First documented by David Douglas (1799-1834) in 1826, though seed only reached Britain around 1851, collected by John Jeffrey (1826-unknown). The epithet heterophylla, meaning ‘different leaves’, refers to the mix of short and long needles in its foliage.
Native to North America, from sea level to 1,800m, and dominant in forests across Canada (Alberta, British Columbia) and the USA (Alaska, Washington, Oregon, California, Montana, Idaho). In coastal temperate rainforests it is often co-dominant with Sitka Spruce, while inland it grows with Douglas-fir.
Monoecious. Extremely shade-tolerant, enduring decades of heavy shade while awaiting a canopy gap. Long-lived, exceeding 1,000 years. In old-growth forests, its fallen trunks become ‘nurse logs’, their decomposing wood fostering tree seedlings.
Tall (50m), elegant and straight, with dense, scented foliage and an always-drooping leader. Bark brown, smooth and thin when young, becoming scaly. Foliage smells of citrus; twigs grey-brown, finely downy. Needles vary in length (10-25mm), dark green above, pale below, flattened and finely toothed, in two ranks. Cones small (2-3cm), pendulous, falling whole.
Thrives in western north-west Europe with over 1,000mm rainfall on deep, moist soils. Dislikes sandy and clay soils and is intolerant of drought and pollution. Cold-hardy but sensitive to spring frosts. Seedlings regenerate freely on suitable soils, even in heavy shade where it outcompetes most trees, making it ideal as a continuous-cover forestry understorey.
No notable associations where introduced. Effective at helping modifying monocultures, helping create more structure and ecological diversity.
Western Hemlock is highly susceptible to root rot (Heterobasidion annosum), although relatively resistant to honey fungus. Palatable to deer and other browsing mammals. Under a warming climate, drought stress will limit suitability.
A high-quality timber, being easy to finish and resistant to splitting, for example when nailing. For a softwood, it has strong colour.
