I have kept the commonly available Dutch cultivar of E. bicolor in the ground here in 7b and have had it return with no special care at all. I just didn't know any better, so I just didn't bother. They eventually watsed away due to being crowded out and lack of good summer irrigation. I was always surprised to see them return. They don't care for our summer heat and humidity, and show that with limp foliage during the day, but they did quite well in spite of that. Robert.