I do not know the answer to your question but I did disagree with your assumption "shade plants all need....soil". I have rather good soil due to years of oak leaves decaying. My mother in law has clay or sandy soil. I got my fern leaf bleeding hearts from her. They grow like weeds for her, self sowing all over the place. Mine have NEVER come up from seed they self sow and when I divide them, only about half survive. I water regularly, she is too frugal to ever water. It is quite possible we are over mothering this particular plant. My largest most vigerous plant is in a front bed near the house that gets more sun and less water than most of my plants. In fact I recently mulched that bed and the bleeding heart does not look happy about it.

arcy: Ok, obviously I now realize my assumption about rich soil for shade plants does not apply to bleeding hearts--they are at least one exception to this rule, as is evident in the fact that they are now dead, and I believe it was due to my soil amendment. I was simply looking for any other explanations for the black lower foliage, since every shade gardening book I have read instructed me to provide rich, organic, well-drained soil.