Hello and greetings. I'm in the south of Thailand, sunny and warm but with 2 months of rain. Now that it's suddenly legal (ish) I'm trying my first non-covert grow, but having trouble working out the lighting. I've built a small greenhouse and the idea is that I'll supplement the natural lighting with LED units. The solar PAR varies between 30 and 45. The three lights I have are putting out a usable 50 PAR each. My first try is growing autos, meaning that I'm able to run the lights at night for 18 - 20 hours total daily combined lighting.. Assuming I have 50 PAR of lighting - how many hours do I need to run the lights at night to maintain an overall level of 40-45 ? I'm still trying to get my head around PAR and its relation to DLI, so all help gratefully received!
.I use a minimum of 850 par so yes you made need some more lights, however local weed strains will have a climatized to your zone saving a lot of work, but more light is needed
Chuckle - my "local weed strains" come from Amsterdam . . . and I don't imagine that you're growing in a greenhouse either!
Do you really need supplemental lighting at all? Considering where you live, I’d think you could crush it with just a good covered greenhouse. have you considered light deprivation instead?
Well, yes, at this time of year it's coming up to our "depths of Winter", with very low light levels until the new year. And, seeing that LEDs from China are very cheap and low powered, they seem perfect for supplement the lightthat's already there but is lacking. Thanks for the thought - I'm off to Google light deprivation
While DLI is a factor for productive growth, most will just use a PPFD reading. Some will use Lux meter instead. Here’s some PPFD numbers to get a baseline for lighting 100- 200 for clones and seedlings 200-300 for early veg plants 300-400 for late veg plants 500-600 transition and early flower 600-900 late flower 900-1200 flower with DIALED IN set up. May need additional Co2 above 800. You can get Lux meters for cheap online
Thank you for lots of interesting figures, and I have not only a LUX meter but a PAR meter also - but you've lost sight of the question I keep asking - Greenhouse ambient solar is 20 PAR. Assuming I have 50 PAR of LED greenhouse lighting - how many hours do I need to run the lights at night to maintain an overall level of 40-45 per day ? Let me try to make it even more simple: My greenhouse doesn't get enough light. It's only getting 20 PAR. It is getting 20 PAR for 12 hours a day. I can run my supplementary greenhouse lighting at night. What light level (how many PAR) do I need to bring the overall 24-hour total to 45 PAR? I have already reached 20 PAR of daylight HOW MANY ADDED HOURS AT 50 PAR DO I NEED to make the total 45 PAR per day, overall?
OF COURSE - IT WOULD HAVE HELPED IFFIN I HADN'T OF MADE A MAJOR BLUNDER. This is my first grow outdoors. I used an online chart , , , and misread it, Here it is corrected . . . with apologies. HOWEVER - my question still stands - only now I'm looking at much higher light levels (blush blush)
Now I've got my head straight on this, everything else has fallen into place, and the "how many additional hours?" thing that has (literally) been keeping me awake at night resolves itself. Instead of trying to pennypinch with Cheap Chinese LEDs, right off I'm gonna get a set of Mars Hydros. to use - giving me a usable range between 986 and 660 PAR. Then there's no need to try and figure out numbers and hours . . . The greenhouse is getting 12 hours of (weak-ish) daylight. If I run the lights for 5-6 hours every night on top of this, I'm hoping that this'll be plenty in combination. Am I beginning to get this right?
Well, I don’t think you were wrong in the first place. Maybe just overthinking it a bit. The relationship between PAR and DLI is indeed intriguing and a rabbit hole that may indeed be worth going down. But I feel as though it’s not necessary for a personal grow. Once you understand signs given to you from your plants you will visibly be able to tell when they are receiving too much light. For instance, when you’re leaves are pointing to the lights at around a 45° angle, that tells me those plants are pretty happy. But, when those plants stick those leaves almost straight up towards the light and start closing up the terminal shoots at the end of the light cycle, that tells me they are receiving too much light and I would lower my PPFD a bit by raising lights or dimming them.