Grobo Light Distance

How close can the tops get to the light in the Grobo before it causes damage to the bud?

This is a hot button issue haha, my belief is anything within 5-6" is too close. @Jamminbear I know has some input on this as well as a device that measures light strength (which I cannot remember the name of, please advise) and @vegetato accomplished expert level at playing “keep away” from the light during the late stages of his latest grow. Guys, can you chime in?


I wouldn’t even mind a little light burn if all the buds developed nicely but from what Ive seen- that’s not the case. As light can not penetrate -the bottom is just larfy and as less light is distributed the longer it takes to flower. In my tent grow and planning for the Grobo. I use a apogee meter to measure the photons hitting the canopy. Most growers and researchers agree that a Par over a 1000 without CO2 supplementation will be unusable - if u have a Par meter that shows values that are within range during flowering then u are okay. For instance the light company Fluence LeD says their light could be used within 6 inches of the canopy while my HLG LeD would burn plants at that height. So short story u need a Par meter to gage the appropriate light distance. Since it’s cost prohibitive for most growers - I normally recommend at least 12 -18 inches.


Really good article explaining what I’m trying to convey lol


Awesome response. Which par meter do you recommend again? I’m going to order one to have on hand. Figure I’ll have more use for it down the road so I don’t want to order a cheap model.

Sun System HGC748205 PAR Meter With Remote Sensor Measure Photosynthetically Active Radiation Gray
I got that one. The sensor is the same. The original one is this which I rather have is twice as expensive.

Our Best Selling Apogee PAR Meter, The MQ-500 Full Spectrum Quantum Meter, Accurate for All Light Sources Including LED, Lightweight, Waterproof Sensor, Long Warranty. Made in Logan Utah by Apogee.


Just over an inch or so away is the sweet spot, any closer and they will crisp up and die. If any of the buds or leaves “touch” the light it’ll kill/bleach that spot pretty quickly.

But, it also somewhat depends on your water level (and plant health in general). As the water levels go down far enough the plant won’t be able to hydrate those leaves as well and they’ll dry up faster. So if it gets that tall make sure to do the mid-week top ups.


Thanks! I believe I’m good then. Already super cropped once

Directly under the center is the warmest spot. If you can pull your tops away to the sides of the light (away from the plastic cover and under metal instead) that helps a lot. If they do hit the roof in the corner they don’t develop as nicely as they do under the light.

The other thing besides burning to watch for is any “sweating” of the leaves. If you see that you might want to increase airflow somehow or trim/tuck/something.