LEDs aren't your grandpa and grandma's lights. They're new school, and with that, we have to make some changes to the old regime. Enough intro stuff, let's dig in.
This is one of the most common issues we see overlooked when someone starts using LED Grow Lights, and not just among novices! Too close and you'll your buds pre-burned or your fruit pre-grilled; too far and you'll be that disillusioned person dismissing LEDs as 'overhyped.'
Most brands include a recommended distance with their lights, and certainly, here at LED Head Grow Lights, we strive to provide this information. However, it isn't always possible to get this information from manufacturers... the good news though is that we can make an educated guess of how far to place our lights...
Unlike HID grow lights, LEDs do not have a standard light-to-plant distance, and instead, the light to plant distance depends on a few factors:
1) The Power of the Individual Diodes...
2) The Actual Wattage of the Light...
3) Growth Cycle, and...
4) Secondary Optics...
Power of Diodes & Actual Wattage
We'll put these together. Here's a handy little chart we whipped up:
Of course this chart is 'rule of thumb' we advise you to investigate the specs before and after you purchase your light. But, if you're not sure, ask me! Right there in the bottom right corner... Don't want to ask? Okay, fine, I get it... but remember this:
An extremely safe starting point for LED grow lights is 24 inches (61cm) from the plant. If your plants seem a little sad, and the light isn't super high powered, you can lower it 2 or 3 inches a day to find the sweet spot. 18 inches is a sweet spot for many LEDs. Above 500w, start your light at 3 feet (for extreme caution) and lower it both gradually and observantly.
During the veg cycle and for leafy plants and herbs, you can position your lights nearly twice as far away, while during the flowering stage and for fruiting/high light plants, you'll want to get those lights as close as you safely can without charbroiling your buds/fruit.
This is a stumper for most people, but we still need to watch out for secondary optics (we've blogged our brains out about optics already, but if you haven't seen our "Buying the Best LED" video, here you go.)
Briefly, some LEDs employ a secondary focusing optic to concentrate the light, with the intention of increasing PPFD numbers and overall canopy penetration. When a grow light is using these optics, you will want to consider giving it an additional 6 to 12 inches depending on how tightly the optic focuses the light. Again, it can't be said enough: Respect the Specs! They're the difference between garbage and gold.
Avoid Screwing Up
Light Burn!!! Nobody wants sauteed fruiting bodies. There are a few signs that you need to be acutely aware of when finding the light-distance-sweet-spot. Signs of light burn include (but are not limited to):
Curling of new leaves
Yellowing of growth near the lights (may be misdiagnosed as nutrient deficiency)
If you notice any of these signs and have ruled out nutrient issues (good luck!), start backing the light off gradually by 4 to 6 inches until you see the leaves recover – in the case of curling new growth, the reaction should be fast, within 24 hours or so. if you're already within the safe distances recommended above it is VERY UNLIKELY to be your light.
Funny thing. HID lights emit an incredible amount of Infra Red radiation
(part of the reason they're wasteful,) but it helps keep your plant about 5-7 degrees warmer than the ambient temperature. While some LEDs do employ IR light in their design, it is only included minimally. 78 degrees Fahrenheit (78F) is the widely accepted optimum temperature for most plants at atmospheric CO2 levels (360PPM). However, it is recommended to increase ambient temperatures in your grow environment to 85 degrees Fahrenheit (down to 83 is okay) in order to make up for the lack of radiant heating from the light. This increase should see larger yields and faster growing plants!
Increase Ambient Temperatures in your
Grow Environment to 85 degrees Fahrenheit
LED lights perform better than other lights when you fit your grow style to the light. To really make your LED light shine (pun intended), LED Head highly recommends using the SOG and SCROG method for cannabis cultivator; for other plants, you want to keep your light as close as possible and maintain an even canopy for the best results.
- Here's your "extreme caution" number: At 24”, most lights will not hurt your plants unless they're 500watt+
- Here's your magic number: 18” is a magic number for many sub 500watt LED Grow Lights.
- Here's your 500w+ number: 32"
See curling new growth or yellowing near the top of your plants? If you're closer than 24”, you should consider light burn, but don't mix it up with nutrient deficienies.
Your LED Grow light doesn't pump out butt loads of unnecessary InfraRed radiation. As a result, you need to keep your ambient grow room temperature at around 83 to 85 degrees.
Even canopy, no matter the plant, will allow you to let your LED light truly shine. SOG an SCROG are recommended for cannabis growers to optimize LED grow light use. Try to keep your canopy of growth even and no deeper than 12 to 18 inches.
That's all for now LED Heads! Keep your eyes on Youtube for a corresponding video either this week or next!
The Head LED Head
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