I bought a fan of Undefinable. Here is what the seller advised me to do with the plant,
"Let me share with you ... UNDEFINABLE will need and should be protected during the winter. Many up North have loss her due to the temps. Myself, I would plant UNDEFINABLE in a 10 gal squat pot and bring her into protection when freezing temps will occur. Or obtain a grow light and keep her in a protected area and use a grow light during the winter season. I would Grow UNDEFINABLE for a year or two (pretty fast grower), then divide her and test a fan (planted in Spring) growing in your winter conditions. I live in the South and I have to cover and protect all my UNDEFINABLE plants during our winter freezes or else I would loose them all. Hope this helps!"
Of course, I will follow her advice which I find it very helpful and sensible. Though I am just curious if there is anyone out there succeed in growing Undefinable outside in zone 6 or higher with just winter protection like heavy mulch? I am also trying to find out what temps may cause the plant's demise or weaken it that it struggles to grow the following year.
