Sugar Maple

Sugar Maple (Acer sacharrum) is one of seven species of the Acer genus that grow in Maine's forests. Six of these "typical" maples (A. saccharum, A. saccharinum, A. rubrum, A. platinoides, A. pensylvanicum, and A. spicatum) have opposite arrangement of their simple leaves and buds. Other trees with opposite features include the ashes, red-osier and flowering dogwoods, the viburnums, and horse-chestnuts. The other thing that these six maples have in common is their palmate venation - the leaf veins originate from a central point at the base of the leaf and fan out, sort of like your fingers fanning out from the palm of your hand. The other vein arrangement is pinnate, like a feather where the veins branch outward all along the central mid-vein. Finally, the maple fruit is a double-winged indehiscent samara. In addition to the six typical maples is Boxelder (A. negundo) which has compound leaves which are oppositely arranged - it also bears the double-winged samara.

So, how do you tell a Sugar Maple from the other simple-leaved maples? From late spring through autumn, you can distinguish it by its leaf margins. Maple leaves are lobed which means there are distinct indentations that don't go all the way to the mid-veins. The leaf depicted here has three large lobes with two smaller lobes at its base. The other simple-leaved maples will have 3-5 lobes with  palmate venation, but the  notches and margins will differ. At the base of each lobe where it meets the next one, the part that reaches toward the center of the leaf is a sinus. The sinus is distinctly "U" shaped on Sugar Maple (A. saccharum) and Norway Maple (A. platanoides). The sinus is notched like a "V" on the leaves of Mountain Maple (A. spicatum) and Red Maple (A. rubrum). Striped Maple (A. pensylvanicum) is fairly "V" notched, and Silver Maple (A. sacharrinum) is very deeply and "U" notched. You can distinguish Sugar Maple from Norway Maple leaves by breaking the leaf stem from the twig and looking for a milky white sap on Norway Maple. 

In winter you can look at bark and buds. Sugar Maple bark is different from Norway Maple - the former has broad ridges whereas the latter has narrowly spaced ridges and furrows. Bark is a little tricky because young, middle-aged, and mature trees have different textures. Striped Maple bark is vertically striped and the tree doesn't get very tall. To me, Sugar Maple's broad ridges don't seem to curl as much as with mature Red Maple or Striped Maple. I don't have much experience looking at the bark of Mountain Maple. The oppositely arranged buds also yield clues. Sugar Maple buds are dark brown and very pointed though not excessively long. Red Maple and Silver Maple buds are rounded and red. Mountain Maple buds are pointed, short-stalked, and green to red in color. Striped maple buds are distinctly stalked. Norway Maple scales are large.