Common Name: Kaya

General Information

Torreya nucifera is an evergreen shrub or a tree. In the wild specimens 25 metres or more tall have been recorded, though in cultivation it is rarely more than 9 metres tall and often only a shrub up to 4 metres tall.. The bole of mature trees can be 90cm in diameter[, ].
The tree is harvested from the wild for local use as a food, medicine and source of wood. It is sometimes cultivated for its edible seed, which is sold in local markets, and is also grown as an ornamental, where it can be trimmed and used as a hedge[].
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. 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. If there were further information on the decline rates or of the area of occupancy, then it it might be close enough to the threatened thresholds to qualify for Near Threatened. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

, ,

Range

E. Asia - central and southern Japan, Korea

Habitat

Scattered in most types of mixed broad-leaved-conifer forest, often in dense shade. In old-growth forest the trees can become quite large but in areas of secondary growth they are more shrub-like; at elevations to 1,100 metres[, ].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	15.00 m
Growth Rate	Slow
Pollinators	Wind
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Torreya nucifera is fairly cold hardy when dormant, able to tolerate temperatures falling to between -17.7°c and -12.2°c[].
Succeeds in ordinary garden soil, tolerating some lime[]. Prefers an acid soil[]. Dislikes wind exposure[]. Requires a sheltered position and either high humidity or a moist riverside soil[]. Tolerates woodland shade very well, but only tolerates full sun in climates with cool summers[, ]. Requires hot, very humid summers for best growth[].
Species in this genus are generally adapted to growing in primary woodland. The seedlings are very shade tolerant, establishing well in the deeper shade of a woodland and then growing up to the light. They can sometimes be found growing in secondary vegetation, but they do not usually persist, being outcompeted by other, more light-tolerant species[].
A tree at Wakehurst Place was 11 metres tall in 1970[]. A shrub growing in the shade of coniferous trees at Kew was about 2.5 metres tall and 4 metres wide in September 1993[], it was carrying a very heavy crop of fruit[]. No fruit was formed in 1994[]. A specimen at Cambridge Botanical Gardens was 6 metres tall and 6 metres wide, it was carrying an enormous crop of seed in the late summer of 1996[]. This plant has an excellent potential as a nut crop in Britain[].
A slow-growing tree[].
Sometimes cultivated for its edible seed in Japan, the variety 'Shibunashigaya' is considered to be the best for seed production[].
This tree is widely planted near temples and in parks and gardens in Japan; all trees north of Tokyo are thought to be originally planted (Wilson 1916) and some of these are champion trees much larger than most trees growing wild 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[].
The seed takes two summers to mature[].
Plants are dioecious so both male and female plants are required if seed is to be produced. Occasional trees are monoecious with dioecious branches. Solitary trees have been seen on a number of occasions with heavy crops of fertile seed, so it would appear that the tree is not dioecious[].

Edible Uses

Seed - raw, cooked or used in confectionery[, , , ]. An agreeable sweet slightly resinous flavour[]. An aromatic flavour[], it is much relished and is eaten in quantity[] though it is said to be laxative if eaten in excess[].

An edible oil is obtained from the seed[, , , , , ]. Used in cooking[]. A high quality cooking oil[].

Medicinal

The seeds are anthelmintic[, , , ]. They are used in the treatment of several parasitic conditions including hookworm, tapeworms, pinworms and roundworms[].

The plant is anodyne, carminative, digestive, laxative and pectoral[, , , ].

Agroforestry Uses:

Plants can be trimmed and grown as a hedge[].

Other Uses

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 also for water buckets[].

Propagation

Seed - best sown as soon as it is ripe in a cold frame. Some of the seed should germinate in the following spring though much of it might take another 12 months. Stored seed requires a period of cold stratification and can take 18 months or more to germinate. Prick out the seedlings into individual pots as soon as growth is observed and grow them on in light shade in the greenhouse for at least the next couple of winters, making sure to pot them on into larger pots as and when required. Plant them out into their permanent positions in early summer when the plants are at least 20cm tall.
Cuttings of half-ripe shoots in late summer[]. Cuttings do not grow well[].
Layering.