The crown jewels of California’s redwood forests are the alluvial flats, the fertile floodplains that line year-round creeks, where the most spectacular stands of redwood grow. Bull Creek Flats is the biggest old-growth alluvial flat of all. Its dense, verdent redwood groves have been called “the world’s tallest forest”.
This day-long loop takes in almost all of the magnificent Upper and Lower Bull Creek Flats. The pleasant, easy meander includes several of the most impressive redwood groves anywhere.
The loop isn’t perfect; a lot of the trail goes around the best groves instead of going through them, so the hike actually feels like a series of 6 or 8 small alluvial-flat groves separated by long stretches of more mundane forest. On the north side of the creek the stillness of the redwoods is interrupted by an occasional passing car, and parts of the trail run right next to the road.
In the summer, the loop can be shortened by about 2 miles by crossing Bull Creek on a seasonal footbridge at the Big Trees Area.
The south side of Bull Creek is fairly popular and it’s normal to see someone every 5 – 10 minutes in summer or 10 – 15 minutes in winter, even when it’s raining. On the north side, it’s rare to see people outside of Rockefeller Forest and the Big Trees parking lot.
At the eastern end of the loop is a seasonal footbridge over Bull Creek. The bridge is normally available between mid-May (but sometimes not until the end of July) and late September. At other times it may be possible to ford the creek, but during heavy rainfall it can turn into a raging torrent, making it impossible to hike the full loop. So from October to May it’s best to start at Rockefeller Grove and hike clockwise. That way, you'll find out right away if the creek is too deep to cross.
The depth of the crossings can change from year to year, but in recent years the recommended crossing has been rather deep, while the crossing a quarter-mile to the east has been shallow enough to cross even in winter. Using it adds 0.8 miles to the recommended hike. In February 2021, when the flow rate was 130 ft³/s (about average for winter), the creek was about 24 inches deep and very fast at this point.
Bull Creek Flats Trail South starts at Grasshopper Road, where there’s enough parking for several cars. The trail begins in a scenic alluvial-flat redwood grove, but soon climbs onto a hillside with few redwoods. From here until the Big Trees area the trail is pleasant if not spectacular. In the winter, it’s also slow going because it gets very muddy; fortunately it’s the only part of the loop that gets muddy.
The scenery improves dramatically as the trail descends to the Big Trees Area, which is one of the best parts of the hike. The trail winds through the impressive cathedral-like forest, passing two side trails that lead across the creek to the Big Trees Area parking lot. The trees then get a little smaller and the forest less open, but it’s a subtle difference and the forest continues to be quite impressive for another mile.
The trail emerges from the redwoods for about a quarter-mile. After re-entering the forest, the trail climbs perhaps 20 or 30 feet up the hillside at the edge of the flat. It remains at that slight elevation, contouring along the hillside for another mile or so. Although the trees on the flat below are quite spectacular, the big old growth only grows on the flat and doesn't extend even the few feet up to the trail. As a result this part of the trail is less engaging because you’re no longer walking among the big trees, but looking at them from a distance. It looks like the trail actually used to go through the flat but was re-routed onto the hillside.
The trail briefly descends to the flat again but then, in one big switchback, climbs even further up the hillside into redwood uplands. As is typical of upland forests, the redwoods are much smaller here and there’s a dense understory of huckleberry bushes. This is the transition between Upper Bull Creek Flat and Lower Bull Creek Flat.
Take the first trail to your left, which makes a scenic descent to a small flat with a very open and somewhat dark old-growth grove. The trail cuts across the flat and crosses Bull Creek on a seasonal bridge.
The north side of Bull Creek feels less remote and pristine than the south, but it has more big-tree alluvial flat groves.
The Bull Creek Flats Trail North begins to your left just as you enter Rockefeller Grove. Although it’s not included in the milage for this hike, I highly recommend taking a 0.6-mile detour and walking around the Rockefeller Loop Trail, which circles around Bull Creek Flat; huge redwoods are especially dense here and the trail is definitely a highlight of Humboldt Redwoods. Traffic noise from Highway 101 is sometimes audible but is not overwhelming.
As it leaves the Rockefeller Loop behind, the Bull Creek Flats Trail North continues through exceptional old growth. There’s a break in the redwoods and the trail is briefly squeezed up against Mattole Road as it passes from Lower to Upper Bull Creek Flat. The trail loops around a little flat with some nice redwoods, located between the upper and lower flats. There’s another break in the redwoods as the trail runs just below Mattole Road again for a short stretch.
The trail then enters Upper Bull Creek Flat. Plunging into the redwoods, the trail passes through a series of what look like three small but very attractive redwood stands. In fact, these stands are actually a single large grove that the trail mostly skirts around and only occasionally dives into. The first stand is a spectacular cathedral-like grove as fine as any in Humboldt Redwoods. The next two follow over the next mile or so and aren’t quite as open, their understory dense with small tanoak trees, but they’re still pretty scenic. Despite the great scenery, this part of the trail seems to be rarely used.
A few stretches of the trail are very close to Mattole Road and the traffic noise can be annoying on a summer weekend. In contrast, on a winter weekday there might only be a car every 10 or 20 minutes (although in the early morning there seem to be a lot of trucks headed for the Lost Coast) so the road isn’t as noticable.
Near Look Prairie, the flat ends and the trail runs right next to the road for a while; it’s advisable to just walk on the road here since the trail is somewhat rough and infested with poison oak. The trail then disappears completely, joining the road as it curves along Bull Creek past a clearing that offers a little sunlight and some very nice views of tall redwoods growing along the creek. There’s a dirt parking lot, the Blue Slide Day Use Area, to your left. The trail begins again, skirting around the lot and diving into the forest. The trees get noticably bigger as you approach the Big Trees Area parking lot.
Past the parking lot, the trail enters an especially scenic grove. This is the longest and one of the most impressive stretches of big-tree alluvial flat scenery on the hike. There are glimpses of tapering sunlit treetops and impossibly tall and thin light beige trunks shooting high into the sky. This grove exemplifies the "cathedral-like" redwood forest, with the fluted columnar trunks illuminated by flecks of sunlight filtered through the stained-glass canopy. In winter, the pleasant sound of rushing water permeates the area.
The best scenery continues for about a third of a mile, after which the trail moves closer to the river and skirts the edge of the forest, where the redwoods are much smaller. The Big Trees Trail ends at Mattole Road; turn left onto the road to cross Bull Creek and reach the end of the hike.
© 2007, 2010, 2016, 2018, 2021 David Baselt