Krummholz or krumholtz (German: krumm, "crooked, bent, twisted" and Holz, "wood") — also called knieholz ("knee timber") — is a type of stunted, deformed vegetation encountered in subarctic and subalpine tree line landscapes, shaped by continual exposure to fierce, freezing winds. Under these conditions, trees can only survive where they are sheltered by rock formations or snow cover. As the lower portion of these trees continues to grow, the coverage becomes extremely dense near the ground.