Common Name: Californian Buckeye

General Information

Aesculus californica is most commonly a deciduous shrub 3 - 5 metres tall with spreading stems that form a broad, dense top. Sometimes it becomes more tree-like, growing up to 9 metres tall with a short bole that can sometimes reach 150cm in diameter and a large, round-headed top[].
The plant was often used as food, medicine and a source of materials by the native N. Americans, but is little used nowadays. It is often grown as an ornamental, valued especially for its floral display.

Known Hazards

All parts of the plant are poisonous, containing the glycoside esculin, the saponin aescin, and possibly alkaloids. Ingestion can cause muscular weakness and paralysis, dilated pupils, vomiting, diarrhea, depression, paralysis, and stupor[].
Honeybees are the chief pollinators of this tree, but the pollen and nectar are toxic to them. Losses of adult honeybees and their larvae due to poisoning can be severe[].
The seed is rich in saponins. Although poisonous, saponins also have a range of medicinal applications and many saponin-rich plants are used in herbalism (particularly as emetics, expectorants and febrifuges) or as sources of raw materials for the pharmaceutical industry. Saponins are also found in a number of common foods, such as many beans.
Saponins have a quite bitter flavour and are in general poorly absorbed by the human body, so most pass through without harm. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of raw foods that contain saponins.
Saponins are much more toxic to many cold-blooded creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish and make them easy to catch[].

Botanical References

, ,

Range

South-western N. America - California

Habitat

Moist stream borders, scrub and the edges of oak and pine woods in canyons and dry slopes below 1,200 metres[, , ].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	5.00 m
Growth Rate	Medium
Pollinators	Bees
Cultivation Status	Wild

Cultivation Details

Aesculus californica is moderately cold tolerant, though it grows best in areas where winter temperatures do not fall below -10°c. It does not do well in areas with higher rainfalls - in Britain for example it grows well in the east and south-east, but less well in the moister west[, ].
Requires a position in full sun[]. Prefers dry sunny locations[]. Prefers a deep loamy well-drained soil but is not too fussy[].
A moderately fast-growing and long-lived tree in the wild[].
Seedlings quickly develop a taproot and larger plants can be difficult to transplant[].

Edible Uses

Seed - cooked[, , , , , ]. It can be dried, ground into a powder and used as a gruel[]. The seed contains about 23% protein and has an agreeable taste[]. The seed is large, and can be up to 5cm in diameter[]. It is often produced abundantly in the warmer areas of Britain and is easily harvested[]. This was the most commonly used Aesculus species in N. America[]. It does, however, contain poisonous saponins (see the notes above on toxicity) and so needs careful preparation before being eaten. The seed needs to be leached of these toxins before it becomes safe to eat - the native Americans would do this by slow-roasting the nuts (which would have rendered the saponins harmless) and then cutting them into thin slices, putting them into a cloth bag and rinsing them in a stream for 2 - 5 days[]. Most of the minerals etc would also have been leached out by this treatment[].

Medicinal

The seed contains saponins and can be used as an expectorant[].

The crushed fruit is applied as a salve on haemorrhoids[].

A decoction of the bark is used in the treatment of toothache and loose teeth[].

Agroforestry Uses:

In its native range, the plant is valuable as a soil binder on stream or river banks and on steep slopes[].

Other Uses

The seed is rich in saponins, these are used as a soap substitute[]. The saponins can be easily obtained by chopping the seed into small pieces and infusing them in hot water. This water can then be used for washing the body, clothes etc. Its main drawback is a lingering odour of horse chestnuts[].

The wood was used as friction sticks for making fire by the North American Indians[].

The heartwood is white or faintly tinged with yellow; it is not clearly demarcated from the thin layer of sapwood. The wood is soft, light in weight, very close grained[]. It is of no value as a lumber[]. It is occasionally used for lumber and paper pulp[].

Propagation

Seed - best sown outdoors or in a cold frame as soon as it is ripe[, ]. The seed germinates almost immediately and must be given protection from severe weather[]. Seedlings develop a large taproot following germination and so, if grown in containers, should be given sufficient root room[]. The seed has a very limited viability and must not be allowed to dry out. Stored seed should be soaked for 24 hours prior to sowing and even after this may still not be viable[, ]. It is best to sow the seed with its 'scar' downwards[]. If sowing the seed in a cold frame, pot up the seedlings in early spring and plant them out into their permanent positions in the summer.