How Important Is UVB Light?

[Celticman]

How Important Is UVB Light?
I ask this because I understand that glass blocks most of this type of light. yet, I hear that UVB light is important for trich and resin production.
So why would anyone put a glass covered hood over their garden?

or is there a "special" glass people use?

I almost bought 2 glass covered 1000watt systems, but i think I will opt for and open reflector. My room will be big enough (in a friends basement) that I think heat won't be a problem. if it is, It looks like I will have to ventilate!

Thanks,
Celticman

PS Should i reconsider the glass covered hood? How has everyone else dealt with this issue?

 

[jojajico]

How Important Is UVB Light?
I ask this because I understand that glass blocks most of this type of light. yet, I hear that UVB light is important for trich and resin production.
So why would anyone put a glass covered hood over their garden?

or is there a "special" glass people use?

I almost bought 2 glass covered 1000watt systems, but i think I will opt for and open reflector. My room will be big enough (in a friends basement) that I think heat won't be a problem. if it is, It looks like I will have to ventilate!

Thanks,
Celticman

PS Should i reconsider the glass covered hood? How has everyone else dealt with this issue?

u dont need UVB light to grow great bud. hps put out little to no UVB yet they with them u can still produce great bud. MH puts out a little but not much more than a HPS ( 0 ). the only way to see the effec tis to supplent with UVB bulbs. ive seen a few experiments but none to completion only ppl saying they are gunna try it. if this is your first grow or your a commercial grower dont even worry about it. the book is still out on wether or not UVB makes the plant produce more cannaboids but there is some good evidence that it does.

 

[Guest]

I agree,and if you go with non-shieded hoods try the vertizontal,its a 4 ft octagonal hood.That and a 1K hortilux and you'll be saying uv what?

 

[Mister Postman]

I have provided supplemental uvb from start to finish for all my indoor closet grows. Do I think it's needed for good buds? Absolutely not, as 90% of indoor growers do not provide it, and buds have always been descent. Does it complete the spectrum, enhance quality, and trich/thc production? I believe it does, and has, so that's why I continue to use them. I got hooked on uvb, and the possible benefits back in the 80's when it started to replace the 'full spectrum' fluorescents widely used in the zoo's I was working with. All forms of life seemed to benefit from the addition of uvb in the natural vivariums. Plants grew stronger, flowers more vibrant, and species that had trouble thriving in captivity now thrived, and soon reproduced.

The uv rays a mh puts off is minimal, and a hps practically none. Glass enclosures will totally irradicate whatever they do prvide. I provide uvb with uvb producing bulbs made for the keeping sun loving reptiles in captivity.They're called reptisun 10.0 and they come both in a cfl, and long fluorescent tubes. All uvb bulbs are not created equal. There is crap on the market. I have tested about 30 different brands, and the reptisun 10.0's is the best you can get as far as providing the most uvb, and projecting it the furthest from the bulbs surface. There are bulbs out there that can match the suns uvb production, but they are a bit to costly, and a bit powerful for me to be experimenting with at this time in my closet http://reptileuv.com/megaray-zoo-externally-ballasted-eb-60-watt-lamp-kit.php.

I've been experimenting recently with turning the uvb lights off 2-3 days before harvest. The same concept as turning off all the lights, but I've only been removing the spectrum that would be causing the most degradation before harvest. The idea is to "stack the trichomes". Basically getting the plant into the rythm of producing trichomes in the night cycle in anticipation for the degrading morning sun, and uvb rays, and then removing the uvb right before harvest, and allowing them to build without being degraded.


couple of links I've found
http://cannabisculture.com/articles/2159.html
http://www.greenmanspage.com/guides/thc.html
http://www.onlinepot.org/medical/marijuanaopticsfinal.htm

 

[Guest]

Great UVB info bro,my friend uses a reptisun for his iguana that he cherishes so I know its about the best out there

 

[jojajico]

the book is still out on weather or not UVB really makes a difference. i think it can under the right conditions and plan to do an experiement with it when i get everything else setup.

has anyone done a side by side comaprision with a UVB setup and anon UVB setup? then done a side by side smoke report. thats about as scientific as we can get as most of us dont have access to the the large and expensive equipemnt to analyis our bud.

