Light intensity during late flower

Hey all, I’m running HLG 300L r-spec in 2 flower tents that are 2×4. All plants are in week 8 flower and I’m waiting for to pistils to be around 50-70% amber or red, as well as the trichomes to be where I want them. So my question is this. Can I turn down the light intensity in late flower and why or why not? Thanks in advance.

I’ll be tagging along for answers id like to know as well haha.

Thats a great question to ask! So i think the easiest way to explain this is look at “mother nature” and how your seasons change and all factors associated. Is the sun more intense in the spring, summer, or fall? Its an apex? correct? As we go from spring to fall, the sun reaches an apex for intensity and then declines.
With that said, all we can do is strive to mimic “mother nature” as accurately as possible inside!
You can also get foxtailing from light intensity, heat stress, light burns, ect.
If you think about it logically, It makes alot of sense!!!
Happy growing!!!


What intensity are you at currently? If they can handle 100%, then why not! You could gradually increase.

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They’re at 100% but the fan leaves are about to start dying off. So I figured the light wouldn’t need to be at 100% when that happens.

That makes perfect sense and in a way I was kinda thinking along the same line. Mine was more to the life cycle of the plant than the seasons.

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Absolutely the more the merrier

Whether it be seasons or life cycle, the same rules still apply….cannabis likes certain conditions at different stages of life. Thats being said, is she going to want the same in veg vs pre-flower vs early/late flower? The answer is in fromt of you lol

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You can monitor your plant’s liquid and nutrient uptake to determine the exact time to reduce lights or follow a chart:



Thats what I was looking for…thanks


Do you really back off on light intensity at flower initiation?
I have seen this chart but where it dips downs, it makes more sense to me to hold steady or increase intensity. Maybe that is why my plants don’t stretch 100%


I’ve been holding at 100 but seems like a waste once the fan leaves start to die off.

That’s a DLI chart. The DLI drops because the light hours drop. Not because the light is turned down. @rookiegrower, I start turning my lights down late in flower. Much like @Northerngreenthumb stated to mimic natural conditions. It does seem to help them finish up.


Thanks that makes sense and was my situation before upgrading a light. Now at least for one grow space, if I can believe the manufactures PPFD maps, I can get close to maintaining the 45+ DLI by using a light intended for a larger space and using it to cover a small space as well as maintaining the height of the light.
I too have been decreasing DLI toward the end of flower. Not necessarily to mimic the sun, but more to reduce the possibility of fox tailing.
I would hate to pay the bill if I tried doing this over a large space. The space is a little over 24x24"


Yep exactly, forgot to mention that as well.


I have also noticed, dimming the lights close to the end helps with fox tailing. This grow, I started dimming about 3ish weeks before finishing slowly, a little every couple of days. It did help minimize fox tailing. Just my 2 cents worth.

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Sounds legit thanks for the input!!