The Importance of Flushing Your Marijuana Plants Before Harvesting

last year

Your plants have been growing for weeks now. You’ve done everything as learned online and those buds on your plants have become nicely big.

You can even see the trichomes on them already and they’re looking really nice. They’ve just started to turn milky in colour. The tops of those plants are starting to look frosty.

Only two weeks anymore and you can harvest your grow. Now is an important stage in the grow process and one which will help you get a smooth flavor for your weed. Nobody likes tasting harsh, throat cutting weed. As if rodents are playing in your throat... no thanks.

It’s time to flush your grow now to get a pleasant smoke.


What is Flushing?

While growing your plants have collected nutrients. These may have come from the soil you used and the supplements you’ve used during the growth. Your plant, and the soil, is now full with these nutrients and minerals.

When flushing your plants, you remove all nutrients and minerals from the soil and force the plant to use up the remaining nutrients it has in it. If done rightly your buds will be free of any nutrients and minerals when you harvest them and you will end up with a nice smooth smoke.

Timing Matters

It’s important to find the right moment to flush your plants. If you start flushing too late you may not have flushed all nutrients out and the taste of your weed is still affected. If you flush too early, your plants’ final growth may be affected and your yield will be lower.

Flushing takes up to two weeks normally. The best time to start flushing is at the beginning of the harvest window.

Almost half of the white hairs (pistils) have turned dark and half of the trichomes have become half cloudy in appearance (milky in colour). This is usually a great time to start flushing.

Beautiful pistils

If you struggle to see if the trichomes are still clear (glass like) or are starting to turn cloudy already, use a cheap jeweler’s loupe or magnifier. The most hardcore growers will even have a microscope to check the trichomes and decide when is the right time to start flushing their cannabis plants.

For most plants this will be 6-8 weeks in the vegetation stage. Make sure you know what is the usual time to harvest for your strain.

Don’t worry about starting on the exact day, cannabis plants have a harvest period of several weeks and will continue to develop during those weeks.

If you’re going for the highest possible THC in your buds, then you have to start flushing early in the harvest window. If you want a smoother effect, start a flushing little later.

How to Flush

Flushing your cannabis plants is as easy as watering them. Just leave the nutrients and supplements out. Water your plants with clear water.

Make sure to still keep an eye on the pH level of your water as you don’t want to shock your plants with an unhealthy pH.


When flushing your plants, water the plant with as much water as the pot can hold. Wait some minutes so the water can absorb as many nutrients as possible. Flood the soil again.

Flush your plants at the same time you would normally water them.

Things to Watch Out For

During the flushing stage it is common that the leaves of your plants start turning yellow. This is because gradually the plant is living of always less nutrients. When almost all fan leaves turned yellow your plant won’t mature any further and you may loose potency in the buds very quickly.

As you near the ideal harvesting time, always more fan leaves will turn yellow. Keep an eye on the small bud leaves, the sugar leaves, though as they should still be green when harvesting.

As soon as the small leaves on the bud have started to turn yellow you should harvest your plant before it starts spreading to the bud.

Generally plants will not mature anymore once the leaves are not green anymore. Make sure to know the genetics about your plant because obviously we now have strains which turn red or dark. But, usually, when the leaves have changed colour and are not green anymore the time to harvest has come.

Note for coco-growers: growers who use a coco-soil mix have a slightly shorter flush period of around a week.

Opinions about the recommended flushing time vary. The ideal duration depends on the soil composition, the grow method, and also how many supplements you’ve given your plants. Fo most regular grows it is safe to say that flushing will take 10-14 days. Some specialists will recommended merely a week of flushing.

When’s the Ideal Time to Harvest?

Depending on what you prefer from your weed, you will harvest sooner or later.

If you want maximum THC, then you will harvest when most trichomes have turned milky in color. Around 2/3 of the pistils will have turned darker as well. Use your jeweler’s loupe to check the trichomes to be sure.

Almost all pistils have turned dark

If you prefer the so-called “couchlock” effect, then you will harvest a little later. You wait until the trichomes have turned darker, amber in colour. More than 3/4 of the pistils have become darker as well now. Now some of the THC will have become CBN (cannabinol), which is responsible for the calming, sedating effect and also helps with insomnia.

The later you harvest, the more sedating your buds will be.

Make sure to take that preference in account when deciding when it’s time to start flushing your cannabis plants.

Inform Yourself Before Starting

If you purchased your seeds from a reputable store or breeder/grower they can advice you on what is the ideal vegetation time and when does the harvest time for that strain usually start.

Practice makes master and an informed grower is a wiser grower.

After harvesting comes the time to cure your cannabis.

Disclosure: This guide contains an affiliate link. We may earn a small commission when you purchase through that link.

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Great article, only thing i would add is that the amount of water needed for a full flush is 3 times the amount of the pot's capacity (24 ltrs of PH balanced water to a 8 ltr pot) :-)


Is that when pouring continuously or do you still let the first pot stand to absorb as many nutrients as possible before flooding the pot again?


the way i do it is i put 3 or 4 pots in the bathtub. If the pots have 2 gallons of medium(in my case coco)i pour with a 2 ltr jug 6 gallons per pot....yes it is time consuming and takes a shit lot of water.I do that 2 weeks prior harvesting, that way in those two weeks the plant has time to eat everything that is left in herself. In those two weeks i keep pouring the normal amount of water on each plant every two days so the plant doesn't dry out. I published a post talking about this a couple of weeks ago:
and in this post you see how the plants have already eaten everything turning yellow:


Loving the tails on that sour diesel.

This method (1+1) you can repeat whenever you would otherwise water as with each watering, after some minutes you replace the water which has absorbed the nutrients from the soil. But it’s more labour-intensive if your grow-room doesn’t have a water management system.


I am re-smoking your post by the way, excellent work, please keep up posting such valuable info ;-)


Thanks, will do my best. I do reserve the right for the odd listicle like my first post here too tho. :D

Great guide. Got any more of those? 😄


Asking the real questions 👆


Too soon? 🤔


YAY for peer pressure?

I read your post about flushing twice till now as the time here pass so slow !

A lot of people here waiting for the same Doctor, who will prescribe us the Hell or Heaven!

90 miuntes passed and I still wait for my turn, to go nowhere !

This is the first time that I comment by mobile, because I went to Hospital by mistake with my password and this is the first time I read original, clear and useful
content about flushing !

Keep the good work mate, you are in the right way and wish me to back home soon as I got bored waiting my F**king Doctor !

Great post. This is exactly what I’m looking for on Upsmoked, resmoked and Followed for more.


Thanks. I will try my best to find a regular flow to publish more guides.

I didn’t know that the leaves turn yellow when ready. Very interesting.


It isn’t really a sign of your buds being ready. It’s a sign that the plant will stop further maturing. The more leaves turn yellow, the less nutrients the plant still has. When most leaves have changed color, the plant can not continue its normal growth anymore (can not turn light in to energy).

It means that the flushing is coming close to an end. You don’t need to wait until all leaves turn yellow btw. If leaves turned yellow faster than you thought they would and your flushing period is shorter, just cure them few days longer to make sure you get a smooth smoke.

Depending on how the plant has survived in last few days, it can go totally yellow almost overnight. If then you wait any longer, it will go to the buds as well and they can lose potency but without going to the high CBD/CBN stage.

If you flood your plants the leaves will go yellow as well. No matter at what stage your plant is.

Haha the whole reason I bought a loupe.


To flush your plants? Isn’t that slightly uncomfortable?



No I meant to check the trichomes.

Waiting for the next article mr!

  ·  last year

Thanks ,very usefull .