Below is a list of 22 trees that can be tapped for sap. Please note the best time to tap a tree is prior to the tree budding. Early Spring when the temps go up during the day and low during the night. But trees can be tapped throughout the year, though the sap will not run as nicely as it does in the Spring. Once the leaves are out the sap tends to be bitter. Unsure if boiling sap that is bitter would help the taste. Lots of good minerals found in tree sap. Also tree sap have also been used for medicinal purposes in different cultures. 22 Trees That Can Be Tapped For Sap And Syrup | Wild Foodism
Tapped a black walnut two years ago, best 1/4 cup of syrup I ever tasted. Served it on a waffle to my wife on Mothers Day.