Search function hasn't found any threads on this so here we go... I've read all sorts of testimony and experimental evidence about UVB and resin production. Some of the information seems totally bogus, but some seems to be pretty well backed up. It seems to me that UVB probably does support resin production.

Now regardless of whether or not UVB does anything, if one was to add supplemental UVB what is the ideal amount?

Currently I have about 80-100 watts of CFL lighting, and I want to add a bit of UVB to the setup once my seedlings hit 2-3 full nodes, and even more once they are in flower. I want to use reptile basking CFLs that come in 23 watt bulbs, and can produce either 2.0, 5.0 or 10.0 % UVB. I understand that UVB can increase resin production, but it also breaks down the compounds in the resin. Also the 2.0 bulbs produce UVB in the 330-390 nm range, which is longer then the recommended UVB wavelength for resin (around 300 nm IIRC). The 10.0% bulbs do produce COPIOUS amounts of UVB in this wavelength, but is this too intense??

Can anyone recommend the best bulb for growing: 2, 5 or 10% (I wanted to check the UVB rating on 5%s but they were out of stock)? And/or point me to some more good reading material?

Thanks
Subcitrusfruit

if you look here you will be able to see some charts showing where the plant is photosynthetically active in different wavelengths.

UVB is within 320 - 280 nm. looking at the pictures in the link provided shows that there is little response to it (UVB). in fact, within the article it states "the weakest response is at about 500 nm."

The stuff I've read speaks of wavelengths in the 280-315nm range. If the lights don't produce those wavelengths, the biosynthetic reaction isn't happening, so supplementation is just using unnecessary electricity.

I don't know that anyone can tell you how much to add. I read at least one comparative study that reported weeds native to the equator or high altitude were found to have increased THC biosynthesis, while greenhouse weeds supplemented with uvB showed no effect. So it seems a lot of intense uvB is necessary to incite a measurable difference.

Thank you very much Red Eyed and Panama. I think the bulbs I got are useless then. It's a good thing I havn't opened them and still have the receipt.



I think the 10.0 bulb is ideal for this application. I've attached an image with the advertised intensities across the spectrum for those interested. Also here's a link for all 3 bulbs.

I'm still looking for info for please feel free to contribute!

I read an article about UV effects on potency and from the graphs it showed you get an increase of about 25% at maximum safe UV (can't recall what the actual levels were). You'd have to decide if it's worth it for a 25% increase or not. I guess any extra UV would help some. This explains why even plants grown under LED still have almost as much THC as sun grown plants, the 25% difference would be barely noticeable.

There are many opinons expressing increased THC content due to many things including UV lights. Most due not provide substantiating data merely a lot of opinions. Many based those opinions on considering UV supplementation on supplying any wavelengths from 300 nm to the 500 nm range. Scientists at this time just merely sy there is no conclusive evidence to support the theory that UV lighting beyond that normally supplied naturally causes any increase in THC. There are results showing areas of the world where there are higher than average levels of UV light wave available in the UVB range and that they believe this contrivbutes to higer THC levels. However there are so many other environmental factors involved this is just speculation. These area are Hash producing areas such as in Pakistan and Afghanistan etc. There are no tests where clones of other plants such as from temperate clin mates were planted there that increases in THC would be realised. There were no controlled tests done at all. The reserachers simply tested THC levels in ares where UBV intensity varied and then tried to draw conclusions from that. As there were so many other vao riables al was merely seculation as they found areas of high UVB lighting that do id not produce high THC but other clamatic parameter swere different. That is why they say unless teasta re done in tightly controoled conditions sich as labs and laboratory green houses no type of conclusive report could possibly be written.