The genus Platanthera is the largest genus of orchids to be found in North America north of Mexico; the woodland and bog rein orchids comprise a significant group of species found throughout much of temperate U.S. and Canada. The luminously green rein orchids, so-called because of the resemblance of some of the flowers to the reins used on horses, are especially abundant in rich woodlands, wetlands, and bogs in the more northerly and cooler habitats. Most are easy to identify based upon their general appearance, range, and time of flowering. Answering three simple questions--when, where, and how does it grow?--and comparing the living plants with the striking photos in this backpack-friendly laminated guide and the information in the simple key should enable both professional and amateur naturalists to achieve the satisfaction of identifying a specific orchid.