Japanese horse chestnut

Profile

Family

Hippocastanaceae

Habit

Tree

Height

20 m

Spread

12 m

Growth

medium

Lifespan

200 years

First yield

after 12 years

Hardiness

zone 6–7

Shade tolerance

partial shade

Soil

Sand, Silt, Loam

Soil moisture

semi-dry – very moist

pH

5.6 – 7.6

Synonyms

Ae dissimilis.

Uses

Edible: Young leaves cooked. Caution is advised, as the leaves probably contain toxic saponins (see the toxicity notes above). Seeds cooked. They can be dried, ground into flour and used as porridge. The starch is extracted and eaten. The seeds are quite large, about 25–30 mm in diameter, and easy to harvest. Unfortunately they are also rich in saponins, which must be removed before consumption. See also the toxicity notes above. The following notes refer to A. californica but are probably relevant here as well: The seeds need to be detoxified before they are edible. The indigenous peoples slow-roasted the nuts for this (which neutralised the saponins) and then sliced them thinly. These were placed in a cloth bag and rinsed in a stream for 2–5 days. This treatment also leached out most of the minerals etc.

Other uses: The saponins contained in the seeds serve as a soap substitute. They are easily obtained by cutting the seeds into small pieces and steeping them in hot water. This water can then be used for washing the body, clothes etc. The only drawback is the lingering smell of horse chestnut. Wood – soft, but beautifully grained. Used for furnishings, household goods etc.

Growing

Prefers a deep, loamy, well-drained soil, but is not very demanding. The plant is very hardy when dormant, although the young shoots in spring can be damaged by late frosts. It prefers a continental climate and grows best in eastern and south-eastern England. Most species in this genus transplant easily, even when quite large.

Propagation

Seed – best sown directly outdoors or in a cold frame as soon as ripe. The seeds germinate almost immediately and must be protected from severe weather. Viability is very limited, and the seeds must not be allowed to dry out. Stored seeds should be soaked for 24 hours before sowing; even then they may no longer be viable. It is best to sow the seeds with the scar facing downwards. When sowing in a cold frame, transplant the seedlings into pots in early spring and plant them out into their final positions in summer.

Origin & habitat

In the mountains, especially in ravines, throughout Japan. In deciduous woodlands, particularly on moist slopes along streams.