Cannabis takes months to flower to maturity, with countless hours and lots of money poured into your investment. Skipping out on a proper ripening phase means ruining your entire crop, flushing money and time down the drain.

Properly ripened flowers will exhibit a much more profound aroma, look and taste while the THC and other cannabinoids will have a better, more usable effect on the body. Most importantly of all, it will burn properly, and you will only be smoking the cannabis, not the nutrients.

If you run a medical grow room (ACMPR), micro cultivation facility or licensed producer you owe it to yourself and your customers to implement proper ripening techniques so that your product is clean and passes lab inspections.


The Stigma is the hair part of the cannabis flower otherwise known as a “pistil”. Its main purpose is to collect the pollen from the male plant when released and it grows out from the Calyx which is what makes up cannabis flowers as we know them. The Calyxes are designed to protect the plants reproductive system, however, in most cannabis grower’s cases other then breeders, you won’t need to protect any seeds.

Your Stigma’s or pistils will be white or soft yellow to start and over time they will turn a shade of red depending on strain. When your plant(s) pistils darken in color (generally red) an overall amount of 60% – 75% of the plant(s) coverage it is time to start the flushing phase for 2 – 3 weeks depending on strain.

Read your plants hairs (Pistils), not the calendars.

Initiate the flushing phase when 60% – 75% of the pistils have turned orange or red.


Flushing should not be overlooked. It is such a crucial part of the growing phase where it inhibits bulking and ripening of the flowers while packing on THC when done properly. Initiating flush when your plant is at the 60% – 75% mark and flushing for 14 – 28 days depending on the strain. This will ripen your flowers fully, giving the most robust flavors and highest THC that strain is capable of while packing on weight and cleaning the flowers out of stored nutrients, yuk!

The Calyxes we explained earlier will swell and harden, your pistols will mostly all turn red, and the leaves will start to cannibalize themselves, turning yellow.Commonly 14 days is enough for most strains, it is only the sativa dominant strains that sometimes need longer but watching your hairs or Stigmas is the best way from the naked eye to know when to harvest as every strain and phenotype is slightly different.

This method is more precise than following the recommended growing length for your seed via the breeder. This is because every phenotype is different and the seed information will be generic or average timelines, while every seed will take on different traits, sometimes more of the mom, sometimes more of the dad.

Flush with RO or clean water for a minimum of 14 days

Watch your pistils color development


When it is just about time to harvest you can look a little deeper into things and look directly at the trichomes of the plant with a 5x microscope or a good phone camera. The trichomes are small factories, creating different cannabinoids and terpenes amongst other things. The head of the trichome will be a clear ball most its life and toward the end of its life it will go through a milky white stage, then amber and finally a darker shade of red as it begins keeling over and dying (we don’t want that!).

I personally prefer to harvest my cannabis when the trichome is a milky white with some starting to turn amber. It will be a high potency at this point with no dying trichomes. Without too much of the couch lock that comes with the amber trichomes (and indica strains).

Use a microscope or good camera to see your trichome development

Do not let the trichomes keel over and die (this would be growing past 100% red hair)


The flushing phase is not the same as your normal water feeds. You will want to feed the plants more then normal, of clean water with zero nutrients and no pH up or down. It is not necessary to adjust your pH when flushing, this is because of not having nutrients in the tank that you want your plant to take in as the only reason to adjust pH is so that your plant takes in the right level of nutrients. This and the fact that adding pH down or up will add PPM, or acid to the tank that your flowers will take in during the last phase of its life, which we don’t want either.

Feed your plants 2x – 3x the amount of water as normal, RO water is ideal in this stage as well as growth if you can. Do not let your run-off water sit in your trays or tables and if in recirculating hydroponics flush out your system much more frequently the normal. This will allow your expelled nutrients built up in your root base or medium to wash off. Of course, recirculating hydroponics run off will reach low PPM quicker than a system with a medium, but it is still just as important to flush for the 14 – 28-day period to allow the plant to go through the ripening process, cannibalizing its leaves, using up stored nutrients, packing on the THC and weight.

Feed 2x – 3x the regular amount of water in a drain to waste system, and flush out 2x – 3x as much in a recirculating hydroponic system during flush

Do not let plants sit in the runoff, allow proper drainage


The grow room design and environment are very important to your success and controlling it properly will be key to producing craft quality bud.

As soon as you see that your stigmas are at the 60%-75% mark you need to either lower your light intensity down 50% or turn half of them off. This mimics the sun being further from the plants at the end of summer because of the earths axis and allows your buds to harden up properly becoming much denser. You will also need to cut c02 off at this point.

Your temperature should also be dropped as well down by about 6 – 8 degrees Celsius from your normal. We want to ease the temperature down gradually like with any transition in growing.

C02 will need to be cut off at this point completely.

All of this will help the plants flowers harden up during ripening and develop the most aromas and THC possible.

Cut off c02 enrichment completely when initiating the flushing phase

Lower light intensity to 50% when initiating flush or turn half you’re lighting off if you can not lower intensity

Lower temperatures in the room by 6 – 8 degrees Celsius the first week of flush


Advanced ripening techniques will bring out the Anthocyanins in your cannabis which are the pigment or flavonoid that causes the purple color, change the colors of your pistils from a orange to a deep red or pink. These techniques can massively increase your THC content or help sugar up the inside of a canopy that did not receive good light.

COLD WATER OR ICE TREATMENT: This method refers to chilling the medium of the plants by either chilling the water of the recirculating hydroponics system or the feed water to your plants in soil, coconut husk or rockwool. You can do this by purchasing the large blocks of ice from gas stations generally used for fishing and placing them in your reservoir tank, setting your water chillers to the lowest setting or adding ice above the plants.

Using this method along with cooling the room will bring out lots of colors in the cannabis as well as THC. THC and other cannabinoids are a defence mechanism for the plant to help bugs stick to it and protect itself, we like it for other reasons though! Adding more stress like this towards the end of the plant’s life will naturally bring out more of what we love.

Cool the water of your feed tanks as cool as possible to bring out colors in the cannabis (Anthocyanins)

Use large blocks of ice to prolong their cooling period and water chillers

ARMAGEDDON: During the final 48 hours of the plant’s life, you can implement what we call “Armageddon” to induce a massive final push of cannabinoids and colors to the plant via light and temperature stress. During this last 48 hours you will want to keep the rooms completely dark and as cold as possible. This should only be done for 48 hours as longer (3 – 4 days) can cause seeds to begin development. The final 48 hours we have tested on countless strains and will be just fine though.

This technique can be great for sugaring up the inside of a canopy by harvesting all the top flowers, then leaving the inside canopy for 2 days before you chop that.

Only implement “Armageddon” for the last 48 hours before harvesting

Make rooms as dark and cold as possible

Be gentle when harvesting cold cannabis as the trichomes are more brittle at this stage

These ripening techniques and all the methods offered by 4trees Cannabis Building are the results of over 23 years in the “field”, we are so glad to be able to share as much as possible with the world so that we can help people grow the best, craft quality cannabis that is possible.

close up image of a cannabis plant

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September 2022


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