 

[Rosy Cheeks]

All forms of life seemed to benefit from the addition of uvb in the natural vivariums. Plants grew stronger, flowers more vibrant, and species that had trouble thriving in captivity now thrived, and soon reproduced.

You almost deserve negative reps for that post Mister Postman, because what you say is erroneous, and potentially dangerous. You gave an unknowing grower the impression UV-B is good for just about everything.

Let's put things straight. Ultraviolet radiation is dangerous and bad for most living organisms, humans and plants included. The kind of ultraviolet radiation that we refer to as UV-B [ 280-320 nm ] is particularly dangerous. It does not penetrate far under the skin (or the epidermis of the plant), but it penetrates the cell structure of an exposed cell and destroys it from within. In both humans and plants, UV-B can cause DNA damage, and mutations (from defect DNA). We know with certainty that UV light causes cancer in humans.

There are a few positive effects from UV radiation, such as production of vitamin D3, which is necessary for calcium metabolism. Vitamin D3 is produced in the skin from UV radiation (sunlight). While vitamin D3 can be supplemented in the diet, certain reptiles make better use of vitamin D3 produced within their bodies than that provided in vitamin supplements, which is why - if they're kept indoors - they profit from restricted doses of artificial UV-B. But for humans, additional UV-B (apart from what you get from sunlight) brings nothing good. So called reptile lights (high in UV-B) should be handled with care.
Any organism exposed to UV-B has to try to protect themselves against this kind of radiation. Plants seem to suffer less from UV-B than humans. Still, research shows that secondary effects of this damage may include reductions in photosynthetic capacity. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity (yield) in many plant species.

Preliminary research made by Pate and Lydon in the early/mid 80's indicated that THC could work as a defense mechanism against UV-B in Cannabis, and that increase in UV-B radiation therfore increased the THC production. Their experiments demonstrate that under conditions of high UV-B exposure, drug-type Cannabis produces significantly greater quantities of THC. They have also demonstrated the chemical lability of CBD upon exposure to UV-B (Lydon and Teramura 1987), in contrast to the stability of THC and CBC. However, studies by Brenneisen (1984) have shown only a minor difference in UV-B absorption between THC and CBD, and the absorptive properties of CBC proved considerably greater than either.

Research made on use of artificial UV-B on indoor grown Cannabis has so far failed to prove any increase in THC levels. We still don't know exactly how the relation between UV-B and THC production in Cannabis works.

 

[jojajico]

You almost deserve negative reps for that post Mister Postman, because what you say is erroneous, and potentially dangerous. You gave an unknowing grower the impression UV-B is good for just about everything.

Let's put things straight. Ultraviolet radiation is dangerous and bad for most living organisms, humans and plants included. The kind of ultraviolet radiation that we refer to as UV-B [ 280-320 nm ] is particularly dangerous. It does not penetrate far under the skin (or the epidermis of the plant), but it penetrates the cell structure of an exposed cell and destroys it from within. In both humans and plants, UV-B can cause DNA damage, and mutations (from defect DNA). We know with certainty that UV light causes cancer in humans.

There are a few positive effects from UV radiation, such as production of vitamin D3, which is necessary for calcium metabolism. Vitamin D3 is produced in the skin from UV radiation (sunlight). While vitamin D3 can be supplemented in the diet, certain reptiles make better use of vitamin D3 produced within their bodies than that provided in vitamin supplements, which is why - if they're kept indoors - they profit from restricted doses of artificial UV-B. But for humans, additional UV-B (apart from what you get from sunlight) brings nothing good. So called reptile lights (high in UV-B) should be handled with care.
Any organism exposed to UV-B has to try to protect themselves against this kind of radiation. Plants seem to suffer less from UV-B than humans. Still, research shows that secondary effects of this damage may include reductions in photosynthetic capacity. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity (yield) in many plant species.

Preliminary research made by Pate and Lydon in the early/mid 80's indicated that THC could work as a defense mechanism against UV-B in Cannabis, and that increase in UV-B radiation therfore increased the THC production. Their experiments demonstrate that under conditions of high UV-B exposure, drug-type Cannabis produces significantly greater quantities of THC. They have also demonstrated the chemical lability of CBD upon exposure to UV-B (Lydon and Teramura 1987), in contrast to the stability of THC and CBC. However, studies by Brenneisen (1984) have shown only a minor difference in UV-B absorption between THC and CBD, and the absorptive properties of CBC proved considerably greater than either.

