Maple Leaf Identification: Sugar, Red, Silver and Norway

Maples are opposite and simple: leaves come in matched pairs on either side of the twig, and each leaf is a single blade rather than a group of leaflets. Only a small number of common trees are truly opposite, so this one check rules out most of the forest before you look at a single lobe.

Then check the margin between lobes, which is where the four common species separate. Virginia Tech's fact sheets are precise about it: sugar maple has 5 delicately rounded lobes with an entire margin, red maple has 3 to 5 lobes with a serrated margin and relatively shallow sinuses, silver maple has 5 deep palmate sinuses with coarsely serrate lobe margins, and Norway maple has 5 to 7 lobes with long pointed teeth.

• Sugar maple (Acer saccharum) - 3 to 6 inch leaf, 5 rounded lobes, smooth untoothed margin, green above and paler below. Twig brown, slender and shiny with lighter lenticels; terminal buds brown and very sharp pointed. Fruit a pair of horseshoe-shaped samaras about 1 inch long, brown in fall.
• Red maple (Acer rubrum) - 2 to 4 inch leaf, 3 to 5 lobes with a serrated margin, shallow but highly variable sinuses, whitened and sometimes hairy beneath. Twig reddish and lustrous, buds usually blunt with several loose scales. Samaras 1/2 to 3/4 inch, often reddish, ripening in late spring and early summer rather than autumn.
• Silver maple (Acer saccharinum) - 2-1/2 to 5 inch leaf, 5 sinuses cut deeply so the lobes stand narrow and separated, pale silvery white underneath. Twig stouter than red maple, often chestnut-brown, with an unpleasant odour when crushed. Samara the largest of any native maple, wings 1-1/2 to 2-1/2 inches.
• Norway maple (Acer platanoides) - 5 to 7 lobes with long pointed teeth, dark green above; the petiole exudes milky white sap when detached. Twig stout with large turban-shaped buds. Samaras widely divergent with a flat seed cavity. Widely planted; the dark purple Crimson King is a variety of this species.

Sugar maple and Norway maple. Both have smooth-edged-looking leaves and are planted along the same streets. The milky sap test settles it: break the leaf stalk off a Norway maple and a whitish sap flows from the break. Sugar maple does not do this. The buds also differ sharply - sugar maple terminal buds are brown and very sharp pointed, Norway maple buds are large and turban-shaped.

Red maple and silver maple. Both have toothed lobes and pale undersides, and Virginia Tech lists each as looking like the other. Sinus depth is the separator: silver maple sinuses are cut deeply so the lobes stand narrow and separated, while red maple sinuses are relatively shallow. Silver maple's underside is distinctly silvery white, its twigs are stouter and smell unpleasant when crushed, and its samaras are much larger.

And then there is boxelder (Acer negundo), an opposite tree whose leaf is pinnately compound with 3 to 5 leaflets, each leaflet often resembling a small maple leaf. Virginia Tech notes it looks like poison-ivy and green ash. Because of the poison-ivy resemblance, handle an unknown compound-leaved plant with gloves or not at all; if a rash develops after contact, see a doctor.

Fruit timing is a strong tiebreaker. Red maple samaras ripen in late spring and early summer, and silver maple samaras germinate as soon as they are released and mature in late spring - so a maple dropping seed in June is one of those two, not a sugar maple, whose samaras turn brown in the fall. Norway maple samaras mature in late summer and persist into winter.

Bark separates the same pairs. Sugar maple bark develops furrows with long, thick, irregular, firm ridges that curl outward at the edges. Red maple is smooth and light gray when young, then breaks into long fine scaly plates. Silver maple is similar to red maple but coarser, breaking into long thin strips loose at the ends. Norway maple is gray-brown, a bit corky, with shallow interlacing ridges.

Winter twigs are just as diagnostic: sharp brown buds mean sugar maple, blunt reddish buds with loose scales mean red maple, and large turban-shaped buds mean Norway maple.

The trade splits maple into hard and soft, and the split follows the species you just identified. The USDA Wood Handbook gives side hardness at 12% moisture content as 1,450 lbf for sugar maple, 950 lbf for red maple and 700 lbf for silver maple - so "maple" flooring made from soft maple is barely more than half the hardness of the hard maple most people picture.

Bending strength follows: modulus of rupture at 12% is 15,800 lbf per square inch for sugar maple against 13,400 for red maple and 8,900 for silver maple. Tangential shrinkage from green to ovendry is 9.9% for sugar maple and 8.2% for red maple.

Maples are also diffuse-porous, which is why they take pigment stain unevenly, and the Wood Handbook lists all maples as slightly or nonresistant to heartwood decay - so no maple belongs outdoors untreated. See oak vs maple for the full comparison, or photograph a board's grain with WoodLens and the app identifies the most likely species.

In winter the same four maples separate on bark and buds, per Virginia Tech's fact sheets. Sugar maple bark darkens with age and forms long, thick, firm ridges that curl outward; its buds are brown and very sharp-pointed. Red maple bark breaks into long, fine scaly plates and its buds are blunt and green or red. Silver maple bark breaks into thin strips loose at the ends, and its twigs smell unpleasant when crushed. Norway maple bark is gray-brown with shallow, interlacing ridges and its buds are large and turban-shaped. See sugar maple bark identification for the side-by-side guide.