Duration of UVB lights

[stellis0358]

I'm sure there is a thread that speaks to this but I couldn't find one. Simple question (or not I'm sure) what is the recommended duration of UVB lighting on my plants, and at what phase is recommended to start exposing plants to UVB?

 

[Creeperpark]

I'm sure there is a thread that speaks to this but I couldn't find one. Simple question (or not I'm sure) what is the recommended duration of UVB lighting on my plants, and at what phase is recommended to start exposing plants to UVB?

You have to be very careful and stay nearby to watch your plants until you get your UVB light dialed in. It's easy to bronze the leaves on some plant's using different substrates. Some grow's that lack adequate calcium can burn easily. That can happen today and not show up for a week or two.

As far as the duration part is concerned, plants' exposure time to UVB exposure lamps should be carefully controlled to avoid overexposure. This would include 1-2 hours per day during the vegetative stage, with exposure times gradually increasing as the plants move into the flowering stage. Google

 

[Rocket Soul]

Id say it depends on which uv light and distance aswell. When adding uvb you should have at least as much uva mixed in aswell

 

[420PyRoS]

Idk but i blast em right from seed with whatever most likely UVA comes with your typical chinese crap LED lights.

 

[Deleted user 4684842]

I use two 24W Reptisun T5 UVB lamps in my 4x6 tent and I run them 11/13. I think that's enough to simulate a "very high" UV index but I haven't measured the UV output so I could be mistaken. I've slightly burned a couple plants this way but that was intentional. I'm hoping that over time, by giving my Ethiopian hybrids as much UVB as they can take and selecting and breeding the best-adapted ones, I'll increase their THCV content. That's the hypothesis anyway. We'll see.

 

[Thegreengrower64]

I'm sure there is a thread that speaks to this but I couldn't find one. Simple question (or not I'm sure) what is the recommended duration of UVB lighting on my plants, and at what phase is recommended to start exposing plants to UVB?

I use the, 'solarcure flower power uvb bulbs'.
I generally start to use them at around 3-4 weeks before harvest. Starting off with just 30mins per day (on). Watching all the time to see how plants react. Then within a couple of days ( plants are all ok) ill raise to 60mins per day. The uvb bulbs are at a distance from canopy of approx 12 -18inches.

 

[Rocket Soul]

I use two 24W Reptisun T5 UVB lamps in my 4x6 tent and I run them 11/13. I think that's enough to simulate a "very high" UV index but I haven't measured the UV output so I could be mistaken. I've slightly burned a couple plants this way but that was intentional. I'm hoping that over time, by giving my Ethiopian hybrids as much UVB as they can take and selecting and breeding the best-adapted ones, I'll increase their THCV content. That's the hypothesis anyway. We'll see.

THCV = genetics and uvb; make sure you start out with genetics prone to thcv. We tried the Novarine from medical seeds which is bred to high thcv; all 7 seeds where duds and wouldnt get out of seedling state. Nowadays medical only sell novarine like an auto flower, my guess so they can control the genetics.

I wholly agree on breeding under uvb, our latests strains come from a breeder doing this but that bud is still in dry and cure so dont know how theyve turned out.

 

[Deleted user 4684842]

THCV = genetics and uvb; make sure you start out with genetics prone to thcv. We tried the Novarine from medical seeds which is bred to high thcv; all 7 seeds where duds and wouldnt get out of seedling state. Nowadays medical only sell novarine like an auto flower, my guess so they can control the genetics.

I wholly agree on breeding under uvb, our latests strains come from a breeder doing this but that bud is still in dry and cure so dont know how theyve turned out.

Yeah, Ethiopian has pretty consistently tested around 2-5% THCV, I think. I had poor results with THC Victory. So I'm breeding Ethiopian hybrids exclusively and the other strains I've selected to breed with were chosen based partially on how likely I think they might be to inherit the THCV trait from the Ethiopian. So Durban is an obvious choice. Emerald Fire OG Auto I chose because I saw a couple White Fire test around 1.5% THCV. Highland Thai I chose because I've seen a number of Blueberry hybrids test high for THCV and there's Highland Thai in Blueberry.