Research made on use of artificial UV-B on indoor grown Cannabis has so far failed to prove any increase in THC levels. We still don't know exactly how the relation between UV-B and THC production in Cannabis works.

good post.... so let me get this right scientist have shown that cannaboids can act as a UV defense but not that the plant uses them in this manner and it has not been shown indoors to increase cannaboid levels?

if anyone does decide to suplpment with UV-B you should setup a system in which if you enter the room or open the cab doors the UV-B lights shut off so that you are not exposed to it.

 

[Mister Postman]

You almost deserve negative reps for that post Mister Postman, because what you say is erroneous, and potentially dangerous. You gave an unknowing grower the impression UV-B is good for just about everything.

Yes your right, it contradicts the science. It's uvb I didn't think I had to explain the science. I said positive effects, in stronger plant growth, more vibrant flowers, and an all around thriving vivarium could be seen with the addition of UVB fluorescent bulbs, but uvb is still uvb, and thus yes always had negative effects as well (not nearly the sun, but enough for vitd3, and calcium absorbtion in the reptiles. I'm not a plant expert, but I sure am a specialist with reptiles, and natural vivaria so I rave uvb LOL. The benefit to the plants was just observation)

in the past there were no bulbs on the market that could match uvb production of the sun in these high altitude locations indoors. Those reptisun 10.0 not even close to the sun. That bulb I linked to is the first that comes that close in reproducing the suns uvb levels. I'll be experimenting with them, but having nothing more then a smoke test to judge potency LOL.. no mass spectrometers here

I say mess around with the fluorescent all you want. They are not of the strength to burn your eyes out. Look at me 15 years under them and still well just as blind as before them LOL, but they just provide a minute percentage ompared to the sun.

I use uvb as addition to the indoor spectrum. Giving my ladies a little taste of home etc. A plant grown indoors would have access to 0 uvb under hps lights, how much of a real difference would 40 microwatts from a fluorescent bulb mean to it.. I don't know, but in my opinion many of the benefits can go unseen. If it's unseen, it's understudied. It took years, and years of killing captive reptiles to before figuring out the correlation, and benefits in captivity. if the bulbs are available to make my indoor lighting more like the outdoor lighting, I'm gonna use it. I run my lights from lights on to lights off, none of that 15 minutes blasts of uvb like in one of the earlier experimental reports i read on line. I know the bulbs produce a fraction, so they stay on while time the lights are on.

That bulb i linked to for zoo enclosures. DO NOT MESS AROUND WITH. Those match the suns UVB strength, and will burn if improperly used.

 

[Rosy Cheeks]

Sorry if I jumped down your throat Mister Postman, but we don't want any kids to end up in hospital due to growing pot, do we (lol)?

As to the dangers of UV-B fluorescents, it's all relative. I believe most of them are somewhere around 5%-8% UV-B, and the output depends on the wattage. On their own I don't think they cause much havoc, but in combination with high doses of sunlight, who knows? Sensitivity to UV varies amongst the world population. A Masai who walks around naked under an equatorial African sun can take higher doses than a fairskinned Finn. The effects of UV exposure is retroactive though, meaning that you can develop a skin cancer as an adult from UV exposure you've received since childhood. So the fact that you've worked with UV lights for 15 years without growing hair on your tongue doesn't mean it won't happen later.

Jojajico, what we know so far is that growers from all over the world report that high altitude growing produces smaller but more potent crops. It is a theory that this is due to higher levels of UV-B present on higher altitudes, and the research made by Pate and Lydon seemed to establish this. But similar experiments performed by Brenneisen did not confirm this, so we must still concider this as a theory without conclusive evidence. If growing with artificial UV-B would have produced similar increase in THC ratios, it would have been a very convincing argument for this theory, but I have yet to see a scientific test grow show that this is the case.
Which leads us to believe that the relation between UV-B and THC is more complex than we understand at present, and that higher potency in high altitude growing could be partially because of other factors. In high altitudes, atmospheric pressure is lower, presence of greenhouse gasses is lower, and a number of microbes and insects are unable to interact with the plants as they do on lower altitudes. It could be that some of these factors are (partially) responsible for the higher potency.

