The very name “sphagnum bog” conjures up a vision of the Scottish moors — a dark, stagnate, acidic wetland with low fertility, tea-colored water and perhaps a well-preserved Iron Age bog body or two. But the misnamed Sphagnum Bog found just inside the west boundary of Crater Lake National Park is nothing of the sort. It’s actually a fen, fed by mineral-rich, alkaline spring water that supports a diversity of peat-adapted plants. A forested 2.3-mile trail leads to Sphagnum Bog, which can then be explored on a cross-country ramble.

Hydrology of Sphagnum Bog

The 35 acres of wetlands at Sphagnum Bog and its 100 plus species of vascular plants are fed
by the surface water flow and groundwater seepage from the Crater Springs complex. These numerous springs and seeps are in turn fed by the prodigious winter snowfalls (over 8’ deep) that commonly blanket the mountain slopes west of Crater Lake. Some subterranean feature in the pumice deposits here, such as a lava dam or a buried glacial moraine, causes the downslope movement of the groundwater to push up to the surface, creating the high water table necessary for fen and peat development (diagram at left).

The pumice layer underlying the peat soils at Sphagnum Bog was deposited by the climactic eruption of Mt. Mazama about 7,700 years ago. It’s thought that fen and peat formation started sometime later, as sedges and herbs invaded shallow pools over the poorly drained pumice. In the millennia since the eruption, the peat deposits at Sphagnum Bog have grown to a thickness of 5 to 6 feet.

Plant Communities at Sphagnum Bog

The most striking feature of Sphagnum Bog, besides its broad extent, is the intricate mosaic of plant communities found in the interconnected wetlands within the forest openings. These plant communities are all arrayed along a gradient, from dry sites with mineral soils at one end, to wet sites with deep peat soils at the other (chart below) — reflecting a subtle hydrology of seeps, moving water channels and depressions where water accumulates and remains year-round.

The driest plant communities are the alder/willow thickets around the edges of the fens on primarily mineral soils. Next comes the bog blueberry community, which makes up over 40% of wetland area at Sphagnum Bog. After the snowmelt disappears, both the alder/willow and bog blueberry communities are dry on the surface, supported by a shallow groundwater table.

Next along the moisture gradient is the tall sedge community, which is soaked in spring and then partially dries as the summer progresses. Finally, in the wettest sites are the low sedge and moss communities, which are inundated year-round and grow in deep deposits of pure peat. These are the heart of Sphagnum Bog, covering over 30% of its surface area. The moss communities here are dominated by spongy carpets of brown mosses, which are typical of a fen — and distinct from a bog, which are dominated by sphagnum mosses.

Hike to Sphagnum Bog

Overall, a two-hour drive from Bend to the Trailhead, the route first follows Hwy 97 south for 75 miles to the Diamond Lake Junction, then goes west on Hwy 138 for about 18 miles to the junction with Hwy 230 on the left. Drive Hwy 230 southwest for another 18 miles to the signed turnoff for National Falls on the left. (See Road Map download below.)

Drive 1.3 miles on this paved road (crossing the Rogue River) to a “Y,” where one bears right on paved Road 6535. From this junction, follow Road 6535 east as it turns into a good gravel road at 3.5 miles, bearing left at a “Y” at 4.3 miles. At 6.0 miles, turn left onto dirt/gravel Road 660, and follow it for 0.8 miles to the trailhead parking area at road’s end. This trailhead is easily reached by any passenger car during the snow-free season from early July to October.

From the parking area, the hike starts east on the unsigned Bert Creek Trail, and climbs gradually to the National Park boundary at 0.5 miles. Past the boundary sign, the trail meanders through thick stands of Shasta red fir and western larch to its junction with the Bald Crater Loop trail at 1.7 miles. Turn right (south) at this trail junction, following the signs to Sphagnum Bog. At 2.1 miles, the route again forks south at a second signed trail junction, ending at 2.3 miles in the short loop trail at Crater Springs.

To explore the fen itself, the best route is cross-country, staying in the drier grass and blueberry communities along its eastern edge (see Trail Map download below). But since the boggy wet soils are almost impossible to avoid, having a pair of light, easy-drying shoes along can be a plus. From the horse hitching rail on the Crater Springs trail loop, first walk cross-country east about 50 yards to a small, 1-acre fen. Circle this fen on the north and east, then follow its drainage swale south for about 250 yards, over a few downed trees, to the Upper Fen.

From here one can venture west out into the wetlands, following the dry ground where possible, but being careful not to tromp on the delicate wet sedge and moss communities. Look for species of carnivorous sundew plants, which trap insects in the sticky hairs on their leaves. One can wander further south for another 300 yards to the Lower Fen, but keep a sharp eye to avoid the deep “bog holes,” which can be hidden in the thick grass. Also look for elk, which graze around the edge of the fen, but will quickly melt back into the surrounding forest if disturbed.

Download (PDF, 678 KB): Photos of Sphagnum Bog Hike
Download (PDF, 530 KB): Road Map for Sphagnum Bog Hike
Download (PDF, 654KB): Trail Map for Sphagnum Bog Hike

DISCLAIMER: Every effort has been made to ensure the accuracy of this information, but the authors do not guarantee that it is either current or correct. The reader assumes full responsibility for any use of this information, and is encouraged to exercise all due caution while recreating.