for years I've been using UV-b in the last few weeks in winter now climate change is here their may well be a need to enhance those trics with the sun being so intermittent, Bugbee scores again Its still good for an old hunch to be proved right ..lol
I'm running a Philips sunlamp, it's supposed to mimic the sun about 97% accurately. I think it's a combination of Mercury and Sodium and a few halides. The plants love it.