How to Flush Autoflowers?

Find out how and when to flush your precious autoflowering cannabis plants!
01 April 2021
6 min read
How to Flush Autoflowers?

  • 1. What is flushing?
  • 2. Why flush cannabis plants?
  • 3. When to flush cannabis plants?
  • 4. Why are plants flushed before harvest?
  • 5. Why are plants flushed during a nutrient lock-out?
  • 6. How to flush autoflowering cannabis plants?
  • 7. Can you flush plants growing in organic soil?

Flushing your cannabis plants is important if you want to harvest some amazing buds. It’s pretty simple with regular cannabis plants, but growers always wonder how to flush autoflowers.

Flushing autoflowers is basically the same as with photos but due to autos having a limited amount of time to grow, you should only flush during the last week.

And, this has everything to do with the lifespan of autos. In this article, you’ll learn everything there is to do about flushing, and when to do it.

What is flushing?

Flushing is nothing but detoxifying your cannabis plants. It is done to remove all the nutrients you’ve previously fed to the plant during its growing and flowering cycle. Just like the human body requires detoxification at times, it’s important to remove built-up nutrients at the end of its cycle.


How to flush autoflowers: what is flushing?

Flushing consists of watering with a higher amount of water to remove the nutrient excess from the substrate.

Flushing is done by feeding a lot of plain water without any nutrients. Generally, you do that at the end of the cycle once the buds turn amber. It’s important to correct the pH of the water before you flush, though. However, one must use plain water sans nutrients to detoxify cannabis plants.

Also, plain water means plain simple water. You shouldn’t add any nutrients, yes, but don’t use any other supplements either. If you flush the plants with added supplements, the point of flushing becomes moot.

Why flush cannabis plants?

Many cannabis growers don’t bother with flushing. In reality, there’s no evidence that flushing actually helps because plants synthesize nutrients in a different way. However, you will notice a slight difference in taste if you put in the effort of flushing. Moreover, flushing helps remove the bad taste of chemicals that can hamper the final outcome of the buds.

Another important factor to remember is that flushing helps reduce the harshness present in the buds. Of course, the harshness is usually reduced if you cure the buds properly, but flushing does contribute to making the buds a lot more smoother.

When to flush cannabis plants?

Flushing can improve the quality of the buds, but only if it’s done right so how often should you flush autos? Well, it depends on why you’re doing it but in general, you should flush up to 3-5 times, allowing the substrate to dry in between flushing, which can take 2-3 days so the flushing process can end up taking up to 1-2 weeks

Now, if you’re wondering when you should start flushing autoflowers, you should know that flushing is done under two conditions, and they are:

  1. Just before harvest
  2. During a nutrient lock-out

Why are plants flushed before harvest?

As mentioned already, plants are flushed a few weeks (at least 2 weeks) before harvest to remove any excess nutrients. For instance, if your plant has a flowering period of about 10 weeks, you can start flushing once it reaches 8 weeks. However, ensure that the plants are almost ready to be harvested before you flush them.

This means that you must check the trichomes or at least take the color of the buds into consideration. If the buds are almost amber with only a few white pistils in between, the plant is ready to be flushed. In case the buds are filled with only white pistils with no amber or red pistils, you will need to wait a bit more.


How to flush autoflowers: why flush before harvest?

Flushing before harvest allows you to get a much smoother smoke while enhancing the aroma and flavor of the buds.

All autoflowers come with a specified flowering cycle, but sometimes the timing changes depending on the nutrients, space, and the way you grow them. For example, if you plant a Gorilla Glue Auto that comes with a specified flowering cycle of 8-9 weeks, you’ll start flushing when it reaches the 6th or 7th week.

However, it’s possible that it needs at least two more weeks to actually complete its cycle. It may need 10-11 weeks at times. This can happen due to the nutrients you have used and even due to temperature. Thus, you need to check the trichomes and the color of the pistils before you start flushing.

