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Lesson 8: Flowering

Discuss Volker’s Flowering lecture here.

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I was once told to leave the plants in total darkness for 3 days when switching from vege to flower. Is this true?


I’ve never heard of this and I’m inclined to say it’s not necessary, you just need to start your 12-12 cycle. @Growernick ?


Growers have claimed for years practice of leaving your plants in total for darkness for three days prior to harvest spikes THC levels, but there have never been any studies to prove this. We largely chalk it up to a long-held growers myth.

Chop your plants right at the end of the normal dark cycle and you should be great! Good luck!


Thank you very much. I appreciate it.


Happy to help :+1:

Let us know if you have any other questions along the way.

Happy Growing :evergreen_tree:


In what week of flowering growers see the first noticeable yellowing on the plants ?
For me is week 4 . And do you think thats more bc of lack or nitrogen , or its more phase where the plant simple dont use the N , no matter you feed them or not with N .
My plants , most of the strains look super yellow when i harvest them week 9 , i dont need even to strip them . Not all strains ,some stay more green .


More then likely your bloom nutrients dont have enough nitrogen in the ratio. To be yellowing at week 4 of flower is pretty early.


At what week are you cutting out your N, @eldindupljak? How many weeks do these particular cultivars usually take to mature to harvest?

Although this can be cultivar-dependent, it sounds like you are doing things right. Your plants should have spent all available N before harvest and the chloresis (yellowing) at harvest is a sign of healthy plants.


I finish late grow with the VEG NUTES with 5 ml per G ; I stay with the same 5 in 1 week of Flowering; 2W= 3ml ; 3W=2ml; 4W=1ml;5W=1 ;
So i stop the VEG NUTES on week 6 , but still the FLORA MICRO contains N which i feed until week 8 . Its light dep , so depend from the sun hours - usually week 9


To be honest i dont believe that changing the formula of nutes in short period is doing something , even on longer i am sceptical . BC of two reasons : 1. The plant is storing food through all the life cycle 2. Even we grow with soilless medium most of them have big enough CEC to keep nutes locked and by the need to exchange cations/nutes with the root zone/plant .


I think your plants are agreeing with you. The fact that different cultivars are yellowing at differing rates while feeding the same NPK to the entire crop is a clear indicator of that


I am doing experiment i have 9 plants in 3 groups (3x3) , one group i feed with half strength 0.7 EC , one with normal 1.4EC and one with double 2.1 EC . If i dont see any noticeable difference i will definitely take my hands from nut formulas and supplements .


You may be able to save some serious overhead by scaling back the amount of nutrients or the frequency of nutrient applications. Always look at your final harvest weights against previous harvests to establish benchmarks or key performance indicators (KPI’s). If you are able to reduce the amount of fertilizer input into your crop without sacrificing final weight, imagine the money you can save in operating costs. This is where your data is king!


Maybe sounds silly but i dont believe in nutes deficiencies , i explain that with : I never in my life have problem with a good establish plant in late VEG (and i grow big plants ) , and thats the time when they eat a lot . Usually the problems occur when the plants are in early VEG stage when the plant is not strong enough and have problems bc of environment : hot,cold,lack or too much light ,cold-hot root zone and ect . After the process of hardening the plant will establish stronger root system and get stronger , meanwhile the grower will do something ( like add Cal-Mag, or repot ) believing that he fix the problem , misleading the cause of the problem . Most of the nutes deficiencies are like that , thats my opinion :smiley:


Could also be vpd issues.


If you have plants that seem to be taking longer than 2 weeks after light flip to start throwing pistils, many growers will suggest giving them a long dark period to really give them the hint: it’s bloom time!

It is, however, unnecessary for your typical flip from veg to bloom.


Sounds stressful to be in the dark for those 3 days. That means no photosynthesis? So no energy which means that the plant starves for the last 2 days or so?

Plants do math … at least outside ones do. They know that the darkness will be a certain length of time so they begin to ration their stored energy accordingly. I can’t see how this would help them in any way. Could be the illusion of a boost in health after the light finally comes back on. But what’s the benefit to the plant in the end? Interesting.

I apologize I’m commenting here without hearing or reading the lecture.


How do plants flower outside when they don’t get 12/12? For example sunsets at 9pm in summer but sunrises at 6:30?


Cannabis uses a process known as photoperiodism so it can know when to flower

It doesn’t necessarily need 12/12 to trigger this. Indoor growers use 12/12 to simulate the autumn equinox which is the point of the year where the length of the day is the same as the length of the night.

The summer equinox is the point in the year where the day is the longest and the night the shortest…I think it’s June 20th in the northern hemisphere. After the summer equinox the plant begins to recognize that the days are shortening by photoperiodism and that is all the plant needs to trigger the flowering process.

Obviously this is a process that happens slower outside because the shortening of days is a gradual process and indoor the grower just changes the schedule all at once, hence when you start 12/12 indoors you do begin to see pre-flowers in about a week or sooner depending.

From there it takes about 8 weeks

Outdoors, even though the plant recognizes the shortening of days, it’s flowering process will be much more gradual just like the shortening of the days is much more gradual.

The plant recognizes this inn late June too early August but many people don’t harvest until late October or even early November outdoors making the actual flower period closer to 12-14 weeks or even longer depending on a number of factors.

Make sense @fusiondesigner?