サイカチ(Gleditsia japonica)はマメ科の落葉喬樹で、30cmの長さになる豆果はサポニンを多く含み、油汚れを落とすため石鹸の代わりとなり、古くから洗剤や入浴に利用されて来ました。また生薬としても用いられてきました。このサイカチの木は、昭和51年(1976)に保存樹木に指定されています。葛飾区では、緑を保存するために、大きな樹木を保存樹木に、まとまった面積をもつ樹林を保存樹林に指定し、維持費の一部として補助金を支給しています。指定された保存樹木は1,300本以上あります。

Honey locust (Gleditsia japonica) is a deciduous tall tree of the leguminous family. The legumes, which are 30 cm long, contain a lot of saponins and have been used as a substitute for soap for detergents and bathing since ancient times becuase it remove oil stains. It has also been used as a crude drug. This honey locust tree was designated as a preserved tree in Showa 51 (1976). Katsushika City has a system to designate large trees as preserved trees and forests with a large area as preserved forests in order to preserve greenery, and subsidies are provided as part of the maintenance cost. There are more than 1,300 designated preserved trees in Katsushika.