This plant may be called giant mullein, common mullein, or, in the western US, cowboy toilet paper.  This is because of the soft fuzzy leaves. Its Latin name is Verbascum thapsus.  It came to the US from the Old World with people who settled the country and it is a great example of a naturalized species.  It is now found all over the country.  It is a biennial, which means that it grows for two years.  In the first year it makes a low-growing rosette of beautiful fuzzy leaves but no flowers.  In the second year it makes a spectacular spike that may be taller than a person, with numerous yellow flowers that open over a long time.  A single plant may produce over 200,000 seeds, and seeds can stay in the soil for hundreds of years, still able to germinate when a disturbance brings them to the surface. Mullein isn't generally considered to be invasive because it is adapted to only grow where most other plants can't--in disturbed ground, including the dry rocky slopes where it is mostly found along the trail. 

The seeds of mullein are very small but seed-eating birds like goldfinches will seek them out.  The leaves may stay green much of the winter and in some areas they are eaten by grazers like deer and elk. It is probably "famine food" because the fuzzy leaves aren't very palatable for grazers or for insect pests. The stalks stay around for a long time and might even be visible over the winter. 

Moth mullein, Verbascum blattaria, is a shorter, more refined and less hairy relative that is also found along the trail.  It is also a naturalized non-native biennial but tends to bloom later in the summer. Flowers may be white or yellow. Again, while some invasive species atlases list this plant, in our area it is restricted to disturbed sites and has ornamental and wildlife value, so we are happy to see the pretty flowers and don't try to control it.