Tsuga Heterophylla, the Western Hemlock, is a species of Hemlock trees native to the west coast of North America, expanding all the way north to the Kenai Peninsula and as far south as Sonoma County, California.
The Western Hemlock is a large growing evergreen coniferous tree, sometimes reaching heights of up to 70m tall, with a trunk that can get as big as 2.7m around. The Western Hemlock is actually the second largest species of hemlock in the world, the first being the Mountain Hemlock. The tip of the tree has a much uniformed cone shape that becomes more cylinder in appearance as the tree ages. At all growth stages of the Western Hemlock it is easily eminent by its pendulous branch tips. The shoots of the branches are a very pale brown color, sometimes almost white and the leaves are needle- like. The needle like leaves can grow from 5mm to 25mm long and approximately 2mm broad, they are dark green in color and are arranged in a spiral fashion. The Western Hemlock produces a cone that is small, slender and in the shape of a cylinder. When the cones are open they are about between 18 to 25mm around and when closed the cones are about 8 to 15mm in circumference. Immature cones will be a pale green color and as the cone ages the green color turns to a gray brown color, which usually happens around five months after pollination. The seeds of a Western Hemlock are small, about a 3mm in size; they are a pale brown color and can be identified by a little wing that is affixed to the seed.
The Western Hemlock is mostly associated with the temperate rain forests and the range of rain forest that the hemlock covers is only about 100km from the Pacific Ocean. There are however smaller inland populations of the hemlock, which can be found throughout regions of the Rocky Mountains that are in Montana, parts of northern Idaho and regions of British Columbia.
The Western Hemlock is a shade friendly tree and their tolerance to shaded areas are comparable to other species of trees, such as Pacific Yew and the Pacific Silver Fir. The hemlock is a tree that is slow to start growing; one year old seedlings of the Western Hemlock will only be 3 to 5cm tall. Seedlings that receive full sunlight most commonly will only average 50 to 120cm per year.