Soap Tree
Gymnocladus chinensis
Family: Fabaceae or Leguminosae
What it is like
Gymnocladus chinensis is a deciduous Tree growing to 12 m (39ft 4in) at a slow rate. See above for USDA hardiness. It is hardy to UK zone 9. It is in flower in April, and the seeds ripen in October. The species is dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required). . The plant is not self-fertile. It can fix Nitrogen. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers moist soil.
Height (m): 12
Where it is found
Plains and foothills to 1200 metres.
E. Asia - China.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 2
Seed - cooked.
Seed: includes nuts, cereals, peas and beans.
Medicine
Rating: 0
Other
Rating:
The fruit is high in saponins and is used as a soap for washing fabrics and the body. Wood - hard, durable, finishes to a fine lustre. It is used for cabinet making.
Soap: Plants used directly as a soap substitute.
Wood: A list of the trees and shrubs that are noted for having useful wood.
Nitrogen Fixer: Plants that fix nitrogen in the soil
How it is grown
Requires a deep rich well-drained moisture retentive soil and a sunny position. A very ornamental plant, it is only hardy in the mildest areas of Britain tolerating temperatures down to about to -5°c. It rarely flowers in Britain, requiring more summer heat than it usually gets here. 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. Dioecious. Male and female plants must be grown if seed is 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.
Propagating it: 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.
Best place to grow: Woodland Garden Canopy; Secondary;
Habit: Tree
Hardiness: 8-11
Growth: Slow
Soil: Light (sandy), medium, heavy (clay)
Shade: No shade
Moisture: Moist