Autumn days aren't darker, in Kristi Mergenthaler's view, when hillsides around the Rogue Valley are ablaze in red, orange, yellow — even purple found at the heart of flames.

Autumn days aren't darker, in Kristi Mergenthaler's view, when hillsides around the Rogue Valley are ablaze in red, orange, yellow — even purple found at the heart of flames.

"The colors to me," Mergenthaler says, "are like a gift in exchange for the shorter day length."

Although most of the region's flowers have quietly expired, deciduous trees and shrubs are putting on the year's final display of color. And the fruits, seed pods and "architecture" of native plants offer plenty to see outdoors, says Mergenthaler, program coordinator for the Native Plant Society of Oregon's Siskiyou chapter.

"Southwest Oregon is exquisite in the fall with the mild temperatures, and the wind kind of clears the air quality."

The fall-color phenomenon happens when the chlorophyll in leaves starts to decay, revealing other pigments, such as carotenoids, which yield yellow and orange hues, says Mergenthaler, a botanist who surveys rare plants on public land. A plant's anthocyanins, she says, show up as red and purple. These chemical compounds act as "sunscreen" for plants, she adds.

Frequently engaged to lead hikes for the Native Plant Society and Ashland's Northwest Nature Shop, Mergenthaler finds no shortage of participants in spring and summer. Fall excursions aren't nearly as popular, she says, although hikers likely will encounter fewer people on the trails.

"I think people need to be reminded that they can go outside," Mergenthaler. "It still is beautiful."

Here are the Native Plant Society's top 10 suggestions for enjoying the fresh air, exercise and soothing landscapes in Southern Oregon's autumn art gallery.

1. Wagner Creek loop:

Drive or bike up Wagner Creek Road outside of Talent until it turns to gravel near a trail head, where there's a "very gurgly mountain creek looking its absolute best," Mergenthaler says. Look for the play of light, water, rock and recently fallen leaves in smaller streams and creeks like this one. After the aquatic insects, fungi and bacteria have broken down most of the leaf structure, the remnant leaf skeletons are quite beautiful. Trees that populate this area are big-leaf maple, flowering dogwood and alder, which drops its leaves while still green. "There are some gorgeous specimens of really big Pacific yew trees," Mergenthaler says, adding that they're distinguished by purplish bark. This area also is home to bright-orange terrestrial algae that lives on tree trunks.

2. Grouse Gap:

The Grouse Gap section of the Pacific Crest Trail on Mount Ashland: Here hikers find a "muted palette of herbaceous yellows and reds," such as small-growth aspen trees, Mergenthaler says. If you take some time to stake out a blue elderberry bush, you may see a flock of birds intent on the berries. After a frost, when the berries ferment, the birds may fly a little dizzily, indicating the effect of a naturally occurring intoxicant. Take Interstate 5 to the Mount Ashland exit and follow the signs to the ski area. Drive 7.2 miles up the Mount Ashland Road and stop where you see a large sign announcing the national forest boundary. There's parking for three or four vehicles. Cross the road and look for the trail on the south side of the road.

3. Dutchman Peak:

Hike the unimproved road that leads to the fire lookout for breathtaking views of the valley, including the contrast of deciduous trees against swaths of evergreens. Most broadleaf trees in Southern Oregon are deciduous, but not all of them, Mergenthaler says. The broad leaves of Pacific madrone, which bears small red berries, are evergreen. And the larch, which grows in the Cascades, loses its tufts of soft, light-green needles each fall. Take Interstate 5 south to the Mount Ashland exit. Follow the signs to Ski Ashland and continue past the ski area to the overflow parking; Forest Road 20 starts at the parking lot. About 15 miles down the road, an unimproved road leads to Dutchman Peak.

4. Bear Creek Greenway:

This watershed is "full of deciduous, broadleaf trees," Mergenthaler says, citing black cottonwood, Oregon ash, willows and black oak. "It's also a who's who of some of our most noxious weeds." Keep your eyes peeled for fall-spawning salmon. The Greenway runs from Ashland north to Central Point with numerous access points along the way.

5. Pacific Crest Trail in the Dead Indian plateau:

Perfect for a "flat, easy stroll," this area is home to vast patches of "glorious" huckleberries. The fruit is gone, but the leaves turn a purplish-red color. "It's just covered," Mergenthaler says. There are several places to access the PCT in this area. From Ashland, drive about 25 miles east on Dead Indian Memorial Road and turn right on Keno Access Road past Howard Prairie Lake. Drive about 4.5 miles; the trail crosses Keno Access Road. Or continue on Dead Indian Memorial Road another five miles to Forest Road 2520, which also cross the PCT about three miles from Dead Indian. The PCT crosses Dead Indian Memorial Road, itself, about 33 miles from Ashland, past the Klamath County line, near Lake of the Woods.

6. Upper Rogue Trail:

The trail between Woodruff Bridge and River Bridge follows the Rogue River, canopied here in crimson and copper-toned vine maple. Take Highway 62 to Prospect and continue past the ranger station. Look for Forest Road 6210 about three miles past the station, turn left and follow the road into the campground.

7. Middle Fork of the Applegate River:

In the lower elevations of this watershed, deciduous trees abound, with vine maple found a bit higher up. From the Applegate (Star) Ranger Station, follow Upper Applegate Road 13 miles to the junction with Carberry Creek Road. Just after crossing the bridge over Applegate Lake, turn left and continue 1.5 miles to the junction of forest roads 1040 and 1050. Turn right onto road 1040 and follow it for five miles to the junction with road 1035. Continue straight ahead and to the trail head sign.

8. Table Rocks:

Climb these mesas "not only for deciduous trees" like black oak and Western white oak, which turn brownish yellow, but for the poison oak. "It's really one of the brighter, more astonishing colors," Mergenthaler says. The rocks also are home to lichens that cover tree trunks and rocks, displaying "a lot of whites and yellows and oranges." From Medford, take Table Rock Road across the Rogue River. To reach Upper Table Rock, turn right on Modoc Road and drive about 1.5 miles to a parking lot. To reach Lower Table Rock, stay on Table Rock Road where it intersects Modoc and drive 2.5 miles to Wheeler Road. Turn left on Wheeler and drive .8 miles to a parking area.

9. Viewpoint Mike:

Just past Lost Creek Lake on Highway 62, this promontory offers excellent views of the lake and entire Cascade Range arrayed for fall. Be ready for a bit of a workout as the trail gains about 1,000 feet over 2.5 miles across several ridges on the way to a rocky outcrop about 600 feet above the dam. Take Highway 62 east from Medford past Shady Cove and Casey State Park. Just upstream from the park, turn right onto Crowfoot Road and drive about a quarter-mile to a parking area on the right side of the road.

10. Limpy Creek Trail:

This one-mile loop just west of Grants Pass meanders through stands of mature conifers, oaks and madrones, wetlands and a meadow. Hikers can see 17 species of trees, ranging from big-leaf and vine maples to Port Orford cedar and Jeffrey pine. There also are three species of oaks and Pacific yew. From Interstate 5, take Highway 199 west to Riverbanks Road and continue about three miles to Limpy Creek Road. Turn left and follow Limpy Creek Road about three miles to the trail head.