How do you mitigate light burn?

I have a problem: whenever I grow a particular strain under intense LED’s, I start to experience some light burn at the tops of the flowers at the crown of the canopy. I have tried raising the lights and altering the light formulas a few times to help mitigate the problem, but to no avail. I have noticed this phenomenon occurring under DE HID’s as well.

There is no appreciable cannabinoid degradation and the terpene profiles are as on point as the rest of the plant, it’s just the bleached appearance of the physical bud. I just instruct trimmers to cut those tops off and I put them into my personal batch. On Halloween next week, if you run into me and I bust out a mason jar packed with pure-snow-white buds, you’ll know the secret to my ways. The buds look scary, but they are still fire!

So, I pose this question to you, @mastergrowers, @CAMasterGrowers, @growopowners, @CAgrowopowners, @GrowOpEmployees, @Caregivers: how do you deal with light burn and the resultant bleaching on your buds?

Thanks for your help, GNET!

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I had the same issue and it really depends on the strain, as you said. Apparently, some are very sensitive and to be quite honest, I have not been able to solve it as well. It is great to know expert’s advice here.

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When I grow certain strains I have to put up a shade cloth. Some strains don’t like direct sunlight . when I grow a few strains I try to give them indirect sunlight. That’s what I do if I run strains sensitive to ligjt.

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Great advice! I suppose I could move these strains under less intense light or even move them out of direct light, I still worry about their development and not getting enough light! What % block do you use?

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check your airflow around those flowers.

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Appreciate that but airflow is solid throughout the room. Airflow definitely could be an issue with other growers’ instances of light burn though.

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My first thought is put a dimmer switch on the lights… second thought is measure ppfd and dim lights accordingly.

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I can always program a light formula that tunes down the light intensity. Great advice, @Dewb!

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I have to ask Nick… When you are rolling through a flower cycle, after first expression, how far along into flower do you start seeing the bleaching?

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Before I forget, what brand/model bulbs ya running?:cowboy_hat_face:

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Hi,

We have see the same effects but we do not relate it to too high intensities!

See: https://www.leafly.com/news/growing/white-tips-on-cannabis-buds

An interesting statement of the articel was:

“We’ve had white tips analyzed separately from the green part of the same bud and found they have higher [concentrations of] THC and much higher terpenes than the rest of the plant,” she noted.

We have seen, so far, that those effects are more related to a combination of the spectrum and the intensity. So the Blue-Red ratio and also the Blue-Green-Red ratio are some aspects we are looking at at the moment.

Cheers

Christoph

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To answer both of your questions, @KrisGrows: the bleach starts to show in about week 5 of flower (this strain finishes in 9-10 weeks) and it matters not what brand I’m running under. I have seen the bleaching happen under every LED brand under which they have been grown as well as under CMH. I have asked other growers who grow the same cut under DE HID’s and they too experience the same bleaching.

I think @ddino made an excellent point when he mentioned that certain strains are just more sensitive than others. I’m just messing with a finicky lady. Happens to the best of us :grin:

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That would stand to reason as well. At that point in the grow cycle I’m pushing a ton of blues, reds and whites in my tunable lights. With my HID cohorts who are experiencing the same bleaching in their cut of the same strain, it makes sense that the 3,000°K lamps that they are using in their double-ended fixtures are causing the same phenomenon.

So let me get this straight, @cschubert: you are saying my pure white Halloween “ghost buds” are actually spookier than all the other ghouls???

Thanks for all this info. I wondered if it had something to do with the spectrum…now I have some evidence to support this. Perhaps I should run a side by side with some 325 Pro’s where I tune down the reds or blues? @cschubert, do you have any idea what color ratio might be causing the effect? At that point it’s 1:1 red:blue, so maybe a variation of that could eliminate the bleaching? Thoughts?

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Nick… Thats what I originally was wondering about as well… your spectrum!

I know you didnt go too low… I have tested down to 350nm, snd 380 is as far as i would stretch it. A long while back, finishing flower, ran a test on 350nm…

Total nanner field, lol!

I think you are spot of with strain specific!:cowboy_hat_face:

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Definitely the strain. She is susceptible to just about everything and a finicky feeder too…just like a picky little girl! Too bad she’s a prize-winning strain!

I always try to incorporate UVB light and far-red as well. I’ve never had issues at 350 nm so I don’t suspect that it’s either extremes of the light spectrum…but maybe…?

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That is where we most likely went wrong in testing them out. Towards the end we did a total flip, so i have two directions to address it… bleeding in during daylight hours instead of a solid switch.

I had another grow in NM that took on the same test, and all of his glass slippers went stoned slipper, lol!

It could be the sudden shift then that popped em, but I will keep trying!

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Yes that could be the case :wink: As you said, Cannabinoids, etc. seem to be on the same level… So I am not sure how accurate your meassuring tools are, because esspecially terpene profiles are hard to measure…

But we have also seen another “version” of bleaching:

The problem here was too high intensity in combination with a Blu-Red spectrum.

Especially under LEDs with lenses, intensity can reach far more than 2,000 µmol/m²/s on specific hot-spots . In nature that would never happen and also not be a big deal since the energy is distributed over the whole range of 350-800nm.

Those Blu-Red solutions provide the whole energy only within the blue and red range of the spectrum. For the photo receptors thats far to much! One strategy of the plant is to move chloroplasts into deeper layers of the leaf or even moving them away from the hot-spot. In the end this could lead to “bleaching” too.

Chloroplasts have not burn they just moved away :slight_smile: The problem here was that in this regions cannabinoids and terpenes had not been developed well…

cheers

Christoph

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That makes sense…it’s like a chloroplast migration…nay exodus!

Great explanation, @cschubert!

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I would not grow that one outdoors. :rofl:

I had an F6 indoor, beautiful plant, hated light, especially the sun. I believe it was the of vreeding in soft light and inadvertently selection for very light sensitive plants. My strain would produce racquet ball sized buds indoor and maybe pingpong sized balled outdoor. It did have a refined yield (cryo crashed wax) that was 50% cannabinoids and 50% terpenes. I kind of want to get it back, stored with an indoor friend, and breed with it, but due to it being an indoor only F6, I probably won’t.

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I ran fruity pebbles this year from crossed the pond. Outdoor the did not like direct light so I put them in a shadier spot and boom locked it in. Sometimes I get strains indoor I put up a shade cloth nothing special seems to do the trick. Again this is strictly hands on experience and my personal opion. I grew 30 plus different strains this year so ive picked up a few tricks along the way!

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