AGRICULTURE: In finding that could upend maple syrup production, sap doesn't always flow from top Published: Monday, February 3, 2014 Researchers have found that sap used to make maple syrup does not exclusively flow top to bottom from older trees. Please subscribe to Greenwire to read the full story. Username: Password: Forgot your access codes? Recover them. Not a subscriber? Sign up for a trial. Ready to subscribe? Click here.