Japanese chestnut

Family

Fagaceae

Habit

Tree

Height

15 m

Spread

12 m

Growth

slow

Lifespan

150 years

First yield

after 4 years

Hardiness

zone 5–9

Shade tolerance

light shade

Soil

Sand, Silt, Clay

Soil moisture

dry – moist

pH

4.5 – 7

Synonyms

Kuri, Japanese Chestnuts

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: The nuts are large and coarse in texture, but distinctly less aromatic in flavour than those of the European chestnut. A characteristic feature is the strikingly large scar at the base of the nut. They are prepared like all chestnuts: boiled, roasted or ground into flour. Raw they taste slightly astringent because of their tannin content.

A slow-growing tree of about ten to seventeen metres with a low trunk and a broad crown. The decisive drawback in Central European cultivation is its pronounced frost sensitivity; in dry years the nuts also stay very small. On top of that the foliage is shed poorly in autumn — early snowfall settles in the still-leafy crown and leads to branches breaking. The leaves are narrow and long-pointed, glossy green, faintly hairy beneath, with a crenate-serrate margin; the shoots are hairy at first and become smooth later. For soil and site the same applies as for the whole genus: acid, deep and free-draining soils, no waterlogging and no lime. Susceptible to: chestnut leaf spot (Mycosphaerella maculiformis, leaf blotches, usually without consequence for the tree), oriental chestnut gall wasp (Dryocosmus kuriphilus, gall formation on young shoots).

True-to-type propagation is by grafting onto seed-raised rootstocks; seed-grown trees are uneven in yield. The seed is stored cool but frost-free over winter, usually beginning to germinate in the process, and is sown outdoors in spring. Because of its resistance to ink disease the species is also raised deliberately as a rootstock. For reliable fruit set at least two, better three genetically different individuals are needed, since the flowering times of male and female flowers on the same tree barely overlap.

Pollination is both by wind and by insects. The flowers are visited heavily by bees and other insects and count as valuable bee forage — the flowering period in June and July fills a gap when little else is in bloom. The nuts are eaten by squirrels, dormice and corvids, which also disperse them.

The most important of the Asian species for breeding: it is resistant to ink disease and only slightly susceptible to chestnut blight. Crosses involving it are usually large-fruited, ripen early and come into bearing quickly, often in the second year after planting — a large proportion of the large-fruited European commercial cultivars go back to it. It differs from the European species in the strikingly large scar on its coarse-grained nut and in its low trunk with a broadly spreading crown.

East Asia: native to Japan and the Korean peninsula, with occurrences in Taiwan as well. In eastern and north-eastern China the species is cultivated without being native there. In Europe it does not occur in the wild, only in cultivation and as a crossing partner in breeding programmes.

Fertile volcanic soils in hill and mountain country, in coniferous woodland as much as in the half-open cultural landscape along the edges of rice fields. It requires mild summers, winters that are not too cold, and high summer rainfall of roughly 1,200 to 1,400 millimetres a year. In the southern part of its range the species climbs to about 1,300 metres. Acid to neutral, free-draining soils are preferred, lime is avoided.