Identify by Leaf Opposite Opposite leaves are directly accross from each other on the stem. Needle or Scale Needles are narrow, frequently pointed and also vary in length. They can be round or flat in cross section and grow as a single needle or in bundles. Scales are short and flat and grow close to the stem. Alternate Alternate leaves are spaced in alternating fashion along the axis of the stem and are seldom, if ever, directly across from each other. Leaf Margins This key uses leaf margins as a way to identify one tree from another. A leaf margin is simply the edge of the leaf. Edges can be smooth, have different types of teeth, be wavy or incised, or have lobes. Here are the classifications used in this key.