I have a M. Speciosa (I think it's Maeng Da, but when I get home I'll take some pictures without the LED's to see if anyone can help with ID) that lives in a 2x4 gorilla grow tent with the extender, reaching all the way to my ceiling, and it's grown its way all the way up to and past the LED's putting on tons of new growth and nodes. I've known for a while that this was unsustainable, and after I had to repot it it only got worse. Not complaining by any means, but the inevitable plan now is to plant it outside next to a pond and with protection from the wind. I live in Austin, TX, which is basically on the edge of zone 8b/9a, and have a pretty protected back yard and microclimate, being just in an oxbow in the nearby creek, and at least to date, have had success with a p. methysticum in the ground in my front yard (it was not having it in the tent, and 3 of its comapnions perished tragically before I moved it outside.
What is the lowest zone someone has had a M. Speciosa survive in the ground, and what special conditions if any, did you have?