It says you can grow in a private, enclosed and locked space.
It's pretty vague by design. Personally, I consider my entire backyard a Private, Enclosed (and if I put a lock on my gate) locked space.
But to bluntly answer your question, yes, I'm pretty sure greenhouses would be allowed -- although I don't think that natural sunlight really replaces the consistency of a 1000w HPS light and a timer.
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