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Botanical name: Sophora japonica
Common name: Sophora flower bud, Pagoda tree bud
Literal name translation: sophora rice
Family: Fabaceae, pea family
Part used in Chinese medicine: flower
Major Chinese medicine actions:
Cools blod, stops bleeding, cools Liver heat
Sophora japonica is native to central and northern China and Korea, and though known commonly as “Japanese pagoda tree”, it is actually not indigenous to Japan. It is now widely cultivated in temperate and subtropical regions around the world, grown for its flower buds and young pods which are a good source of rutin. Rutin has “vitamin P-like” properties, and the flower buds been the object of much research in the treatment of conditions characterized by increased capillary permeability and fragility.
Growing and Propagation
The tree is deciduous, fast growing in warm climates, and can reach 65-70 feet tall. It is frost tender when young, then as it becomes older and more established, is very tolerant to heat, drought, pollution and frost. It is hardy to USDA zone 5, withstanding temperatures down to -25 degrees F. The tree does well in a wide range of soils, though needs adequate moisture especially when young. It grows in full sun and does not do well in shade.
Sophora japonica has a symbiotic relationship with certain soil bacteria. The bacteria form nodules on the roots that fix nitrogen, some of which is utilized by the growing plant but some can also be used by other plants growing nearby.
The Japanese pagoda tree does not start flowering until it is about 3-4 years old, and plants that are grown from seed can take 30 years to come into flower. The flowers appear in August to September and fruits in October to November.
Propagation may be accomplished by seed, root cuttings, or grafting. Seeds should first be soaked in hot water or the cortex of the seed should be scarified. Seedlings need special care and should be grown in containers in a greenhouse until established. The trees do not transplant well so should be planted directly to a permanent location outdoors.
Harvesting and Preparation
There are various parts of the Sophora japonica tree that are used in Chinese medicine. Sophora flower buds (Huai Mi) are the unopened flowers harvested in early summer just before the buds begin to open. The inflorescences, or clusters of flowers on stems of secondary branches, are gathered by cutting off the budding branches. Twigs, leaves and other auxiliary plant material are removed and the buds are immediately dried in the sun. Good quality Huai Mi contains about 20% rutin. The dried flower buds should be undamaged and yellowish green in color.
Sophora flowers (Huai Hua) are harvested when the flower is in full bloom in mid-summer. They are considered to be less potent than the flower buds and contain about 8% rutin. The flowers are dried in the sun immediately after picking. The best quality Huai Hua are the dried flowers that have been stored for a long period, known as Chen Huai Hua, or aged Sophora flowers.
Huai Jiao is the young fruit of the Sophora japonica tree. They are harvested in the fall and should be thoroughly dried. Good quality fruits are long, yellowish green pods that have a strong fragrance.