Western hemlock, native to the western parts of North America, is the largest of the hemlocks. Capable of standing deep shade, it grows in mixed forest on mountain slopes and forms dense stands. The crown is narrowly conical and the branches almost horizontal, though the leader and tips of the branches droop in typical hemlock fashion. The needles vary in length, growing outwards and upwards from the branches, covering them so that with age they appear from a distance to be covered in mossy layers.
The climate of the west coast of North America favours trees that grow to enormous size, one of them being the western redcedar. In its natural range it can achieve 70m in height, a giant conifer with brown-grey fibrous bark and shiny scale-like leaves.
The endangered Lawson cypress occurs naturally only in the valleys of the Klamath Mountains on the borders of Oregon and California. It is a heavyweight among trees, as it can grow to 70 metres tall and 4 metres in diameter. The oldest living specimen is said to be over 1800 years old. The species is now threatened by a fungus, Phytophtora lateralis, which has apparently spread through human agency into the tree’s last outposts. It has no resistance to this fungus, which spreads through the roots, and the infected tree slowly dies.
The Nootka cypress with its long sweeping branches and drooping foliage is the exact opposite in appearance to the Mediterranean cypress (Cupressus sempervirens). The dense blue-green foliage almost completely hides the beautiful cinnamon-coloured bark, which peels from the trunk in long strands. On hot days, the trees give off a strong smell, sometimes described as “like a pencil”.
The Pacific silver fir is generally considered the most beautiful fir growing in Arboretum Mustila. It has duly earned its binomial name, where amabilis stands for amiable or lovely. The dark green needles of the Pacific silver fir are sublimely decorative. Its growth habit is majestic: the branches overlap evenly in whorls, creating a harmonious and peaceful appearance. When mature, this fir grows vigorously into a stately, dense tree, but the young seedlings grow frustratingly slowly, and are as demanding and whimsical as might be expected from a princess of firs.