Hey DGC, I’ve heard UV mentioned several times on recent shows. You’ve either talked about using UV in intervals or on for the last few weeks of flower.
I purchased a LED light a couple of years ago on Alibaba.com from Driverkerr (yes I know your thoughts on these lights 😄) the light has been working very well and there customer service has been excellent. The light I went for was a true 900w 12 bar light system with UV and inferred for a wider spectrum range.
So my question is what would be the pros and cons of UV being on the for the entirety of flowering.
I’ve noticed an increase in trichome production and most of the strains I’ve grown have had an extra layer of frost. I’ve not noticed any negatives since using the light but would be interested in what you guys think. I’ll add some photos of the light information below. Thanks DGC, stay higher my friends.
Hey
So I have been used UV for 2 years now, with all the reading a testing done by me next can say UVB works and you will see a difference. Now the UV your lights have and most of all are UVA which is more used for drying glue and more on the blue spectrum, it will have no significant advantages you get from a UVB. They add UVA to make it appealing to the end user.
What you need is a 20-24watt UVB Fluorescent bulb that will cover a 4×4 at 24-40” above canopy’s. I got mine from Migrolights.
I run them in my last 2 weeks for 2 hrs a day in the middle of to light cycle. I saw a huge difference in color, trichomes and terpines. Then I added another step by using New Millennium Winterfrost that added more to my end product.
Remember you need UVB not UVA.
According to Dr. Bugbee, constant on UV causes the plant to create defensive pigments to filter out the UV entirely. Pulsed UVB is what you want to create the increased terpenes. I have the AgroMax Pure UV which is 75% UVB and 25% UVA. Also do not use any sort of cover on your fixture itself as the covers will filter out the UV.
There are no LED’s currently in existence that emit a usable quantity of UVB for cannabis. There are some extremely expensive ones (like $20/diode) that can emit 285nm (at about 100mW) so even if money was no object, that would need around $1000 just in UV LEDs alone to make any difference.
The UV wavelengths that have been shown to benefit cannabis are 300-350nm. UVA in the 380-400nm range hasn’t been demonstrated to provide any effect at all. And I say this as a guy who ran “UV” at 385nm through my entire last flowering grow.
This grow cycle I’m adding a true UVB (300nm-340nm) bulb, intending to run it approximately 60 mins/day at about 2.5′ over canopy. At 24″ height, it’s providing roughly the same UV as ambient summer sunlight outside. From what I’ve read (some of this is anecdotal, some has been researched and tested) it’s really UVB you’re looking for and you’re not going to pull that off with LEDs, at least not with 2022’s technology.