Trees Planet: Tsuga mertensiana

General Information

Common Name	Mountain Hemlock
Scientific Name	*Tsuga mertensiana*
Sun Tolerance	Full Sun
Height	20 - 60 m (66 - 132 ft)
Spread	10 - 15 m (33 - 50 ft)
Growth Rate	Fast
Bloom Time	Spring
Color	Green,
Flower Color	Yellow
Type	Tree
Native	USA, Europe.

Classification

Kingdom	Plantae – Plants
Subkingdom	Tracheobionta – Vascular plants
Superdivision	Spermatophyta – Seed plants
Division	Coniferophyta – Conifers
Class	Pinopsida
Subclass
Order	Pinales
Family	Pinaceae – Pine Family
Genus	Tsuga – Hemlock
Species	T. mertensiana

Tsuga mertensiana - Mountain hemlock

Tsuga mertensiana commonly known as Mountain Hemlock, is native to the west coast of North America, from Alaska to California, British Colombia, and the mountains of Washington. It is also found in the Rockies of northern Idaho and Montana.

Mountain Hemlock is a large tree, growing 20 – 40 m (66 – 132 ft) in height, some exceptional specimens grows up to 59 m (194 ft) in height. Its trunk diameter can be up to 2 m (7 ft). It is also a long loving tree, the oldest are known to be over 500 years old but some may be over 1000 years old. The Bark is thin and square-cracked or mortise, and gray to reddish-brown in color. The crown is a slender, breezy, conic shape in young trees with a tilted or drooping lead shoot. It becomes cylindrical when grow older. All ages of the trees are distinguished by the slightly pendulous branchlet tips. The shoots are small and orange-brown in color, with frequent pubescence all most 1 mm long.

T. mertensiana is an evergreen tree. The leaves are shape in needle-like, 7 – 25 mm (0.3 – 1 in) long and 1 – 1.5 mm wide. These are soft, edgeless-tipped, only little flattened in cross-section. The color of leaves are pale glaucous blue-green on above, and with two broad bands of bluish-white stomata below with only a narrow green midrib between the bands; and this is the differ the Mountain Hemlock from the other species of hemlock. There also having stomata on the top surface of leaves, and are arranged spirally all around the shoot.

Tsuga mertensiana as Ornamental Plant

There are both sexes flowers found in the same tree. The tree is monoecious, that is, male and female flowers are separate. Male flowers are small, round yellow cone shapes near the ends of branches. The female cones are also small but much longer than any other species of hemlock. It is cylindrical, pendulous, 3 – 8 cm (1 – 3 in) long and 8 – 10 mm broad before the open. After the mature when open it become 1 – 4 cm broad, superficially somewhat like a small spruce cone. They have thin, flexible scales 8 – 18 mm long. The immature cones are dark purple, after the pollination it become red-brown within 5 -7 months. The seeds are red-brown, 2 – 3 mm long, with a slender shape, and 7 – 12 mm long pale pink-brown wing.

Mountain Hemlock is a wood tree, but outside the native area, it is manly plant as an ornamental tree. It is planted as a specimen tree in USA, Europe and some Asian Countries as landscaping, in garden or road side. Mountain Hemlock cultivation is limited by the very slow growth of young plants and its susceptibility to urban air pollution.