

How many lumens do I need for lettuce to grow?


















Hope it helps a little :)







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Enigma ( Even with all the answers, there doesn't appear to be a mention of recommended lux/lumen for lettuce. )

The reason no one is saying a real true number is as was pointed out by one other person in thread lux/lumen and foot candle have nothing to do with what the plants need to accurately give a number you need to talk in plant light requirements which means the need for par (Photosynthetically Active Radiation), or ppfd amount of light photons that hit a surface (your plant canopy) in one second. It’s measured in units called micromoles (μmols) for light wavelength that is usable by your plant. and these are converted to DLI Daily light integral (DLI) describes the number of photosynthetically active photons (individual particles of light in the 400-700 nm range) that are delivered to a specific area over a 24-hour period.

If you happen to have an iPhone, there is an app call KORONA - cut a small piece of 3/4 pvc about 1/2 inch long and super glue a piece of bright white 20lb paper over it to act as a filter. place this over the iphone front camera lens and use korona to measure light and korona has options to show ppfd - dli - and if curious lux plus can upgrade app to also show kelvin scale

So its not simple thing pop a couple bulbs out throw a lumen number at them and say ok plants will grow, yes maybe they will grow but not at the best or optimum for the plant. so now if that has you all confused its not that hard to go by ....

Lettuce needs 12-14 mol/m-2/day which equals if you have a light system putting out 280 ppfd the DLI will be about equal to the number of hours the lights are on 12 hr = 12.1 dli , 14 hrs = 14.11 dli .

My current LED lights are 2:1 ratio of 3000K/5000K running dual meanwell 100 watt drivers with a real Watt draw at kill-a-watt of 209Watt, produce at 9.5 inches from canopy 295 ppfd @ 12 hrs a DLI of 12.7 and not that it has any cross correlation to plant because it refers to visible light 16300 lux meter/sq ( SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time ) and not all light plants use is visible, hence the difference in the unit of measurement to judge light for plants.

But a grow light the gives actual numbers as stated in lux and ppfd as tested in sphere and watch out for lights that tell you " yes replaces lights of XXX watt much lower watt but dont give you a hard data sheet of the light wave length, and actual wall watt draw. i wouldnt swap out my led for any t5 cfl or metal halide out there for power ppfd/watt light efficiency.

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