It's when the crown of the plant gets long and woody and the leaves come out of the end of it. Some heucheras are prone to it after a few years, others are not. Depends on their genetics, I think. I've read that if you cut off the turkey neck and plant it in soil that it'll root and grow a new plant. So far mine haven't wilted but they have stopped putting out new leaves. Once they start growing again then I'll know they've taken root. You have to do it fairly early in the season so they have time to root and then time to establish when planted in the ground. Some people stick them directly in the ground but I like putting them in pots so I have better control of watering.
