Ash is the general name of the white wax genus of the Oleaceae family, also known as cén (cén). Because the white wax insects are stocked on the tree, it is named Ash tree, and it is also a sand-fixing tree species. There are about 70 species of this genus, mainly distributed in the temperate zone of the northern hemisphere, with a few extending south to the tropics. There are about 20 species in China, and the most widely distributed is the ash tree. The wood is tough and resistant to water and humidity, and is used to make furniture, farm tools, plywood, etc.; the branches can be weaved into baskets; the bark is called "Qinpi", which is used as a heat-clearing medicine in Chinese medicine.

Ash has a high ecological value. Ash tree is an important street tree species in landscaping. In various places in Shandong, Beijing, Tianjin, Hebei, Henan, Jiangsu, Anhui, Hubei and other places, many roads use white wax as a tree species for street greening. White wax has good greening effect, high survival rate after transplanting, and low cost. It is one of the most commonly used tree species in the north. The material is excellent and can be used as furniture and joinery. The branches can be used to make baskets.