With the exception of rocky alpine regions in the highest mountains, the Trinity River watershed is almost entirely forested. Mixed coniferous (fir and pine) forests dominate the landscape at elevations of up to . Common tree species include ponderosa pine, Jeffrey pine, Douglas fir, white fir, red fir, sugar pine, knobcone pine and incense cedar. The watershed also includes some hardwood forests, typically located along canyon bottoms and streams, which are home to California black oak (Quercus kelloggii), madrone, tanbark oak, canyon live oak and bigleaf maple. Stands of Port Orford cedar are common along the upper Trinity River; Oregon white oak is widespread throughout lower elevations. Fir forests comprise almost 74 percent of the forests in the Trinity River watershed; pine and hardwoods account for 13 percent each. There are also limited amounts of chaparral, brush and grass/rangeland within the basin. Wildfires are common in the dry summers which receive little to no precipitation, aside from the occasional high elevation thunderstorm.