Interesting chart from Lumigrow…actually Clemson researchers. The sun in the north isn’t as dim as I thought (compared to down south). July in Massachusetts is brighter than August in South Carolina for example
https://www.lumigrow.com/content/wp-content/uploads/2018/02/dli-hero-revised.jpg
Now we just have to convince @Muleskinner to build a good green house, lol.
99%
of course the DLI chart doesn’t account for trees! You have to subtract that out. with a chainsaw. 
Cool find @Muleskinner!
Thanks for sharing.
Thats so weird I was looking at this an hour ago
Are you stalking me?
It was the LED thread PPF numbers that made me look
no, but I"m guessing we’re both on their email list. 