Most people can tell an oak or maple leaf when they see one, but distinguishing the different species within the Quercus genus or Acer genus takes careful observation.

First, let's define a few terms. Simple leaves are those with a single leaflet per leaf stem, as opposed to compound leaves, which have many leaflets on a each leaf stem. Lobed leaves have bulges, either rounded or pointed, and may or may not have teeth as well. The negative space between two lobes is known as a sinus.

Oaks

Oak leaves are alternate (not meeting in pairs along the twig) and have lobes arranged along both sides of a leaf that is longer than it is wide. There are two groups of oaks, known collectively as the Quercus genus. The white oak group has rounded lobes, while the scarlet / pin oak group has pointed lobes with a tiny bristle at the end of each lobe. The seeds of oaks are the familiar acorns. Buds at the tips of twigs are clustered, with white oak buds being rounded and scarlet / pin oak buds pointed, just as the leaves are. Here are the most common oaks found in the Northeastern region of the U.S., also distributed through other parts of North America:

White oak group

White oak: leaf with a few rounded lobes; deep sinuses between the lobes. Flaky, layered bark.

Chestnut oak: wavy-edged leaf with many small lobes and shallow sinuses. Bark not flaky, with deep furrows and flat ridges.

Scarlet / Pin oak group

Red oak: leaf with a few pointed, bristle-tipped lobes; deep sinuses between the lobes. Bark not flaky, flat, dark grey and very rough, with occasional smooth and lighter grey plates, especially higher on the trunk.

Black oak: leaves and bark similar to red oak. Leaves tend to be more shiny and buds smaller than in red oak.

Pin oak: deeper sinuses than red or black oaks, and the lobes tend to occur at right angles to the midrib. Lower branches usually point downward. Rough, non-flaking bark.

Willow oak: The only oak with lanceolate (long and narrow) rather than lobed leaves. Leaves have bristle-tips. Bears acorns like other oaks. Shallowly grooved bark.

Maples

Members of the Acer genus are opposite, occurring in pairs on opposite sides of the twig. The lobes of maple leaves are pointed and occur in a palmate fashion, radiating out from a central point. The seeds are known as “keys” and look like pairs of wings, with papery membranes carrying the seeds on the wind. Here are distinguishing characteristics of some common species:

Sugar maple: five blunt-pointed lobes with a few blunt teeth. Bumpy, non-flaking grey bark, often partially covered by a whitish-grey lichen. Sharply pointed brown buds with overlapping scales.

Red maple: five sharply pointed lobes with many tiny, sharp teeth and the two upper lobes (nearest the stem) much smaller than the others. Bark smooth and light grey when young, often with a powdery texture; turning flaky when older. Buds, flowers, young leaves, autumn leaves, and leaf stems all red or reddish.

Silver maple: five pointed lobes with deep sinuses and many teeth, silvery white underneath. Flaky bark. Buds similar to red maple.

Striped maple: three lobes, many small teeth. Bark smooth and striped green, white, and brown. Smallish tree occurring in open woods.

Norway maple: leaves similar to sugar maple but larger and broader, with about twice the number of teeth. Bark has deep furrows and ridges that form diamond patterns, as in ash and tulip-tree. A European import, found mostly in cities and parks, occasionally in the countryside. The Schwedler variant has dark reddish-purple leaves.

For information on other kinds of simple leaves, see Trees with Oval Leaves.