The meadows in Bridger Canyon used to be edged with hawthorn bushes, which formed a transition between the grass and the aspen. Hawthorn grows about 6' tall in very dense thickets that cattle love to hide in on a hot summer day; they are in the Rose family and have woody thorns about 2" long, so horses and cowboys don't like to go through them at any time. Which may be one reason cattle love the thickets. However, in the fall, hawthorn make up for their barbarity by turned a wonderful orange-red that shades into purple; the contrast with the golden aspens and green pines is incredible, and has made Bridger Canyon highly photographed.
Hawthorn provides good cover for wildlife, and is well used by birds during the nesting season and when the fruit ripens. Hawthorn also has a long history with people, filling many roles besides cattle-den. It is used for herbal remedies, especially for heart problems. "The Greeks and Romans linked it to hope, marriage, and fertility. Greek bridesmaids wore fragrant hawthorn blossoms, and brides carried a bough. The Romans placed hawthorn leaves in babies' cradles to ward off evil spirits. Christianity changed hawthorn's image dramatically. Christ's crown of thorns was reputedly made of hawthorn, and as a result, it became a symbol of bad luck and death." (Source)
A few years ago, the hawthorns in Bridger Canoyn caught a rust that killed off all the leaves. At the time, the local paper said that the rust wouldn't kill the plants; but the next summer, the branches were bare and no leaves grew. The rust might not normally kill the hawthorn, but it seems to have overwhelmed drought-weakened plants this time. Now the meadows are edged with grey bands that just get darker in the fall. New growth is slowly appearing, but it will be several years before the fall colors are spectacular again.
The interesting thing about the rust, called juniper-hawthorn rust, is that its life cycle requires two hosts to complete: juniper and hawthorn. The rust spends about a year and a half on the juniper, without doing much damage, then migrates to the hawthorn (or other plants in the Rose family, such as apple trees) for a few months. Without both hosts, the rust won't survive.