Flushing weed: this is what you should know

Growing

Flushing roots or washing out weed roots is a very simple technique, but one that you cannot afford to overlook as it can make the difference between a smooth smoke or an unpleasantly rough experience. Flushing weed sounds more difficult than it actually is although knowing when and how to flush does require a bit of research. This article will explain precisely why you need to wash weed and how to go about it.

What exactly does flushing weed roots involve?

Nutrients are added during the period that the cannabis plant grows and flowers to increase the yield and keep the plant as healthy as possible. These nutrients are absorbed by the roots and enter the plant through that way. However, these nutrients can affect the taste of the weed and can make your throat feel sharp. In addition, you obviously do not want all those nutrients to enter your body via the weed. You can prevent this by flushing – and rinsing the roots completely clean.

Technically, flushing cannabis is the process of eliminating surplus nutrients from the soil to prevent the roots from continuing to absorb them and ensuring that plants that have a surplus of nutrients are balanced before harvest. Flushing cannabis is a technique that is performed when a cannabis plant is almost ready for harvest. Flushing is nothing more than rinsing the soil where the marijuana plant is located, to rinse out the fertilizers so that the marijuana buds are nicely clean when they are harvested.

The method is very simple. All you have to do is cease providing your plants with fertilizer and only give them water. The timing is the important factor.

The advantages of flushing weed plants

Cannabis, just as any other living organism, needs optimal nutrients to thrive. When these values ​​are inadequate, the plants will fail to thrive and may even die. However, when we give the plants too much in the way of nutrition, the excess nutrients are not absorbed by the plant or used to grow, but remain as a deficit – in a similar way to the human body. When the plant has those excess residual nutrients at harvest, the end product will be of poor quality. Even though the buds may look healthy, you will notice that:

  1. It is difficult to smoke; the weed is hard to ignite and may even noticeably glisten;
  2. The taste is noticeably unpleasant and harsh because of the surplus of mineral salts in the flower heads;
  3. The smoke causes feelings of irritation; many users report soreness and itchiness in the throat and extreme coughing.

When to flush cannabis plants?

There are several times in the growth cycle of your cannabis plants when it may be appropriate to flush:

  1. In the transition stages of feeding and growth cycles – cannabis plants’ need for nutrients varies, and it can be beneficial to give the roots a clear out before switching to different fertilizer;2
  2. Nutrient lockout, which occurs when your weed plants are unable to absorb the nutrients in the soil or substrate;3
  3. Pre-harvest – this is the time when flushing is essential and is the focus of this article.

Pre-harvest, the moment you should flush your plants depends on the type of substrate

If you use soil, then you should flush two weeks before harvest. If you do use Rockwool or coconut coir, then you should aim to start rinsing seven days before harvest. If your plantation is based on a hydroponics system, flushing can be commenced three days before harvest.

There is only one scenario when flushing should be avoided and that is if you are using super-soil or organic soil. Flushing would result in the destruction of all the valuable microorganisms and harm the biodiversity of the soil.

It is, therefore, vital to be able to identify the signs that show when your cannabis plants are ready to be harvested. You can use a small microscope to view the hairs on the tips, which will allow you to see how long the plant should remain. The strands are white in the beginning, but later they will become darker (more cloudy); when about 50% of the hairs are brown, the plant can be harvested.

You should start flushing when the bulbous trichomes start to turn milky white as opposed to crystal clear.

How to flush weed? 

If you are going to flush the weed, rinse the soil (also called the substrate) of the cannabis plant. In many cases this is soil, but it can also be a hydro substrate, such as rock wool, hydro granules or coconut coir.

It is useful to purchase a pH meter before flushing. When you are going to rinse the soil from your cannabis plant(s), it is important to use water with soil with a pH value of 6. Are you growing weed on a hydro substrate? Then a pH value of 5.6 is better. You can put the pH meter in the water to find out the level.

You will need to add plenty of water to the soil – at least three times the water of the size of the container in which the plant sits, although this is just an estimation since it will largely depend on the nutritional program of the plant.

The water must have the correct PH and EC (electroconductivity) level. Untreated tap water is usually the right acidity, but it is advisable to carry out a quick pH test to ensure that it is between 6 and 6.5.

It is also essential to ensure that the EC level of the water is very low. It really needs to be 0.0. If you struggle to get suitable EC and pH values, we recommend using a commercial enzyme cleaning product, which also means that you won’t need to use as much water for the irrigation. The plants can suffer stress from flushing and need a few days to recover. Using the product means that you only need to soak the soil until it starts to leak from the base of the container.

It might be advisable to take your plants outside or place in the bath as the process does involve a lot of water. Water until the substrate no longer absorbs and wait for the surplus to filter, repeating the process as many times as necessary.

When you water the plants, you have to control the drainage. The last few litres should emerge practically transparent; the best sign that the root washing is complete.

Take a sample of the drained water and use an EC meter. If the sample has a low EC value of under 0.5, the flushing has been successful and will have eliminated surplus nutrients from the soil. The plants will have to use their reserves to balance their internal levels with those of the soil. This will lower their levels, and stop unnecessary amounts of salts passing to the flowers.

When you have finished flushing (until harvest time), the plants will be rinsed clean of all nutrients that were still in the roots and plant. It does have consequences for the plant: because it no longer receives nutrients, the nutrients are taken from the plant itself. You will notice that the leaves will lighten in colour and eventually turn yellow and dry, but this does not influence the quality of your buds.

However, it does ensure that the weed is ultimately clean and tastes better; besides, you can be sure that your weed won’t contain any nutrients. You know what you smoke, that is the major advantage of growing and flushing your own marijuana.

How many times do I flush weed?

Flushing the roots really only needs to be done once before harvesting, unless your plants are showing signs of nutrient-lock during the growing phase.

Once your weed plants have been flushed and harvested, take time and care to dry and cure your weed. All your hard work will be rewarded in excellent quality marijuana that is a pleasure to smoke. Your buds will have achieved their highest potential and will be the envy of all your friends.