The timberline is the term for the point at which the mountain microclimate becomes too cold for pine trees, and smaller alpine plants and shrubs take over the terrain. The Timberline Trail is a twenty-four mile hiking trail encircling Mt. Hood, dipping above and below treeline, crossing glacial rivers and canyons and passing through designated wilderness areas in its course. Sections of this trail may be accessed at numerous points around the mountain, and can be completed as day hikes, which is what I have done. Timberline Lodge is the historic starting point for many.