This post was originally published on snow.news, my free Substack on snow science and the state of the snowpack.
Krummholz and Mount Sopris, seen from the slopes of Colorado’s Snowmass ski area, in January 2025. Photo by Mitch Tobin.
Treeline is one of my favorite places to ski. There’s something magical about that progression from barren tundra to the widely spaced trees at the start of the forest. If you spend time in these high-elevation transition zones, you’re likely to see small trees/bushes that take on strange, warped shapes. Welcome to krummholz, which Merriam-Webster defines as a “stunted forest characteristic of timberline.”
The word’s etymology is German: krumm means “crooked, bent, twisted” and holz means “wood,” according to Wikipedia, which also notes that an alternate word, knieholz (“knee timber”), is used to describe the diminutive vegetation.
These tenacious trees have been reduced to shrubs by the harsh environment in which they live. Throughout the year, strong winds rake the mountainsides, inhibiting vertical growth and easily breaking branches. Some trees are so affected by the wind that they only grow branches on their leeward side, leading to the creation of “banner” or “flag” trees (similar formations are seen in places like the Oregon coast).
Krummholz must contend with frigid temperatures and a very short growing season, which also keeps the vegetation’s height in check. Poor soils and intense UV radiation can inhibit growth. And during the winter, snow loads can easily damage the trees and prevent them from growing tall.
Over the eons, krummholz trees have evolved an effective survival strategy to persist in places where you and I would quickly perish from exposure to the elements. These dwarf forests may not evoke the majesty of the lofty redwoods, but they still provide essential habitat for wildlife and are enchanting in their own right.
Krummholz trees are hearty survivors in an unforgiving environment. Photo by Mitch Tobin.
