Torreya nucifera

Scientific name: Torreya nucifera (Linnaeus) P. Siebold & Zuccarini 1846

Synonyms: Caryotaxus nucifera (L.) Zucc. ex Henkel & W.Hochst., Foetataxus nucifera (L.) J.Nelson, Podocarpus nuciferus (L.) Loudon, Taxodium nuciferum (L.) Brongn. ex Voigt, Taxus nucifera L., Torreya ascendens Nakai ex Uyeki, Torreya fruticosa Nakai, Torreya igaensis Doi & Morik., Torreya macrosperma Miyoshi, Torreya unda Miyoshi, Tumion nuciferum (L.) Greene

Common names: Japanese nutmeg tree, Japanese nutmeg-yew, Japanese torreya (English), Kaja, Kaya (Japanese)

Description

Shrub, or tree to 15(-28) m tall, with trunk to 0.9(-2.0) m in diameter. Bark light reddish brown when fresh, peeling in long, thin flakes, weathering grayish brown and becoming shallowly furrowed between flat-topped ridges. Crown dense, expanding from conical to dome-shaped with age, with thin, gently upwardly angled to horizontal or finally drooping branches bearing pairs of horizontal or drooping branchlets densely clothed with closely spaced to fairly widely separated foliage. Twigs passing from green to shiny reddish brown in their second or third year. Leaves unpleasantly aromatic when crushed, 1.5-2.5(-3.5) cm long, 2-3(-4) mm wide, stiff and slightly drooping, shiny bright or dark green to bluish green or pale green and flat around the midrib above, with shallowly sunken white to pale yellow stomatal bands beneath. Individual needles straight or slightly curved toward or away from the twig tip, widest before the middle or nearly parallel-sided, tapering very gradually and then abruptly to the roundly triangular tip with a stiff prickle 1-2 mm long, and abruptly to the rounded base on a very short petiole 0.5-1 mm long. Pollen cones greenish yellow, about 7-9 mm long and 4-5 mm across. Seeds with aril dark green, variably blotched or suffused with purple, sometimes very thinly waxy, (1.5-)2-3(-3.5) cm long and (1-)1.5-2 cm thick. Female gametophyte inside the light reddish brown stony layer almost smooth or only slightly wrinkled.

Central and southern Japan (Honshu, Shikoku, and Kyushu) and Cheju at the southern tip of Korea. Scattered singly or in small groves (rarely a dominant) in various temperate deciduous or mixed conifer and hardwood forests, often near streamsides or on moist slopes; 0-1,100 m.

Conservation Status

Red List Category & Criteria: Least Concern

This species has a wide range and most of the population reduction is thought to have taken place more than three generations ago. There is evidence of decline today, but it seems to be a fairly slow rate of decline and confined to the smaller subpopulations. If there were further information on the decline rates or of the area of occupancy, then it might be close enough to the threatened thresholds to qualify for Near Threatened. In the absence of this information it has to be assessed as Least Concern. Further research is required to determine the true status of this species.

Torreya nucifera is a woodland species occurring scattered in most types of mixed broad-leaved-conifer forest in the southern half of Japan. Wilson (1916) mentioned a locality SW of Tokyo, where it is more abundant, growing with Abies firma on steep slopes composed of shale on a hill ca. 500 m high. In other sites, including some islands in South Korea, it holds out in secondary vegetation where it becomes shrubby. Old-growth forest with ancient trees of Torreya nucifera in large numbers occurs in Korea's Pija-Rim National Park, with trees estimated to be 500-800 years old. The altitudinal range is from near sea level to at least 1,100 m a.s.l. Besides Abies firma and Tsuga sieboldii, the most common conifers among which Torreya nucifera is found, Chamaecyparis obtusa, Podocarpus macrophyllus, Nageia nagi, Taxus cuspidata, and Sciadopitys verticillata are often associated with this species. Locations dominated by conifers in the mixed mesophytic forests of warm temperate Japan are often on rocky south-facing slopes with poorly developed soils.

The population has become very fragmented due to historic clearance of large areas of habitat and as a result the remaining plants are increasingly isolated from each other and as a result regeneration is declining. In some cases, there is no regeneration taking place and when the trees die there is local extinction, but it is hard to quantify what proportion of the population is impacted by this.

The wood of this species is valued in Japan for its lustrous, pale brown leaf colour and its durability especially in contact with water. It is used for furniture and cabinet making, chests and boxes, Japanese chessmen, and formerly water buckets. The seeds are rich in edible oils and these as well as the arils are used in Japanese cuisine. This tree is widely planted near temples and in parks and gardens in Japan; all trees N of Tokyo are thought to be originally planted (Wilson 1916) and some of these are champion trees much larger than most trees in the forests. In Europe and North America it is an uncommon ornamental shrub or tree in arboreta, botanic gardens, and occasionally in private gardens.

It occurs in a number of protected areas across its range. Further research is required into the population size and trends of this species, the area of occupancy and also the nature of any threats. This information is needed to make a better assessment of its conservation status.

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

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