Another way to check when to flush is to check the trichomes carefully with a magnifying glass. Trichomes are the crystals found on cannabis buds and sugar leaves. Generally, the trichomes appear clear at first. Then, they turn cloudy until they become a little milky in color. As soon as they begin to look a little cloudy or milky, you can start flushing them.

Flushing your autos should be a planned event. Thus, time it well. What happens if you flush at the wrong time? You simply force the plant to get rid of its own food and render it helpless.

Why are plants flushed during a nutrient lock-out?

The amount of nutrients you sometimes feed to your autoflowers can increase to such an extent that it results in a nutrient lock-out where the plant can no longer feed itself. This situation can be threatening to the plant and usually results in small yields. If the leaves look like they are burnt or are abnormally dark green in color, it’s a sign of a nutrient lock-out. Overfeeding can also result in nutrient lock-out. For example, excess nitrogen can result in nitrogen toxicity where the leaves begin to look like claws.

Gorilla Glue Auto
5 out of 5
first time ever growing and got some amazing colors from this strain with low temps ran it at about 58-64 for 2 weeks and got this color
Jackin Meoff.
Verified customer
Reviewed 26 December 2017

In such situations, it’s important to restore the plant back to normalcy. And, that can be done only by flushing. Flushing removes all the excess nutrients and allows the plant to grow normally. Of course, you cannot correct the problem immediately, but it takes at least 2-3 days for the plant to reset itself and get back to normalcy.

Remember that while flushing to remove excess chemicals is done during the vegetative stage, flushing to make the buds smoother is done during the final flowering stage. There’s a lot of difference between the two.

How to flush autoflowering cannabis plants?

Flushing your autos is pretty simple. Let’s imagine that your plants are ready to be flushed. If you’re feeding 2-3 liters of water, simply use plain water after correcting the pH without any nutrients. If the size of the container is about 3 gallons, you can use about 6-10 gallons to remove all the excess nutrients.


How to flush autoflowers: how to flush autoflowering cannabis

How to flush autoflowering cannabis.

Generally, tap water is used to flush plants. However, make sure you keep an eye on the pH. If you’re too worried about chlorine in the tap water, just let the water sit in an open space for about 24 hours and you’re good to go.

Keep pouring the water into your pots until you see it draining out of the pot. Also, the drained water might look dirty due to excess chemicals. Use your TDS meter to check the PPM. The PPM of the drained water will usually be high. Sometimes it can go up to 1500 PPM. Continue with flushing the plant until the PPM reduces and goes down to 50 PPM. If you cannot achieve that, make sure that the PPM matches at least the tap water you’re using.

Can you flush plants growing in organic soil?

There’s a lot of difference between growing in organic or super soil and using chemicals. It’s best to not flush your plants if they are growing in organic soil because you will kill all the microorganisms present in the soil. It takes time for the microbes to build a suitable ecosystem and you might just ruin it all. 


How to flush autoflowers: can you flush in organic soil?

It's not recommended to flush in organic soil because it may drown the beneficial microorganisms.

The microbes and other microorganisms are already doing a fantastic job of delivering the nutrients to the plant, so they don’t need you to interfere. The ecosystem is pretty delicate and the soil you’ve worked so hard for (if it’s your own super soil) will all go for a waste.

Many people grow organic cannabis simply because they don’t believe in using chemicals. It’s not necessary to flush such plants since they will not produce a weird taste when you’re smoking the buds. Of course, you will have to cure the buds whether they are grown organically or inorganically but flushing is not necessary.

Blackberry Auto
5 out of 5
Grew blackberry in my past 3 runs, love the Fruity berry smell and taste. Everything I grew it always comes out purple buds.
Verified customer
Reviewed 9 July 2021

Last but not the least, remember that flushing helps to improve the taste of the buds. You can experiment by flushing one plant and experience the difference yourself. Flushing + curing = mind-blowing taste, so don’t forget to flush your autoflowering cannabis plants!


This post was most recently updated on April 1, 2021.

01 April 2021