Soak the roots in dilute soluble fertilizer overnight.
They do better with good drainage.
I had one come back three years,but it did not flower this past season.
I have a white one which gave flowers this past season. (The first summer).
Do not plant too deep---the crown should be only 2 or 3 inches below soil surface.
They do not like winter wet, so plant on a slope or where you know the water does not sit.
The dried up roots will not grow.
Find nice plump clusters which have a visible, cream, growth at the crown.
I am pushing the zones on this plant in zone 3.