Pinus pumila, described in 1859 by Eduard August von Regel (1815–1892), in Index Seminum (St. Petersburg), is commonly known as Japanese stone pine, or Siberian dwarf pine; as well as Кедровый стланик (kedrovy stlanik / creeping cedar) in the Russian language; as Сибирийн давжаа нарс (Sibiriin davjaa nars) in Mongolian; ハイマツ (Haimatsu) in Japanese; 偃松 (Yǎn sōng) in Chinese; and as 눈잣나무 (nunjasnamu / snow pine) in Korean. The species name translates into "dwarf" in the Latin language.
Description. Japanese stone pine is a shrubby, evergreen, coniferous species of tree that grows to mature heights of 20 feet (6 m), usually with creeping branches extending up to 35 feet (10 m).
Bark is gray-brown and flaking
Branchlets are initially brown, later dark red-brown in their 2nd or 3rd year, and are densely pubescent.
Winter foliar buds are red-brown in color, shaped conical-ovoid, and are slightly resinous.
Leaves (needles) are borne 5 per fascicle, and are thick, stiff, and trapeziform in cross section. Each measures 1.6 to 2.4 inches (4 - 6 cm) long by circa 0.04 inches (1 mm) wide.
Seed cones are erect, maturing to pale purple- or red-brown, conical-ovoid or ovoid shaped, measuring 1.2 to 1.8 inches (3 - 4.5 cm) long by 1 to 1.2 inches (2.5 - 3 cm) wide, and are indehiscent or imperfectly dehiscent at maturity.
Seed scales are broadly subrhombic or rhombic-obovate in outline; apophyses are broadly triangular, thick, swollen, with a slightly recurved margin. Umbos are purple-black in color, and distinct, ending in a slightly recurved protuberance.
Seeds are dark brown, triangular-obovoid in shape, measuring 0.28 to 0.4 inch (7 - 10 mm) long by 0.2 to 0.28 inch (5 - 7 mm) wide, wingless, with a ridged abaxial margin.
Distribution. This species is native to Japan, North Korea, northern Mongolia, Siberia (east from Yenisey River); and China — Heilongjiang, Jilin, Nei Mongol, growing at elevations of 3,200 to 7,500 feet (1,000 - 2,300 m) above sea level. Forms broad belts just above timberline, pure or with alders or willows on eastern shores. In eastern and northeastern parts of its area and in cold intermontane valleys, it descends to sea level.
This is a pine well adapted to the extreme climate which prevails above the line of forests of Pinus sylvestris in the southern part of its range, while it replaces Larix gmelinii or birch forests at high altitude in the northern regions. It can be found scattered in the under-story of these forests, too, especially on exposed mountain slopes close to the summer snowline it forms extensive, dense thickets. Its seeds are distributed by birds in the family Corvidae.
Hardy to USDA Zone 1, cold hardiness limit below -50°F (-45.6°C), making it one of the most cold-hardy trees known.