subgenusPinus, section, Pinus, subsectionPinus. This is one of the “classic” old-world, 2-needled, hard pines.
Pinus densiflora, as described in 1842 by Philipp Franz von Siebold (1796–1866) and Joseph Gerhard Zuccarini (1790–1848), in Flora Japonica, 2nd edition, is commonly known as Japanese red pine; as well as, or as アカマツ (aka-matsu) in the Japanese language, 赤松 (chì sōng) in Chinese, 소나무 (sonamu) in Korean, and Сосна густоцветная (Sosna gustotsvetnaya) in Russian. The species name describes the dense growth of pollen cones that grow at the tips of the previous year's growth.
There are three known varieties:
Pinus densiflora var. densiflora, which is synonymous with P. densiflora var. brevifolia (Liou and Q.L. Wang), P. densiflora var. funebris (Komarov) Liou et Q.L. Wang ex Silba, P. densiflora f.liaotungensis (Liou et Q.L. Wang) Kitagawa, P. densiflora var. liaotungensis (Liou and Q.L. Wang), P. funebris (Komarov) and P. scopifera (Mique)
Pinus densiflora var. ussuriensis (Liou and Q.L. Wang 1958) which is synonymous with P. densiflora f.ussuriensis (Liou et Q.L. Wang) Kitagawa and P. takahasii (Nakai ).
Pinus densiflora var. zhangwuensis (S.J. Zhang et al. 1995).
Ethnobotany. Historically, this pine has been one of the most important species used in Japanese architecture. The principal structural woods in most surviving structures of the Muromachi period (14th to 16th Centuries) and the Edo period (1603-1867) are Pinus densiflora and P. thunbergii, although surviving structures also contain a great deal of Chamaecyparis obtusa.
Besides following agriculture as a 'weedy' species, it is also one of the more popular ornamental pines, used as such in Japan since ancient times and now widely planted in Europe and North America.
Description. Japanese Red pine is an evergreen coniferous tree which grows straight to contorted (particularly in coastal settings) up to 100 feet (36 m) tall, with an open, irregular or umbrella-shaped crown. Lower branches are shed early even in open settings.
Bark is red-brown in color, forming large plates (on older trees) or is flaky and papery.
Branches are colored gray-green, rapidly becoming smooth with age, developing papery reddish bark.
Leaves (needles) are colored light green. They are pliable, growing in bundles or 2 per fascicle, measuring 3.2 to 3.75 inches (8 - 12 cm) long with acute tips, minute teeth along the margins, and stomatal lines on all surfaces, presented in bunches at ends of twigs. Foliar sheaths are retained for the 2 to 3 year life of the needle fascicles.
Pollen cones are small, ellipsoidal shaped, pale yellow or yellow-brown in color, appearing at the ends of shoots.
Seed cones are conic-ovoid shaped, colored tan to golden brown, measuring 1.6 to 2.8 inches (4-7 cm) long, growing in whorls of 2 to 5 at branch nodes, remaining closed and attached for several years, on a 0.04 to 0.12 inch (1 - 3 mm) long, somewhat flexible peduncle.
Cone scales are cuneate (wedge) shaped, the exposed part flattened. Aphophyses are rhomboidal with a central, short-mucronate umbo. About 50 scales may contain fertile seed.
Seeds with attached wing are 0.4 to 0.7 inch (10 - 17 mm) long.
Distribution. The species is native to China — Shandong, and Jiangsu provinces, Korea, Japan — southern Hokkaido, Honshu, Shikoko, Kyushu islands, and Russia where it is rare in southern Ussuriland on rocky slopes at elevations from sea level to 1,500 feet (0 - 500 m) above sea level, or in sandy soils, seashores, Khanka Lake islands.
Hardy to USDA Zone 5 — cold hardiness limit between -10° and -20°F (-23.3° and -28.9°C).