Maple syrup is the boiled-down sap of the sugar maple (Acer saccharum) and a few related maples, concentrated from a faintly sweet spring "sap water" into a thick amber syrup of about 66% sugar. It is one of the very few sweeteners made from a tree, harvested over a short late-winter-to-spring window when freeze–thaw cycles drive sap up the trunk. Graded by colour from pale Golden through Amber and Dark to near-black Very Dark, it carries a deep, unmistakable "maple" aroma built mainly on the trace furanone known as maple furanone, with caramel, vanilla and toasty notes layered behind it.