 

[jojajico]

hmm interesting. perhaps a combo of low atmospheric pressure and higher levels of UV-B. lol time to build an airtight grow closet and run a few experiments.

 

[Mister Postman]

hmm interesting. perhaps a combo of low atmospheric pressure and higher levels of UV-B. lol time to build an airtight grow closet and run a few experiments.

Yeah man why not give it go.. get the space aged grow chamber fired up LOL.. The truth is, no one is gonna put the money up, and take up marijuana research for us. They'd rather put money into anti commercials, and research on any negative effects it may have. Not much into the advancement of cultivation, or making higher quality product. Most of that work comes from us who have passion, and common interests (but usually no money LOL), and come here to share our info.

There is a correlation but how it exactly works, and what exactly is taking place is unknown. It may be many factors as rosy cheeks stated. It always made some sense to me as the trichomes are there to protect the developing seeds from the degrading sun rays on top many other things Thus providing the UVB gives the plant a reason to produce more trichomes. This is why harvest takes place before sun up as the suns rays start to degrade the trichomes. I've been experimenting with using the UVB straight through the grow, and then cutting them 2-3 days before harvest. In theory this would cause a stacking of the trichomes. Basically getting the plant into a rhythm of needing to produce trichomes during the night cycle in anticipation for the early suns rays, and then taking away the most degrading rays, and allowing th thc to build. I run the regular lighting as always, but just remove the most degrading aspect which is the uv.

I've also been messin around with humidity which may also play a huge part in potency, trichomes production, and the structure on the buds.. Whether a bud is fluffy or dense may have a lot to do with humidity. They say growers and sellers want the tight dense heavy buds, but selection for this may be bringing potency down.when it comes to potency, and the actual potential for trichomes, the fluffy bud has more surface area on which to produce trichomes on..


All the different aspects of potency really interests me. I try to duplicate to the best of my ability through humidy, and lighting to reproduce a natural enviroment indoors. Not much I can do as far as altitute being underwater, so I try to make up for it in others ways LOL..

 

[jojajico]

the lower atmosphere chamber wouldnt really be hard to build. build it like a regular sealed cab. weather stripping and silicon gel to seal it tight. then paint with a caot of flat white latex paint to really make its air tight. add air pump to create a pressure differential.... yea could work real nice.

 

[Guest]

this is what i find
I can not stress enough the importance of creating as close to natural conditions as possible when it comes to artificial lighting....

One key element...and man do I mean KEY...that all indoor growers should be looking to have included in the arsenal of hardware, is some sort of UVA/UVB light source. UVB being the more important of the two for whopping THC production.

They're are available at most large chain pet stores, small independant pet stores...and of course the ebays of the world.

Best to find an 8-10% UVB, and perhaps suppliment with a 3-5% somewhere else in your space.

 

[Guest]

if you add a mh it will be enough uvb light..
MH will net you a slightly smaller yield, but the bud is more potent due to the UVb inherent in the MH spectrum. Use a cool MH during the veg cycle to maintain tight internode spacing and a warm MH during the bud cycle to add more red in the spectrum for better yield.

One isn't better than the other, it's a matter of preference. HPS puts out plenty of usable light for growing throughout the plant's lifecycle and it will produce a larger yield of plenty potent buds (genetics willing). It's redder spectrum causes a little stretchiness so the plants get to the desired height faster.

 

[jojajico]

if you add a mh it will be enough uvb light..
MH will net you a slightly smaller yield, but the bud is more potent due to the UVb inherent in the MH spectrum. Use a cool MH during the veg cycle to maintain tight internode spacing and a warm MH during the bud cycle to add more red in the spectrum for better yield.

One isn't better than the other, it's a matter of preference. HPS puts out plenty of usable light for growing throughout the plant's lifecycle and it will produce a larger yield of plenty potent buds (genetics willing). It's redder spectrum causes a little stretchiness so the plants get to the desired height faster.

ive seen alot of people say how a MH will produce better bud cause of the UV-B but i have yet to see any proof. like someone posted above test have been done and have not shown to increase cannaboid output. besides a MH puts out almost no UV-B.

