mrgreen23

Yeah, I don’t wanna shit on who ever wrote this as it’s well written and laid out, but unfortunately it’s mostly not accurate and or is misleading, which seems to be the story with a lot of online canna info these days 😞 Some points below (Edit: I wrote most of below pretty quickly and apologise in advance if I missed any small details): •1 Lumens or lux is not a metric for measurable light utilised by plants, as the human eye is more sensitive to green light by several orders of magnitude vs red/blue which lux meters account for. PAR is the metric for plants (photosynthetic active radiation), which adds up all the umols of lightwaves between 400 and 700nm. •2 While LED’s do not have traditional ballasts, they do have drivers to convert current from AC to D.C. Not quite plug and play like the author says. •3 Stating that an LED fixture is better due to ‘less wasted light’ as it is closer to the canopy is only half the story. Reflection losses are definitely a factor which changes depending on the material you chose to line your grow room walls with. However the stand out best reason for LED is the fact that the spread of PPFD (Photon Synthetic Flux Density) is much much more even. Without CO2 supplementation cannabis can usually handle up to 1000 PAR before showing signs of stress. Because the light is more spread, this allows growers to get great coverage to the edges of the tent as well as the middle, unlike HID, where in order to not burn your plants, you may have 1000 PAR in the centre but only 300-400 PAR on the edges, thus increasing reflective losses (as the photon has more opportunity to bounce off of walls/floors etc). It is also important to note that not ALL LED’s are good at spreading light, COB vs bar style lights for example have huge differences in PPFD footprints. Bar style LED’s are currently the best widely used light delivery method on the market today. •4 ‘In terms of yield and quality, LED’s are now as good if not better than HID’s’ Again, this is a very vague representation of the facts. Depending on the LED, some are in fact twice as efficient and can therefore produce up to 2 times more yield per watt of power used vs traditional HID/HPS. HOWEVER, some LED’s like a lot of the blurple type fixtures with fans/large heat sinks actually produce less light per watt than HID/HPS. •5 ‘LED’s are almost 50% more efficient than HIDs’ Not true, as mentioned in last paragraph, some lights are only 80% as efficient as HID, others are over 100% more efficient which I am more than happy to link models that are. •6 ‘Cannabis plants need around 30-40w per square foot of grow space’ After the points I have made in 4 & 5 it is becoming clear that you can not use watts as a metric for light delivery per square foot due to the fact there is huge parity between the best and the worst LED’s on the market. Looking at PPFD charts from reputable LED companies is the best way for a grower to judge how well a fixture suits their grow space. As a rule of thumb, flowering plants need at least 500 PAR to grow properly. 700 - 1000 PAR is optimum and growers buying new lights should try to find lights that achieve close to these numbers across the grow space they have. If an LED company does not provide a PAR map, I would be dubious about buying from them as if they understand the science, they would know this is very important information. •7 ‘For cannabis cultivation, we only need two different colours, blue for veg and red for flowering’ This is a myth, which stems from the HID vs HPS days. Light colour and spectrum only affects plant morphology, not yield or quality. The reason why people used to choose HID for veg was due to the bluer light making stockier, shorter plants. HPS lights are chosen for flowering because they’re MORE efficient than HID. HPS is 10-15% more efficient than HID and therefore confirmed people’s beliefs that it was the red spectra that was beneficial when it was actually the amount of usable light per watt the fixture delivered. Bluer spectrum lights lead the plant to believe it is growing in an open area with little competition for light, as the blue concentrations of light without any shade are higher than in shade. This leads the plant to grow shorter simply because it doesn’t need to outperform any other plants. It is important to note that blue light does not penetrate leaves as deeply as green and red. Redder spectrum light causes the plant to believe it is growing in shade, this is because red light penetrates through leaves much better than blue. Thought experiment: Think of a cannabis plant growing underneath a canopy of trees, as the light comes down and hits most of the leaves on the tree just above, those leaves act as a filter, holding onto most of the blue and passing some of the red, by the time the light hits the cannabis plant the sore trim shifts heavily towards the red, this indicates the plant to bush out in order to increase its chances of growing into direct sunlight. This is a good video about light spectrum and it’s affects on plant growth: https://youtu.be/oK8e5bgqgT8 I could continue to go into greater detail but I am pretty sure most people will not read this far. Again, the layout and the presentation of this article is spot on, but the information is not, with GD being a great platform for growers, at the very least the published information on this site should be as accurate as possible. If you would like to discuss further/develop a new article I am more than happy to help, otherwise I suggest you take this down before more unsuspecting growers receive poor information. Thanks, Nug