These girls popped up a few days ago and have been under 24 hours of light since then When is the time to switch to 18/6 or 20/4 I will go with the consensus they are photo period female seeds under about 300 PAR
IMHO, anytime you want. I have done 24 on through veg, 18 on, 20 on and no real change in growth or vigor noted. Maybe a little faster growth with the longer lights on time. Some say giving the plant a "rest" during the lights off period helps the plant become more robust. I did not notice that to any real definitive conclusion. IMHO if $ for energy is tight or heat is a problem, I would go now to an 18/6 schedule. If not, keep on 24 hours bc it is just one less thing to control. YMMV.
I go 24/7 for the first 2 weeks then flip 18/6 after that I see it, as all the action is subsurface right now, being root development so I give them more heat than light good luck
Ive been doing 24/7 with a 1000w HID since they came out in 1978. Ive got the 1000w HID at 24 inches, and a fan blowing a small breeze 24/7. 80f-85f temps. Early on I used a 1000w Halide, but switched to 1000w Hortilux in the 90s, when they added some Blue. Ive been thinking about going to a Hortilux BLUE 1000w as it is very close to the spectrum, of the sun. But either will work. We keep Mothers under 1000w Hortilux Blue. Some say I use to much light for seedlings, but I digress. If I was in the mountains of Columbia ect, they would get extremely high amounts of light, from day one. I let the plants grow towards the light. I also have extremely good fresh air exchange, which I think is one of the most important things, when using really high amounts of light. Ive never had light stress. Every 4 days, I turn the lights out, for 4 hours, to give the ballast a rest.
i have a 600 Metal halide i am going to use now probably dimmed to 250 watts and i have a heat mat around 80f thanks for the advice So you never got on the LED train? i am still HPS and loving the results i get
We use both LED, and HID. LED we sometimes switch out for HID. Im actually not dont anything at this time, but Ive got a buddy, Ive been doing things with since 1980. I buy all the lights, fertilizer, medium, clones, seeds, pay half of the electric. ect, and I get half, and also get his half, at a reduced price. He doesnt smoke much anymore, and his ife may smoke an oz a month. They are both in their 70s, and we grow exactly the same way. So if I say mine, or whatever, its actually physically my buddies. Not long ago, I bought 2 880w Mammoth Mint White Series LED, and 3 years ago, bought a 645w Gavita 1700e, and sometimes use it for veg, in the summer when its hot. I also bought 2x 1150w DE Gavita HID, and 2 1000W DE CMH. We switch up which ones we use for flowering, but havent used the LED for flowering. I tend to like the 1000w CMH for flowering, as it is extremely close to the spectrum of the sun, as is the 1000w Hortilux Blue. But for me, whatever light we use, I blast seedling fro the beginning, and always have. I believe the main thing is to have really really good fresh air exchange, or you will run into trouble using that much light, on anything. but be it Dual End, Single End Halide, HPS, CMH, LED, they get blasted from the start. At the equator, they can get 2100umol, and if at high altitude, even more than that. which is my reasoning, for blasting from the beginning. Havent used the 880w Mammoths yet.