 

[Rosy Cheeks]

Brainthor didn't add anything to the topic except some current ideas about UV-B that circulates in the grow forums jojajico. He's right about the superiority of the sunlight spectrum in comparision to existing artificial light, but I dare say he doesn't know any more about UV radiation's impact on Cannabis than the world's foremost scientists on the subject do, and they're pretty much guessing at the moment, so...
Metal Halides do not produce more potent weed than High Pressure Sodium lights. If anyone claims so, please back it up with some serious research, and we'll take it from there. Brainthor simply assumes it produces more potent weed because he heard that UV-B increases THC production, and he knows Metal Halides produces more UV-B than HPS bulbs. The thing is, because of safety regulations concerning UV-B radiation, modern MH bulbs have a titanium coating that filters almost all UV-B. Thanks to that coating, they put out insignificantly more UV-B than a HPS. It can hardly even be measured.

 

[Mister Postman]

ive seen alot of people say how a MH will produce better bud cause of the UV-B but i have yet to see any proof. like someone posted above test have been done and have not shown to increase cannaboid output. besides a MH puts out almost no UV-B.

What kind of proof are you looking for, and who are you waiting to prove it to you? That's a serious question, I'm not trying to be a smart ass LOL. A lot of people saying it has not convinced you, so I'm just wondering what will? If it's scientific research, don't hold your breath LOL. If the goverment is funding studies they certainly would not share how to increase potency with us.. It may take setting up a mh and giving it a go yourself as this topic usually goes back and forth to some degree. Some say pointless, some say I wouldn't do without. It's probably something in the middle hehe.

Mh puts out a little uvb which is better then hps which provides none. Is it enough to make a noticable difference I don't know, but some people say it does When they are usually getting none a little may be a big difference. it would depend how much is needed to preform the function. The fluorescent bulbs I use provide about 1/10 the uvb of the natural sun, which is about 10x more then a mh.

I don't think it's so much a visual output although IME it is to some degree, but what I'm banking on is rather the ability with uvb to turn less pshycoactive cannibinoids such as cbd,cbc etc. into the higher active thc.. I look at my trichomes under the microscope often, and at times have noticed that the trichomes facing my uvb mounted on the back wall are plumper. It's hard to tell if the overall number increases as I have been changing my nutirnet regimen, and have been dialing everything in as i've been growing. On another note I've also noticed the trichomes arn't so quick to go amber. For those who like headier, speedier, more psychoactive highs there may be something here to look into.

I'm pretty much banking on this

(5) "Pate (1983) indicated that in areas of high ultraviolet radiation exposure, the UVB (280-320 nm) absorption properties of THC may have conferred an evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD. The extent to which this production is also influenced by environmental UVB has also been experimentally determined by Lydon et al. (1987)."

The writer's own experience allow for a more specific conclusion: If the UVB photon is missing from the light stream(a), or the intensity as expressed in µW/cm2 falls below a certain level(b), the phytochemical process will not be completely energized with only UVA photons which are more penetrating but less energetic, and the harvested resin spheres will have mostly precursor compounds and not fully realized THC(c).

 

[jojajico]

What kind of proof are you looking for, and who are you waiting to prove it to you? That's a serious question, I'm not trying to be a smart ass LOL. A lot of people saying it has not convinced you, so I'm just wondering what will? If it's scientific research, don't hold your breath LOL. If the goverment is funding studies they certainly would not share how to increase potency with us.. It may take setting up a mh and giving it a go yourself as this topic usually goes back and forth to some degree. Some say pointless, some say I wouldn't do without. It's probably something in the middle hehe.

Mh puts out a little uvb which is better then hps which provides none. Is it enough to make a noticable difference I don't know, but some people say it does When they are usually getting none a little may be a big difference. it would depend how much is needed to preform the function. I don't think it's so much a visual output although IME it is to some degree, but what I'm banking on is rather the ability with uvb to turn less pshycoactive cannibinoids such as cbd,cbc etc. into the higher active thc..

Were pretty much banking on this

(5) "Pate (1983) indicated that in areas of high ultraviolet radiation exposure, the UVB (280-320 nm) absorption properties of THC may have conferred an evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD. The extent to which this production is also influenced by environmental UVB has also been experimentally determined by Lydon et al. (1987)."

