Beware of any plants of H. hercegovinus which do not have known provenance. The only way to ensure you have to authentic plant is to buy a division of a wild collected plant (probably impossible in the US), or to buy a plant grown from wild collected seed. I wouldn't touch an acaulescent species hellebore grown from cultivated seed. The plants within that group hybridise too easily.

H. hercegovinus would almost certainly die down in the fall for you, and re-appear in early spring. Strictly speaking, no hellebore is evergreen. the foliage of all hellebores lasts, and is useful to the plant, for only one year. H. foetidus for example gives the impression that it is evergreen because there is always growth to be seen, but that isn't what evergreen means to me.