Koyama's spruce; ヤツガタケトウヒ Yatsugatake-tohi [Japanese] (Iwatsuki et al. 1995).
Syn.: Picea koyamai (orth. err.).
Monoecious. Evergreen tree to 20 m tall and 40 cm dbh, with a straight round trunk and long, slender, horizontally spreading branches. Bark smooth and brown on young trees, turning gray-brown, peeling off in thin scales; on old trees black-grey, rough and scaly. Branchlets brown, grooved, glabrous; pulvini stout, 0.8-0.9 mm long. Leaves linear, quadrangular, 8-12 mm long, 1.5 mm across, acute on young branches, obtuse on fruiting ones, pale green, with a prominent stomatiferous band in each surface; resin canals one or two, marginal. Flowers May to June. Pollen cones on previous year's shoots, cylindric, red-brown, with numerous stamens. Seed cones erect, solitary, terminal on previous year's shoots, reddish purple, cylindric, pendulous, 4-8 cm long, 2-2.5 cm across. Seed scales thinly woody, orbicular-obovate, cuneate to base, ca. 15 mm long, 13-16 mm wide, minutely denticulate on upper margin. Bract scales ca. 3 mm long, obovoid, apex acute. Seeds fusiform, black-brown, ca. 3 mm long, 2 mm across; wings pale brown, oblong-obovate, ca. 10 mm long, 5 mm wide (Iwatsuki et al. 1995).
Japan: Honshu, in the Yatsugadake Mountains, where it grows in small groves of 10-20 trees (there are only a few hundred trees in all) or mixed stands on north-facing slopes at 1500-2000 m elevation. Climate is cool, with snowy winters and 1000-2000 mm annual precipitation. There are frequent typhoons, which are a principal disturbance and have reduced the population in historic times. It usually grows with Larix kaempferi, Picea alcoquiana var. acicularis, Picea maxomowiczii, and various angiosperm trees and shrubs (Farjon 1990). Hardy to Zone 5 (cold hardiness limit between -28.8°C and -23.3°C) (Bannister and Neuner 2001).
Wilson (1916) states that the largest tree he found was 20 m tall with a girth of 150 cm.
Named for botanist Mitsua Koyama, who discovered it in 1911 on the slopes of Yatsuga in central Hondo, which is the only known locality (den Ouden 1965).
den Ouden, P. (ed.). 1965. Manual of Cultivated Conifers Hardy in the Cold- and Warm-Temperate Zone. Netherlands: Kluwer.
Shirasawa, H. and M. Koyama. 1913. Some new species of Picea and Abies in Japan. Botanical Magazine (Tokyo) 27: 127-132, pl. 2.
The species account at Threatened Conifers of the World.
Farjon 1990 (good line drawings).
Iwata and Kusaka 1954 (illustrations).
Kurata, S. 1971. Illustrated important forest trees of Japan. Vol. 1. Second edition. Tokyo (color plates, range maps).
Wilson (1916) provides text (pp. 39-40) and photos of the tree in habitat (plates XXIII-XXIV).
Last Modified 2017-11-12