Bleeding Heart & Black Walnut - Knowledgebase Question

Rochester, NY
Question by acapurso0
May 10, 2001
I inherited many bleeding hearts when I bought this house a few years ago. They do not blossom. I suspect the reason is that the black walnut tree in my yard is now huge (& beautiful)& that its canopy is over the bleeding heart plants. Could the toxin in the soil be the cause of their not blossoming?

Answer from NGA
May 10, 2001


Black walnut (Juglans nigra) has a reputation for being allelopathic--that is, for inhibiting the growth of other plants. Small amounts of a substance called juglone are released by the tree roots, but a far greater amount of this growth-inhibiting chemical is found under the canopy of the tree.

Bleeding heart is sensitive to juglone. Some plants that are tolerant include: arborvitae, cedar, catalpa, clematis, daphne, elm, euonymous, forsythia, hawthorn, hemlock, sycamore, astilbe, begonia, bellflower, orange hawkweed, hosta, pansy, phlox, marigold, primrose, snowdrop, sweet woodruff, trillium and zinnia. Since your walnut tree is there to stay, try to plant one of the less-susceptible plants in the vicinity of the trees roots or canopy.

And, if you relocate your bleeding hearts to another shady area, they'll probably perk right up!

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