PAR readings; also, to flush or not to flush?

@dbrn32, and others, I have a question about PAR readings. With my new(ish), dimmable HLG 260 rspec, I learned not to keep it full blast, after scorching some poor auto seedlings this spring. But in my 2x3 tent, I’ve got Girl Scout Cookies Extreme (l.) and Gorilla Glue (r.), both photos, and they are super hardy.

For instance, throughout veg, they were getting over 700 PAR, which is higher than the recommended upper level, but there was no burning or any related problem. (I use the Photone app on my iPhone to read the levels.) Now we’re 9 days into flower, and they’ve stretched a lot, but I forgot to move my light up or turn it down. Canopy levels were reaching 1400+ PAR but still no visible harm to the plants. I’ve since pulled the light up and turned it down, and the central hot spot is now around 1200.

Is this level safe for flower? Can I trust my Photone app if it’s giving me such high readings with no bad results? And are the recommended PAR levels meant to be followed at all costs, or is there room to push it, the way I apparently have done?

Oh, and by the way, today I accidentally fed them instead of watering them. They’ve now gotten two doses of Fox Farms nutes three days apart. Should I flush, or would that have the effect of over watering them?


To get a true idea of where you’re at, you need to take an average from your entire light footprint. You may be 1200 in the center but only 400 on the edges.

Doubt you need to flush. Maybe throw in two water only in a row depending on your runoff ppm next time you water.


I think Bobbydigital has you set.

There is no textbook data that will apply to every plant you run. Some plants may show light stress at lower levels than others. And if you’ve had plants under higher intensity they may have just hardened off to the stronger intensity better.

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Thanks, guys. Appreciate it.

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Gg58, my opinion I wouldn’t trust what an app is telling me, 1 app told me 240-, other app stops at 650, so those are my findings. I have a 4000 led Dimmable and 85% is more then 240@12-16”. I wouldn’t flush them plants. Hope that helps you

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I’m currently using this sensor and I found this website to be quite helpful with the PAR info

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