Examine the leaves for a dark green color on the outside, and a lighter green on the underside.
Look for leaves that are segmented into 5 lobes. There should be 3 large, main lobes and 1 smaller lobe on either side, although some leaves have only 3 or 4 lobes. The lobes are characterized by sharp teeth, and are connected by shallow, U-shaped notches.
Measure the leaves. Mature leaves on a sugar maple average between 3 inches (7.72 cm) and 5 inches (12.7 cm) long, and equally as wide.
Look for three main veins in the leaf, one running through each main lobe. These veins are detectable on the underside of the leaf, but lie smooth on top.