Sorry angie, I'm a bit late replying, but you don't have to harvest the whole plant, just break off a stem when you need one.

The plant would be better indoors, rather than in an unheated greenhouse. Having rooted through the pot into the ground, just cut the root, and, its probably the wrong time of year, but pot it up into a slightly larger pot, and as I say, bring it in to the house. You can keep the plants growing for years.

valmarg