At mid-elevations sugar pine, incense-cedar, white fir and Jeffrey pine join Douglas-fir, ponderosa pine, and canyon live oak, while the other pines and oaks drop out of the mix. Huckleberry oak, shrub tanoak, greenleaf and pinemat manzanitas, and bush chinquapin, are important understory components. In the Cascades east and north of Mt. Shasta, bitterbrush and tobacco brush are very common. On the serpentines of Trinity County's mid-elevation Klamath Mountains, incense-cedar and Jeffrey pine woodlands are inhabited by shrubby Congdon's silktassel, leather oak, and hoary manzanita. Farther west, on the long ridge of South Fork Mountain that divides the Shasta-Trinity and Six Rivers National Forests, the tree form of tanoak grows mixed with Douglas-fir and golden chinquapin.