There are so many variables when it comes to growing. The best thing you can do is eliminate as many as possible. Genetics are number one, I have seen good results with good genetics and terrible lights, also seen poor results with good genetics, good lights and poorly applied nutrients. Even larger strains at times can have a shorter pheno. Good companies usually have a better success rate when it comes to individualizing them. I sent pop some seeds of the biggest autos I have ever grown, he ended up with super short plants that took 100 days to grow out. Mine would have been 8 feet tall if they weren’t in a scrog.
20/4 is a great schedule. I do recommend people give their plants a little rest which also helps them get a bit taller too. Spectrum also plays a big roll. I regularly grow with different spectrums, 3000,3500,4000 and 6500k. There is a noticeable difference between them as far as plant growth goes. As far as intensity you are absolutely correct. The more intense the lights are and the higher the ppfd the shorter the plants tend to be. If you wanted stretch stick a cfk in there and remove your real lights.
It’s been around a year since I discovered that the dli was really the main thing affecting my plants. Everyone else grew with higher wattages and did fine, I grew with the same lights but had burnt crisps. I was also on a photo prodominent forum too. It hit me one day when some photo grower was trash talking autos saying how they saved money by flowering with 12 hours on vs us up to 24 hours on. Then I did the math on how long I would veg for to get my auto sized plants as photos. Ext... in doing this it hit me that I was giving my plants twice the amount of light as they were. Photos 12 autos 24. It also struck me that most auto growers were using leds and I knew that these “300” watt leds were only around 25 par watts. Waaaay less than cobs or even hps. So most auto growers think they are giving more but are actually giving less. That’s why I think it hasn’t caught on. I can’t imagine someone going with 11 watts per square foot with a 300w eBay led. By face value that’s 27 sq feet lol. Now I’m here and my plants are better than ever. Less wattage, better spectrum, amazing growth and after recently adding up my lighting cost per month for an 8x20 filled with AutoCobs it’s crazy to consider a change.
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