|Several of my helleborus orientalis are developing black spots on their leaves and then the plant dies.
|Sounds like Black Spot, one of the most serious diseases of Helleborus in the United States. Large irregular black spots develop on both sides of the leaves and move to the stems. The stems shrivel at the point of attack and fall over. To control, cut off and destroy all diseased leaves. Spray the remainder with a fungicide at two week intervals. If your plants are gone, and you'd like to replace them, be sure to plant them in another garden spot.