My most successful plant for pushing zones has been the Piper sarmentosum. It is
supposed to be hardy only to USDA zone 10 and I live in zone 8b.
But I cannot take any credit for the success. It was the plant itself that 'taught' me what it needs. I had planted some in pots to bring inside for the winter, some in pots outside and allowed some to remain in ground for the winter. One of the outdoor potted plants sent out a long runner - 4 feet long - rooting itself as it progressed. It made a new home for itself under the shelter of an American beautyberry/Callicarpa americana which itself was under the shelf of a hug pine tree. The plant knew where the most frost-free area was.
July 2014
Here (bottom center) the plant is sending out a runner to look for a better home
Plant looks ragged and winter-worn but it is alive; pruning shears point to the path of the runner.
This is the happy new growth