 

[synapse57]

It will increase all the trichome production. More on the sugar leaves as well. So. Yeah. more THC, CBD, and THC-v is included in those.

I just grew Purple Caper - Luxor's Chocolate CBD. it has some THC-v in there, from my own smoke-testing.

I use the UVB lights around week 6 in flowering until the end. Those T5 10.0 % reptile bulbs work best for me. The jack herer plants that were next to them came out amazing. That's aside from the other UVA lighting I have going on.

The UVA lights made stuff way more purple. The UVB lights made stuff way more fuzzy. It also seems to keep the size down. So, therefore, I wait until later in the flowering.

The Far Red/IR "redlight therapy" type panel seemed to bulk up the buds. The UV light was more for colors & trichomes.

 

[goingrey]

It will increase all the trichome production. More on the sugar leaves as well. So. Yeah. more THC, CBD, and THC-v is included in those.

Interesting that you mention sugar leaves... In this study UV increased THC in sugar leaves only:

Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content

Cannabis (Cannabis sativa) flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its high market value. It is commonly believed that cannabis secondary metabolite levels may be enhanced ...

www.ncbi.nlm.nih.gov

By chance just read about it today in Soft Secrets 2024-02.

 

[Prs2xs]

I use the, 'solarcure flower power uvb bulbs'.
I generally start to use them at around 3-4 weeks before harvest. Starting off with just 30mins per day (on). Watching all the time to see how plants react. Then within a couple of days ( plants are all ok) ill raise to 60mins per day. The uvb bulbs are at a distance from canopy of approx 12 -18inches.

In an 8x8 room, I use 3 - 4ft solacure tubes placed 12 to 24 inches from the canopy, for 5 hrs per day, for the entire veg/flower cycles. I have not had any issues with burning, etc. Using a solarrmeter 6.2, I'm seeing 25uw at the canopy. I cannot really say that I notice any difference in the quality or potency of the final product, but using it in the manner described above, it does limit the vertical growth, which enables me to grow varieties which wouldn't "fit" into my room.
This has been my experience with uvb for the last 4 or 5 yrs. The company that sells the flower power bulbs says it enhances trichome/thc production, but I can't tell a difference- I originally thought it did make a difference, but I think I just wanted to believe it did because of the financial outlay!
One caveat though, I think it does suppress infestations of bugs, and you will notice that the trichs mature, or "age" to an amber more quickly than without.
I will continue to use them because I like to simulate natural sunlight as closely as possible, and because I have a whole case of tubes!

 

[synapse57]

Putting the grow room to bed. Red Lights turn off half an hour after the others. UV lights are on a separate timer. and I really haven't even put up the rest of them yet. they're off til flower. My dumbass ordered 6 x 8ft led tube lights. guess i'll have a wall of lights on the other side. gonna grow a bunch of food. sorry if anyone is OCD about cable control/cords. I'll be adding in a couple more red lights for the other half of my grow.

Bedtime. Reds/IR still on for an extra half hour.

 

[Rocket Soul]

Putting the grow room to bed. Red Lights turn off half an hour after the others. UV lights are on a separate timer. and I really haven't even put up the rest of them yet. they're off til flower. My dumbass ordered 6 x 8ft led tube lights. guess i'll have a wall of lights on the other side. gonna grow a bunch of food. sorry if anyone is OCD about cable control/cords. I'll be adding in a couple more red lights for the other half of my grow.

Bedtime. Reds/IR still on for an extra half hour.
View attachment 19015978

Using both reds AND far reds/IR at the same time doesnt really accomplish anything, youd need only far reds (and much less than 30mins! Watch out for stretch) to do far red end of day treatment. Combining them with reds under 700nm will sabotage your efforts.

