Common Name: Soap Tree

General Information

Gymnocladus chinensis is a deciduous tree growing 5 - 12 metres tall[].
The plant is harvested from the wild for local use as a medicine, source of soap and sometimes as a food. The seedpods are sold in local markets for use as a food, medicine and a soap[]. The tree is sometimes grown as an ornamental.

Known Hazards

The seedpod contains saponins and has been used as a fish poison[].
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

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Range

E. Asia - southeastern China (Anhui, Fujian, Guangdong, Guangxi, ?Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, ?Yunnan, Zhejiang).

Habitat

Plains and foothills to 1200 metres[]. Slopes, mountain sides, mixed forests, sides of rocks, near villages and beside houses; at elevations from 100 - 1,500 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	12.00 m
Growth Rate	Slow
Self-fertile	No
Cultivation Status	Wild

Cultivation Details

Gymnocladus chinensis is not a very cold-hardy tree, able to tolerate occasional temperatures falling to around -5°c when it is fuly dormant. It requires hot summers if it is to thrive and rarely flowers in areas with cool summers[, ].
Requires a deep rich well-drained moisture retentive soil and a sunny position[, ].
The plant is polygamous. Trees can bear male flowers, female flowers or hermaphrodite flowers, or a mixture. Effectively, the tree is often dioecious - both male and female forms must be grown if fruit and seed are required.
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[]. At least some members of this genus do not have these nitrogen-producing bacteria on the roots[].

Edible Uses

Seed - cooked[, ]. They are roasted and then eaten[]. The yellowish to reddish-brown seedpods are 7 - 10cm long and about 3cm wide, containing 2 - 4 seeds in a bitter, strong-smelling flesh, each seed is about 2cm in diameter[, ].

Medicinal

The seedpods are used in the treatment of rheumatism, dysentery and haematuria[].
Applied externally, the pods are used to treat eczema, favus, venereal sores, swellings and abscesses[, ].

The seeds are carminative[].

Agroforestry Uses:

The tree has a light canopy so does not cast much shade and is therefore a good species for the top canopy of a woodland garden.

Other Uses

The fruit is high in saponins and is used as a soap for washing fabrics and the body[, , ]. The pods are roasted, then pounded into a pulp, and kneaded into balls. These are usually as large as children's marbles, and were formerly
much used for washing clothes and the body[]. They have a strong smell[].

An oil obtained from the seeds is used in making paints[].

The oily seeds have been used by makers of artificial flowers as a source of wax to wax their threads[].

The wood is hard, durable, finishes to a fine lustre. It is used for cabinet making[].

Propagation

Seed - best sown in a greenhouse as soon as it is ripe[]. The seed can also be sown in early spring in a greenhouse[]. Scarification and pre-soaking the seed for 24 hours in warm water, especially if it has been stored, will improve germination[]. Make sure the seed has swollen after soaking, soak it again if it has not and, if it still does not swell, try filing away some of the seedcoat but be careful not to damage the embryo. As soon as they are large enough to handle, prick the seedlings out into fairly deep individual pots and grow them on in the greenhouse for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Consider giving them some protection against the cold for their first couple of winters outdoors
Root cuttings 4cm long and 1cm thick in a greenhouse in December[]. Plant the roots horizontally in pots[]. Good percentage.