Diagnose this leaf issue, wrinkly and a bit of tacoing?!

Smokenpassout said:

Thanks for your detailed response. I got a lot of good information from it! I have been on the side of over caution with PPFD at 2ft above tops. Mainly because I fear light stress with powerful Led light! However, I also fear stretchy girls, and like them short and compact until stretch. I realize light needs to be lowered as close to plants tolerance as possible. Do you suggest lowering it from 24” to 18” and keeping intensity at 40% and observe growth? That would bump up the PPFD. I dont have a way to test PPFD accuratley and the phone apps ask for a filter to be accurate. I have yet to find a decent app to measure light at the canopy without an external filter contraption. I really dont have the. $150-$200 to invest in a nice dedicated meter at the moment. Hence, the extra height of 24” and power setting.

I do think stretch is strain specific. Others are same strain and all looking identical short bushy, growing more outward than upward like stretch. Now I just have to figure how to get stretch down to same height as rest of canopy that Im measuring the light height from. Perhaps I can fix that will the trellice I will add soon. Cheers!

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At 30 days, cannabis has almost matured its ability to process light (via photosynthesis). 18" and 40% is quite low but "observe growth" is the most important thing. A meter tells you how much light is falling on your plant but only your plant will tell you how much light it can use. I use an Apogee which allows me to measure and, therefore, document light values but it's the leaf curling up that lets me know that enough is enough,

If you're referring to Photone, IIRC, you have to pay for the filter to get the right spectrum, right? If you can get a lux reading, check out the document I wrote that will help convert lux to PPFD. I'm no fan of Photone. I tested it when it was named Korona and, after trading email with the programmer, bought an Apogee. I am (was) a software engineer for > 30 years so I have some insight into what Photone does but, for a variety of reasons, don't use it. Their recommended light levels where it ramps up in veg and then drops, are just silly,

Rather than a PAR meter, a lux meter is about $25 and is sufficiently accurate. Per above, the meter will get you in the ballpark but it's up to the grower to observe the plant.

Re. stretch—plants that aren't getting much light will be tall, with slender branches, large internodal space, and a limited number of large leaves. If you check out grow journals, you can spot them easily. A plant that's getting lots of light will grow tall but will have a lot of foliage, a large number of smaller leaves, and short internodal space. The spectrum of the light impacts those characteristics ("morphology") as well but most growers are using "white" LED's so the morphology of most grows is a function of light intensity (and duration).

A high PPFD can overwhelm a plant but cannabis plants don't get too much light by having a long photoperiod. Plants don't get "tired" from high light levels, contrary to popular belief. Photosynthesis really is light a car engine—you can rev it up and keep it running hard. As long as the cooling system and the lubrication system (water uptake) are sound, it just keeps going. I run my autos 24/0 in veg at 70-80 DLI and then 20/4 or 21/3 in flower (same DLI range) and they love it.

I commend on being cautious but part of the process is the grower getting figuring out their processes and part of that is learning how the plants react to changes in all part of the grow environment, not just lighting.