 

[synapse57]

Using both reds AND far reds/IR at the same time doesnt really accomplish anything, youd need only far reds (and much less than 30mins! Watch out for stretch) to do far red end of day treatment. Combining them with reds under 700nm will sabotage your efforts.

ah man. that panel is 660nm/850nm. seems to be putting my plants right to sleep tho, over the last 2 days. it's over my 3 auto plants. they're flowering. the rest are photos in veg.

 

[Rocket Soul]

ah man. that panel is 660nm/850nm. seems to be putting my plants right to sleep tho, over the last 2 days. it's over my 3 auto plants. they're flowering. the rest are photos in veg.

I dont think ots going to work the way you intend or whats scientifically supported. Its generally done with only far red 730nm, for a relatively short duration (10w, well spread out/ m2 , for about 2mins) and to be honest of all the times ive seen it done online (not seen a decent science paper on this ever) ive never seem clear cut metrics of this working. Some indications of being able to run 14/10 photocycle without extending the flower cycle but thats about it.



But im very interested in your board, do you log your grow anywhere?

 

[synapse57]

I dont think ots going to work the way you intend or whats scientifically supported. Its generally done with only far red 730nm, for a relatively short duration (10w, well spread out/ m2 , for about 2mins) and to be honest of all the times ive seen it done online (not seen a decent science paper on this ever) ive never seem clear cut metrics of this working. Some indications of being able to run 14/10 photocycle without extending the flower cycle but thats about it.



But im very interested in your board, do you log your grow anywhere?

I just set the REDS on their own timer like 3 days ago. it goes off a half hour later, and all those plants under it, their leaves droop at bedtime. it's like a 40 watt light panel.. over probably 2 sq m.

I've been confused as crap about this "EOD redlight treatment" "put them to bed" advertising. ever since I got this FINNCHY light. like. wtf are they talking about?? i gotta flip switches to ONLY have reds on. confusing marketing.

So. Right now.. Reds are on 1 timer. UVB are on another timer, running 10mins on/ 50mins off. and those are just over my Autos that are flowering right now.

 

[Rocket Soul]

I just set the REDS on their own timer like 3 days ago. it goes off a half hour later, and all those plants under it, their leaves droop at bedtime. it's like a 40 watt light panel.. over probably 2 sq m.

I've been confused as crap about this "EOD redlight treatment" "put them to bed" advertising. ever since I got this FINNCHY light. like. wtf are they talking about?? i gotta flip switches to ONLY have reds on. confusing marketing.

So. Right now.. Reds are on 1 timer. UVB are on another timer, running 10mins on/ 50mins off. and those are just over my Autos that are flowering right now.

The theory: "falling asleep" takes the flower about 2 hours unassisted but in nature its helped by some natural signals. The plant have two photosystems, one for redlight <700 (typical daylight) one for >700nm (typical dusk, reactive mainly to far red 730nm). During daylight these two systems find a balance but in natural dusk conditions the second system prevails and helps the plant to know its bed time. Thing is that the plant will usually have other triggers for this aswell; many times the leaves are going down just before lights off a bit. So not entirely sure how much this actually plays in. When ever ive seen it tried theres always been some other condition put on top of this procedure such as shorter day cycle (11/13 or 10/14) or having far red on during the day aswell so hard to know how much this works really.
Your light; 660 +850nm, even if the 850nm was able to trigger +700nm ( im fairly sure it wont) the 660 will sorta cancel this out by being able to stimulate the <700nm system.

To do this right: use far red, 730nm and nothing else. Youd need around a total of 3000-4000 umols in total per m2 to make the switch. If using fairly modern and efficient far red i usually estimate efficiency of 3ppf/w.
For 1 m2 the equation looks like this:
Watts of far red x efficiency in ppf/w x times in seconds = 3000-4000 per m2

Say 10 w well spread out efficiency 3:
10 x 3 x X= 3000-4000 gives X around 120; 2 minutes about.
But im not too sure how well it actually works. Leave far red on for much longer than this and you will see a looot of stretch.