Pot is not nearly as harmful to this society asalcohol.
That being said, it's kind of hard to know what to do as it would depend on the size of the operation (I know long island alluded to the size in the original post, but I'm afraid I'd have to see it for myself to figure out what I would do)
I would probably not turn them in for growing it no matter how large it was...not because I would be scared, just because I don't agree with the law regarding pot.
I would probably just act like I never saw it and keep hunting there, but my point of reference comes from WV where I would not really be scared of even large "garden" owners (as they're all probably goodol boys (if not they'd be too scared to go in the woods around here, because the may "look like a hawg!! Squeel!!!"

)). NY though, may contain a more "sinister" character protecting there assetts, so my comfort level there may be to find another spot. I may even report them if I was severely irratated enough about their potential threat to me/my hunting spot.