The most common trees are coast live oak (Quercus agrifolia) and blue oak (Quercus douglasii), with the largest blue oak growing in Alameda County. There are also good populations of California buckeye (Aesculus californica), and California black oak (Quercus kelloggii). The gray pine (Pinus sabiniana) and rarer Coulter pine (Pinus coulteri) can be found at all elevations, especially between 800 ft. and 3000 ft. Coulter pine reaches its northern limit on northern of Mt. Diablo. The conifers at higher elevations in the Diablo Range include knobcone pine (Pinus attenuata), Jeffrey pine (Pinus jeffreyi) and ponderosa pine (Pinus ponderosa).