The principal trees are the Engelmann spruce, which forms extensive
primeval forests in the subalpine region, the lodgepole pine, the
prevailing tree of middle elevation, very common in second growth, and the
ponderosa pine, a large spreading tree, occurring mainly in the lower
valleys and foothills. The limber pine is frequent in high rocky places,
assuming picturesque forms at timberline, and the Douglas fir, or false
hemlock, is widely distributed, while the blue spruce and alpine fir are
confined to moist stream banks. In addition to the coniferous trees, there
are three species of poplar, of which the commonest is the well-known
quaking aspen, growing in scattered groves throughout the park.
[Illustration: ICEBERG LAKE FROM TRAIL RIDGE ROAD]
_Clatworthy photo._