Over 200 species of pine trees exist around the globe, with 62 different types growing in North America. The pine trees are evergreen, with a multitude of needles that remain on the tree year round. The pine needles on each species of pine grow in bundles on the branches. These bundles are known as fascicles in botanical circles. While you can often use the size, the bark, the cones and other aspects of a pine tree to tell which species of pine it is, you can also identify many pines simply by closely inspecting their needles.
Count the number of needles in each bundle as they grow on a pine tree. The number is an excellent indicator of what type of pine tree you have encountered. For example, eastern white pine has needles that grow five to a bundle on the branches, while red pine is a species of pine with two needles per fascicle. Needles per bundle is vital information regarding the type of tree upon which the needles grow.
Measure the lengths of the pine needles, which typically grow to different sizes depending on the species. Some species of pine have very long needles, such as the 10-inch long needles of digger pine and sugar pine. Others will be considerably shorter, such as the inch and a half long needles on a jack pine. Needle length provides you with another clue to the species of pine tree you are looking at.
Observe the color of the pine needles and use this to aid in identifying the tree. Some pines have dark green needles; the lodgepole pine is one example of such a species. Other pine trees have needles of a different shade of green, like the darker yellow-greenish needles belonging to a species called shortleaf pine that grows in the Southeast.
Feel the pine needles to determine if they are soft or stiff. This facet of pine needles is another way to distinguish among types of pine. For example, western white pine has flexible soft needles that easily bend, while species like the slash pine and bishop pine possess stiff bristle-like needles.
Look at the needles to discern if they are straight or curved in appearance. Most pines have straight needles, like those on a loblolly pine. Some pines, however, have slightly curved needles, such as those on a pitch pine.
Combine your observations of the needles of a pine to make a final determination of the species using a field guide to trees. In a book such as the "National Audubon Field Guide to Trees" part of the listing for each species of pine is the length and color of the needles, the number of needles in a fascicle, and other pertinent information about the needles. Some field guides have several indexes, including one based on characteristics of leaves and needles.
Chart the features of the needles when in the field for later reference in your guide, or bring the guide with you to make a positive identification in the field.