LEC light burn- signs symptoms and distance

[rangerjake]

Running two 315 LECs (Vivosun vertical bulb orientation) with Philips 3100k bulbs. Have two large plants under the two lights. Currently at 3.5 weeks into flowering we are an average of 12-14" below the light, with the biggest colas only 7-8" below (but not directly under). Back of hand heat test yields no issues at 4-6" below lights, but not sure if this is a good predictor of the effect on plants.

Feels like much of my upward stretch is complete and any remaining will be minimal spread out in SCROG with so many colas. What do people feel like is a minimum acceptable distance below these lights/bulbs? I have read for the similar Sun System fixture that 18" is ideal, and though I am closer than that it isn't too much closer on average. Do people have different experiences they can relate?

Thanks.

 

[s62]

I’d be careful running them that close. I’ve seen LECs cause real burn on a plant that was too close. Your numbers sound too close.

 

[rangerjake]

yeah, I am kinda in it. What I got is as good as it's gonna get. I may be able to use some creativity to prop the lights another inch or two higher, but that is all. Just trying to see who out there has real life experience with LECs and light burn, how it happened (leaves first, or flowers first- what distance- if hand temp was a halfway reliable indicator).

 

[s62]

I didn’t do the hand test with the specific plant I saw that was burned. Plant was maybe 10-12” from the LEC. Both leaves and flower were burned/blanching. Can you do any lst, or is it too late?

 

[rangerjake]

I trained the fuck out of these things. Between quadlining, consistent defoliation, LST, and now the SCROG. I basically got nearly the entire square footage of a 5x5 tent covered in colas with 2 plants. My most recent attempts to LST are very tenuous. Things are getting brittle. I almost lost 1/4 of one plant as I gently started to direct one of its main branches and it ripped out from it's base. Didn't disconnect fully, just halfway and I was able to duct tape it back together and tie a support around the branch across from it to keep it supported as it healed- which it has fully. But between the density of the buds forming on colas and the brittleness of the stems/branches I would hate to fuck up something like that. I'll post photos of the plants/room.

 

[rangerjake]

The across shot is about 5 days ago after a defoliation. Not much upward growth, so that is essentially where we are at. The top down shot was 4 days ago. Looking good. 4-6 weeks left for them roughly. Trying to hold out- no burn. Another fella on here growing one of my two strains in there (Blue Mystic and Rasp Cough from Nirvana) said that at this point in flowering BM didn't grow much if at all. Plus with the SCROG that the spread of that upward energy maybe added an inch of canopy height. So, granted the RC is a sativa and may want to go higher, the BM really should be where it is, and that is predominantly 12-14" with the exception of the two tallest colas which aren't directly under the light but only have about 7-8" clearance at the moment. They can be seen on the far left of the first photo.