Hi Donna, I'm not familiar with using kelp on trees ( other much smaller plants, but not huge trees). It certainly won't hurt but I have to admit it seems odd to use an ocean product on your MN trees. It does contain trace elements. https://solve.mit.edu/challenges/climate-ecosystems-housing/solutions/59983/application https://www.sciencedirect.com/science/article/pii/S<personal data hidden>02557 I guess I would prefer to use leaves and local wood chips because that is what it would have in nature. Are your trees stressed/ starting to decline ? If you are concerned about them and the price is acceptable to you than you might want to try it. I still recommend letting the leaves stay around the tree for natural compost to feed the tree. Thanks for your question, Sally Granath Hennepin County MG