The Merced River is a very special place for viewing wildflowers. A most spectacular display can be seen during the spring and early summer months. For those less inclined to hike, the river can be accessed by car along a six mile BLM road (the old Yosemite railroad grade) beginning at the Briceburg Visitor Center and ending at the three BLM campgrounds. Beyond the campgrounds, only pedestrians and bicycles can continue along the ungroomed 18-mile river trail.
http://www.blm.gov/ca/st/en/fo/folsom/mflowers.html