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Common Name: Western Hemlock

General Information

Tsuga heterophylla is an evergreen tree with a narrowly conical, lightly branched crown; it can grow up to 70 metres tall. The straight, cylindrical bole can be up to 200cm in diameter[, ].
Western Hemlock is an important timber tree in the Pacific Northwest (USA) and W Canada[]. It has become the most important timber hemlock in North America. This species has been introduced in Britain and other parts of NW Europe as a forestry plantation tree; in the wetter parts near the Atlantic coast it will regenerate spontaneously[]. It is also sometimes grown as an ornamental.
Tsuga heterophylla is a very widespread and extremely abundant species. It is probably increasing in forests where fires are suppressed and/or as a result of removal of large competitors through past logging. 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 northern California, also in Idaho and Montana.

Habitat

Forests, especially where moist and especially in deep forests; at elevations from sea level to 1,500 metres[, ].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	70.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Tsuga heterophylla is found in the cool maritime climate along the coast of N. America and in the cold montane regions of the interior, the annual precipitation varies between (500-)900-3,800 mm, decreasing towards the interior. Dry summers limit its range in the Rocky Mountains[].
An easily grown plant, it thrives best when growing in a deep well-drained soil in the western parts of Britain where it appreciates the higher rainfall[]. It grows on a variety of soils with an acid organic top layer (pH 3.5-5)[]. However, it succeeds in most soils and positions, being especially good on acidic sandy soils[] but also tolerating some lime[] so long as there is plenty of humus in the soil[]. 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[]. As an extremely shade tolerant conifer it is suitable as an under planted tree in deciduous broad-leaved forest; however, as it in turn shades out every growth under it, this should not be done in (semi) natural woodland where the indigenous flora is valued[].
Once established, the plant can grow 60 - 150cm per year[, ].
New growth takes place from late spring to early autumn, at first it hangs downwards but begins to straighten towards the end of the season[].
There are trees more than 50 metres tall in Britain[].
The tree is highly sympatric with Picea sitchensis in most of the range. It is extremely shade tolerant, but has a shorter life span than Pseudotsuga menziesii or Picea sitchensis. Close along the coast it may form occasionally pure stands, but more commonly it is an important constituent of the (maritime) mesothermal coniferous forest. On the Olympic Peninsula of Washington it reaches maximum size, together with other giant conifers[].
The plant's tolerance to shade allows it to grow up under the canopy of other trees, but a thick moss layer usually prevents the light seeds from reaching the soil. Instead, seeds germinate massively on fallen trees ('nurse logs'), from where a few saplings are able to send roots down into the soil; as a result Tsuga heterophylla often stands in rows ('collonades') long after the nurse log has rotten away[].
Trees take around 30 years from seed before they produce appreciable quantities of seed[]. They can live for several centuries in the wild and often produce large quantities of seed[].
Tsuga heterophylla is a dominant species over much of its broad distributional range. The wood is superior to that of other hemlocks for building purposes and it makes excellent pulp for paper production[].
Tsuga heterophylla is the state tree of Washington[].
Plants often form pure stands and cast a dense shade, thus preventing the regeneration of other trees whilst being able to reproduce itself[].
Plants in this genus are notably resistant to honey fungus[].

Edible Uses

Inner bark - raw or cooked[, ]. It can be dried, ground into a powder and then used as a thickening in soups etc or mixed with cereals when making bread[]. It has also been used as a sweetener for other foods[]. The inner bark was often cooked and then dried for use in the winter[]. At its best in spring[], it was one of the staple foods of the Alaskan Indians[]. An emergency food, it is only used when all else fails[].

The leaves and twigs yield 'spruce oil', used commercially to flavour chewing gum, soft drinks, ice cream etc[].

Pitch, obtained from crevices in the bark, has been chewed as a gum[].

The leaves and young shoots have been chewed as an emergency food to keep one alive when lost in the woods[].

A herbal tea is made from the leaves and shoot tips[, ]. These tips are also an ingredient of 'spruce beer'[].

Medicinal

Western hemlock was commonly employed medicinally by several native North American Indian tribes who used it to treat a variety of complaints[]. It is little, if at all, used in modern herbalism.

The bark is astringent, diaphoretic and diuretic[]. A decoction of the pounded bark has been used in the treatment of haemorrhages, tuberculosis and syphilis[]. The boiled bark, combined with liquorice fern (Polypodium glyccyrhiza), has been used in the treatment of haemorrhages[].
The powdered bark can be put into shoes for tender or sweaty feet or as a remedy for foot odour[].

An infusion of the inner bark or twigs is helpful in the treatment of kidney or bladder problems[]. It can also be used as a good enema for treating diarrhoea and as a gargle or mouthwash for mouth and throat problems[].
Externally, it can be used as a wash on sores and ulcers[, ].

A poultice of the plant has been applied to bleeding wounds[]. A moxa of the twigs has been used to get rid of warts[].

The gum obtained from the trunk has been applied to cuts[]. It has been applied to the skin to prevent chapping and sunburn[].

A poultice of the chewed leaves has been used in the treatment of burns[].

Agroforestry Uses:

Tolerant of light trimming, plants can be grown as a hedge[]. This species makes a good hedge in Britain[, ].
The tree is used in forested riparian buffers to help reduce stream bank erosion, protect aquatic environments, enhance wildlife, and increase biodiversity.[]

Other Uses

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

The bark contains 8 - 18% tannin and is a major source of tannin in America[, , , ].
A reddish-brown dye is obtained from the tannis in the bark[, , , ]. It can be used on wool and plant fibres, and was also used as a facial cosmetic and hair remover[].
A decoction of the bark has been used to clean rust off iron and steel[].

A pitch (called hemlock pitch), is obtained by distillation of the young branches[].
The pitch is rubbed on the hair to get rid of head lice[].

The wood is light in weight, hard, tough, moderately strong and pliable, durable, easy to work. Commercially superior to other members of this genus, it is an important tree for construction, the outside of buildings etc and is also used for interior finish, kitchen cabinets, flooring, ceiling etc. Other uses include.carving into spoons, pilings, poles, railway sleepers etc[, , , , , , , , , ]. It is also a major source of pulp[, ].
The wood makes a slow-burning fuel and so can be used to bank up a fire to keep it burning overnight[].

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[].