Washing Marijuana Roots: What It Is and Why It Matters

Cannabis root washing: a simple technique that makes the difference between a very pleasant result and a not so pleasant one. We explain to you how to wash the roots of marijuana plants.

What is Marijuana root washing?

Technically, it consists on removing nutrients excess from the substrate, to prevent the roots continue to absorb them and to balance those plants that have a surplus of nutrients.

The technique is very simple. Simply watering our plantation with water, but now we will see the process in detail.

Why is it important to wash the roots of marijuana?

Like any other living thing, weed will need optimal nutrient values. When these values are insufficient, the viability of the plants is compromised to the point where they can die.

However, when we go too far in providing the plant with food, what the plants are doing is simply absorbing it in a preventative way, in order to use the nutrients in case of a deficit that might arise later on (exactly as the human body does).

But when the plant has that excess of residual nutrients at the time of harvest, the resulting product will not be the best possible. No matter how good the harvested buds look, you’ll see that:

• It’s hard for you to light the joints, sometimes they’ll even sparkle.
• The taste is quite unpleasant due to the excess of mineral salts present in the buds.
• The smoke is irritating when swallowed, leaving a very unpleasant itchy throat that sometimes causes a violent cough.

Apart from that, more problems can arise if the plants are fertilised in excess,  resulting even in the death of them.

How do I know if it is needed to wash the roots?

Cannabis nutrition is a progressive process. The plant does not have the same needs throughout its life cycle.

At first, it requires very little amount of food. And, as it grows, we will have to enrich its nutrition until it reaches a peak that coincides with the last weeks of flowering (sixth, seventh or eighth week depending on the strain). Visit our article on basic NPK nutrients for marijuana.

At that point, you have to be very careful because the last few days will see a drop in demand. And, if we continue with rising the amount of nutrients, we will be spoiling the harvest after so much work.

If we ignore the signals sent by the plant and continue to provide fertilizer, we will be overfeeding.

These clues are easy to see: if our marijuana plant has an excessively bright green color, it’s probably trying to metabolize an unnecessary amount of mineral salts. visit our article about the shortages and excesses of the marijuana plant.

How do you do a root wash?

As we said before, what you’re going to need is to add a lot of water to the substrate. To give you an idea, you will need three times as much water as the capacity of the container in which the plant is located. Although this is an approximation, as it will depend to a large extent on the nutritional program of the plant.

When it is time to fertilize, what you will do is simply watering, although with clean water, it is very important that the water has the correct pH and EC.

Untreated tap water usually has the correct acidity. But it doesn’t hurt to do a simple check using a meter to make sure it’s between 6 and, at most, 6.5.

It is also important to check that the EC (electroconductivity) level is as low as possible. A suitable value is 0.0.

In case you cannot achieve these pH and EC values with your water, it is recommended to use a cleaning product with enzymes.

This product is also recommended to not have to use so much water, which can cause a shock to the plant, from which it will take several days to recover. If you do not want to be at risk of this shock it is best to always use the product and watering with the normal amount of water. This is, as usual,  until the water soothes all the soil and starts to come out from the bottom of the pot.

You can take your pot to the bathtub because you’ll need plenty of water. Water until the substrate no longer absorbs more and wait for it to filter the excess, then repeat the process as many times as necessary.

While watering you have to control the drainage. The last litres you will see must be practically transparent. That’s the best sign that root washing is complete.

If you want to test it in a more scientific and accurate way, you can use an EC meter with a sample of the drained water. If the measurement returns low EC values (less than 0.5), you can be sure: root washing has worked.

What we seek with this great irrigation is, as we said, to remove the excessive nutrients from the substrate.

Thanks to that, the plant will be forced to use its reserves to balance its internal levels with those of the substrate. This will, of course, lower their fertilisers levels and prevent unnecessary amounts of salts and harmful particles from entering the flowers.

How many times should I wash the roots?

In principle, avoid doing it as long as the plants look healthy and do not have excessively high greens.

We would recommend that you do not wash them during the growth process. Keep in mind that if you limit the nutrients at this stage, the size of the plant will be affected.

Once in full bloom, it is much more appropriate to do a root wash, especially in the last 15 days just before harvest.

Always keep in mind that it is better to use a specific cleaning product than to use so many liters of water, which can shock the plant and also flood the substrate for much longer.

After all, this is the time when we will be closer to harvesting and, as we have already said, we do not want too many nutrients to ruin our experience.

Igor Vieira