Follow-up on this related MY question relating to the bracha on coffee or tea.
I initially surmised that to say "ha'etz" you must eat the fruit that protrudes from a tree branch. However, I have heard that one would say *ha'etz" on cinnamon sticks, which is the bark.
Maple syrup (the real stuff, not the "corny" Aunt Jemima) comes from the sap of sugar maple trees. (There are probably other types of drinkable tree sap, though, I can't think of others.) It is still part of the tree, but it's in liquid form.
I had heard from a rav that the bracha on maple syrup is shehakol, but, I'm not sure why it wouldn't be ha'etz considering that it's part of the tree.