MC,
@fettled6 tagged me in on this a bit earlier. I've done a lot of looking and a lot of speculating on this topic but still no definitive answers. However my speculation has been lighting intensity's effect on stretch rather than overall finishing time. Over the last few years, as I transitioned from HID to LED, I noticed almost no stretch on any of my LED grows, and at first I thought it was due to the intensity (went from 250W HID to 325W LED). I started growing auto strains under HID and got beautiful stretch and some fine yields - at least 6 oz., and as much as 11+ oz off single plant grows. But as I transitioned to LED I couldn't help but see something missing. No stretch = no training = less yields, IMHO. A couple of LED exceptions (8 oz Pineapple Express and 11.75oz Auto Original Bubblegum), but mostly less yields under LED.
But now that you mention it, I do see my LED grows running longer, if I include the seedling time I run my plants under CFL while establishing a solid root mass and at least three nodes before transplanting. Hmmmm…. But discounting this time (2-3 weeks) most of mine have finished in 65-75 days.
But after perusing a ton of grower threads and asking for input (not enough received to be definitive) I'm slowly changing my suspicion to lighting spectrum rather than intensity. All my LED grows have been under MARS Hydro 325Watts-at-wall "system style" lights - their Mars II 700 and MARS PRO-II-Cree 128 systems, both of which are "blurple" style spectrums (blue & red = blurple???). Others who replied who claimed stretch under LED seemed to be running "white light" or full spectrum LED. Am I on to something? I've purchased a couple of BigSm0's 3500K COB's and I intend to keep chasing this after Fall gets here and runs me back indoors.
But until then, I'm going to a party at the BEACH!!!!! And then the U.P. for some backpacking and trout fishing. Thank goodness for my hydro autopilots!!!
If you want to chase this with me, have a look at the thread in my sig below, be glad to have you aboard.
BTW, you by chance know Midlife (here, little piggy
) He's in Cz and I've missed him for a few years.