Flower:

Drooping clusters at branch tips appearing about the same time as leaves emerge. Male and female flowers are long stalked, greenish yellow, and borne on separate branches of the same tree, sometimes on separate trees or on the same branch. Occasionally flowers are perfect (contain both male and female parts). The stalks are hairy, the calyx is 5-lobed and without petals, the male stamens extend just beyond the calyx, the females with two stigmas extending below the calyx.

Leaves and bark:

Leaves are simple and opposite, the blade up to 6 inches long and 7 inches wide with 5 palmate lobes, the upper 3 large and squarish below the pointed tips, the two basal lobes much reduced or nearly lacking. The stalk is hairless or with a few sparse hairs at the base, and is about the same length as the blade.

Upper surface is dark green and smooth, the lower surface paler, smooth or with minute, fine, appressed hairs mostly along major veins or just in the axil of the lateral veins across the surface. Edges are smooth between the 5 to 11 points on each side. Fall color is yellow to orange to red.

One year old twigs are smooth and brown to gray. Older branches and the trunk develop hard, ridged bark. The trunk can grow to 48 inches in diameter at breast height (dbh). 

Fruit:

Fruit is a pair of winged seeds (samara), that can be up to 1¾ inches long but more typically around an inch. Fruit matures from late August into October. The wings form an angle between 60 and 90 degrees.

Notes:

Sugar Maple is the quintessential North American maple known for its hard premium wood, gorgeous fall color, and maple syrup, even decorating the national flag of our Canadian neighbors. Its preferred habitat is rich, moist woodland soils were its saplings can exist for many years in the dark, shady understory until a large canopy tree over head gives way, releasing them to grow into its place. It also makes a desirable urban tree where it can produce a large, round, dense crown with beautiful fall color. Too often however it is placed into too compacted or sandy sites where it does not fair well.

As well known as it is, people can confuse Sugar with a number of other maples. Red Maple (Acer rubrum) equals its fall color but its spring flowers are in bright red clusters and its leaves finely toothed from stalk to tip. The widely urban planted and now increasingly naturalized Norway Maple (A. platanoides) has larger, open clusters of yellow flowers, larger, less deeply lobed leaves with seven central veins radiating from the base, plus the leaf stalk and veins exude a milky sap when broken. The native but less familiar (due to its limited southeastern range) Black Maple (A. nigrum) is the most similar, especially with similar variations in leaf shape, but can be distinguished by consistent fine, erect hairs across the entire lower surface that give it a velvety feel, and also the presence of distinctive stipules at the base of the leaf stalk. Less reliable is Black Maple typically having 1 to 6 points per side of a leaf and Sugar Maple typically with 5 to 11 points per side. Something we observed with Sugar Maple is a spot of purplish red at the base of leaf stalks in spring, seen on many trees in various locations, but a trait not mentioned in any reference. Curious thing.