The writer's own experience allow for a more specific conclusion: If the UVB photon is missing from the light stream(a), or the intensity as expressed in µW/cm2 falls below a certain level(b), the phytochemical process will not be completely energized with only UVA photons which are more penetrating but less energetic, and the harvested resin spheres will have mostly precursor compounds and not fully realized THC(c).

when i say proof i mean atleast a first or second hand account where a person actually grew clones side by side one with UVB one without. what we get instead is people saying well ive heard this and then presenting it as fact or people syntheisizing data without testing the theory. ie. resin can protect against UVB plants that naturally recieve more UVB tend to be more potent so if i simply add UVB then i will produce more potent pot.... sry doesnt work that way. dont get me wrong im not saying that it wont work matter a fact after a little tinkering i think it will work. o yea and correct me if im wrong buyt HPS do put out some UVB just such a small amount that it doesnt really matter and a MH puts out only a slight bit more than that.

the increase in potency that u precieve may be simply due to slightly denser nugs as a result of smaller internodes... i dunno. but that science man there area alot of factors to consider. those high altitude plants may produce more THC and resin because there is a bacteria that only thrives in low atmosphere conditions and for whatever reason it helps the plant produce greater levels of resin. there are just too many factors and even when we think weve got it nailed down we dont. b4 i start growing under only MH light i will def do a small personal study b4 hand to make sure its even worth it.

 

[Mister Postman]

when i say proof i mean atleast a first or second hand account where a person actually grew clones side by side one with UVB one without. what we get instead is people saying well ive heard this and then presenting it as fact or people syntheisizing data without testing the theory. ie. resin can protect against UVB plants that naturally recieve more UVB tend to be more potent so if i simply add UVB then i will produce more potent pot.... sry doesnt work that way. dont get me wrong im not saying that it wont work matter a fact after a little tinkering i think it will work. o yea and correct me if im wrong buyt HPS do put out some UVB just such a small amount that it doesnt really matter and a MH puts out only a slight bit more than that.

the increase in potency that u precieve may be simply due to slightly denser nugs as a result of smaller internodes... i dunno. but that science man there area alot of factors to consider. those high altitude plants may produce more THC and resin because there is a bacteria that only thrives in low atmosphere conditions and for whatever reason it helps the plant produce greater levels of resin. there are just too many factors and even when we think weve got it nailed down we dont. b4 i start growing under only MH light i will def do a small personal study b4 hand to make sure its even worth it.

No way to judge potency and its effectiveness even with a side by side test with clones. The benfits go unnoticed for the most part as it's dealing with the chemicals themselves which none of us can test regularly. maybe pics of the trichomes would help, and I have noticed more vibrant colors, but You'd have to smoke it to really tell the difference, and even then i know I have trouble judging potency even of different strains sometimes. Some are so close in potency, but have subtle diffrences. You really need the mass spectrometer gas chromatigraph mumbo jumbo they use to test potency. We really need further studies in this direction IMO there is a lot to be learned here. I say give it try. I have, and have always been happy with my results. it certainly doesn't seem to be hurtin any. I'd do a test grow with a clone, but I doubt you'd be able to ntice anything in pics. If anything my plants are living i more natural enviroment. Worse case I'm paying for 40 extra watts. Worser case like rosy cheeks said I could have hair on my tongue in a month

Thats the thing.. no one knows. Where looking at data from the latest 87. For Gods sakes these bulbs have come light years in the last 10 years. If I remember correctly they were using tanning bed lights, and only turning them on for 15 minute intervals in some studies. Tanning beds have whopping levels of uva (which in high consentrations burns deep), and very little uvb. There are bulbs out now that come extrmely close to reproducing the suns level of uvb. These bulbs have come a looongg way in a very short time. I'd love to try a dual spectrum mh/hps, and high output uvb grow one of these days.

The topic of the thread though was of it's importance, and although I believe it may have many benifits both that we know of, and don't know of yet I still think it's of little importance for a sucsessful indoor crop. Do you want to provide a more natural light spectrum for your plants, and produce the best buds you possibly can indoors, with the benifits of possibly increasing potency then I see some importance in providing uvb.