M.Van Campo-Duplan and H.Gaussen (1948) postulated that this taxon originated by hybridization between Picea and Tsuga . Although this is unlikely, some characteristics such as leaf arrangement and shape, phenolic chemistry, and pollen grain structure lend some support for this hypothesis[].

Common Name: Mountain Hemlock

General Information

Tsuga mertensiana is an evergreen tree with a conic crown; it can grow up to 40 metres tall, though is often dwarf and stunted when growing at higher elevations. The straight, cylindrical bole is up to 150cm in diameter[].
The tree is harvested from the wild for local use as a food, medicine and a source of materials. It is sometimes harvested on a commercial basis for its wood, but is considered to be somewhat inferior to the wood of western hemlock (Tsuga heterophylla). It also makes an excellent ornamental tree for gardens with its dense foliage growing from long and short shoots and naturally conical habit. Despite this, it is uncommon in gardens and only a limited number of cultivars is known.
This species has a vast range and is of only minor importance as a timber tree. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

, ,

Range

Western N. America - Alaska to California.

Habitat

Exposed ridges and slopes at high altitudes, often ascending to 3,000 metres[]. The best stands are found in sheltered areas with deep moist well-drained soils, high precipitation and long cold winters[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	45.00 m
Growth Rate	Medium
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Tsuga mertensiana is a subalpine species growing in areas of western N. America that have a cool to cold maritime climate that includes mild to cold winters, a short, warm to cool growing season and moderate to high precipitation[]. It occurs from near sea level in Alaska to elevations of 1,500 metres, and gradually ascending further south in its range so that in California it is found at 1,800 - 3, 350 metres[]. Subspecies mertensiana is restricted to a climatic zone with high precipitation, in British Columbia it is between 2,000 - 4,000mm per year, with long, snowy winters and short, cool summers. Subspecies grandicona grows further south in a much drier climate, but there it is found primarily on high, north-facing slopes[]. The growing season (frost-free period) ranges from 49 - 148 days[].
An easily grown plant, it thrives best in cultivation when growing in a deep well-drained soil in the moister regions of the temperate zone, where it appreciates the higher rainfall[]. However, it succeeds in most soils and positions, being especially good on acidic sandy soils[]. In the wild it grows on a variety of non-calcareous acidic soils, sometimes on peat, more commonly on mor humus with a pH 3.1 - 3.9[]. Plants are very shade tolerant when young, but need more sunlight as they grow older[, ]. Plants are thin and poor when grown in dry or exposed places[]. Dislikes atmospheric pollution[].
This is a very handsome tree, with its branches densely clothed with pale, spreading leaves and is adaptable to a wide variety of climatic conditions[, ]
Among the range of cultivars, the 'blue' or glaucous leaf forms or selections are especially valued. High altitude provenances may be susceptible to 'late' frost, but those from more coastal northern areas should not suffer from this kind of damage as much[].
The tree is slow growing for the first few years, averaging 30cm a year, but older trees, especially in areas with cool moist summers, are growing rapidly[].
Trees live 400 - 500 years in the wild with specimens more than 800 years old recorded[, ]. They commence bearing seeds when about 20 - 30 years old, years of high production alternating with years of low production[].
In several areas, e.g. In the Coast Mountains of British Columbia, the Olympic Mountains of Washington, and in Lassen Volcanic National Park (Cascades), this species is invading subalpine meadows and late-lying snow basins. In some areas this has been going on for 150 years or longer, in other areas it seems to have begun more recently. The warming climate is likely responsible[].
Plants in this genus are notably resistant to honey fungus[].

Edible Uses

Inner bark - raw or dried, ground into a powder and then used as a thickening in soups etc or mixed with cereals when making bread[]. It is best used in the spring[]. An emergency food, it is only used when all else fails[].

A herbal tea is made from the young leaves and shoot tips[, ].

Medicinal

The bark is astringent, diaphoretic and diuretic[]. A tea made from the inner bark or twigs is helpful in the treatment of influenza, colds, kidney or bladder problems, and also makes a good enema for treating diarrhoea[, ]. It can also be used as a gargle or mouthwash for mouth and throat problems or externally to wash sores and ulcers[].
The powdered bark can be put into shoes for tender or sweaty feet or as a remedy for foot odour[].

A poultice of the chewed leaves has been used to treat burns[].

The warm gum obtained from the trunks has been used as a dressing on cuts[].

Agroforestry Uses:

Tolerant of light trimming, plants can be grown as a tall hedge[, ].

Other Uses

The slightly unripe cones are used in pot-pourri. They retain an attractive scent for several years[].

The tree yields a resin similar to Abies balsamea, it is gathered by incisions in the trunk or by boiling the wood[, , ].

The bark contains 8 - 14% tannin[, ]. The inner bark is used according to one report[].

A brown dye is obtained from the bark[, ].

The boughs are steamed or rubbed on furniture and used as a room deodorant and disinfectant[].

A pitch (called hemlock pitch), is obtained by distillation of the young branches[].

The light-coloured wood is close-grained, moderately strong and pliable[, , , , ]. It is used for heavy construction[]. It is light in weight, soft and weak according to other reports, which go on to say that it is occasionally manufactured into lumber when other wood is not available[, ].
This slow growing species produces moderately strong wood, but its use is limited due to environmental considerations. It is soft and close-grained, with brown heartwood, sometimes pinkish, and lighter sapwood; its uses are now restricted to carpentry and some limited construction applications[].

Propagation

Seed - it germinates better if given a short cold stratification[, ] and so is best sown in a cold frame in autumn to late winter. It can also be sown in early spring, though it might not germinate until after the next winter. If there is sufficient seed, an outdoor sowing can be made in spring[]. Pot-grown seedlings are best potted up into individual pots once they are large enough to handle - grow them on in a cold frame and plant them out in early summer of the following year. Trees transplant well when they are up to 80cm tall, but they are best put in their final positions when they are about 30 - 45 cm or less tall, this is usually when they are about 5 - 8 years old[]. Larger trees will check badly and hardly put on any growth for several years. This also badly affects root development and wind resistance[].