Black walnut sap or resin

Asked September 2, 2019, 2:24 PM EDT

I have a very old black walnut tree in my yard. It’s big and beautiful and I love it but the sap (or resin?) from the leaves get all over my cars, patio and fence. If I was to tap the tree for sap, will this prevent or lessen this? If so, should I keep tap in from spring through the fall? If not, is there anything I can do? I assume the sap drops only under the leaves. Is that true? Thanks

Suffolk County New York

5 Responses

Thank you for your question. It is difficult to diagnose what is going on with your tree without a photo. Often, sticky stuff dropping from a plant means that there are aphids feeding on the leaves, and they produce a sweet, sticky goo that drops on everything. But you describe it as being sap, which should stay inside the tree (transporting water and nutrients from the soil to the leaves and stems, and carbohydrates back to the roots.) If you have sap oozing from the trunk, you have a more serious problem, and should contact your county Extension office, with photos. Sap that is tapped in the spring (typically in maple trees) is the sugary mixture moving from the roots back up to the leaves to produce new foliage. I hope this is helpful. Good luck!

Thank you so much for your response! As you probably figured, I know nothing about trees, which is why I referred to the sticky stuff dropping from the tree as sap. I've attached a few pictures of the tree. If you would take a look, I would greatly appreciate it.

I googled aphids and found some information but honestly, its like reading a foreign language to me. I have noticed more of the sticky stuff over the past few years and also noticed less walnuts than the past.

Thanks - Pegeen

Well, I hate to throw more of the foreign language at you, but I am concerned that your trees might be infected with the fungus causing anthracnose, one of the walnut pests described here: You have a couple of options: take your photos and some leaf samples into your county Extension office ( for a closeup examination or hire an arborist to come examine the tree. Or both. It looks like a lovely tree, and I hope you can save it. Good luck!

Thank you so much for your help. I really appreciate it. I will definitely do as you suggest. This old black walnut is the personality of my yard and I want to keep it healthy. I am so glad I posted my question.

Thanks a bunch!


You’re welcome, Pegeen! Let me know what the diagnosis is!