Scientific name: Tsuga diversifolia (Maximowicz) M.T. Masters 1881

Synonyms: Abies diversifolia Maxim., Pinus araragi var. diversifolia (Maxim.) Voss, Tsuga blaringhemii Flous, Tsuga diversifolia subsp. blaringhemii (Flous) A.E.Murray

Common names: Northern Japanese hemlock, Kome-Tsuga, Kuro-Tsuga (Japanese)

Description

Tree to 25 m tall, or shrubby at high elevations in the northern part of its range, with straight or forked trunk to 1 m in diameter. Bark furrowed, scaly, cinnamon brown to gray-brown. Crown rounded, opening up with age. Twigs hairy at first, becoming smooth. Winter buds rounded, 2-3 mm long. Needles variable in length (hence the species name, from the Latin), 0.7-1.5(-1.8) cm long, slightly widening from the base to the notched tip, the edge smooth, the white stomatal bands beneath each with 8-10 lines of stomates. Pollen cones 3-4 mm long, yellow-orange. Seed cones green before maturity, ripening light brown, 1.5-2(-2.5) cm long on stalks 0.5 mm long, opening to 1.5-2 cm wide, the seed scales 7-9(-12) mm long. Seed body 3.5-4.5 mm long, the wing 3.5-4.5 mm longer.

Japan, widespread in northern and central Honshu with outliers in Shikokū and Kyūshū. Moist slopes and ridges of mixed montane and subalpine forests; (700-)1,200-2,500 m. The climate is cool, with cold, snowy winters and abundant rainfall in summer (annual precipitation 1,000 mm to 2,500 mm).

Conservation Status

Red List Category & Criteria: Least Concern

A fairly widespread and common species with no major threats and hence it is listed as Least Concern.

It is a very abundant and widespread species in Honshu, elsewhere the populations are small.

Tsuga diversifolia is an evergreen tree (to 25 m) which occurs in the mountains at altitudes between 700 m and 2,500 m a.s.l., on usually podzolic soils developed on volcanic or igneous rock. It is in many areas the most common tree species in mixed coniferous forests, being very shade tolerant. Other common conifers are Picea jezoensis, Abies homolepis, Abies veitchii, Abies mariesii (at high elevations), Larix kaempferi, Pinus parviflora, Thuja standishii, and Thujopis dolabrata var. hondae; broad-leaved trees are e.g. Betula ermanii, Betula corylifolia, Sorbus japonica, Alnus hirsuta var. sibirica, and Quercus mongolica var. grosseserrata. Rhododendron spp. and/or Sasa spp. may form a dense undergrowth in the shrub layer, in other, very wet areas only thick moss layers carpet fallen logs and the forest floor. It regenerates very well as it can tolerate dense shade; forms pure stands in places.

Northern Japanese hemlock is exploited in Japan for timber. In the past it mainly provided pulp for paper, but now this commodity, requiring vast resources, mainly comes from abroad. Instead, the use of this species has largely shifted to construction, carpentry, and joinery and, as the wood is generally dense and moderately hard and sometimes attractively figured with reddish brown heartwood and lighter sapwood, it is used for furniture. As and ornamental tree it is planted in Japanese gardens and parks; it is also used in bonsai culture. In Europe and North America it is less commonly used, being slow growing. A dwarf form (cultivar) which grows very slow is used for rockeries. Hemlocks are unsuitable as Christmas trees, because when cut and taken indoors they loose their leaves sooner than any other conifer.

Occurs in many protected areas including national parks.

References

Farjon, A. (2010). A Handbook of the World's Conifers. Koninklijke Brill, Leiden.
Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland.
IUCN Red List of Threatened Species, International Union for Conservation of Nature and Natural Resources. Cambridge, UK /Gland, Switzerland