On the upper reaches of the Rogue River, there are still signs of the explosion that created Crater Lake almost 8,000 years ago.

On the upper reaches of the Rogue River, there are still signs of the explosion that created Crater Lake almost 8,000 years ago.

The river flows past tall bluffs of ash and pumice that were expelled when Mount Mazama blew its top. There are also some stunning stands of old-growth trees along this part of the river, just north of Union Creek.

A 6-mile section of the Upper Rogue River Trail (No. 1034) follows the river through this vast deposit of "pummy," sometimes climbing the bluffs as it wanders past the big trees. This section of the trail is almost flat, except for the little climbs up the bluffs, and the river flows quietly compared to its noisy whitewater stretches farther downstream

The best big trees can be found about two miles upstream from the trailhead, where old-growth trees, mostly Douglas fir and Western hemlock, stand undisturbed for about two miles.

The two are easy to tell apart once you know what to look for. Hemlock needles are shorter and broader, and the small cones (1 inch or so) always grow at the end of little branches. The bark is usually distinctly brown. Douglas firs have longer needles, larger cones (3 to 4 inches) that grow along the length of the branches, and bark that tends toward dark gray or black.

There are also occasional Western white pines to liven up the mix. They can be told by their long slender needles, and especially their bark, which separates into small gray rectangular blocks a few inches across.

About four miles upstream, the trail climbs to the top of the first of two bluffs that provide excellent vantage points of the pumice deposits along the river. Highway 230, up above the river, also cuts through these deep gray banks, which become dry and dusty during Southern Oregon's long, hot summer. On windy days, tourists unfamiliar with the area have sometimes mistaken the blowing dust for smoke from forest fires.

The bluffs make a good spot to turn around and retrace your steps downstream for an eight-mile round trip.

Past the bluffs, the trail leaves the river, crossing a series of small streams and more big trees before dropping back down to the river for another 1.5 miles. At 6.5 miles the trail fords Foster Creek just upstream from where the creek enters the river.

The bridge over the Rogue on Highway 230 at Foster Creek is a good place to turn to leave a second vehicle on Highway 230 for a shuttle rig. It's about 4.2 miles upstream from the turnoff for Forest Road 6510, where this section of trail begins.

To reach the trail, take Highway 62 east from Medford and continue past Prospect to the little community of Union Creek. Take Highway 230 toward Diamond Lake for about one mile, and turn left on Forest Road 6510. It's less than a mile to the trailhead, on the north (right) side of the road.

Directions and a trail description can be found in "Best Old-Growth Forest Hikes Washington & Oregon Cascades," by John and Diane Cissel (Mountaineers Books, $16.95). This guide describes 100 trails (including 17 in Southern Oregon) that have outstanding big trees.

Reach reporter Bill Kettler at 776-4492 or e-mail:bkettler@mailtribune.com