Uv-b last 2 weeks?

[Chefbjy]

This is interesting. If running 2 lights I could get the best of both worlds. And just cut the mh earlier then the hps. Maybe I'll just experiment when I get another hood.

[DrPhoton]

No, i have not seen any papers on the subject. I would like to. Can only go by the very little data out there at the moment.

[Chefbjy]

My mh is also 90k ultra blue hortilux and always where my shades.

[Chefbjy]

From what I understood it's not quite proven but 10% is quite a bit. Thanks for another good read.

[DrPhoton]

LED does not naturally produce any significant amount of UV, HPS and Fluorescent have higher levels in comparison. Although you can get very specialized UV LED diodes, they are vert inefficient. Its not very practical.

Even CMH does not produce any significant levels of UV either, likely because of the ceramic material used to enclose the tube.

[KingKush]

Yea I have one it's a 10,000k metal halide by Ultra Sun they just put out the most UV spectrum out of any h.i.d. grow light. Tons of manufacturers make the claim of it being a "finishing bulb" but I just use mine for veg. I'm sure it works if lots of different people are making the same claim (and isn't that the claim LEDs make about more terpenes, because they have more UV?)
DoctorJohnson I also definitely recommend wearing sunglasses and skin protection because it's easier to see than under hps but it's actually more damaging so you get this false sense of security because it's not as seemingly intense.
My 1000w hps states 155,000 initial lumens
vs 1000w mh states 90,000 lumens
so it doesn't APPEAR to be anywhere near as intense to the eyes but it definitely feels intense on the skin. And my eyes do take a beating I've spent too much time already without donning the shades and it starts getting to be serious when you grow for more than a few cycles and disregard the gravity of permanent eye damage.

*edit: I don't mean the brand Ultra Sun puts out the most UV necessarily (perhaps?), but any manufacturers 10,000k metal halide bulb puts out max UV blue.

[DoctorJohnson]

Be careful with uv tubes! They can burn your skin and permanently damage your eyes! Seriously.

[DrPhoton]

Have not found a whole lot of information on the subject, if anyone has anything interesting i would love to see it. But as far as i have found, UV seems to have a small effect on resin production. Dr Who has looked into it, with some experimenting for himself. Showing on average around 10 percent increase in THC when using metal halide for the last couple weeks of flowering. I think some horticulturists like mel frank report similar findings.

Thats all i got unfortunately ^.^

[Chefbjy]

Was doing a little reading and wonder if any one that uses mh/hps lights have tried switching out to mh the last couple weeks.

Reading trichs are a defense for plants from UV-B rays is the reason I ask, and I'm thinking of doing this. This is what I read on gwe...perhaps DrPhoton could elaborate on this article.

UV-B/Sun/Metal Halide exposure

Some growers (including some famous ones like Ed Rosenthal) believe that exposing cannabis buds to UV-B light for the last 2-3 weeks before harvest can increase trichome production and overall potency. Although not yet proven, this may be partly because trichomes are theorized to help protect the plant from UV-B rays.

UV-B is the name for a "color" of light in the lower blue/violet spectrum that humans can't see. It is produced by the sun and causes damage to plants and humans.



In fact, nearly all organisms on earth have defenses to protect themselves from UV-B rays. Humans get sun-burned if exposed to too much UV-B and can even get cancer in extreme cases, so our skin protects us by becoming darker in response to sunlight. Instead of a tan, plants produce trichomes which can help protect against UV-B rays (though trichomes also have many other uses such as producing cannabinoids and terpenes/essential oils/smells).

Metal halide grow lights produce UV-B light just like the sun! Although MH lights are generally only used in the vegetative stage like for these plants below, it may be helpful to expose buds to UV-B light for the last 2 weeks before harvest to increase trichome production.



Learn more about how light spectrum affects your plants

The most common source of UV-B light for growers (besides the sun of course) are Metal Halide grow lights. UVB light is also produced by incandescent bulbs but they aren't really bright enough to be used for this purpose.

Just remember that glass blocks UV-B rays, so if you're using a metal halide bulb in an enclosed hood, it's important to remove the glass (and find another way to cool the light) so UV-B rays actually reach your plant's buds. Another option for UV-B light is reptile lamps, though not a lot of growers have those hanging around the house, and they're not as powerful as a Metal Halide lamp