserves stored inside the plant’s cells. Any excess nutrients that remain in the soil around the roots or in the plant and its flower buds will be put to use. It’s a useful technique that makes intuitive sense, suited for any growing approach.

Now, the subject of flushing cannabis is slightly controversial in grower circles. Some say that flushing doesn’t produce any real effects, while others claim they never harvest without flushing their plants. Research has been inconclusive so far, and there are sensible arguments (and growers) on both sides of the debate. Still, the majority of growers do flush, and flushing is a relatively harmless technique to use. Whether you want to flush your weed is entirely up to you, but if you do, here’s how to do it.

amsterdam genetics bud
Last steps towards that perfect harvest!

Flushing Cannabis, Step By Step

Step 1: Observe The Growth Of Your Plants

Flushing is done just before harvesting. That means you’ll need to keep a close eye on your plants to determine when to start. The best moment comes at the point when the buds look ready for harvest. Although some of the large fan leaves may have turned yellow at this stage, the small sugar leaves should still be mostly green. Depending on plant genetics and circumstances, this stage can last several weeks, giving you enough time to start flushing.

Step 2: Just Add Water

If you’ve been adding nutrients up to this point, now is the time stop doing so. Use only water during flushing. The one factor you need to control is the pH-value of the water. At slightly acidic pH values between 5.8 and 6.0, you’re right in the zone where all the important nutrients are soluble in water. Don’t change the volume of the water supply. If you start overwatering now, you run the risk of causing nutrient deficits that could damage your crop right before the finish line.

flushing cannabisThe advice is to keep flushing cannabis for several days at least. If you’re growing in soil, a two-week flushing period is fine. Coco or hydroponic growers should flush for about one week. If you’re using organic soil, there’s no real need to flush extensively. A single flush should be more than enough. The soil is already balanced of its own nature; micro organisms have seen to every single need of your plants already. It’s nature’s own way of preventing excess nutrients from stacking up.

Nothing But Water?

Flushing means not giving your plants any extras anymore. However, the following exceptions are made:

  • Bacteria: in hydroponics, beneficial bacteria are employed to help develop healthy root systems, provide protection, and breaking down waste materials in the soil. These bacteria don’t count as nutrients, so you can still add them to the flushing water if you like.
  • Keep checking water pH, and adjust if necessary.

Step 3: Keeping Track Of Leaf Colour

Keep a close eye on the colour of your leaves. Right before harvesting, it’s usual for the fan leaves to turn yellow. The best time for harvesting (and therefore, flushing) is before the sugar leaves start turning yellow. Be wary of fungus, too: bud rot occurs easily at this stage, and that’s the last thing you want right before you haul in those big fat colas.

Step 4: Enjoy Excellent Flavour And Scent

If you get the timing just right in flushing cannabis and harvesting your plants, now is the time to enjoy the outstanding taste and smell of your weed. Remember to dry and cure your harvest before you dig in, but from here on out, it’s only going to get better! All the time and effort you’ve invested is about to be rewarded, big-time…

Flushing Cannabis: Two More Reasons

Two additional reasons for flushing cannabis exist. These are not related to harvesting, but can instead solve problems at other points of your grow.

  • Switching to different nutrients: You can choose to flush halfway through your grow. This can be useful for easing your plants’ transition from the vegetative stage to the flowering stage of the cannabis life cycle. Both stages set different nutrient demands for your plants. If you flush your plants before you switch nutrients, you start out with a clean slate. This prevents accumulation of nutrients still present from the previous stage.
  • In case of nutrient lockout: Your plants may be affected by nutrient lockout. That happens when they are unable to absorb nutrients from the soil. Nutrient lockout can be caused by erratic pH values, preventing the roots from functioning properly, or by excess nutrients in the grow medium. Apply flushing to cleanse the soil and the plants, and adjust nutrient dosages accordingly.

Is Flushing Cannabis Really Necessary?

flushing cannabis rootsAs mentioned before, there are ate least as many views on growing cannabis as there are growers on this planet. Likewise, opinions on flushing cannabis differ from one grower to the next. Some say they tried working with and without flushing without noticing any differences. They claim flushing doesn’t cause any difference in scent or flavour. In fact, some say the flushing cannabis causes more problems than it actually solves. If you do it at the wrong time or in the wrong way, you could decrease or even spoil your harvest.

And yet, if flushing was truly useless, there wouldn’t be so many growers who keep recommending it. So, to flush, or not to flush? It’s easy to figure out what works best for you. Simply grow your cannabis seeds and divide your batch in two. Flush one half before harvesting and don’t flush the rest. You are in the best position to judge your own results. We’re keen to find out whether you notice a difference!