Here is some information on hellebore that I didn't know before. What we think of as the petals on the flower are actually sepals.
And what usually kills a hellebore, as in my 'Kingston Cardinal', is damaging the meristem.
A meristem is the tissue in most plants containing undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place. Meristematic cells give rise to various organs of the plant and keep the plant growing.
That is why mine didn't come back from the roots. When the leaves were pulled out as weeds it damaged the meristem causing the death of the plant, probably through allowing bacteria into this delicate area causing rot to the root system.
