Flush your Cannabis Plants for Best Results!


What’s up cannabis growers, my name is Dylan and welcome back for another episode of GreenBox Grown!  Today I will be explaining how and why you should flush your plants right before harvest, and will also give you a demonstration of me flushing out my plants.  Flushing is one of the most important processes in growing quality bud, and it is the process of actually flushing out anything that has been left behind in your plants and soil from the nutrients you used to grow.  In the end, you have a much smoother, better tasting smoke which isn't full of harmful chemicals!  So now that you now why we flush the plants, lets go see how it’s done.

Alright so here are the plants we will be flushing, 4 blue dreams which I SCROGed and Lollipoped below right before flower.  Now most people say flush for 5-10 days, but I always push for 2 weeks and I highly recommend you do that as well.  You really want to get all those nutrients and anything else left behind in your buds, out of there!  If you’ve ever smoked unflushed bud then you’ll know why.  If not, let me explain.  The smoke tastes horrible and is extremely harsh!  It’s really an unpleasant experience, plus it can be very unhealthy smoking those chemicals left behind from the nutrients.  There’s a really cool way to tell if the weed you are smoking has been flushed properly besides those.  After smoking the bud, look at the color of the ash.  If it is white, then it was properly flushed, and if it is black or dark, then that means the weed wasn't flushed enough or at all!

So now that you understand why were are flushing these plants, it’s time to discuss when it should be done!  This is very important because you want the flush to finish right when your buds are ready to be harvested, so timing is key.  Also, I always recommend starting earlier than later with the flush, because you can always extend it if the plants aren't ready after 2 weeks.  If you wait too long, then the buds may be over developed by the time the flush is finished.  And of course that isn't the end of the world because the buds will still be smokeable, I am more just talking about the optimal way of doing this!  

So as you can see we are looking at the trichomes for making this decision as they are what I use for making the final decision of when to harvest.  I find that over 2 weeks time the trichomes become 15-20% more amber.  For example, I like to harvest at 25% amber, so I start my flush at around 5-10% amber because it will change close to 20% during the flush.  And here in this shot you can see we are just in that 5-10% range of amber so we are going to start flushing.  Just a quick reminder to always check the buds and not the sugar leaves when looking at trichomes, as sugar leaves mature much faster than buds and aren't an accurate indicator.

Since it is time to start the flush, I am going to wait until the plants are ready for another watering and at that point I will provide them with a flushing agent.  A flushing agent is something that comes with most nutrient packs and is just a mix you add to water and then feed to your plants at the very start of your flush.  It helps dissolve and release everything out of your soil and plants so when you start with the plain pH’d watering, it washes out much more easily!  I am using the Fox Farm Sledge Hammer flush as it came with my Dirty Dozen Nutrient Kit, and I will be mixing 2 tsp per gallon.  

These plants are pretty large so I am giving each one about a gallon to a little over.  Also, you can using flushing agents over the course of your grow to help prevent a build up of nutrients.  I do a short flush every month and a half or so and have found it to help with plant health a lot!  When watering try to get about 10-15% runoff out the bottom before finishing!

You will still want to wait for the soil to dry properly before watering again, so that is what I am doing in this shoot.  The soil is still too wet, but once it dries up I will be doing the first plain pH’d watering of this flush.  That will be all these plants get for the rest of the grow as well.  On these close ups you can see how frosty the buds are, and over the period of this flush you will notice them fatten up some more.  

A couple days later, and the soil is now ready for more water.  I will be mixing at a 5.8 pH since I am growing in coco coir, and I am using about 1 and a half gallons per plant.  You really want to flush them out good so try to get 15-20% runoff with each watering from here on out.  Be sure to soak all parts of the soil and don't leave anything out.  This process seems easy and not super critical, but if done properly it can really take your bud to that next level of quality!  And here’s a great shot of the buds so you an see how big they are getting.

Here we are 2 weeks later and the flushing is now complete.  Before I harvest however, I’m going to check out the trichomes just to make sure they have developed enough.  I said my goal was to harvest at 25% amber and it looks like they are right around that level of development!  Again, remember to focus on the buds and not the sugar leaves for making this decision.  Since the trichomes are where I want them, I’m going to begin the harvesting process with these plants.

Alight guys, so that’s everything you need to know about flushing your cannabis plants before harvest!  Remember, the best way to tell if it has been properly flushed is by the ash test.  If after smoking the ash turns white, then the plants were properly flushed.  If the ash is black or some sort of dark color, then the plants weren't flushed at all or just needed to be flushed for longer.  Also, remember how important it is to time the start of your flush by the development of the trichomes, as you don't want to be harvesting late, overdeveloped buds!  As always, thank you for watching and until next time…


Dylan @ GreenBox Grown