Well from the looks of those graphs, 4000k looks well rounded
keep in mind that red photons produce the highest amount of photosynthesis per photon as compared to cyan or blue so technically the 3000k spectrum has a greater portion the photons produced being used at the highest efficiency by the plant. anyways like i said you can grow with a 3000k or a 4000k just fine or you can get nerdy. this is why you'll notice that a lot of the newer leds coming out have a pink spectrum as they are taking advantage of the efficiency of red but providing enough blue for proper plant morphology.
Compare the relative blue intensity of HPS spectrum to 3000k quantum board. The HPS would be considered a warm, yellowish/red white light and probably is around 2700K color temp a 3000k QB on the other hand has 5x more relative blue intensity. At any spectrum QB you will get a more balanced spectrum with more blue light than traditional horticulture lighting units, stretch just wont be as big of a problem (plant genetics aside).
Correct me if I'm wrong, but isn't that exactly the opposite of how the color spectrums work for plants? Blue light more towards the 6500K spectrum helps promote short stocky plants with tight internodal spacing, while lower spectrum, like 3000K normally helps with blooming... although full spectrum is generally recommended as the best route to go for peppers, which is somewhere between the 5000K and 6500K spectrums.
I've grown under 3000K before without issues, but I've been using 6500k for the last 9 years now.
you aren't wrong- it is conventional wisdom but these are generalities based around growing plants with MH and HPS or Fluorescent based light sources which have spectrum that completely differ from these phosphor coated led chips. i get compact growth on multiple species of plants (peppers, orchids, epiphyllum and a multitude of other houseplants) using 3000k white LEDs. having the spectrum more blue especially if you only have one light source spread across an array of plants causes the plants to experience more phototropism towards the light and makes my plants contort towards the highest intensity light. stretch is also much more of a function of how far the plants are from the light source with these leds. before I got a QB 65 (3000k) for the ghost pepper im growing at my desk at work it was stretching like crazy under a much bluer 50w led array (5000k). the quality of light is just better from these chips. that is why I'm suggesting it probably doesn't matter much- the light produces a much more natural plant growth response compared to other light sources. this is just my experience working with these newer leds over the past year.
This is the future right now with led growing lights, it is time to get rid of your old crappy ineffective light systems with huge power draw.
And yet we're still seeing people do "reviews" for crappy inefficient blurple lights so they can get free stuff on amazon on this forum and elsewhere. Those lights are cheaply made and aren't giving you the efficiency and quality of light that these high CRI white spectrums can give you. The premise that you need a bloom or grow spectrum and the premise that plants cant use green light are proven to be false and based on improper interpretations of old scientific papers. Plants can use green light and they can be vegged and flower under a single spectrum of white light. Paying an extra $100 will get you something many, many times more effective than a mars hydro or any other blurple light people are still getting conned into buying.
The color tone of those new ones are really nice and the added bonus is the accidental stand up comedy of the video.
I bought this last year on Aliexpress on sale for 250, light is really bright. I have it 1m away from a plumeria and almost 2 meters away from some orchids that tolerate high light. The light is bright. Currently will be testing on a bunch of pepper seedlings as they sprout.
what soil are you growing them in? when this stuff is happening at the top of the plant I always suspect that there might be root damage either from being too soggy (no gas exchange at the roots) or pests/pathogens in the roots. Often times its both. If you still suspect its nutrient related try changing to quarter strength every watering as opposed to full strength every 2 weeks- when growing in containers large bolus feeding can lead to salt build up and nute burn. Does MG have calcium and magnesium in it? does your growing media have lime in it? could also be a magnesium deficiency or a calcium/magnesium imbalance. If all your plants are grown the same way the nutrients don't necessarily explain it though.
If you are using white leds to grow and flower you want between 3000-3500k color temperature. The spectra of this color temp is red enough to not limit flowering.
I've used roleadro 300w warm white on peppers with good results but I will be upgrading to cobs for all my indoor plants. The roleadro lights are not the latest tech but they are cheap and have a higher quality spectrum. I also have fruit and flower on a ghost pepper with a much whiter (more blue) led spectrum. I hate looking at the "blurple" grow lights not to mention the cutting edge is far ahead. Additionally some of the flowering may simply be based on genetics and not light at all assuming a quality spectrum.
Looking for good lights?
Check out the wire frame kits from timbergrowlights.com a 300-400w 4X4 cob array should give you great results in a 3X3 - 4'X4' area. Obviously you can go crazy with the lights and production by buying bigger arrays and co2.
Chilledgrowlights.com are the absolute top of the line with a proprietary spectrum that includes uv deep red and some ir.
Do not judge leds based on watts judge them by the photons produced. An inefficient led chip may consume a lot of power at the wall but produce poor quality light or even worse create a lot of heat. It's all about efficiency and many led arrays are not efficient. This means for every watt you consume you should yield more light than heat compared to other light sources. Running LEDs at max current often is not the most efficient means to run them. Many of the cob arrays run the leds at half their max watts (50-60 watts instead of 100) to reach peak efficiency which is the ratio of heat produced:to photons.
I am old school: 1.000 High Pressure Sodium n Metal Halide. Blew the ballast on an HPS (smoke and all) and all my bulbs are old enough that i should replace them. So thinking this might be the time to make the leap to LEDs. Thing is, oh damn it is confusing to an old fart like me. With the HPS n MH I could consider square foot coverage and work the lumens using a information from people who grow something else in their basements. Lots of information there. If I look up information at greenhouse sites, I get information on supplemental lighting.
Is here a guide on how to replace HPS and MH so that you achieve the same results? Would be cool to stop burning the top of my head too.
There is a number of diy LED cob videos on youtube. Check out the ones from growmau5 (he uses the lights to grow other things...). From his noob guide to DIY led you can begin to get calculations to figure out how to get equivalency with an HPS. Alternatively the current best on the market LEDs are supposedly: https://chilledgrowlights.com/product-category/commercial-led-grow-lights
Also check out Vitaly's youtube channel (creator of chilled grow lights) its a really cool story about how he got into making them so he could grow his own food.
from listening to a tech talk with the maker 400-600w of his leds is equivalent to a 1000w HPS this would run you about $1,200 bones for the top of the line. not only that the chilled grow lights have some UV spectrum as well as IR and deep red so you are getting something that stimulates your plants much closer to how a sun would. higher up front cost but in the end you are paying much less per year on electricity (at the wall as well as cooling)
Other diy and led kit company's I have researched:
I have a 200w cxb cob lighting fixture that does pretty well but I'm not trying to replace an HPS so i have no bearing.