Q.Sticky Substance on Deck From Trees
Our deck gets covered with a black sticky substance every summer and anything that is left out on the deck. It takes a lot of effort to wash it off every few weeks. Flies, wasps, and bees seem to be attracted to the leaves of the trees. The trees that shade the deck are: sassafras, sumac, white oak, and cotton wood. Is one of these trees causing the problem, and what should be done to prevent it next year?

Certified GKH Gardening Expert
Here is an article or two that you may find helpful: https://www.gardeningknowhow.com/ornamental/trees/tgen/how-to-remove-tree-sap.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/what-is-tree-sap.htm