Anyone experiment with UVA supplementation?

I’ve been considering adding a few small UVA LED bulbs to my tents. It seems like there are a number of benefits to adding 3-5% UVA spectrum.

  • “Almost all supplemental UV-A irradiation treatments resulted in increased leaf area and fresh weight.”

  • 340 nm UV-A enhanced photosynethesis by 8-10% with non-saturating background PAR at 500 umol m-2s-1.

  • Increased photosynthesis by 12%

  • Increased leaf size and dry weight of plant.

They’re cheap enough on ebay…


From what I’ve heard even if it’s not part of par itself the light outside the usable spectrum helps the rest penetrate the canopy better. Something about higher energy and all carrying other photons farther than they can on their own.


Most “full spectrum led grow bulbs” searches on ebay will turn up 1watt array fixtures.
I’d hold out for 3 watts


I like to use a reptisun from start to finish, but wouldnt say I’ve ever even seen proper experimentation on cannabis with and without UV.

Highly suggest introducing uv during veg and sticking to recommendations (sp?) for reptiles.


I’ll add on that make sure it’s actually able to keep the reptiles healthy as some are scams just like all types of lights

Yeah I already have COBs and QBs in my setup, so I’m looking into bulbs that just provide UV only. I’ve found some at 3, 5, 9 and 15W, with UV options of 360, 370, 380 and 390nm wavelengths.

I was thinking about buying a few 9W bulbs at 370nm.


What about mixing them for a larger scale of UV light to use. Although if you want to test each wavelength individually go with your option obviously.

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This is ultimately what I want to do. I think you can buy ‘kits’ where you solder on 3x3W LEDs into an E27 bulb fixture. Those would be ideal and I could use multiple colors of UVA.


Cool! I stumbled across some high power UVA COBS on eBay yesterday. These claim up to 100W in the UVA 395nm 400nm range but I would suspect they spectrum will be at least a little fuzzier than one pure wavelength, especially given they are cheap Chinese units, in our case this is a benefit right?. I think these lights are used for curing certain plastics so it may be that they are becoming commodity? Anyway, they seem to becoming much cheaper than they have been, especially in the UVA range. UV LED’s, especially in B/C have been expensive, inefficient and reasonably short lived I think, so this has made them impracticable for anyone but the obsessives. :laughing:

I have also read varying accounts of UVC increasing trichome coverage and THC levels, some of it even well documented, but after looking into it, it seemed reptile UVB/UVC bulbs were still the only real practical solution, and well to be honest that sounded like a clusterfk that was more effort than my lazy ass could be bothered with. If UVA has similar benefits as well, then I’ll be really interested to see what your experiment turns up.


UVC is used as a germicidal, tatoo parlors use it to sterilize stuff. One hockey rink I played at had 4 footers in the locker rooms. The light they give off makes you want to get the hell outta there.
This is really a different post since many posts focus on UVB, which is well worth the $ imo.
I ran a grow last year with two UVB 10 reptile bulbs while my buddy had no UV and there was a marked increase in potency from the UVB. I only ran them the last 3 weeks of flower as they wear out quick.
Pet stores have these UVB sensitive cards that darken under UVB but not UVA.
Anyway here’s a breakdown of the bulbs I currently use:
22Red+8Blue+1White+1Warm white+2UVA+2IR

Not sure how plants use infrared but it warms the pots up when they’re on.


Always good to see people doing something new and experimental, there is always a never ending amount of stuff to mess about with. Amazing plant this!:+1:
IR would be just so out of the question for me here lol. Just the air temperature is too hot most of the time in summer, If I forget to fill the buckets even one day I can burn through 12 litres and come home to find completely crispy dried plants. :sweat:


Are you running a hempy bucket system?
One summer a few years back I was away more than home and these little guys saved me.

They don’t work well with nutrient solution as after a few months they get clogged also need black drip line tubing. Clear tubes algae up.


Yeah I’m interested in UVB as well, but there’s also a lot of evidence that UVA is beneficial from a plant health perspective, so I’m starting there.

What wavelength IR do you use? I have started using 730nm in one of my tents but only at the end of the light cycle. I’ve also thought about supplementing extra 660nm. I think there’s an active phytochrome around that specific wavelength.


Yes UVA has a response. I don’t have the documents on hand rn. I’ll dig them up later if needed. Definitely test it if possible. I’ll have to look at what wavelength the zxmean I have use later also. I did notice whatever they use for UV had a good response, but it was intense.


Yeah, I so should have done this, that would have been the sensible thing to do right? I was running DWC in 20 l buckets, but was manually filling them when they got down. Of course being a stoner, forgetting is inevitable, though coming home to 1/2 finished plants completely dried is a lesson that works as a good reminder lol. For exactly this reason I have just finished a reticulating system, it’s only two buckets but they are 30l and sit on a 70l res. The only issue with this so far is it takes 10 mins to equalise the PH when adjusting, and being 130 litres, it uses a lot of nutrients to get it to where it needs to be. That said, I am hoping not to have to change it often if at all during the bud cycle and once PH is dialed in, it’s going to be a LOT more stable.
Plan is that once I have dialed it in a bit and am not going to embarrass myself I’ll post a grow. :grin: I literally have just put a Cindy 99 (my own seeds) and a Tutankhamen( new for me) in to give it a run, so I might give it a few weeks to get things sorted and so long as I don’t kill them, I’ll post some pics! In the mean time I’ll see wha this experiment comes up with :slight_smile:

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For overall photosynthetic response, take a look at the YPF (yield photon flux). See, for example:

That normalized spectra details the known response of the photosynthesis systems and the relative quantum efficiency of conversion. If anything, it’ll give you an idea of the breadth of the spectrum and how efficient the plant utilizes that spectra. You’ll note that it does extend into the UV regions. It will not provide necessarily any more information that might be useful beyond that. Such as the differentiation between the PSI/II systems or the effects of heavy UV, etc…



That was my problem with SIP’s and soilless mediums, the ph would drop right before the end of the grow.
Since I’m home more and use at least 1gal regular pots, watering hasn’t been an issue.
King Tut sounds like fun!


This is from the manufacturer:

Red 650~660nm, 620-630nm---- the best spectrum for plant flowering and fruiting;
Blue 430-440nm, 450-460nm ---- It is maximum peak points for vegetative growth and absorption;
White LEDs ---- Full-spectrum / wide-Kelvin provide fill for all missing spectrums and add Lux.
UV 380 - 400 nm ---- Process of chlorophyll absorption begins. UV (ultraviolet) has the unique function of sterilization and kills phytopathogenic bacteria.
IR 730 nm— There is little absorption by Chlorophyll here, but uses a nice portion. Flowering and germination is influenced.

The IR is supposed to have the same effect on a plant as from the light at sunset.

They say the UVA kills bugs too.


UV also degrades THC though right? So I’m guessing there is a fine line between tweaking UV levels and degrading the stuff you want? So then, it’s how much, for how long in what UV wavelengths is ideal? it’s a bit like messing with things like GA,salysilic acid,methyl jasmonate etc. The limited amount of info means you are just going to have to make some controlled experiments. Luckily it’s getting cheaper to do!


That’s a great question, I don’t really know. Short term, possibly. Long term, probably. Heat most certainly volatilizes terpenes.

[quote=“slain, post:19, topic:17950”]
it’s a bit like messing with things like GA,salysilic acid,methyl jasmonate etc.

Oh yea! That’s what so great about it. Some good scientific literature out there but much is left wide open for discovery…

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