Sophora japonica belongs to the Leguminosae, Papilionoideae tree plants, Sophora japonica, is a good green species, often for the Court of shade trees and street trees, and a certain economic value and medicinal value. Sophora japonica P. orientalis have become Beijing City tree, Sophora japonica is also the city of Xi'an, Shaanxi Province, Dalian City, Liaoning Province, Shandong Province Tai'an City of trees. 
 Ash, pinnate, leaflets smaller, so the dense canopy. Ash of a collateral thick crown Therefore, cloud-like. Locust tree rhizobia, nitrogen nutrition is adequate, so the leaf color is deep, dark green. From a distance, the locust tree crown as a mass of dark green, thick clouds, dark green is the color of a dark, thick clouds also bring dull. Ash reduction constriction beaded shrink constriction at the very fine. Shrink save the tree, locust tree pods angle to the second year of the rainy season encounter rainfall, shrinking constriction at the soaked by rain and breaking down, the peel has been soaked rot, exposing the seeds to the ground under the shade of dyed dark green. Ash is susceptible to aphids, aphid secretions to reach the ground will be the ground dyed black. Huaiyin so often black, also has a dark meaning. So, Ash from a "dull". "Cassia" and "dark" word pronunciation is similar to the "Ash" is the "dark tree", said a tree crown dull.