Tsuga diversifolia / Northern Japanese hemlock

<em>Tsuga diversifolia, </em>commonly known as Northern Japanese Hemlock, was described in 1881 by Maxwell Tylden Masters (1833-1907). Its Japanese name is コメツガ (kome-tsuga). The epithet is derived from the Latin roots <em>diversis </em>(different, differing, or variable) and <em>folia</em> (leaves), a reference to the length of the needle-like leaves.
Description. <em>Tsuga diversifolia </em>is an evergreen coniferous tree growing to 80 feet (25 m) in height, though in high elevations at the northern end of its range, it may adopt a shrubbier habit. The trunk is either straight or forked, to 3.3 feet (1 m) in diameter. The furrowed, scaly bark ranges in color from cinnamon brown to gray-brown. The crown is dense, narrow, and conical with youth, becoming rounded and open with age, with spreading branches. Twigs are hairy at first, becoming smooth later on. Winter buds are dark brown, rounded, 0.08 to 0.12 inches (2 - 3 mm) long. Needle-like leaves are densely arranged in two ranks, with shorter leaves above, ranging from 0.27 to 0.7 inches (7 - 18 mm) long, 0,08 inches (2 mm) wide, with a smooth edge and notched tip, glossy green above, and with two white stomatal bands on the underside. Pollen cones are yellow to yellow-orange, 0.12 to 0.16 inches (3 - 4 mm) long. Seed cones are numerous on outer branches and are initially green, ripening to light (to reddish) brown, ovoid, 0.6 to 1 inch (15 - 25 mm) long.
Distribution. <em>Tsuga diversifolia </em>is endemic to Japan, widespread in northern and central Honshu, with additional populations in Shikoku and Kyushu. It inhabits moist slopes and ridges of mixed montane and subalpine forests at elevations of 2,300 to 8,200 feet (700 - 2,500 m). The climate is cool with snowy winters and high summer rainfall, with annual precipitation ranging from 40 to 100 inches (1,000 - 2,500 mm). It is highly frost hardy and wind tolerant. Of Japan's two native Hemlock species, <em>Tsuga diversifolia </em>occurs at higher elevations. Although their ranges overlap in central Honshu and the southern islands, <em>T. diversifolia </em>and <em>T. sieboldii </em>are not known to hybridize. It regenerates very well and can tolerate rather dense shade, forming pure stands in places. In mixed settings, its coniferous companions include <em>Picea jezoensis, Abies homolepis, A. veitchii, A. mariesii, Larix kaempferi, Pinus parviflora, Thuja standishii, </em>and <em>Thujopsis dolabrata </em>var. <em>hondae. </em>Broad-leaved companions include the genera <em>Rhododendron, Betula, Sorbus, </em>and <em>Quercus. </em>Northern Japanese Hemlock is abundant and widespread in Honshu, has a stable population, including significant tracts in protected national parks, and is not considered threatened. It is managed in Japan as a timber resource, being used for construction, carpentry, and furniture making.
Tsuga diversifolia, commonly known as Northern Japanese Hemlock, was described in 1881 by Maxwell Tylden Masters (1833-1907). Its Japanese name is コメツガ (kome-tsuga). The epithet is derived from the Latin roots diversis (different, differing, or variable) and folia (leaves), a reference to the length of the needle-like leaves. Description. Tsuga diversifolia is an evergreen coniferous tree growing to 80 feet (25 m) in height, though in high elevations at the northern end of its range, it may adopt a shrubbier habit. The trunk is either straight or forked, to 3.3 feet (1 m) in diameter. The furrowed, scaly bark ranges in color from cinnamon brown to gray-brown. The crown is dense, narrow, and conical with youth, becoming rounded and open with age, with spreading branches. Twigs are hairy at first, becoming smooth later on. Winter buds are dark brown, rounded, 0.08 to 0.12 inches (2 - 3 mm) long. Needle-like leaves are densely arranged in two ranks, with shorter leaves above, ranging from 0.27 to 0.7 inches (7 - 18 mm) long, 0,08 inches (2 mm) wide, with a smooth edge and notched tip, glossy green above, and with two white stomatal bands on the underside. Pollen cones are yellow to yellow-orange, 0.12 to 0.16 inches (3 - 4 mm) long. Seed cones are numerous on outer branches and are initially green, ripening to light (to reddish) brown, ovoid, 0.6 to 1 inch (15 - 25 mm) long. Distribution. Tsuga diversifolia is endemic to Japan, widespread in northern and central Honshu, with additional populations in Shikoku and Kyushu. It inhabits moist slopes and ridges of mixed montane and subalpine forests at elevations of 2,300 to 8,200 feet (700 - 2,500 m). The climate is cool with snowy winters and high summer rainfall, with annual precipitation ranging from 40 to 100 inches (1,000 - 2,500 mm). It is highly frost hardy and wind tolerant. Of Japan's two native Hemlock species, Tsuga diversifolia occurs at higher elevations. Although their ranges overlap in central Honshu and the southern islands, T. diversifolia and T. sieboldii are not known to hybridize. It regenerates very well and can tolerate rather dense shade, forming pure stands in places. In mixed settings, its coniferous companions include Picea jezoensis, Abies homolepis, A. veitchii, A. mariesii, Larix kaempferi, Pinus parviflora, Thuja standishii, and Thujopsis dolabrata var. hondae. Broad-leaved companions include the genera Rhododendron, Betula, Sorbus, and Quercus. Northern Japanese Hemlock is abundant and widespread in Honshu, has a stable population, including significant tracts in protected national parks, and is not considered threatened. It is managed in Japan as a timber resource, being used for construction, carpentry, and furniture making.

Attribution from: James E. Eckenwalder; Conifers of the World: The Complete Reference; ©2009

Tsuga diversifolia The Harper Collection of Dwarf & Rare Conifers located at Hidden Lake Gardens in Tipton, MI. Photo taken August of 2005. The leader on this specimen seems to be missing making it not the best of examples for this species.
Photo by Dax Herbst
Tsuga diversifolia
Photo by Crusier
Natural forest of Tsuga diversifolia in Fukushima
Photo by Forestry and Forest Products Research Institute, Japan
Tsuga diversifolia - foliage detail
Photo by Sigma64
Tsuga diversifolia - foliage detail
Photo by Wikipedia
Tsuga diversifolia - branch detail with ripening seed cones
Photo by Arboretum Mustila, Finland

Comments