The trailhead is on Forest Road (FR) 1030-500 about 4 miles up from its junction with FR 1030. FR 1030-500 is accessible to 2WD vehicles. It may be closed by snow between November and May and by fallen trees at other times. The trailhead is unsigned but is marked by metal tags on a nearby tree.
The Green Valley Trail #904 still appears on USGS and Forest Service maps but has been dropped from the Rogue-Siskiyou National Forest's inventory (and website). It no longer receives any maintenance but has been kept alive by hunters who have marked key turns in its tread with large cairns. The old tread is quite apparent under the forest canopy but is very faint where it crosses open areas covered with seasonal vegetation. Pay close attention to the cairns to avoid veering off the trail.
Shortly after leaving its unsigned trailhead, the #904 crosses a small spring-fed creek and climbs the bank to the southwest. It continues climbing to the southwest, alternating between abrupt climbs and gentle traverses through the forest. After less than 0.75 miles, it ends at an unsigned junction with the Boundary Trail #1207 in Green Valley below Swan Mountain. This junction is marked only with a cairn and can be hard to see if you're trying to find where to descend the #904 from the Boundary Trail #1207.
Despite its steepness and poor definition, it is one of the quickest ways to reach the Boundary Trail #1207 and the wildflower meadows along the Siskiyou Crest from an accessible forest road.